A PROCESS FOR PURIFYING PROPYLENE OXIDE

Abstract

Disclosed is a process for purifying propylene oxide. A stream S0 containing propylene oxide, acetonitrile, water, and an organic compound containing one or more of acetone and propionaldehyde is provided. Propylene oxide is separated from S0 by subjecting S0 to distillation in a first distillation unit, obtaining a gaseous top stream S1c enriched in propylene oxide, a liquid bottom stream S1a enriched in acetonitrile and water, and a side stream S1b containing propylene oxide and enriched in the carbonyl compound; reacting the carbonyl compound in S1b with an organic compound containing an amino group to obtain a reaction product; separating propylene oxide from the reaction product in a second distillation unit, obtaining a gaseous top stream S3a enriched in propylene oxide and a liquid bottoms stream S3b enriched in the reaction product; and introducing stream S3a into the first distillation unit.

Claims

1. A process for purifying propylene oxide, the process comprising (i) providing a stream S0 comprising propylene oxide, acetonitrile, water, and an organic compound comprising a carbonyl group C(O), wherein said organic compound comprising a carbonyl group C(O) comprises one or more of acetone and propionaldehyde; and (ii) separating propylene oxide from the stream S0 by distillation by (ii.1) subjecting the stream S0 to distillation conditions in a first distillation unit, obtaining a gaseous top stream S1c which is enriched in propylene oxide compared to the stream S0, a liquid bottoms stream S1a which is enriched in acetonitrile and water compared to the stream S0, and a side stream S1b comprising propylene oxide which is enriched in the carbonyl compound compared to the stream S0; (ii.2) reacting the carbonyl compound comprised in the side stream S1b with an organic compound comprising an amino group NH.sub.2 obtaining a reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group; (ii.3) separating propylene oxide from the reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group in a second distillation unit, obtaining a gaseous top stream S3a which is enriched in propylene oxide and a liquid bottoms stream S3b which is enriched in the reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group; and (ii.4) introducing the top stream S3a which is enriched in propylene oxide propylene oxide into the first distillation unit.

2. A process for purifying propylene oxide, the process comprising (i) providing a stream S0 comprising propylene oxide, acetonitrile, water, and an organic compound comprising a carbonyl group C(O), wherein said organic compound comprising a carbonyl group C(O) comprises one or more of acetone and propionaldehyde; and (ii) separating propylene oxide from the stream S0 by distillation by (ii.1) subjecting the stream S0 to distillation conditions in a first distillation unit, obtaining a gaseous top stream S1c which is enriched in propylene oxide compared to the stream S0, a liquid bottoms stream S1a which is enriched in acetonitrile and water compared to the stream S0, and a side stream S1b comprising propylene oxide which is enriched in the carbonyl compound compared to the stream S0; (ii.2) admixing the side stream S1b with an organic compound comprising an amino group NH.sub.2 and reacting the organic compound comprising a carbonyl group with the organic compound comprising an amino group, obtaining a stream S2 comprising propylene oxide and a reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group; (ii.3) subjecting the stream S2 to distillation conditions in a second distillation unit, obtaining a gaseous top stream S3a which is enriched in propylene oxide compared to the stream S2, and a liquid bottoms stream S3b which is enriched in the reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group compared to the stream S2; and (ii.4) introducing the stream S3a into the first distillation unit.

3. A process for purifying propylene oxide, the process comprising (i) providing a stream S0 comprising propylene oxide, acetonitrile, water, and an organic compound comprising a carbonyl group C(O), wherein said organic compound comprising a carbonyl group C(O) comprises one or more of acetone and propionaldehyde; and (ii) separating propylene oxide from the stream S0 by distillation by (ii.1) subjecting the stream S0 to distillation conditions in a first distillation unit, obtaining a gaseous top stream S1c which is enriched in propylene oxide compared to the stream S0, a liquid bottoms stream S1a which is enriched in acetonitrile and water compared to the stream S0, and a side stream S1b comprising propylene oxide which is enriched in the carbonyl compound compared to the stream S0; (ii.2) subjecting the side stream S1b to distillation conditions in a second distillation unit and adding an organic compound comprising an amino group NH.sub.2 to the second distillation unit, preferably at the top of the second distillation unit, and reacting the organic compound comprising a carbonyl group with the organic compound comprising an amino group, obtaining a reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group, and obtaining a gaseous top stream S3a which is enriched in propylene oxide compared to the stream S1b, and a liquid bottoms stream S3b which is enriched in the reaction product of the organic compound comprising a carbonyl group and the organic compound comprising an amino group compared to the stream S1b; and (ii.3) introducing the stream S3a into the first distillation unit.

4. The process of claim 1, wherein the organic compound comprising a carbonyl group C(O) comprised in the stream S0 further comprises one or more of acetaldehyde, formaldehyde, butyraldehyde, isobutyraldehyde, 2-butanon, 1-pentanal, 2-pentanon, 3-pentanon, and 2-methylpentanone.

5. The process of claim 1, wherein at least 95 weight % of the stream S0 consist of propylene oxide, acetonitrile, water, and the organic compound comprising a carbonyl group.

