Part-stream distillation

Abstract

A continuous process for the preparation of propylene oxide, comprising (a) reacting propene, optionally admixed with propane, with hydrogen peroxide in a reaction apparatus in the presence of acetonitrile as solvent, obtaining a stream S0 containing propylene oxide, acetonitrile, water, at least one further component B, optionally propene and optionally propane, wherein the normal boiling point of the at least one component B is higher than the normal boiling point of acetonitrile and wherein the decadic logarithm of the octanol-water partition coefficient (log K.sub.ow) of the at least one component B is greater than zero; (b) separating propylene oxide from S0, obtaining a stream S1 containing acetonitrile, water and the at least one further component B; (c) dividing S1 into two streams S2 and S3; (d) subjecting S3 to a vapor-liquid fractionation in a fractionation unit, obtaining a vapor fraction stream S4 being depleted of the at least one component B; (e) recycling at least a portion of S4, optionally after work-up, to (a).

Claims

1. A continuous process for preparation of propylene oxide, the process comprising (a) reacting propene with hydrogen peroxide in a reaction apparatus in the presence of acetonitrile as solvent, obtaining a stream S0 leaving the reaction apparatus, S0 comprising propylene oxide, acetonitrile, water, at least one further component B, wherein a normal boiling point of the at least one component B is higher than a normal boiling point of acetonitrile and wherein a decadic logarithm of an octanol-water partition coefficient represented by log K.sub.OW of the at least one component B is greater than zero; (b) separating propylene oxide from S0, obtaining a stream S1 comprising acetonitrile, water and the at least one further component B; (c) dividing S1 into two streams S2 and S3, wherein a total weight of S3 relative to a total weight of S1 is in a range of from 0.01 to 25%; (d) subjecting S3 to a vapor-liquid fractionation in a fractionation unit, obtaining a vapor fraction stream S4 being depleted of the at least one component B, and obtaining a liquid bottoms stream S4b being depleted of acetonitrile; and (e) recycling at least a portion of S4 to (a).

2. The process of claim 1, wherein in (c), the total weight of S3 relative to the total weight of S1 is in a range of from 0.05 to 20%.

3. The process of claim 1, wherein from 90 to 99.9 weight-% of S1 consist of acetonitrile and water and wherein from 0.01 to 5 weight-% of S1 consist of the at least one component B.

4. The process of claim 1, wherein in (d), vapor-liquid fractionation is carried out in the fractionation unit so that from 10 to 30 weight-% of the liquid bottoms stream S4b consist of acetonitrile and from 0.1 to 10 weight-% of the liquid bottoms stream S4b consist of the at least one further component B.

5. The process of claim 1, wherein in (d), vapor-liquid fractionation is carried out in the fractionation unit at an absolute pressure in a range of from 0.1 to 10 bar.

6. The process of claim 1, wherein in (d), a number of theoretical trays of the fractionation unit is in a range of from 1 to 100.

7. The process of claim 1, wherein a fraction of S4 is used after condensation as reflux.

8. The process of claim 1, wherein the fractionation unit is operated without reflux and S3 is fed to a top of the fractionation unit.

9. The process of claim 1, wherein from 95 to 99.99 weight-% of S4 consist of acetonitrile and water, and wherein from 0.0001 to 0.2 weight-% of S4 consist of the at least one component B.

10. The process of claim 1, wherein (e) comprises recycling at least a portion of S4 to (a), and recycling at least a portion of S2 to (a).

11. The process of claim 1, wherein (e) comprises working-up S4, said working-up comprising combining at least a portion of S4 with S2 obtaining a liquid stream, subjecting said liquid stream to acetonitrile-water separation obtaining a stream enriched in acetonitrile, and recycling said stream enriched in acetonitrile to (a).

12. The process of claim 11, wherein (e) comprises (i) preparing a liquid stream S5 by adding a liquid stream P to S2, or to at least a portion of S4, or to the liquid stream obtained from combining S2 and at least the portion of S4, wherein P comprises at least 95 weight-% of C3, based on a total weight of P, wherein C3 is propene; (ii) subjecting S5 to a temperature of 92° C. at most and a pressure of at least 10bar, obtaining a first liquid phase L1 and a second liquid phase L2, wherein at least 95 weight-% of L1 consist of C3, acetonitrile, water and the at least one component B, the water content of L1 being less than 10 weight-% based on a total weight of L1, and wherein at least 95 weight-% of L2 consist of C3, acetonitrile, water and the at least one component B, a C3 content of L2 being 5 weight-% at most, based on a total weight of L2, and an acetonitrile content of L2 being less than 45 weight-%, based on the total weight of L2; (iii) separating L1 from L2; and (iv) recycling L1 as the stream enriched in acetonitrile to (a).

13. The process of claim 12, further comprising working up L1, said working-up comprising subjecting L1 to a distillation stage wherefrom a bottoms stream BL1 is obtained, wherein at least 95 weight-% of BL1 consist of C3, acetonitrile, water and the at least one component B, wherein a C3 content of BL1 is in a range of from 7 to 18 weight-%, and recycling BL1 as the stream enriched in acetonitrile to (a).

14. The process of claim 13, wherein from 0.01 to 5 weight-% of BL1 consist of the at least one component B.

15. The process of claim 1, wherein (b) comprises (I) separating propene from S0, obtaining a stream S01 enriched in propylene oxide, acetonitrile, water, and the at least one component B; and (II) separating propylene oxide from S01, obtaining a stream S02 enriched in acetonitrile, water and the at least one component B and wherein a weight ratio of acetonitrile relative to water is greater than 1:1.

16. The process of claim 15, wherein (b) further comprises (IIIa) subjecting S02 obtained from (II) to hydrogenation to obtain a hydrogenated stream; and/or (IIIb) subjecting the stream obtained from (II) or (IIIa) to distillation to obtain a bottoms stream, wherein the hydrogenated stream obtained from (IIIa) or the bottoms stream obtained from (IIIb) is subjected to (c) as S1.

17. The process of claim 1, wherein in (a), propene is reacted with hydrogen peroxide in the presence of a heterogeneous catalyst.

18. The process of claim 1, wherein from 90 to 97 weight-% of S0 consist of acetonitrile, water, and propylene oxide, and wherein from 0.01 to 3 weight-% of S0 consist of the at least one component B.

19. The process of claim 1, wherein the at least one component B is propionitrile, 1-nitropropane, 2-nitropropane, 3-methylbutanenitrile, n-pentanenitrile, 1-pentanol, 2-pentanol, 2-butanone, 2-pentanone, 2-hexanone, 4-methyl-2-heptanone, 2,6-dimethyl-4-heptanol, 4,6-dimethyl-2-heptanol, 2,6-dimethyl-4-heptanone, 4,6-dimethyl-2-heptanone, 2,6-dimethyl-4,6-heptandiol, 2,4-dimethyloxazoline, 2,5-dimethyloxazoline, cis-2,4-dimethyl-1,3-dioxolane, trans-2,4-dimethyl-1,3-dioxolane, at least one impurity contained in the hydrogen peroxide employed in (a), or a combination of two or more of these compounds.

20. The process of claim 19, wherein the at least one impurity contained in the hydrogen peroxide employed in (a) is an alkyl phosphate, a nonyl alcohol, an alkylcyclohexanol ester, an N,N-dialkyl carbonamide, an N-alkyl-N-aryl carbonamide, an N,N-dialkyl carbamate, a tetraalkyl urea, a cycloalkyl urea, a phenylalkyl urea, an N-alkyl-2-pyrrolidone, an N-alkyl caprolactam, or a combination of two or more of these compounds.

Description

EXAMPLES

Example 1

A Preferred Process According to the Invention—General Setup

(1) As to the abbreviations, reference is made to the scheme according to the FIGURE, generally described in the section “Description of the FIGURE” hereinbelow. All pressures given are absolute pressures.

(2) 1.1 Preparation of Stream S0 (Step (a))

(3) a) Epoxidation in an Epoxidation Main Reactor (Epoxidation Unit A)

(4) The main reactor A was a vertically mounted tube-bundle reactor with 5 tubes (length of the tubes: 12 m, internal tube diameter: 38 mm), each tube being equipped with an axially placed multi-point thermocouple with 10 equally spaced measuring points encased in a suitable thermowell with a diameter of 18 mm. Each tube was charged with 17.5 kg of the ZnTiMWW catalyst moldings as prepared according to Reference Example 1, section 1.8 (post-treated moldings). Free space eventually remaining was filled with steatite spheres (diameter of 3 mm). The heat of reaction was removed by circulating a thermostatized heat transfer medium (water/glycol mixture) on the shell side in co-current to the feed. The flow rate of the heat transfer medium was adjusted so that the temperature difference between entrance and exit did not exceed 1° C. The reaction temperature referred to hereinbelow was defined as the temperature of the heat transfer medium entering the reactor shell. At the reactor exit, the pressure was controlled by a pressure regulator and kept constant at 20 bar.