6. The process of claim 1, wherein the stream S0 is or obtained by a process comprising (a) providing a liquid feed stream comprising propene, hydrogen peroxide, water, and acetonitrile; (b) passing the liquid feed stream provided in (a) into an epoxidation zone comprising an epoxidation catalyst comprising a titanium zeolite, and subjecting the liquid feed stream to epoxidation reaction conditions in the epoxidation zone, obtaining a reaction mixture comprising propene, propylene oxide, water, acetonitrile, and the organic compound comprising a carbonyl group; (c) removing an effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, water, acetonitrile, propene, and the organic compound comprising a carbonyl group; (d) separating propene from the effluent stream by distillation by subjecting the effluent stream to distillation conditions in a distillation unit, obtaining a gaseous stream which is enriched in propene compared to the effluent stream subjected to distillation conditions, and a liquid bottoms stream which is enriched in propylene oxide, water, acetonitrile and the organic compound comprising a carbonyl group compared to the effluent stream subjected to distillation conditions; wherein said liquid bottoms stream obtained in (d) is the stream S0.

7. The process of claim 1, wherein said providing (i) comprises (a) providing a liquid feed stream comprising propene, hydrogen peroxide, water, and acetonitrile; (b) passing the liquid feed stream provided in (a) into an epoxidation zone comprising an epoxidation catalyst comprising a titanium zeolite, and subjecting the liquid feed stream to epoxidation reaction conditions in the epoxidation zone, obtaining a reaction mixture comprising propene, propylene oxide, water, acetonitrile, and the organic compound comprising a carbonyl group; (c) removing an effluent stream from the epoxidation zone, the effluent stream comprising propylene oxide, water, acetonitrile, propene, and the organic compound comprising a carbonyl group; (d) separating propene from the effluent stream by distillation by subjecting the effluent stream to distillation conditions in a distillation unit, obtaining a gaseous stream which is enriched in propene compared to the effluent stream subjected to distillation conditions, and a liquid bottoms stream which is enriched in propylene oxide, water, acetonitrile and the organic compound comprising a carbonyl group compared to the effluent stream subjected to distillation conditions; wherein said liquid bottoms stream obtained in (d) is the stream S0.

8. The process of claim 1, wherein the first distillation unit employed in (ii.1) is at least one distillation tower.

9. The process of claim 1, wherein a rectifying section of the first distillation unit employed in (ii.1) consists of from 40 to 60% of theoretical trays and a stripping section of the distillation unit consists of from 60 to 40% of theoretical trays.

10. The process of claim 1, wherein the first distillation unit employed in (ii.1) is operated at a top pressure of from 0.1 to 2.0 bar.

11. The process of claim 1, wherein the first distillation unit employed in (ii.1) is operated at a top temperature in the range of from 50 to 70 C.

12. The process of claim 1, wherein the first distillation unit employed in (ii.1) is operated at an internal reflux ratio in the range of from 1 to 10.

13. The process of claim 1, wherein the side stream S1b obtained in (ii.1) is removed from a rectifying section of the first distillation unit.

14. The process of claim 1, wherein the side stream S1b obtained in (ii.1) is removed from a rectifying section of the first distillation unit at a position which is at least 1 theoretical tray above a stripping section of the first distillation unit.

15. The process of claim 1, wherein the side stream S1b obtained in (ii.1) is removed from a rectifying section of the first distillation unit at a position which is from 1 to 15 theoretical tray above a stripping section of the first distillation unit.

16. The process of claim 1, wherein the organic compound comprising an amino group NH.sub.2 comprises one or more of RNH.sub.2, wherein R is a substituted or unsubstituted, branched or unbranched C.sub.1-C.sub.5-alkyl; R1-NH.sub.2, wherein R1 is a C6-C10-aryl group with at least one further substituent R2 selected from the group consisting of hydrogen, CH.sub.3, and NO.sub.2 positioned at the aryl group; NH.sub.2R3-NH.sub.2, wherein R3 is selected from the group consisting of a C2-C3-alkylene group and a phenyl group; a NC1-C6-aminale; a carbonic acid amide; an amide of mono-methylester of methylphosphonic acid; an amide of a carbonic acid; an amino acid; anthranilic acid; a nitrile of an alpha-amino carbonic acid; cyanamide; hydroxylamine; O-methylhydroxylamine; hydroxylamine-O-sufonic acid; hydrazine; hydrazine monohydrate; a monoC1-C4-alkyl hydrazine; an aryl hydrazine; a dialkyl hydrazine; a hydrazide; and a hydrazide of a thiocarbonic acid of formula R4(SO).sub.2NHNH.sub.2 wherein R4 is selected from the group consisting of C6-C10-aryl and C1-C6-alkyl.

17. The process of claim 1, wherein said reacting (ii.2) is carried out in one or more reactors.

18. The process of claim 1, wherein the second distillation unit employed in (ii.3) is at least one distillation tower.

19. The process of claim 1, wherein the gaseous top stream S3a obtained in (ii.3) is introduced into the first distillation unit in (ii.4) in a rectifying section of the first distillation unit at a position which is at least 1 theoretical tray above a stripping section of the first distillation unit.