(5) The reactor was fed from below with a liquid monophasic stream (1). Stream 1 was prepared by mixing three streams (2), (3), and (4). The temperature of stream (1) was not actively controlled, but was usually in the range from 20 to 40° C.: Stream (2) having a flow rate of 85 kg/h. At least 99.5 weight-% of stream (2) consisted of acetonitrile, propene and water. This stream (2) came from the bottoms of the acetonitrile recycle distillation unit (J). Stream (3) having a flow rate of 15 kg/h was an aqueous hydrogen peroxide solution having a hydrogen peroxide concentration of 40 weight-% (“crude/washed” grade from Solvay with a TOC in the range of 100 to 400 mg/kg. The aqueous hydrogen peroxide solution was supplied from a storage tank, allowing for a continuous feeding, and fed using a suitable metering pump. Stream (4) was a make-up stream of pure acetonitrile (chemical grade, from Ineos, purity about 99.9%, containing between 70-180 weight-ppm propionitrile, 5-20 weight-ppm acetamide and less than 100 weight-ppm water as impurities). Enough fresh acetonitrile was added to compensate for losses in the process. Under regular conditions, an average of from 100 to 150 g/h of make-up acetonitrile were added. Optionally, a further stream can be used, and the stream 1 is prepared by mixing four streams (2), (3), (4), and said further stream. The further stream is an aqueous stream which comprises at least one dissolved potassium salt such as potassium dihydrogen phosphate. The further stream can be supplied from a storage tank, allowing for a continuous feeding, and can be fed using a suitable metering pump. A conceivable concentration of the potassium salt is, for example, 2.5 weight-%, a conceivable feed rate of the further stream is, for example, 370 g/h.

(6) The output stream leaving the epoxidation unit A was sampled every 20 minutes in order to determine the hydrogen peroxide concentration using the titanyl sulfate method and to calculate the hydrogen peroxide conversion. The hydrogen peroxide conversion was defined as 100×(1-m.sub.out/m.sub.in) wherein m.sub.in is the molar flow rate of H.sub.2O.sub.2 in the reactor feed and m.sub.out is the molar flow rate of H.sub.2O.sub.2 in the reactor outlet. Based on the respectively obtained hydrogen peroxide conversion values, the inlet temperature of the heat transfer medium was adjusted in order to keep the hydrogen peroxide conversion essentially constant in the range of from 90 to 92%. The inlet temperature of the heat transfer medium was set at 30° C. at the start of a given run with a fresh batch of the epoxidation catalyst and was increased, if necessary, to maintain the hydrogen peroxide conversion in the mentioned range. The required temperature increase was usually less than 1° C./d.

(7) b) Intermediate Removal of Propylene Oxide (Distillation Unit B)

(8) After pressure release, the effluent from the epoxidation unit A (stream (5)) was sent to an intermediate propylene oxide removing column (distillation unit B) operated at about 1.1 bar. The column was 6 m high, had a diameter of 200 mm and was equipped with 30 bubble trays, an evaporator, and a condenser. The feed to the column entered above bubble tray 25 (counted from the top). The overhead stream leaving the column with about 50° C. mainly contained propylene oxide, unconverted propene and small amounts of oxygen formed as byproduct. This stream was partly condensed (T=15-25° C.), and the condensed liquid served as an internal reflux stream whereas the gaseous part (stream (6)) was sent to the lights separation column (distillation unit D).

(9) The bottoms temperature of the intermediate propylene oxide removal column was about 80° C. The bottoms stream (stream (7)) was almost free of propylene oxide (<300 wt.-ppm) and was a mixture of acetonitrile (about 78-80 weight-%), water (about 18-20 weight-%), unconverted hydrogen epoxide and heavy boilers having a normal boiling point of above 100° C., the main heavy boiler being propene glycol. This bottoms stream (7) was subsequently cooled to 35° C. and pumped pump to the finishing reactor (epoxidation unit C; see section c) below) using a suitable metering pump.

(10) c) Epoxidation in a Finishing Reactor (Epoxidation Unit C)

(11) The total feed stream to the finishing reactor C was obtained by mixing stream (7) obtained according to section b) above with a stream (8) of polymer grade liquid propene containing propane (purity about 99.5%, feed rate: 0.9 kg/h, at ambient temperature). Both streams (7) and (8) were mixed using a static mixer and fed to the bottom of the finishing reactor C.

(12) The finishing reactor C was a fixed bed reactor operated adiabatically. In this context, the term “adiabatic” refers to an operation mode according to which no active cooling is carried out and according to which the finishing reactor is suitably insulated in order to minimize heat losses). The finishing reactor C had a length of 4 m and a diameter of 100 mm. The reactor was filled with 9 kg of the same epoxidation catalyst which was used in the main epoxidation reactor A. Spare space was filled with steatite spheres (diameter of 3 mm). The operating pressure of the finishing reactor C was 10 bar which was kept constant by a suitable pressure regulator at the reactor exit. The output of the finishing reactor C was sampled every 20 min in order to determine the hydrogen peroxide concentration using the titanyl sulfate method.

(13) The effluent of the finishing reactor C, stream (9), was depressurized into a flash drum, and both the liquid and the gas from this drum were fed to a light boiler separation column (distillation unit D).

(14) The stream (6) obtained from the top of the intermediate propylene oxide removing column (distillation unit B) and the stream (9) obtained as effluent from the finishing reactor C (epoxidation unit C) together constitute the stream S0 according to the present invention.

(15) This stream S0 had in average an acetonitrile content of from 69 to 70 weight-%, a propylene oxide content of 9.8 weight-%, a water content of 17 weight-%, a propene content of about 3 weight-%, a propane content of about 0.05 weight-%, a hydrogen peroxide content of about 250 weight-ppm, a propene glycol content of about 0.1 weight-% and an oxygen content of about 150 weight-ppm.

(16) 1.2 Separation of Propylene Oxide from Stream S0 to Obtain Stream S1 (Step (b))

(17) a) Separation of Light Boilers from Streams (6) and (9) (Stream S0) to Obtain a Stream (II) (Stream S01 According to Step (I) of the Present Invention)

(18) The top stream from the intermediate propylene oxide removing column (distillation unit B) (stream (6), see section 1.1 b) above) and the depressurized outlet stream of the finishing reactor C (stream (9), see section 1.1 c) above) were sent to a light boiler separation column (distillation unit D) operated at 1.1 bar. The distillation column had a length of 8.5 m, a diameter of 170 mm, and was equipped with 40 bubble trays, an evaporator at the bottom and a condenser at the top. The column was operated as a mixed washing/distillation tower. As a washing agent, part of the bottoms stream of distillation unit E (stream 14, about 20-30 kg/h) was taken off, cooled to 10° C. and introduced at the top of the column. Liquid and gaseous inlet streams were introduced the column at different points. The feed point of the liquid stream (stream (6) plus the liquid portion of stream (9)) was above bubble tray 37; the gaseous stream was introduced into the column above bubble tray 28 (counted from the top).

(19) The gaseous stream (10) leaving the cooling means at the top of the column contained mainly propene, propane (which was contained as impurity in the polymer-grade propene used), oxygen formed as a by-product and small amounts of other light boilers (acetonitrile (about 4.7 volume-%), propionaldehyde (about 200 volume-ppm), acetone (about 100 volume-ppm, H.sub.2 (about 400 volume-ppm), CO.sub.2 (about 400 volume-ppm) and acetaldehyde (about 100 volume-ppm)), and was essentially free of propylene oxide (less than 300 volume-ppm). This top stream was sent to the flare for disposal.

(20) The bottom stream of the light boiler separation column (stream (II), that is stream S01 of the present invention) having a temperature of 70° C., had a propene content of from 100 to 200 weight-ppm.

(21) b) Separation of Propylene Oxide from Stream (II) (Stream S01) to Obtain a Stream S02 According to Step (II) of the Present Invention

(22) The stream S01 obtained according to section 1.2 a) above was introduced into a distillation column (distillation unit E) in order to separate propylene oxide from the stream S01. The column had a height of 50 m and a diameter of 220 mm and was equipped with a packing (Sulzer BX64) with a total packing length of 27.5 m divided into 8 beds with a length of 3060 mm each and two beds with a length of 1530 mm each. Between each bed intermediate flow distributors were installed. The column was operated at a top pressure of 750 mbar. The feed point of stream S01 was located below the fourth packing bed, counted from the top.

(23) The overhead stream of the column was condensed and partly returned to the column as reflux (reflux ratio approximately 5:1). The remainder (stream (12)), having a flow rate of 10.1 kg/h, was taken as overhead product and essentially consisted of propylene oxide having a purity of more than 99.9 weight-%.

(24) The bottoms evaporator was operated in such a way that the propylene oxide concentration in the bottoms stream was below 100 weight-ppm. The resulting temperature of the bottoms stream was about 69° C. The stream S02 was then divided in two. The major portion of it (stream (13), with a flow rate of ca. 85 kg/h) was sent to the next distillation column (distillation unit F). The remainder (stream (14), 20-30 kg/h) was cooled and recirculated to the top of the light boiler separation column (distillation unit D) as washing agent as described above in section 1.2 a).

(25) This stream S02 had an acetonitrile content of about 80 weight-%, a propylene oxide content of less than 100 wt.-ppm, a water content of about 20 weight-%, a propene glycol content of about 0.1 weight-% and a hydroxypropanol content of about 0.1 weight-%.

(26) c) Separation of Light Boiling Compounds from Stream (13) (Stream S02) to Obtain a Stream (16) (Stream S1 According to Step (IIIb) of the Present Invention)

(27) The stream S02 obtained according to section 1.2 b) above was introduced into a lights separation column (distillation unit F). This lights separation column had a height of 8 m and a nominal diameter of 150 mm and was equipped with 35 bubble trays. The column was operated at a top pressure of 2 bar, and the stream S02 was introduced above bubble tray number 7 (counted from the bottom).

(28) The overhead stream obtained (stream (15), flow rate about 1 kg/h) left the column with a temperature of from 40 to 45° C. and was not condensed as the column was operated with no internal reflux stream. Besides acetonitrile (6500 vol.-ppm), this overhead stream contained mainly nitrogen which was employed to keep the column operating pressure at a value of 2 bar) and small amounts of light boilers (acetaldehyde (900 vol.-ppm), oxygen (300 vol.-ppm), and propionaldehyde (320 vol.-ppm). This top stream was sent to the flare for disposal.

(29) The sump evaporator was operated by feeding it with a constant amount (5 kg/h) of saturated steam at a pressure of 16 bar. The bottom temperature of the column was 100° C. The bottoms stream, stream S1 of the present invention, mainly consisted of acetonitrile and water, the remainder being high boilers. This stream S1 had an acetonitrile content of about 80 weight-% and a water content of about 20 weight-%.

(30) 1.3 Dividing Stream S1 into Streams S2 and S3 (Step (c))

(31) According to present invention, step (c), the stream S1, flow rate 86 kg/h, obtained according to section 1.2 c) above, was divided into two streams, streams S2 (stream (16a according to the FIGURE) and S3 (stream 17 according to the FIGURE). Stream S2 had a flow rate of 84 kg/h and stream S3 had a flow rate of 2 kg/h. Stream S3, 2.3% of stream S1, was subjected to part stream distillation unit G (part stream distillation column).

(32) 1.4 Part-Stream Distillation of Stream S1 (Step (d))

(33) The part stream distillation column had a height of 9.5 m and a diameter of 85 mm and was equipped with 6.5 meters of metal structured Rombopak 9M packing installed in three identical beds. Below the first bed of structured packing counted from the top, the stream S3 was introduced in the part stream distillation column. The temperature of the feed stream was in the range of 89° C.±5° C. The column was operated at a top pressure of 1.5 bar and exhibited a pressure drop of less than 10 mbar. No reflux was applied. The amount of steam fed to the bottoms evaporator was controlled in such a way that the concentration of acetonitrile in the bottoms was in the range of from 10 to 25 weight-%. At the pressure used this translated into a bottom temperature of the column in the range of from 94 to 98° C. Depending on the respective amounts and chemical nature of the heavy boilers contained in the stream S3, the bottoms consisted either of one or two liquid phases. If present, the upper organic phase made up less than 10 weight-% of the total amount of the bottoms stream. From the bottoms, a constant stream of 50 g/h was removed and after analyzing, was discarded. This stream consisted mainly of water (72-85 weight-%) and acetonitrile (10-24 weight-%). The sum of all the analyzed high-boiling components (27 components) varied in the range of 4-10 weight-%.

(34) An external overhead condenser was applied to fully condense the vapor top stream leaving the part stream distillation column (stream S4 according to the present invention). The condensed stream S4 had an acetonitrile content of about 80 weight-% and a water content of about 20 weight-%.

(35) 1.5 Recycling of the Stream S4 (Step (4))

(36) a) Preparing a Liquid Stream S5 According to Step (i)

(37) The condensed stream S4, (stream 18 according to the FIGURE) was admixed with stream S2 (stream (16a) according to the FIGURE). Thus, the condensed stream S2 was pumped back into the bulk process acetonitrile solvent stream. Mixing took place at a point downstream of where stream S3 was diverted from stream S1.

(38) This combined stream having a flow rate of 86 kg/h was mixed with a liquid stream P (referred to as stream (23) in the FIGURE) to obtain a stream S5. Stream P was fresh propene stream containing propane (polymer grade, purity>96 weight-%, liquefied under pressure, feed rate: 10 kg/h).

(39) According to this specific embodiment of the present invention, in order to obtain the stream S5, the combined stream of S2 and S4 was further mixed with two other streams: the first one of these streams is stream (19) according to the FIGURE, said stream being obtained from the top of the distillation unit I. The second one of these streams is stream (22) according to the FIGURE, said stream being obtained from the acetonitrile recovery unit J. Both streams (19) and (22) are described in detail hereinunder.

(40) b) Adjusting the Temperature of Stream S5 and Separating Liquid Phases L1 and L2 (Steps (ii) and (iii))

(41) The stream S5 having a flow rate of 150 kg/h±10 kg/h was then fed to a mixer-settler unit operated at 18 bar and a temperature in the range of 30±5° C. The settler tank had a volume of 5.3 liters. Two liquid phases L1 and L2 were obtained, an aqueous phase L2 and an organic phase L1. The upper organic phase L1 was removed from the settler tank as stream (20), the lower aqueous phase L2 was removed from the settler tank as stream (21). The stream (20) had a flow rate in the range of 130 kg/h±13 kg/h.

(42) The stream (20) then was passed to the acetonitrile recycle unit J, the stream (21) was passed to the acetonitrile recovery unit I from which the stream (19) mentioned above was obtained.

(43) The stream (20) thus obtained had an acetonitrile content of about 46 weight-%, a propene content of about 51 weight-% and a water content of about 3 to 4 weight-%.

(44) The stream (21) thus obtained had an acetonitrile content of about 21 weight-%, a water content of about 79 weight-% and a propene content of less than 0.5 weight-%.

(45) c) Acetonitrile Recovery (Acetonitrile Recovery Unit I)

(46) In order to recycle as much solvent as possible, and in order to minimize acetonitrile losses, the stream (21) was introduced into a distillation column from which the stream (19), also referred to as stream TL2, was obtained as top stream which in turn was recycled into the solvent stream as described above.

(47) For this purpose, a distillation column with a height of 9.5 m and a diameter of 100 mm, equipped with 50 bubble trays was used. The column was operated at a top pressure of 1.5 bar with a reflux ratio of 1:4. Stream (21) was fed to the column above bubble tray 26 (counted from the bottom).

(48) The bottoms temperature was about 113° C., and the bottoms product consists mainly of water containing high boiling by-products. A typical composition of the bottoms stream was as follows (weight-% given in parenthesis): water (>99.0), propene glycol (0.5), acetonitrile (at most 0.001), dipropylene glycol (0.06), acetamide (0.01), acetic acid (0.03), TOC (2.4)). After optional metering and analyzing, this stream was discarded.

(49) The overhead product (stream (19)=stream TL2) had the following typical composition ranges (weight-% given in parenthesis): acetonitrile (75-80), water (15-20), low boilers (e.g. propene, 1). As described above stream (19) is recycled to the feed stream which is passed to the mixer-settler unit.

(50) d) Acetonitrile Recycling (Acetonitrile Recycling Unit J), Step (iv)

(51) For acetonitrile recycle, the stream (20) obtained from the mixer-settler unit H was introduced into a distillation column with a height of 10 m and a nominal diameter of 200 mm, equipped with 40 bubble trays. The column was operated at a top pressure of 18 bar with a reflux ratio of 1:4. Stream (20) was fed to the column above bubble tray 26 (counted from the top). The top product (stream (22)), also referred to as stream TL1, containing mainly propene (ca. 97 vol.-%) with small amounts of propane (ca. 1-3 vol.-%) was returned to the feed of the mixer-settler unit H as described above. Thus, excess propene was removed from steam (20) and recycled.

(52) The bottoms stream (stream (2), also referred to as stream BL1), had a temperature in the range of from 106 to 110° C. The precise operation parameters of the column, like energy input in the sump, are adjusted in such a way that the amount of propene returned to the reactor with stream (2) is in a range such that the molar ratio of propene to hydrogen peroxide in stream (1) was about 1:1.3. For the above mentioned feed rate of 15 kg/h of aqueous hydrogen peroxide, this means that the conditions needed to be adjusted such that the flow rate of propene in stream (2) was about 9.7 kg/h.

(53) Prior to feeding stream (2) to the main epoxidation reactor A, acetonitrile (stream (4), chemical grade, from Ineos, purity about 99.9%, containing between 70-180 weight-ppm propionitrile, 5-20 weight-ppm acetamide and <100 weight-ppm water as impurities) was optionally added to compensate for possible solvent losses. The exact amount of additionally added acetonitrile required depended on the losses in exit streams and in by-products but also on the number of samples taken for analytics. A typical amount of additionally added acetonitrile for the above-described process design may be in the range of from 100 to 150 g/h.

Example 2a

Comparative (without Part-Stream Distillation, without Hydrogenation)

(54) The process as described above in Example 1 was first taken into operation using a fresh charge of epoxidation catalyst and fresh acetonitrile (same quality as for make-up stream (4), see section 1.5 d) above) but without using the inventive part-stream distillation. Thus, from stream (16) (stream S1), no stream (17) (stream S3) was separated and subjected to distillation in unit G. Stream 1 was admixed as such with streams (19), (22), and (23).

(55) The starting temperature for the cooling medium loop of the epoxidation main reactor was set at 30° C. At the beginning, the hydrogen peroxide conversion in the epoxidation main reactor A was almost complete. Within 24 hours, the hydrogen peroxide conversion started to decrease, and when it had reached the desired value of approximately 90% (after about 100-200 hours), the temperature of the cooling medium was slowly raised to keep the hydrogen peroxide conversion in the epoxidation main reactor A constant. The rate of the temperature increase of the cooling medium was always less than 1° C./day).