20. The process of claim 1, wherein the gaseous top stream S3a obtained in (ii.3) is introduced into the first distillation unit in (ii.4) in a rectifying section of the first distillation unit at a position which is 0 to 3 theoretical trays above the theoretical tray where the side stream S1b obtained in (ii.1) is removed from the rectifying section of the first distillation.

21. The process of claim 1, which is a continuous process.

Description

EXAMPLES

Reference Example 1: Preparation of a Catalyst Comprising a Titanium Zeolite Having Framework Type MWW

1.1 Preparation of Boron Containing Zeolite of Structure MWW (BMWW)

[0165] A 2 m.sup.3 stirred tank reactor was first loaded with 470.4 kg of deionized water. After starting the stirrer at 70 rpm, boric acid (162.5 kg) was added and the suspension was stirred for 3 h. Subsequently, piperidine (272.5 kg) was added at once causing the temperature to rise from 28 C. to 46 C. To this solution colloidal silica (Ludox AS040, 392.0 kg) was added. The reactor was then slowly heated to 170 C. within 5 hours and then kept at this temperature under stirring for 120 hours. The maximum pressure during the reaction was 9.3 bar. Afterwards the reactor was cooled down to 50 C. The gel obtained had a pH of 11.3 and a viscosity of 15 mPa.Math.s at 20 C. The gel was then filtered and the filter cake washed with deionized water until the conductivity of the washings was below 500 microSiemens/cm. The filter cake was then suspended in deionized water and the suspension was spray-dried at 235 C. using nitrogen as the carrier gas. The white powder obtained (174.3 kg) contained 3.5 weight-% water. This white powder was then calcined at 650 C. in a rotary kiln to give 138.2 kg of boron containing zeolite of structure type MWW (BMWW) as a white powder.

1.2 Deboronation of BMWW with Water

[0166] A 5 m.sup.3 stirred tank reactor was loaded with 125 kg of the BMWW obtained according to the previous step 1.1 and 3750 kg of deionized water. The reactor was then slowly heated to 100 C. within 1 hour under stirring at 70 rpm, and then kept at this temperature for 20 hours and finally cooled to a temperature below 50 C. before it was filtered. The filter cake was then washed with deionized water until the washings had conductivity below 15 microSiemens/cm. The filter cake was then dried for 6 hours under a nitrogen stream. The filter cake was then removed and suspended in 850 kg of deionized water. This suspension was then spray-dried at 235 C. using nitrogen as the carrier gas. The spray dried material weighed 118.5 kg and contained 42.5 weight-% Si, 0.06 weight-% B and 0.23 weight-% C (total organic carbon, TOC).

1.3 Preparation of Titanium Containing Zeolite of Structure Type MWW (TiMWW)

[0167] A 2 m.sup.3 stirred tank reactor was first loaded with 111.2 kg of the spray-dried material from the previous step 1.2. In a separate 2 m.sup.3 stirred tank reactor were placed 400 kg of deionized water. After starting the stirrer at 80 rpm, piperidine (244.0 kg) was added. After the addition of piperidine was finished the mixture was stirred for 5 minutes before tetrabutyl orthotitanate (22.4 kg) was added. The pipe through which the titanate was added was then flushed with 40 kg of deionized water. The mixture was then stirred for 1 hour before being added to the first stirred tank reactor containing the spray-dried powder under stirring (50 rpm). The reactor was then heated to 170 C. and kept at this temperature for 120 h before being cooled to 50 C. The maximum pressure during the reaction was 10.6 bar. The cooled suspension was then filtered and the filter cake was washed with deionized water until the washings had conductivity below 1300 microSiemens/cm and an approximately neutral pH value. The filter cake was then dried under a nitrogen stream for 6 hours. The filter cake containing about 80 weight-% of water was used directly for the next step. The filter cake from the previous step and 1000 kg of deionized water were filled in a 2 m.sup.3 stirred tank reactor. Then 1900 kg of nitric acid (53 weight-% in water) were added under stirring at 70 rpm. The reactor was then heated to 100 C. and kept at this temperature for 20 hours before being cooled to 50 C. The suspension obtained was then filtered and the filter cake was washed with deionized water until the conductivity was below 10 microSiemens/cm and the washings were approximately neutral. Subsequently the filter cake was dried under a stream of nitrogen for 6 hours. This filter cake was then suspended in water and spray-dried at 235 C. using nitrogen as the carrier gas. 96 kg of a spray-dried powder were obtained. This material was then calcined in a rotary kiln at 650 C. 84 kg of titanium zeolite of structure type MWW (TiMWW) were obtained as a powder containing 43 weight-% Si, 2.0 weight-% Ti and 0.2 weight-% C (TOC). The pore volume determined by Hg-porosimetry according to DIN 66133 was 7.3 ml/g and the BET surface area determined according to DIN 66131 was 467 m.sup.2/g.