(56) The plant was then operated as described above in Example 1 for 441 h. At the end of this period, the temperature of the cooling medium of the epoxidation main reactor was 35° C. At this point, several components (either by-products of the epoxidation reaction and/or impurities in the feed streams which had not been present at the beginning of the run) had accumulated in the solvent loop. The accumulation increased linearly with no signs of reaching a steady state. The concentration of the components which had accumulated in stream (2), the acetonitrile recycling stream obtained from unit J, after 441 hours on stream is given in Table A.

(57) TABLE-US-00001 TABLE A Results of Example 2a Concentration in stream (2) after 440 hours on stream/ Component weight-ppm propionitrile 44 4,6-dimethyl-2-heptanol 390 2,6-dimethyl-4-heptanol 815 2,6-dimethyl-4-heptanone 14 4,6-dimethyl-2-heptanone 8 1-nitropropane 29 2-nitropropane 45

(58) This experiment shows that in the absence of the inventive part-stream distillation, the overall process including solvent recycling suffers from an accumulation of several compounds in the solvent loop. No steady-state was reached relative to the concentration of these compounds.

Example 2b

According to the Invention (with Part-Stream Distillation, without Hydrogenation)

(59) The run as described in Example 2a was continued, and at t=441 hours on stream, the part-stream distillation (unit G) was taken into operation. The run was then continued until a time on stream of 1800 hours was reached. During this period, a stream S3 with a constant flow rate of 2 kg/h (±0.1 kg/h) was taken off from the stream S1 and fed to the distillation column (unit G), corresponding to about 2.3% of the total amount of stream S1. A bottoms stream with a constant flow rate of 40 g/h (±10 g/h) was removed at the bottom of the distillation column (unit G) and discarded. The composition of this bottoms stream after 1800 hours on stream was as follows (weight-% in parenthesis): water (77.5), propene glycol (6,1), acetonitrile (14.1), dipropylene glycol (0.20), tripropylene glycol (0.12), acetamide (0.16), 2,6-dimethyl-4-heptanol (0.16), 4,6-dimethyl-2-heptanol (0.08), 1-nitropropane (0.004), 2-nitropropane (0.004), hydroxyacetone (0.4), acetic acid (0.6), ammonia (0.02), TOC (0.02), acid value=1.4 mg/g (determined according to DIN EN ISO 2114). The concentration of the impurities in the solvent loop (in stream (2) just before starting the part-stream distillation (at 441 hours on stream) and at the end of the run with part-stream distillation (after 1329 hours on stream) is given in Table B.

(60) TABLE-US-00002 TABLE B Results of Example 2b Concentration in stream (2)/weight-ppm Before starting the part-stream At the end Stationary distillation of the run since/ (at 440 hours (at 1800 hours hours on Component on stream) on stream) stream propionitrile 44 26 .sup.a) 4,6-dimethyl-2-heptanol 346 48 1700 2,6-dimethyl-4-heptanol 722 20 .sup.a) 2,6-dimethyl-4-heptanone 13 2 1700 4,6-dimethyl-2-heptanone 7 2 1700 1-nitropropane 26 4  950 2-nitropropane 40 8  950 .sup.a) Concentration of this component was still falling when the experiment was finished.

(61) At the end of the run, all respective concentrations in stream (2) had reached steady-state, and no accumulation was observed any more. This inventive example clearly shows that making use of the inventive part-stream distillation according to which only a minor fraction of the stream S1 is separated and subjected to distillation, the accumulation of by-products and impurities during solvent recycling can be stopped and a steady-state at very low concentration levels can be reached. Yet further, the example shows that the inventive part-stream distillation method even allows to significantly reduce the concentration of by-products and impurities accumulated in the acetonitrile solvent loop.

(62) It also shows that it is sufficient to work-up a small side stream to obtain the desired result, thus offering large savings in energy and investment.

Example 3a

Comparative (without Part-Stream Distillation, with Hydrogenation)

(63) In a new run, the process as described above in Example 1 was first taken into operation using a fresh charge of epoxidation catalyst and fresh acetonitrile (same quality as for make-up stream (4), see section 1.5 d) above) but without using the inventive part-stream distillation. Thus, from stream (16) (stream S1), no stream (17) (stream S3) was separated and subjected to distillation in unit G. Stream 1 was admixed as such with streams (19), (22), and (23).

(64) In this example, stream (13) (steam S02)) was passed through a hydrogenation reactor (not shown in the FIGURE) located downstream the unit E and upstream the unit F. The hydrogenation reactor was a tubular reactor with a diameter of 53 mm and a height of 3.25 m, filled with a fixed bed catalyst (0.3 weight-% Pd on Al.sub.2O.sub.3, strands with 4 mm diameter, H0-13 S4 from BASF SE, operated adiabatically. The reactor was operated as a packed bubble column with gas and liquid flowing in co-current from the bottom to the top of the reactor at a pressure of about 15 bar. Hydrogen was provided was fed at a constant rate of 100 g/h. The temperature of the liquid feed stream (13) to the hydrogenation reactor was adjusted to 70° C. and kept constant throughout the run. At the hydrogenation reactor exit, the pressure was reduced to 1 bar, and the liquid phase and the gas phase leaving the hydrogenation reactor were separated. The gaseous phase was discarded and the liquid phase was fed to unit F as described hereinabove.

(65) The starting temperature for the cooling medium loop of the epoxidation main reactor A was set at 30° C. At the beginning, the hydrogen peroxide conversion in the epoxidation main reactor was almost complete. Within 24 hours, the hydrogen peroxide conversion started to decrease, and when it had reached the desired value of approximately 90% (after about 100-200 hours) the temperature of the cooling medium was slowly raised to keep the hydrogen peroxide conversion in the epoxidation main reactor A constant. The rate of the temperature increase of the cooling medium was always less than 1° C./day).

(66) The plant was then operated as described above in Example 1 for 864 h. At the end of this period, the temperature of the cooling medium of the epoxidation main reactor was 39.2° C. At this point, several components (either by-products of the epoxidation reaction and/or impurities in the feed streams which had not been present at the beginning of the run) had accumulated in the solvent loop. The accumulation increased linearly with no signs of reaching a steady state. The concentration of the components which had accumulated in stream (2), the acetonitrile recycling stream obtained from unit J, after 864 hours on stream is given in Table C.

(67) TABLE-US-00003 TABLE C Results of Example 3a Concentration in stream (2) after 864 hours on stream/ Component weight-ppm propionitrile 237 4,6-dimethyl-2-heptanol 1121 2,6-dimethyl-4-heptanol 2168 2,6-dimethyl-4-heptanone 23 4,6-dimethyl-2-heptanone 20 1-nitropropane 204 2-nitropropane 229

(68) This experiment shows that in the absence of the inventive part-stream distillation, the overall process including solvent recycling suffers from an accumulation of several compounds in the solvent loop. No steady-state was reached relative to the concentration of these compounds.

Example 3b

According to the Invention (with Part-Stream Distillation, with Hydrogenation)

(69) The run as described in Example 3a was continued, and at t=864 hours on stream, the part-stream distillation (unit G) was taken into operation. The run was then continued until a time on stream of 1600 hours was reached.

(70) During this period, a stream S2 with a constant flow rate of 2 kg/h (±0.1 kg/h) was diverted from the stream S1 and fed to the distillation column (unit G), corresponding to about 2.3% of the total amount of stream S1. A bottoms stream with a constant flow rate of 50 g/h was removed at the bottom of the distillation column (unit G) and after being analyzed was discarded.

(71) The composition of the stream S2 after reaching steady-state was as follows: water (76.1), propene glycol (0.43), propionitrile (0.11), acetonitrile (14.1), dipropylene glycol (0.20), tripropylene glycol (0.13), acetamide (0.17), 2,6-dimethyl-4-heptanol (0.14), 4,6-dimethyl-2-heptanol (0.12), 1-nitropropane (0.10), 2-nitropropane (0.11), hydroxyacetone (0.34), acetic acid (0.46), ammonia (0.03), TOC (0.02), acid value=1.4 mg/g.

(72) The concentration of the impurities in the solvent loop (in stream (2) just before starting the part-stream distillation (at 864 hours on stream) and at the end of the experiment (after 1600 hours on stream) is given in Table D.

(73) TABLE-US-00004 TABLE D Results of Example 3b Concentration in stream (2)/weight-ppm Before starting the At the end of part-stream distillation the run (at 1600 Component (at 864 hours on stream) hours on stream) propionitrile 237 139 4,6-dimethyl-2-heptanol 1121 370 2,6-dimethyl-4-heptanol 2168 783 2,6-dimethyl-4-heptanone 25 9 4,6-dimethyl-2-heptanone 20 5 1-nitropropane 204 87 2-nitropropane 232 107

(74) Between 1370-1580 hours on stream, all the concentrations in stream (2) had reached steady-state, and no accumulation was observed any more. Until the end of the run no accumulation was observed any more.

(75) This inventive example clearly shows that making use of the inventive part-stream distillation according to which only a minor fraction of the stream S1 is separated and subjected to distillation, the accumulation of by-products and impurities during solvent recycling can be stopped and a steady-state at very low concentration levels can be reached. Yet further, the example shows that the inventive part-stream distillation method even allows to significantly reduce the concentration of by-products and impurities accumulated in the acetonitrile solvent loop.

(76) It also shows that it is sufficient to work-up a small side stream to obtain the desired result, thus offering large savings in energy and investment.