1.4 Preparation of a Zinc Containing TiMWW (ZnTiMWW) by Impregnation

[0168] a) In a vessel equipped with a reflux condenser, a solution of 981 kg deionized water and 6.0 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 32.7 kg of the calcined Ti-MWW material obtained according to 1.3 above were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m. [0169] b) In a vessel equipped with a reflux condenser, a solution of 585 kg deionized water and 3.58 kg zinc acetate dihydrate was prepared within 30 min. Under stirring (40 r.p.m.), 19.5 kg of the calcined Ti-MWW material obtained according to 1.3 above were suspended. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 r.p.m.

[0170] In all batches a) and b), the mixture in the vessel was heated to 100 C. within 1 h and kept under reflux for 2 h a 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) and b), the cooled suspension was subjected to filtration, and the mother liquor was transferred to waste water discharge. 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. In total 297 kg of nitrogen dried filter cake were obtained. The thus dried Zn-impregnated TiMWW material (ZnTiMWW), had a Si content of 42 weight-%, a Ti content of 1.8 weight-%, a Zn content of 1.3 weight-.%. From 297 kg of the mixture of the filter cake obtained 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: [0171] apparatus used: spray tower with one nozzle [0172] operation mode: nitrogen straight [0173] configuration: dehumidifier-filter-scrubber [0174] dosage: [0175] flexible-tube pump VF 10 (supplier: Verder) [0176] nozzle with a diameter of 4 mm (supplier: Niro) [0177] filter material: Nomex needle-felt 10 m.sup.2

TABLE-US-00001 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/ spray tower (out) 151 151 151 151 151 C. 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/ Filter 1.7 1.7 1.8 1.8 2.1 mbar Scrubber 3.8 4.1 4.2 4.2 4.2 Pressure/ spray tower 103 1.2 0.9 0.9 1.1 mbar 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

[0178] 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 41 weight-%, and a TOC content of <0.5 weight-%. The spray-dried product was then subjected to calcination for 2 h at 650 C. under air in a rotary furnace, yielding 43.8 kg of calcined spray-dried ZnTiMWW. The calcined spray-dried material thus obtained had a Zn content of 1.3 weight-%, a Ti content of 1.8 weight-%, a Si content of 42.5 weight-%, and a C content of <0.1 weight-%. The bulk density of the calcined spray-dried ZnTiMWW was 90 g/I (gram/liter). The mesopores of the micropowder had an average pore diameter (4V/A) of 20.2 nm as determined by Hg porosimetry according to DIN 66133. The macropores of the micropowder had an average pore diameter (4V/A) of 67.6 nm as determined by Hg porosimetry according to DIN 66133. The micropores of the ZnTiMWW contained in the micropowder had an average pore diameter of 1.06 nm as determined by nitrogen adsorption according to DIN 66134 (Horward-Kawazoe method). The Dv10 value of the particles of the micropowder was 4.10 micrometers. The Dv50 value of the particles of the micropowder was 8.19 micrometers. The Dv90 value of the particles of the micropowder was 14.05 micrometers. The degree of crystallization determined via XRD was (77+/10) %, the average crystallite size 35.0 nm+/10%. It was found that the crystalline phase exhibits a pure MWW structure. No other crystalline titania phases such as anatase, rutile or brookite, or crystalline zinc silicate (Zn.sub.2SiO.sub.4) such as willemite could be detected.

1.5 Preparation of Moldings Containing ZnTiMWW and Silica Binder

[0179] Starting from the calcined spray-dried ZnTiMWW material obtained according to 1.4 above, a molding was prepared, dried, and calcined. Therefor, 12 batches were prepared, each starting from 3.5 kg of the calcined spray-dried ZnTiMWW material obtained above, 0.226 kg Walocel (Walocel MW 15000 GB, Wolff Cellulosics GmbH & Co. KG, Germany), 2.188 kg Ludox AS-40 and 6.6 l deionized water, as follows:

[0180] 3.5 kg ZnTiMWW and 0.226 kg Walocel were subjected to kneading in an edge mill for 5 min. Then, during further kneading, 2.188 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 12 batches), 56 kg white strands with a diameter of 1.7 mm were obtained. 56 kg of the dried strands were subjected to calcination in a rotary furnace at 550 C. for 1 h under air, yielding 52 kg calcined strands. Thereafter, the strands were sieved (mesh size 1.5 mm), and the yield, after sieving, was 50.0 kg. The thus obtained moldings exhibited a bulk density of 322 g/l (gram per liter) and had a Zn content of 1.1 weight-%, a Ti content of 1.4 weight-%, a Si content of 43 weight-%, and a C content of <0.1 weight-%. The mesopores of the micropowder had an average pore diameter (4V/A) of 20.9 nm as determined by Hg porosimetry according to DIN 66133. The macropores of the micropowder had an average pore diameter (4V/A) of 50.0 nm as determined by Hg porosimetry according to DIN 66133. The degree of crystallization determined via XRD was (70+/10) %, the average crystallite size 32.5 nm+/10%. The crush strength of the moldings as determined according to the method using a crush strength test machine Z2.5/TS01S was 4.4 N (standard deviation: 0.5 N). The minimum value found when testing the 10 samples was 3.5 N, the maximum value 5.1 N. In the .sup.29Si MAS NMR, after the curve had been deconvolved by the proper Gaussian-Lorentzian line shapes, six peaks were clearly observed. The Q.sup.3/Q.sup.4 ratio was found to be 2.2. The total amount of adsorbed water as determined according to Reference Example 6 of the molding was 6.9 weight-%. The Langmuir surface are determined via nitrogen adsorption at 77 K according to DIN 66133 was 518 m.sup.2/g, the mulitpoint BET specific surface area determined via nitrogen adsorption at 77 K according to DIN 66133 was 373 m.sup.2/g. The total intrusion volume determined according to Hg porosimetry according to DIN 66133 was 1.3 ml/g (milliliter/gram), the respective total pore area 100.2 m.sup.2/g. It was found that the crystalline phase of the moldings exhibits a pure MWW structure. No other crystalline titania phases such as anatase, rutile or brookite, or crystalline zinc silicate (Zn.sub.2SiO.sub.4) such as willemite could be detected via XRD.