Example 4a

According to the Invention (with Off-Line Part-Stream Distillation, Rectification with Reflux)

(77) To further illustrate the invention batch distillations were performed. For a first distillation used acetonitrile process solvent from the general set-up as described above was spiked with selected components to represent worst case impurities levels. An initial charge of 3912 grams of this solution of known composition (see table E) was filled into a lab distillation apparatus comprised of a column with 43 mm diameter and equipped with 4 meters of Montz A3-1000 packing.

(78) TABLE-US-00005 TABLE E Composition of the initial feed mixture (components with log K.sub.OW > 0) Concentration of component in Component initial charge/weight-ppm propionitrile 3533 1-nitropropane 77 2-nitropropane 44 2,6-dimethyl-4-heptanol 15639 4,6-dimethyl-2-heptanol 2523 2,6-dimethyl-4-heptanone 561 acetonitrile 74.7 weight-% water 20.2 weight-%

(79) This mixture was distilled under reflux at a pressure of 950 mbar using a reflux ratio of 1.

(80) During the distillation the amount and composition of the distillate were recorded, the composition being determined by calibrated gas chromatography for all organic components and by Karl-Fischer titration for water. At regular intervals the remaining sump was also sampled and the concentration of water and acetonitrile were determined. With this data, the percentage of each component that has been collected in the distillate as well as the concentration of acetonitrile in the sump during the distillation could be obtained. To illustrate the invention it is best to observe the amount of impurities collected overhead as a function of the concentration of acetonitrile in the sump. Table F shows the percentage of undesired components that have distilled overhead at a point when the concentration of acetonitrile in the sump was 35.2 weight-%. At this point a total of 3211 g had been distilled overhead, containing 92% of the acetonitrile initially present in the feed. This means that under these conditions 8% of the acetonitrile in the feed would be lost. Impurities that distill overhead will return to the system, which is undesired, so a low percentage of impurities in the distillate are desired.

(81) TABLE-US-00006 TABLE F Results of Example 4a Percentage of the amount initially present in the feed that has distilled overhead when the concentration of Component acetonitrile in the sump is 35.2 weight-% propionitrile 66% 1-nitropropane 0% 2-nitropropane 6% 2,6-dimethyl-4-heptanol 0% 4,6-dimethyl-2-heptanol 0% 2,6-dimethyl-4-heptanone 0%

(82) The example shows that it is possible, by using a distillation tower with reflux to very efficiently retain most of the undesired by-products in the sump and even two thirds of the relatively light boiling propionitrile can be retained in the sump. However, this can only be achieved by allowing for a loss of 8% of the initially fed acetonitrile.

Example 4b

According to the Invention (with Off-Line Part-Stream Distillation, Example 4a Continued)

(83) The distillation of the previous example 4a was continued until the concentration of acetonitrile in the sump was only 16.1 weight-%. At this point a total of 3411 g had been distilled overhead, containing 97% of the acetonitrile initially present in the feed. This means that under these conditions only 3% of the acetonitrile in the feed would be lost. Table G shows the percentage of undesired components that have distilled overhead at this point.

(84) TABLE-US-00007 TABLE G Results of Example 4b Percentage of the amount initially present in the feed that has distilled overhead when the concentration of Component acetonitrile in the sump was 16.1 weight-% propionitrile 74% 1-nitropropane 0% 2-nitropropane 6% 2,6-dimethyl-4-heptanol 0% 4,6-dimethyl-2-heptanol 0% 2,6-dimethyl-4-heptanone 0%

(85) The example according to the invention shows that it is possible, by using a distillation tower with reflux to very efficiently retain most of the undesired by-products in the sump and even one quarter of the relatively light boiling propionitrile can be retained in the sump, while only loosing 3% of the initially fed acetonitrile.

Example 4c

Example 4b Continued

(86) The distillation of the previous example 4b was continued until the concentration of acetonitrile in the sump was only 4 weight-%. At this point a total of 3554 g had been distilled overhead, containing 99% of the acetonitrile initially present in the feed. This means that under these conditions only 1% of the acetonitrile in the feed would have been lost. Table H shows the percentage of undesired components that have distilled overhead at this point.

(87) TABLE-US-00008 TABLE H Results of Example 4c Percentage of the amount initially present in the feed that has distilled overhead when the concentration of Component acetonitrile in the sump was 4 weight-% propionitrile 99% 1-nitropropane 87% 2-nitropropane 81% 2,6-dimethyl-4-heptanol 14% 4,6-dimethyl-2-heptanol 1% 2,6-dimethyl-4-heptanone 95%

(88) This example shows that if the concentration of acetonitrile in the sump is reduced too much, in an attempt to minimize the losses of acetonitrile, the efficiency of the separation of the by-products—while still being achieved to a certain extent—significantly decreases.

Example 5a

According to the Invention (with Off-Line Part-Stream Distillation, Rectification without Reflux)

(89) To further illustrate the invention a second batch distillation was performed in the same distillation apparatus as in examples 3a-c, but with a reflux ratio of 0. For this distillation a different batch of used acetonitrile process solvent from the pilot plant described above was spiked with selected components to represent worst case impurities levels.

(90) An initial charge of 3934 grams of this solution of known composition (see Table J) was filled to the still of the distillation apparatus and distilled at a pressure of 950 mbar.

(91) TABLE-US-00009 TABLE J Composition of the initial feed mixture (components with log K.sub.OW > 0) Concentration of component in Component initial charge/weight-ppm propionitrile 3526 1-nitropropane 94 2-nitropropane 35 2,6-dimethyl-4-heptanol 15478 4,6-dimethyl-2-heptanol 2502 2,6-dimethyl-4-heptanone 564 acetonitrile 74.8 weight-% water 19.9 weight-%

(92) As in Example 4a, during the distillation the amount and composition of the distillate were recorded. At regular intervals the sump was also sampled and the concentration of water and acetonitrile were determined. With this data, the percentage of each component that has been collected in the distillate as well as the concentration of acetonitrile in the sump during the distillation could be obtained. Table K shows the percentage of undesired components that have distilled overhead at a point when the concentration of acetonitrile in the sump was 37.1 weight-%. At this point a total of 3255.7 g had been distilled overhead, containing 90% of the acetonitrile initially present in the feed. This means that under these conditions 10% of the acetonitrile in the feed would be lost. Impurities that distill overhead will return to the system, which is undesired, so a low percentage of impurities in the distillate are desired.

(93) TABLE-US-00010 TABLE K Results of Example 5a Percentage of the amount initially present in the feed that has distilled overhead when the concentration of Component acetonitrile in the sump is 37.1 weight-% propionitrile 83% 1-nitropropane 53% 2-nitropropane 82% 2,6-dimethyl-4-heptanol 1% 4,6-dimethyl-2-heptanol 0% 2,6-dimethyl-4-heptanone 53%

(94) The example shows that it is also possible, by using a distillation tower without reflux to efficiently retain the major undesired by-product (2,6-dimethyl-4-heptanol) in the sump. However, this can only be achieved by allowing for a loss of 10% of the initially fed acetonitrile.

Example 5b

According to the Invention (with Off-Line Part-Stream Distillation, Example 5a Continued)

(95) The distillation of the previous example 5a was continued until the concentration of acetonitrile in the sump was only 18.2 weight-%. At this point a total of 3459.4 g had been distilled overhead, containing 96% of the acetonitrile initially present in the feed. This means that under these conditions only 4% of the acetonitrile in the feed would be lost. Table L shows the percentage of undesired components that have distilled overhead at this point.

(96) TABLE-US-00011 TABLE L Results of Example 5b Percentage of the amount initially present in the feed that has distilled overhead when the concentration of Component acetonitrile in the sump is 18.2 weight-% propionitrile 91% 1-nitropropane 68% 2-nitropropane 96% 2,6-dimethyl-4-heptanol 2% 4,6-dimethyl-2-heptanol 0% 2,6-dimethyl-4-heptanone 64%

(97) The example shows that it is possible, by using a distillation tower even at a reflux ratio of zero to very efficiently retain the dimethylheptanols in the sump. For all other components the degree of retention is lower, but still considerably less than 100% escape back into the system with the distillate, while only loosing 4% of the initially fed acetonitrile. Although this demonstrates, that it is even possible to work at a reflux ratio of zero, it is none the less preferred to work with a reflux ratio greater than zero.

Example 5c

Example 5b Continued

(98) The distillation of the previous example 5b was continued until the concentration of acetonitrile in the sump was only 3.9 weight-%. At this point a total of 3724.4 g had been distilled overhead, containing 98% of the acetonitrile initially present in the feed. This means that under these conditions only 2% of the acetonitrile in the feed would have been lost. Table M shows the percentage of undesired components that have distilled overhead at this point.

(99) TABLE-US-00012 TABLE M Results of Example 5c Percentage of the amount initially present in the feed that has distilled overhead when the concentration of Component acetonitrile in the sump was 3.9 weight-% propionitrile 99% 1-nitropropane 95% 2-nitropropane 100% 2,6-dimethyl-4-heptanol 64% 4,6-dimethyl-2-heptanol 43% 2,6-dimethyl-4-heptanone 98%

(100) This example shows that if the concentration of acetonitrile in the sump is reduced too much in an attempt to minimize the losses of acetonitrile, the efficiency of the separation of the by-products—while still being achieved to a certain extent—significantly decreases. Some components, like 2-nitropropane cannot be retained in the sump.