[0181] Starting from the calcined strands, a post-treatment stage was performed as follows: 1,000 kg deioinized water were filled in a vessel. Then, 50 kg of the calcined moldings 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 49.1 kg. The thus obtained water-treated moldings exhibited a bulk density of 332 g/I (gram per liter) and had a Zn content of 1.1 weight-%, a Ti content of 1.4 weight-%, a Si content of 42 weight-%, and a C content of <0.10 weight-%. The mesopores of the micropowder had an average pore diameter (4V/A) of 22.1 nm as determined by Hg porosimetry according to DIN 66133. The macropores of the micropowder had an average pore diameter (4V/A) of 52.0 nm as determined by Hg porosimetry according to DIN 66133. The degree of crystallization determined via XRD was (69+/10) %, the average crystallite size 30.5 nm+/10%. The crush strength of the moldings as determined according to the method using a crush strength test machine Z2.5/TS01S was 13.7 N (standard deviation: 2.5 N). The minimum value found when testing the 10 samples was 10.2 N, the maximum value 17.6 N. In the .sup.29Si MAS NMR, after the curve had been deconvolved by the proper Gaussian-Lorentzian line shapes, six peaks were clearly observed. The Q.sup.3/Q.sup.4 ratio was found to be 1.39. The total amount of adsorbed water of the molding was 6.9 weight-%. The intensity ratio of the infrared band in the region of (3746+/20) cm.sup.1 attributed to the free silanol groups, relative to the infrared band in the region of 3688+/20 cm.sup.1 attributed to vicinal silanol groups was smaller than 1.4. The Langmuir surface are determined via nitrogen adsorption at 77 K according to DIN 66133 was 421 m.sup.2/g, the multipoint BET specific surface area determined via nitrogen adsorption at 77 K according t DIN 66133 was 303 m.sup.2/g. The total intrusion volume determined according to Hg porosimetry according to DIN 66133 was 1.3 ml/g (milliliter/gram), the respective total pore area 98.7 m.sup.2/g. It was found that the crystalline phase of the moldings exhibits a pure MWW structure. No other crystalline titania phases such as anatase, rutile or brookite, or crystalline zinc silicate (Zn.sub.2SiO.sub.4) such as willemite could be detected via XRD.

Reference Example 2: Characterization of the Catalyst

Reference Example 2.1: Determination of Dv10, Dv50, and Dv90 Values

[0182] 1.0 g of the micropowder is suspended in 100 g deionized water and stirred for 1 min. The sample was subjected to the measurement in an apparatus using the following parameters: 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 MS017; shadowing 16.9%; dispersion model 3$$D; analysis model polydisperse correction none.

Reference Example 2.2: Determination of the Silanol Concentration of the Moldings of the Present Invention

[0183] 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 s Tr/4 (microsecond 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 2.3: Determination of the Crush Strength of the Moldings

[0184] 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/TS01S, 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 fr die Material-Prfmaschine Z2.5/TS01S, 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 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 2.4: .SUP.29.Si Solid-State NMR Spectra Regarding Q.SUP.3 .and Q.SUP.4 .Structures

[0185] The effect of the inventive water treatment on the molding related to Q.sup.3 and Q.sup.4 structures in the material was characterized by comparing the changes in .sup.29Si solid-state NMR spectra under comparable conditions. All .sup.29Si solid-state NMR experiments were performed using a Bruker Advance 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 the 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. After the water treatment of the invention, a decrease of signal intensity at the left hand side of the spectrum was observed, a region that includes Q.sup.3 silanol structures (here especially: around and above 104 ppm, i.e. left of 104 ppm). Further, an increase of signal at the right hand side of the spectrum (here: below 110 ppm, i.e. right of 110 ppm) was observed, which region comprises Q.sup.4 structures exclusively. 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 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 2.5: Water Adsorption/DesorptionWater Uptake

[0186] 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 weight-%). 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 weight-% 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 weight-% to 5 weight-% with a step of 10% and the change in the weight of the sample (water uptake) was monitored and recorded.

Reference Example 2.6: FT-IR Measurements

[0187] 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 3000-3900 cm.sup.1 region were analyzed and for comparing multiple samples, as reference the band at 18805 cm.sup.1 was taken.

Reference Example 2.7: Determination of Crystallinity Via XRD

[0188] The crystallinity of the zeolitic materials according to the present invention were determined by XRD analysis. The data were collected using a standard Bragg-Brentano diffractometer with a Cu-X-ray source and an energy dispersive point detector. The angular range of 2 to 70 (2 theta) was scanned with a step size of 0.02, while the variable divergence slit was set to a constant illuminated sample length of 20 mm. The data were then analyzed using TOPAS V4 software, wherein the sharp diffraction peaks were modeled using a Pawley fit containing a unit cell with the following starting parameters: a=14.4 Angstrom (1 Angstrom=10.sup.10 m) and c=25.2 Angstrom in the space group P6/mmm. These were refined to fit the data. Independent peaks were inserted at the following positions. 8.4, 22.4, 28.2 and 43. These were used to describe the amorphous content. The crystalline content describes the intensity of the crystalline signal to the total scattered intensity. Included in the model were also a linear background, Lorentz and polarization corrections, lattice parameters, space group and crystallite size.

Reference Example 3: Epoxidation Process

[0189] A 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 multipoint 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 (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, also referred to as TR, 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 (abs). The output stream (5) 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(1m.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 K/d. The output stream (5) leaving the epoxidation unit A was passed through a heat exchanging unit. The stream leaving the heat exchanging unit (stream S) was fed to Epoxidation Unit B.

[0190] Epoxidation in a Finishing Reactor (Epoxidation Unit B): The finishing reactor B 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 B 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 B was 10 bar which was kept constant by a suitable pressure regulator at the reactor exit. The output of the finishing reactor B was sampled every 20 min in order to determine the hydrogen peroxide concentration using the titanyl sulfate method. The effluent of the finishing reactor B, stream (6), was preferably 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 C).

[0191] The main reactor A was fed from below with a liquid monophasic stream (1). Stream (1) was prepared by mixing five streams (2), (2a), (3), (4) and (5). The temperature of stream (1) was in the range from 20 to 40 C. The streams were premixed at an absolute pressure of 23 bar. The liquid feed stream (1) consisted of one single liquid phase: [0192] Stream (2) was an acetonitrile stream and had a flow rate of 69 kg/h. [0193] Stream (2a) was a water stream and had a flow rate of 3 kg/h. [0194] Stream (3) having a flow rate of 12.9 kg/h was a propylene stream (containing 0.35 kg/h propene) and was supplied from a storage tank, allowing for a continuous feeding, and fed using a suitable metering pump. [0195] Stream (4) 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. [0196] Stream (5) was an aqueous stream comprising dissolved potassium formate. The further stream was supplied from a storage tank, allowing for a continuous feeding, and was fed using a suitable metering pump. The concentration of the potassium formate was 2.5 weight-%, the feed rate of the stream was 500 g/h (1000 mol potassium/mol hydrogen peroxide). Stream (5) was thoroughly mixed with stream (4) before the combined stream was mixed with the stream resulting from mixing streams (2), (2a) and (3).

[0197] The epoxidation was performed in a continuous manner.

[0198] The reactor effluent stream downstream the pressure control valve was collected, weighed and analyzed (effluent stream (6)). Organic components, with the exception of oxygen, were analyzed in two separate gas-chromatographs. The hydrogen peroxide content was determined colorimetrically using the titanyl sulfate method. Effluent stream (6) comprised 66.5 weight-% acetonitrile, 17.4 weight-% water, 11.6 weight-% propylene oxide, 3.8 weight-% propylene, 0.13 weight-% propylene glycol, 0.5 weight-% propane, 0.03 weight-% oxygen, 0.02 weight-% acetaldehyde, 0.01 weight-% propionaldehyde.

Reference Example 4: Separation of Propylene from Stream (6) to Obtain Stream S0

[0199] Separation of Light Boilers from Stream (6) to Obtain a Stream (8) (Stream S0)

[0200] Stream (6) was sent to a light boiler separation column (distillation unit C) 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 D (stream 11, 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 to the column at different points. The feed point of the liquid portion of stream (6) was above bubble tray 37; the gaseous portion of stream (6) was introduced into the column above bubble tray 28 (counted from the top). The gaseous stream (7) leaving the column at the top 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 (1-2 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. Stream (8) (that is stream S0) was taken off of the light boiler separation column as bottoms stream.

Example 1: Separation of Propylene Oxide from Stream S0 to Obtain a Top Stream S1c Enriched in Propylene Oxide and a Bottoms Stream S1a Depleted of Carbonyl Compounds

[0201] Stream S0 comprised acetonitrile (70.7 weight-%), water (18.9 weight-%), propylene oxide (10.1 weight-%), propionaldehyde (196 weight-ppm), acetaldehyde (145 weight-ppm), acetone (102 weight-ppm) and propylene glycol (0.21 weight-%) and was introduced into a first distillation column (distillation unit D) with 3.0 kg/h at a temperature of 40 C. and a pressure of 1 bar The column had a height of 8.1 m and a diameter of 5 mm and was equipped with a high-performance packing (Sulzer CY) with a packing of 3.6 m below the S0 feed point, 0.9 m packing between feed and side take-off and 3.6 m packing above the side take-off (counted from the bottom). The column was operated in continuous mode at a top pressure of 500 mbar and at a top temperature of 16 C. The overhead stream of the column was condensed and partly returned to the column as reflux (1200 g/h, reflux ratio approximately 4:1). A Stream S1b was taken off from the distillation unit D with 60 g/h via the side-take off by a dosing pump.