Reference Example 1

Preparation of the Epoxidation Catalyst (ZnTiMWW)

(101) 1.1 Preparation of Boron-Containing MWW

(102) 470.4 kg de-ionized water were provided in a vessel. Under stirring at 70 rpm (rounds per minute), 162.5 kg boric acid were suspended in the water. The suspension was stirred for another 3 h. Subsequently, 272.5 kg piperidine were added, and the mixture was stirred for another hour. To the resulting solution, 392.0 kg Ludox® AS-40 were added, and the resulting mixture was stirred at 70 rpm for another hour. The finally obtained mixture was transferred to a crystallization vessel and heated to 170° C. within 5 h under autogenous pressure and under stirring (50 rpm). The temperature of 170° C. was kept essentially constant for 120 h; during these 120 h, the mixture was stirred at 50 rpm. Subsequently, the mixture was cooled to a temperature of from 50-60° C. within 5 h. The aqueous suspension containing B-MWW had a pH of 11.3 as determined via measurement with a pH electrode. From said suspension, the B-MWW was separated by filtration. The filter cake was then washed with de-ionized water until the washing water had a conductivity of less than 700 microSiemens/cm. The thus obtained filter cake was subjected to spray-drying in a spray-tower with the following spray-drying conditions: drying gas, nozzle gas: technical nitrogen temperature drying gas: temperature spray tower (in): 288-291° C. temperature spray tower (out): 157-167° C. temperature filter (in): 150-160° C. temperature scrubber (in): 40-48° C. temperature scrubber (out): 34-36° C. pressure difference filter: 8.3-10.3 mbar nozzle: top-component nozzle supplier Gerig; size 0 nozzle gas temperature: room temperature nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 1,900 kg/h filter material: Nomex® needle-felt 20 m.sup.2 dosage via flexible tube pump: SP VF 15 (supplier: Verder) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening. The spray-dried material was then subjected to calcination at 650° C. for 2 h. The calcined material had a boron (B) content of 1.9 weight-%, a silicon (Si) content of 41 weight-%, and a total organic carbon (TOC) content of 0.18 weight-%.
1.2 Preparation of Deboronated MWW

(103) Based on the spray-dried material obtained according to section 1.1 above, 4 batches of deboronated zeolite MWW were prepared. In each of the first 3 batches, 35 kg of the spray-dried material obtained according to section 1.1 and 525 kg water were employed. In the fourth batch, 32 kg of the spray-dried material obtained according to section 1.1 and 480 kg water were employed. In total, 137 kg of the spray-dried material obtained according to section 1.1 and 2025 kg water were employed. For each batch, the respective amount of water was passed into a vessel equipped with a reflux condenser. Under stirring at 40 r.p.m., the given amount of the spray-dried material was suspended into the water. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. Under stirring at 70 r.p.m., the content of the vessel was heated to 100° C. within 10 h and kept at this temperature for 10 h. Then, the content of the vessel was cooled to a temperature of less than 50° C. The resulting deboronated zeolitic material of structure type MWW was separated from the suspension by filtration under a nitrogen pressure of 2.5 bar and washed four times with deionized water. After the filtration, the filter cake was dried in a nitrogen stream for 6 h. The deboronated zeolitic material obtained in 4 batches (625.1 kg nitrogen-dried filter cake in total) had a residual moisture content of 79%, as determined using an IR (infrared) scale at 160° C. From the nitrogen-dried filter cake having a residual moisture content of 79% obtained according to section a) above, an aqueous suspension was prepared with deionized water, the suspension having a solid content of 15 weight-%. This suspension was subjected to spray-drying in a spray-tower with the following spray-drying conditions: drying gas, nozzle gas: technical nitrogen temperature drying gas: temperature spray tower (in): 304° C. temperature spray tower (out): 147-150° C. temperature filter (in): 133-141° C. temperature scrubber (in): 106-114° C. temperature scrubber (out): 13-20° C. pressure difference filter: 1.3-2.3 mbar nozzle: top-component nozzle: supplier Niro, diameter 4 mm nozzle gas throughput: 23 kg/h nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 550 kg/h filter material: Nomex® needle-felt 10 m.sup.2 dosage via flexible tube pump: VF 10 (supplier: Verder)

(104) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening. The spray-dried MWW material obtained had a B content of 0.08 weight-%, an Si content of 42 weight-%, and a TOC of 0.23 weight-%.

(105) 1.3 Preparation of TiMWW

(106) Based on the deboronated MWW material as obtained according to section 1.2 above, a zeolitic material of structure type MWW containing titanium (Ti) was prepared, referred to in the following as TiMWW. The synthesis was performed in two experiments, described in the following as a) and b):

(107) a) First Experiment

(108) TABLE-US-00013 Starting materials: deionized water: 244.00 kg piperidine: 118.00 kg tetrabutylorthotitanate:  10.90 kg deboronated zeolitic material:  54.16 kg

(109) 54.16 kg of the deboronated zeolitic material of structure type MWW were transferred in to a first vessel A. In a second vessel B, 200.00 kg deionized water were transferred and stirred at 80 r.p.m. 118.00 kg piperidine were added under stirring, and during addition, the temperature of the mixture increased for about 15° C. Subsequently, 10.90 kg tetrabutylorthotitanate and 20.00 kg deionized water were added. Stirring was then continued for 60 min. The mixture of vessel B was then transferred into vessel A, and stirring in vessel A was started (70 r.p.m.). 24.00 kg deionized water were filled into vessel A and transferred to vessel B. The mixture in vessel B was then stirred for 60 min. at 70 r.p.m. At the beginning of the stirring, the pH of the mixture in vessel B was 12.6, as determined with a pH electrode. After said stirring at 70 r.p.m., the frequency was decreased to 50 r.p.m., and the mixture in vessel B was heated to a temperature of 170° C. within 5 h. At a constant stirring rate of 50 r.p.m., the temperature of the mixture in vessel B was kept at an essentially constant temperature of 170° C. for 120 h under autogenous pressure. During this crystallization of TiMWW, a pressure increase of up to 10.6 bar was observed. Subsequently, the obtained suspension containing TiMWW having a pH of 12.6 was cooled within 5 h. The cooled suspension was subjected to filtration, and the separated mother liquor was transferred to waste water discharge. The filter cake was washed four times with deionized water under a nitrogen pressure of 2.5 bar. After the last washing step, the filter cake was dried in a nitrogen stream for 6 h. From 246 kg of said filter cake, an aqueous suspension was prepared with deionized water, the suspension having a solid content of 15 weight-%. This suspension was subjected to spray-drying in a spray-tower with the following spray-drying conditions: drying gas, nozzle gas: technical nitrogen temperature drying gas: temperature spray tower (in): 304° C. temperature spray tower (out): 147-152° C. temperature filter (in): 133-144° C. temperature scrubber (in): 111-123° C. temperature scrubber (out): 12-18° C. pressure difference filter: 1.8-2.8 mbar nozzle: top-component nozzle: supplier Niro, diameter 4 mm nozzle gas throughput: 23 kg/h nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 550 kg/h filter material: Nomex® needle-felt 10 m.sup.2 dosage via flexible tube pump: VF 10 (supplier: Verder)

(110) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening. The spray-dried TiMWW material obtained from the first experiment had a Si content of 37 weight-%, a Ti content of 2.4 weight-%, and a TOC of 7.5 weight-%.

(111) b) Second Experiment

(112) The second experiment was carried out in the same way as the first experiment described in section a) above. The spray-dried TiMWW material obtained from the second experiment had a Si content of 36 weight-%, a Ti content of 2.4 weight-%, a TOC of 8.0 weight-%

(113) 1.4 Acid Treatment of TiMWW

(114) Each of the two spray-dried TiMWW materials as obtained in the first and the second experiment described in sections 1.3 a) and 1.3 b) above was subjected to acid treatment as described in the following in sections a) and b). In section c) hereinunder, it is described how a mixture of the materials obtained from a) and b) are spray-dried. In section d) hereinunder, it is described how the spray-dried material is calcined.

(115) a) Acid Treatment of the Spray-Dried Material Obtained According to Section 1.3.a)

(116) TABLE-US-00014 Starting materials: deionized water: 690.0 kg nitric acid: (53%): 900.0 kg spray-dried Ti-MWW 1.3. a):  53.0 kg

(117) 670.0 kg deionized water were filled in a vessel. 900 kg nitric acid were added, and 53.0 kg of the spray-dried TiMWW were added under stirring at 50 r.p.m. The resulting mixture was stirred for another 1 5 min. Subsequently, the stirring rate was increased to 70 r.p.m. Within 1 h, the mixture in the vessel was heated to 100° C. and kept at this temperature and under autogenous pressure for 20 h under stirring. The thus obtained mixture was then cooled within 2 h to a temperature of less than 50° C. The cooled mixture was subjected to filtration, and the filter cake was washed six times with deionized water under a nitrogen pressure of 2.5 bar. After the last washing step, the filter cake was dried in a nitrogen stream for 10 h. The washing water after the sixth washing step had a pH of about 2.7. 225.8 kg dried filter cake were obtained.