[0202] The amount of fed stream S0, the amount of stream S1b and the amount of the reflux were kept constant by flow controller. The amount of top stream S1c was taken off from the distillate container under level control. In order to regulate the energy supply to the sump, the average value of two temperature measuring points positioned between feed and side take off was taken as guidance value and was kept constant at 39 C. in that the temperature of the oil used for heating the sump boiler was adjusted.

[0203] Stream S1b contained propylene oxide (94 weight-%), propionaldehyde (1.0 weight-%), acetonitrile (4.5 weight-%), acetone (0.4 weight-%). The acetaldehyde content was less than 0.01 weight-%. The water content of S1b was not determined. Stream S1b was taken off from distillation unit D with 60 g/h via the side-take off by a dosing pump and mixed with a stream containing an aqueous hydrazine solution (3 weight-%, 10 g/h) in a static mixer. The resulting mixed stream had a molar ratio hydrazine:carbonyl compound of 0.6:1 and was conveyed to a tubular reactor. The reactor had a length of 0.28 m and a diameter of 10 mm. The temperature in the tubular reactor was adjusted to 60 C. by a double jacket with a circulating heat transfer medium therein. The temperature was controlled by thermostat.

[0204] The liquid stream leaving the reactor was then fed to the head of a second column (second distillation unit D2, second column D2). The second distillation unit D2 was a glass column with 30 mm diameter, equipped with a high-performance packing (Sulzer CY) with a packing height of 1.0 m (10 theoretical trays). Second column D2 was operated in continuous mode at a top pressure of 750 mbar and at a bottoms temperature of 38 C.

[0205] In order to regulate the second column D2, the amount of bottoms stream was taken off from the sump of D2 under level control. The temperature in the sump was taken as guiding value and kept constant at 38 C. in order to regulate the energy input in the sump. The temperature of the oil for the sump boiler was taken as controllable variable.

[0206] The gaseous top stream S3a from second column D2 was recycled to the first distillation column D via a feed positioned above the same theoretical tray as the side take-off.

[0207] The distillation was kept running until all compositions were stationary, especially the composition within the stream S1b, which was achieved after approximately 15 h. Thereafter, balancing was done over 6 hours.

[0208] The bottoms stream S3b from second column D2 had a red color and was discarded. No propylene oxide could be detected in S3b.

[0209] The top stream S1c was taken as overhead product from the first distillation unit D with 300 g/h and consisted of propylene oxide (99.8 weight-%) acetaldehyde (0.15 weight-%), water (50 weight-ppm), propionaldehyde (11 weight-ppm), acetonitrile (13 weight-ppm) and acetone (4 weight-ppm). The hydrazine content was <10 weight-ppm.

[0210] The stream S1a was taken as bottoms stream from the first distillation unit D with 2640 g/h and was free of (free of=content less than 50 wt.-ppm) propylene oxide, acetaldehyde, propionaldehyde, acetone, hydrazine and hydrazine derivatives. S1a had an acetonitrile content of about 80 weight-% and a water content of about 20 weight-%. Table 1 showed the compositions of streams S0, S1a, S1b and Sic.

TABLE-US-00002 TABLE 1 compositions of streams S0, S1a and S1c in Example 1. component Stream S0 Stream S1a S1b Stream S1c propylene 10.1 weight- <50 weight- 94 weight- 99.8 weight- oxide % ppm % % acetaldehyde 145 weight- <50 weight- <0.01 0.15 weight- ppm ppm weight-% % water 18.9 weight- 20 weight- <1 weight- 50 weight- % % ppm ppm propionaldehyde 196 weight- <50 weight- 1.0 weight- 11 weight- ppm ppm % ppm acetonitrile 70.7 weight- 80 weight- 4.5 weight- 13 weight- % % % ppm acetone 102 weight- <50 weight- 0.5 weight- 4 weight- ppm ppm % ppm Propylene 0.21 weight- 0.25 <1 weight- <1 weight- glycol % weight-% ppm ppm Hydrazine 0 <50 weight- <1 weight- <10 weight- ppm ppm ppm ---: not determined

[0211] It could be observed that by taking a second stream from a first distillation unit, addition of an organic compound comprising an amino group NH.sub.2 (NH.sub.2-compound), followed by distillation in a second column and recycling of a propylene oxide containing top stream from the second column to the first column, organic compounds comprising a carbonyl group, especially acetone and propionaldehyde, could be depleted to more than 99 weight-% without contaminating the acetonitrile containing bottoms stream from the first column with NH.sub.2-compounds or their derivatives. The loss on propylene oxide was less than 0.02 weight-ppm in relation to the total weight of propylene oxide contained in S0. Acetaldehyde, which was not taken off with the stream S1b from the distillation unit D, could be separated easily later in a further distillation stage, whereby the amount of NH.sub.2-compound could be minimized.