(118) b) Acid Treatment of the Spray-Dried Material Obtained According to Section 1.3.b)

(119) TABLE-US-00015 Starting materials: deionized water: 690.0 kg nitric acid: (53%): 900.0 kg spray-dried Ti-MWW 1.3. b):  55.0 kg

(120) The acid treatment of the spray-dried material obtained according to section 1.3.b) was carried in the same way as the acid treatment of the spray-dried material obtained according to section 1.3.a) as described in section 1.4 a). The washing water after the sixth washing step had a pH of about 2.7. 206.3 kg dried filter cake were obtained.

(121) c) Spray-Drying of the Mixture of the Materials Obtained from 1.4.a) and 1.4 b)

(122) From 462.1 kg of the mixture of the filter cakes obtained from 1.4.a) and 1.4 b), an aqueous suspension was prepared with deionized water, the suspension having a solid content of 15 weight-%. This suspension was subjected to spray-drying in a spray-tower with the following spray-drying conditions: drying gas, nozzle gas: technical nitrogen temperature drying gas: temperature spray tower (in): 304-305° C. temperature spray tower (out): 151° C. temperature filter (in): 141-143° C. temperature scrubber (in): 109-118° C. temperature scrubber (out): 14-15° C. pressure difference filter: 1.7-3.8 mbar nozzle: top-component nozzle: supplier Niro, diameter 4 mm nozzle gas throughput: 23 kg/h nozzle gas pressure: 2.5 bar operation mode: nitrogen straight apparatus used: spray tower with one nozzle configuration: spray tower-filter-scrubber gas flow: 550 kg/h filter material: Nomex® needle-felt 10 m.sup.2 dosage via flexible tube pump: VF 10 (supplier: Verder)

(123) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening. The spray-dried acid-treated TiMWW material had a Si content of 42 weight-%, a Ti content of 1.6 weight-%, and a TOC content of 1.7 weight-%.

(124) d) Calcination of the Spray-Dried Material Obtained According to 1.4. c)

(125) The spray-dried material was then subjected to calcination at 650° C. in a rotary furnace for 2 h. The calcined material had a Si content of 42.5 weight-%, a Ti content of 1.6 weight-% and a TOC content of 0.15 weight-%.

(126) 1.5 Impregnation of TiMWW with Zn

(127) The acid-treated, spray-dried and calcined material as obtained according to 1.4 d) was then subjected to an impregnation stage.

(128) TABLE-US-00016 Starting materials: deionized water: 2610.0 kg zinc acetate dihydrate:  15.93 kg calcined Ti-MWW 1.4.d)::  87.0 kg

(129) Impregnation was carried out in 3 batches a) to c) as follows: a) In a vessel equipped with a reflux condenser, a solution of 840 kg deionized water and 5.13 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 28 kg of the calcined Ti-MWW material obtained according to 1.4.d) were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. b) In a vessel equipped with a reflux condenser, a solution of 840 kg deionized water and 5.13 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 28 kg of the calcined Ti-MWW material obtained according to 1.4.d) were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. c) In a vessel equipped with a reflux condenser, a solution of 930 kg deionized water and 5.67 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 31 kg of the calcined Ti-MWW material obtained according to 1.4.d) were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m.

(130) In all batches a) to c), the mixture in the vessel was heated to 100° C. within 1 h and kept under reflux for 4 ha t a stirring rate of 70 r.p.m. Then, the mixture was cooled within 2 h to a temperature of less than 50° C. For each batch a) to c), the cooled suspension was subjected to filtration, and the mother liquor was transferred to waste water discharge.

(131) The filter cake was washed five times with deionized water under a nitrogen pressure of 2.5 bar. After the last washing step, the filter cake was dried in a nitrogen stream for 10 h. For batch a), 106.5 kg nitrogen-dried filter cake were finally obtained. For batch b), 107.0 kg nitrogen-dried filter cake were finally obtained. For batch c), 133.6 kg nitrogen-dried filter cake were finally obtained.

(132) The thus dried Zn-impregnated TiMWW material (ZnTiMWW), for each batch, had a Si content of 42 weight-%, a Ti content of 1.6 weight-%, a Zn content of 1.4 weight-% and a TOC of 1.4 weight-%.

(133) 1.6 Preparation of a Micropowder

(134) From 347.1 kg of the mixture of the filter cakes obtained according to 1.5 above, an aqueous suspension was prepared with deionized water, the suspension having a solid content of 15 weight-%. This suspension was subjected to spray-drying in a spray-tower with the following spray-drying conditions: apparatus used: spray tower with one nozzle operation mode: nitrogen straight configuration: dehumidifier-filter-scrubber dosage: flexible-tube pump VF 10 (supplier: Verder) nozzle with a diameter of 4 mm (supplier: Niro) filter material: Nomex® needle-felt 10 m.sup.2

(135) TABLE-US-00017 Runtime/h 0.5 1.5 2.5 3.5 4.5 Flow rate gas/(kg/h) 550 550 550 550 550 Temperature spray tower (in) 305 305 305 305 305 drying gas/° C. spray tower (out) 151 151 151 151 151 Filter (in) 140 137 130 127 126 Scrubber (in) 110 110 110 108 105 Scrubber (out) 14 14 15 15 15 Differential spray tower 3.1 3 3 2.8 2.9 pressure/mbar Filter 1.7 1.7 1.8 1.8 2.1 Scrubber 3.8 4.1 4.2 4.2 4.2 Pressure/mbar spray tower −103 −1.2 −0.9 −0.9 −1.1 Nozzle gas Flow rate kg/h 23 23 23 23 23 Temperature/° C. r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) Pressure/bar 2.5 2.5 2.5 2.5 2.5 Spray-dried Temperature/° C. r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) r.t.*.sup.) product *.sup.)room temperature

(136) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening. The spray-dried material thus obtained had a Zn content of 1.4 weight-%, a Ti content of 1.7 weight-%, a Si content of 40 weight-%, and a TOC content of 0.27 weight-%. The spray-dried product was then subjected to calcination for 2 h at 650° C. under air in a rotary furnace, yielding 76.3 kg of calcined spray-dried ZnTiMWW. The calcined spray-dried material thus obtained had a Zn content of 1.4 weight-%, a Ti content of 1.7 weight-%, a Si content of 42 weight-%, and a C content of 0.14 weight-%. The bulk density of the calcined spray-dried ZnTiMWW was 90 g/I (gram/liter).

(137) 1.7 Preparation of a Molding

(138) Starting from the calcined spray-dried ZnTiMWW material obtained according to section 1.6 above, a molding was prepared, dried, and calcined. Therefor, 22 batches were prepared, each starting from 3.4 kg of the calcined spray-dried ZnTiMWW material obtained in Example 1, 0.220 kg Walocel™ (Walocel MW 15000 GB, Wolff Cellulosics GmbH & Co. KG, Germany), 2.125 kg Ludox® AS-40 and 6.6 l deionized water, as follows:

(139) 3.4 kg ZnTiMWW and 0.220 kg Walocel were subjected to kneading in an edge mill for 5 min. Then, during further kneading, 2.125 kg Ludox were added continuously. After another 10 min, addition of 6 l of deionized water was started. After another 30 min, further 0.6 l of deionized water were added. After a total time of 50 min, the kneaded mass had become extrudable. Thereafter, the kneaded mass was subjected to extrusion under 65-80 bar wherein the extruder was cooled with water during the extrusion process. Per batch, the extrusion time was in the range of from 15 to 20 min. The power consumption per batch during extrusion was 2.4 A. A die head was employed allowing for producing cylindrical strands having a diameter of 1.7 mm. At the die head out outlet, the strands were not subjected to a cutting to length. The strands thus obtained were dried for 16 h at 120° C. in a drying chamber under air. In total (sum of the 22 batches), 97.1 kg white strands with a diameter of 1.7 mm were obtained. 65.5 kg of the dried strands were subjected to calcination in a rotary furnace at 550° C. for 1 h under air, yielding 62.2 kg calcined strands. Thereafter, the strands were sieved (mesh size 1.5 mm), and the yield, after sieving, was 57.7 kg. The thus obtained moldings exhibited a bulk density of 322 g/l (gram per liter) and had a Zn content of 1.2 weight-%, a Ti content of 1.4 weight-%, a Si content of 43 weight-%, and a C content of 0.13 weight-%. The sodium (Na) content was 0.07 weight-%.

(140) 1.8 Post-Treatment of the Molding

(141) Starting from the calcined strands obtained according to 1.7 above, a post-treatment stage was performed as follows:

(142) 590 kg deionized water were filled in a vessel. Then, 29.5 kg of the calcined moldings obtained according to section 1.7 above were added. The vessel was closed (pressure-tight), and the obtained mixture was heated to a temperature of 145° C. within 1.5 h and kept at this temperature under autogenous pressure (about 3 bar) for 8 h. Then, the mixture was cooled for 2 h. The water-treated strands were subjected to filtration and washed with deionized water. The obtained strands were heated in a drying chamber under air within 1 h to a temperature of 120° C. and kept at this temperature for 16 h. Subsequently, the dried material was heated under air to a temperature of 450° C. within 5.5 h and kept at this temperature for 2 h. Thereafter, the strands were sieved (mesh size 1.5 mm), and the yield, after sieving, was 27.5 kg. The thus obtained water-treated moldings exhibited a bulk density of 340 g/I (gram per liter) and had a Zn content of 1.3 weight-%, a Ti content of 1.4 weight-%, a Si content of 43 weight-%, and a C content of 0.10 weight-%.

Reference Example 2

Determination of Dv10, Dv50, and Dv90 Values

(143) 1. Sample Preparation: 1.0 g of the micropowder is suspended in 100 g deionized water and stirred for 1 min. 2. Apparatus and respective parameters used: Mastersizer S long bed version 2.15, ser. No. 33544-325; supplier: Malvern Instruments GmbH, Herrenberg, Germany focal width: 300RF mm beam length: 10.00 mm module: MS17 shadowing: 16.9% dispersion model: 3$$D analysis model: polydisperse correction: none

Reference Example 3

Determination of the Silanol Concentration

(144) For the determination of the silanol concentration, the .sup.29Si MAS NMR experiments were carried out at room temperature on a VARIAN Infinityplus-400 spectrometer using 5.0 mm ZrO.sub.2 rotors. The .sup.29Si MAS NMR spectra were collected at 79.5 MHz using a 1.9 microseconds pi/4 pulse with 10 s recycle delay and 4000 scans. All .sup.29Si spectra were recorded on samples spun at 6 kHz, and chemical shifts were referenced to 4,4-dimethyl-4-silapentane sulfonate sodium (DSS). For the determination of the silanol group concentration, a given .sup.29Si MAS NMR spectrum is deconvolved by the proper Gaussian-Lorentzian line shapes. The concentration of the silanol groups with respect to the total number of Si atoms is obtained by integrating the deconvolved .sup.29Si MAS NMR spectra.

Reference Example 4

Determination of the Crush Strength of the Moldings

(145) The crush strength as referred to in the context of the present invention is to be understood as determined via a crush strength test machine Z2.5/TS1S, supplier Zwick GmbH & Co., D-89079 Ulm, Germany. As to fundamentals of this machine and its operation, reference is made to the respective instructions handbook “Register 1: Betriebsanleitung/Sicherheitshandbuch für die Material-Prüfmaschine Z2.5/TS1S”, version 1.5, December 2001 by Zwick GmbH & Co. Technische Dokumentation, August-Nagel-Strasse 11, D-89079 Ulm, Germany. With said machine, a given strand as described in Reference Example 1 is subjected to an increasing force via a plunger having a diameter of 3 mm until the strand is crushed. The force at which the strand crushes is referred to as the crushing strength of the strand. The machine is equipped with a fixed horizontal table on which the strand is positioned. A plunger which is freely movable in vertical direction actuates the strand against the fixed table. The apparatus was operated with a preliminary force of 0.5 N, a shear rate under preliminary force of 10 mm/min and a subsequent testing rate of 1.6 mm/min. The vertically movable plunger was connected to a load cell for force pick-up and, during the measurement, moved toward the fixed turntable on which the molding (strand) to be investigated is positioned, thus actuating the strand against the table. The plunger was applied to the stands perpendicularly to their longitudinal axis. Controlling the experiment was carried out by means of a computer which registered and evaluated the results of the measurements. The values obtained are the mean value of the measurements for 10 strands in each case.

Reference Example 5

29Si Solid-State NMR Spectra Regarding Q3 and Q4 Structures

(146) All .sup.29Si solid-state NMR experiments were performed using a Bruker Avance spectrometer with 300 MHz .sup.1H Larmor frequency (Bruker Biospin, Germany). Samples were packed in 7 mm ZrO.sub.2 rotors, and measured under 5 kHz Magic Angle Spinning at room temperature. .sup.29Si direct polarization spectra were obtained using (pi/2)-pulse excitation with 5 microsecond pulse width, a .sup.29Si carrier frequency corresponding to −65 ppm in the spectrum, and a scan recycle delay of 120 s. Signal was acquired for 25 ms under 45 kHz high-power proton decoupling, and accumulated over 10 to 17 hours. Spectra were processed using Bruker Topspin with 30 Hz exponential line broadening, manual phasing, and manual baseline correction over the full spectrum width. Spectra were referenced with the polymer Q8M8 as an external secondary standard, setting the resonance of the trimethylsilyl M group to 12.5 ppm. The spectra were then fitted with a set of Gaussian line shapes, according to the number of discernable resonances. Relating to the presently assessed spectra, 6 lines in total were used, accounting for the five distinct peak maxima (at approximately −118, −115, −113, −110 and −104 ppm) plus a clearly visible shoulder at −98 ppm. Fitting was performed using DMFit (Massiot et al., Magnetic Resonance in Chemistry, 40 (2002) pp 70-76). Peaks were manually set at the visible peak maxima or shoulder. Both peak position and line width were then left unrestrained, i.e., fit peaks were not fixed at a certain position. The fitting outcome was numerically stable, i.e., distortions in the initial fit setup as described above did lead to similar results. The fitted peak areas were further used normalized as done by DMFit. For the quantification of spectrum changes, a ratio was calculated that reflects changes in the peak areas “left hand” and “right hand”, as follows. The six peaks as described were labeled with 1, 2, 3, 4, 5, and 6, and the ratio Q was calculated with the formula 100*{[a.sub.1+a.sub.2]/[a.sub.4+a.sub.5+a.sub.6]}/a.sub.3. In this formula, a.sub.i, i=1 . . . 6 represents the area of the fitted peak to which this number was attributed.

Reference Example 6

Water Adsorption/Desorption

(147) The water adsorption/desorption isotherms measurements were performed on a VTI SA instrument from TA Instruments following a step-isotherm program. The experiment consisted of a run or a series of runs performed on a sample material that has been placed on the microbalance pan inside of the instrument. Before the measurement were started, the residual moisture of the sample was removed by heating the sample to 100° C. (heating ramp of 5° C./min) and holding it for 6 h under a N.sub.2 flow. After the drying program, the temperature in the cell was decreased to 25° C. and kept isothermal during the measurements. The microbalance was calibrated, and the weight of the dried sample was balanced (maximum mass deviation 0.01 wt. %). Water uptake by the sample was measured as the increase in weight over that of the dry sample. First, an adsorption curve was measured by increasing the relative humidity (RH) (expressed as weight-% water in the atmosphere inside of the cell) to which the samples was exposed and measuring the water uptake by the sample at equilibrium. The RH was increased with a step of 10 wt. % from 5 to 85% and at each step the system controlled the RH and monitored the sample weight until reaching the equilibrium conditions and recording the weight uptake. The total adsorbed water amount by the sample was taken after the sample was exposed to the 85 weight-% RH. During the desorption measurement the RH was decreased from 85 wt. % to 5 wt. % with a step of 10% and the change in the weight of the sample (water uptake) was monitored and recorded.

Reference Example 7

FT-IR Measurements

(148) The FT-IR (Fourier-Transformed-Infrared) measurements were performed on a Nicolet 6700 spectrometer. The molding was powdered and then pressed into a self-supporting pellet without the use of any additives. The pellet was introduced into a high vacuum (HV) cell placed into the FT-IR instrument. Prior to the measurement the sample was pretreated in high vacuum (10.sup.−5 mbar) for 3 h at 300° C. The spectra were collected after cooling the cell to 50° C. The spectra were recorded in the range of 4000 to 800 cm.sup.−1 at a resolution of 2 cm.sup.−1. The obtained spectra are represented in a plot having on the x axis the wavenumber (cm.sup.−1) and on the y axis the absorbance (arbitrary units, a.u.). For the quantitative determination of the peak heights and the ratio between these peaks a baseline correction was carried out. Changes in the 3000 to 3900 cm.sup.−1 region were analyzed and for comparing multiple samples, a reference the band at 1880±5 cm.sup.−1 was taken.

Reference Example 8

Definition and Determination of the Octanol-Water Partition Coefficient KOW

(149) The octanol-water partition coefficient K.sub.OW of a given compound is defined as the ratio of said compound's chemical concentration in the octanol phase relative to said compound's chemical concentration in the aqueous phase in a two-phase system of 1-octanol and water at a temperature of 25° C.

(150) The octanol-water partition coefficient K.sub.OW of a given compound is determined using the shake-flask method which consists of dissolving the compound in a volume of high-purity 1-octanol and deionized water (pre-mixed and calibrated for at least 24 h) and measuring the concentration of the compound in each the 1-octanol phase and the water phase by a sufficiently exact method, preferably via UV/VIS spectroscopy. This method is described in the OECD Guideline for the testing of chemicals, number 107, adopted on Jul. 27, 1995.

DESCRIPTION OF THE FIGURES

(151) The FIGURE shows a block diagram of a preferred process of the present invention. In the FIGURE, the letters and numbers have the following meanings: A epoxidation unit B distillation unit C epoxidation unit D distillation unit E distillation unit F distillation unit G part stream distillation unit H mixer-settler unit I acetonitrile recovery unit J acetonitrile recycle unit (1)-(23) streams according to a specifically preferred process as described in the examples S0, S01, S02, S1, S2, S3, S4, S4b, S5, L1, L2, TL1, TL2, TL2, BL2 streams according to a preferred process as described in the general description and the examples

CITED PRIOR ART

(152) WO 2011/006990 A1 US 2007043226 A1 WO 2007/000396 A1 EP 0 427 062 A2 U.S. Pat. No. 5,194,675 US 2004068128 A1 K. J. Lissant, Making and Breaking Emulsions, Res. Lab., Petrolite Corp., St. Louis, Mo., USA, in: K. J. Lissant (ed.), Emulsion Technology (1974), chapter 2, pp 111-124, Dekker, New York S. E. Taylor, Chem. Ind. (1992), pp 770-773