Example 2: Separation of Propylene Oxide from Stream S1b to Obtain a Top Stream S3a Enriched in Propylene Oxide and a Bottoms Stream S3b Depleted of Carbonyl Compounds

[0212] In analogy to Example 1 a Stream S1b was fed to the head of a second column (second distillation unit D2, second column D2). Stream S1b contained acetaldehyde (420 weight-ppm), propylene oxide (78.1 weight-%), propionaldehyde (590 weight-ppm), acetonitrile (21.7 weight-%), acetone (390 ppm-%). Further, a hydrazine stream was added at the top of the second column D2. The second distillation unit D2 was a glass column with an inner diameter of 50 mm equipped with a high-performance packing made of stainless steel (Sulzer DX) with a packing height of 1.045 m (about 20 theoretical trays). Second column D2 was operated in a semi-continuous mode at a top pressure of 540 mbar and at a bottoms temperature of 59 C.

[0213] The bottom stream S3b was collected in the bottom pot of the glass column. The pot was heated electrically with a heating jacket providing constant energy input.

[0214] The gaseous top stream S3a from second column D2 was collected in glass flasks and analyzed.

[0215] The distillation was kept running until a stationary temperature profile was observed, which was achieved after approximately 20 min. Thereafter, the distillate stream S3a was collected in a fresh flask for about 20 min to do the mass balancing.

[0216] Table 2 shows the compositions, Table 3 the flow rates of streams Sib, S3a, S3b as well as of the stream comprising the NH.sub.2 compound.

TABLE-US-00003 TABLE 2 compositions of the streams in Example 2 NH.sub.2 S1b S3a S3b compound [weight- [weight- [weight- [weight- component %] %] %] %] acetaldehyde 0.042 0.01 0 0 propylene oxide 78.1 95.0 2.8 0 propionaldehyde 0.06 0.01 0 0 acetone 0.04 0.02 0.09 0 acetonitril 21.76 3.56 83.1 0 acetaldehyde-azin 0 0 0.14 0 propionaldehyde- 0 0 0.23 0 azin acetone azin 0 0 0.02 0 propylene glycol 0 0 0 0 hydrazine 0 0 0.21 1.8 water 0 1.4 13.4 98.2 Total 100 100 100 100

TABLE-US-00004 TABLE 3 flow rates of the streams in Example 2 NH.sub.2 S1b S3a S3b compound component [g/h] [g/h] [g/h] [g/h] acetaldehyde 0.35 0.08 0 0 propylene oxide 660.7 655.3 5.3 0 propionaldehyde 0.50 0.06 0 0 acetone 0.33 0.11 0.18 0 acetonitril 183.6 24.9 158.6 0 acetaldehyde-azin 0 0 0.26 0 propionaldehyde- 0 0 0.42 0 azin acetone azin 0 0 0.04 0 propylene glycol 0 0 0 0 hydrazine 0 0 0.40 0.63 water 0 9.2 25.6 34.5 Total Flow 845.4 689.7 190.8 35.1

[0217] It could be observed that by distillation in a second column under addition of an organic compound comprising an amino group NH.sub.2 (NH.sub.2-compound) to the second column, organic compounds comprising a carbonyl group (propionaldehyde, acetonaldehyde and acetone) could be reduced in the top stream S3a by 55% to 89% in relation to their amount in stream S1b. The stream S3a was not contaminated with NH.sub.2-compounds or their derivatives. The NH.sub.2-compounds and their derivatives were found in the bottom stream S3b.

SHORT DESCRIPTION OF THE FIGURES

[0218] FIG. 1 shows a block diagram of the process according to Reference Examples 3 and 4 and Examples 1 and 2. In FIG. 1, the letters and numbers have the following meanings: [0219] A epoxidation unit A [0220] B epoxidation unit B [0221] C distillation unit [0222] D first distillation unit [0223] D2 second distillation unit [0224] (1)-(11) streams according to a specifically preferred process as described in the examples [0225] S0, S1a, S1b, S1c, S3a, S3b streams according to a preferred process as described in the general description and the examples

[0226] FIG. 2 shows a block diagram of the distillation units D and D2 from FIG. 1 in detail for Example 1. In FIG. 2, the letters and numbers have the following meanings: [0227] D first distillation unit [0228] D2 second distillation unit [0229] R reactor [0230] NH2-compound organic compound comprising an amino group NH.sub.2 [0231] S0, S1a, Sib, S1c, S2, S3a, S3b streams according to a specifically preferred process as described in the general description and in Example 1

[0232] FIG. 3 shows a block diagram of the distillation unit D2 from FIG. 1 in detail for Example 2. In FIG. 3, the letters and numbers have the following meanings: [0233] D2 second distillation unit [0234] NH2-compound organic compound comprising an amino group NH.sub.2 [0235] S1b, S3a, S3b streams according to a specifically preferred process as described in the general description and in Example 2

CITED LITERATURE

[0236] EP 0 004 019 A2 [0237] WO 2011/123541 A1 [0238] Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A 13 (1989) pages 443-466 [0239] EP 1 122 249 A1