Process for the production of alkenols and use thereof for the production of 1,3-butadiene

Abstract

Process for the production of alkenols comprising the dehydration of at least one diol in the presence of at least one catalyst based on cerium oxide, wherein said catalyst based on cerium oxide is obtained by precipitation, in the presence of at least one base, of at least one compound containing cerium. Preferably, said diol may be a butanediol, more preferably 1,3-butanediol, still more preferably bio-1,3-butanediol derived from biosynthetic processes. Said alkenols may advantageously be used for the production of 1,3-butadiene, in particular of bio-1,3-butadiene.

Claims

1. Process for the production of alkenols comprising: dehydrating 1,3-butanediol in the presence of at least one catalyst based on cerium oxide in at least one diluent at a process temperature ranging from 300 C. to 430 C. to produce alkenols; wherein said catalyst based on cerium oxide is obtained by precipitation, in the presence of at least one base, of at least one compound containing cerium; wherein said catalyst based on cerium oxide is pre-treated at a temperature the same as said process temperature before said dehydrating; said dehydrating being carried out in said at least one diluent selected from: inert gas; or from a compound having a boiling point greater than or equal to 50 C. and a melting temperature of less than or equal to 40 C. as follows: in the case in which the diluent is selected from said inert gas, at a molar ratio between diol and diluent of at least 0.5; in the case in which the diluent is selected from said compound having a boiling point greater than or equal to 50 C. and a melting temperature of less than or equal to 40 C., at a molar ratio between diol and diluent ranging from 0.4 to 100.

2. Process for the production of alkenols according to claim 1, wherein said catalyst based on cerium oxide is obtained by a process comprising: preparing a solution including at least one compound containing cerium; adding to said solution at least one base in a time ranging from 1 minute to 16 hours to obtain a reaction mixture; allowing said reaction mixture to react at a temperature ranging from 15 C. to 100 C., for a time ranging from 1 minute to 120 hours, to obtain a precipitate; recovering the precipitate and subjecting it to drying and, optionally, to calcination.

3. Process for the production of alkenols according to claim 1, wherein said catalyst based on cerium oxide is obtained by a process comprising: preparing a solution including at least one base; adding to said solution at least one compound containing cerium in a time ranging from 1 minute to 16 hours, to obtain a reaction mixture; allowing said reaction mixture to react at a temperature ranging from 15 C. to 100 C., for a time ranging from 1 minute to 120 hours, to obtain a precipitate; recovering the precipitate and subjecting it to drying and, optionally, to calcination.

4. Process for the production of alkenols according to claim 2, wherein said solution including at least one compound containing cerium or said solution including at least one base, is an aqueous solution comprising from 5% by weight to 70% by weight, relative to the total weight of said aqueous solution, of at least one compound containing cerium or of at least one base.

5. Process for the production of alkenols according to claim 2, wherein said solution including at least one compound containing cerium or said solution including at least one base is a water-alcohol solution comprising from 5% by weight to 95% by weight, relative to the total weight of said water-alcohol solution, of at least one alcohol selected from ethanol, 2-methoxyethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, tert-butanol, or mixtures thereof.

6. Process for the production of alkenols according to claim 1, wherein said cerium containing compound is selected from: soluble cerium salts; or cerium alkoxides.

7. Process for the production of alkenols according to claim 2, wherein, in the case in which said solution containing at least one compound containing cerium mainly comprises cerium(III), at least one oxidising agent is added to said solution.

8. Process for the production of alkenols according to claim 2, wherein, in the case in which said solution containing at least one compound containing cerium mainly comprises cerium(III), the recovered precipitate, before being subjected to drying and, optionally, calcination, is treated with at least one oxidising agent.

9. Process for the production of alkenols according to claim 1, wherein said base is selected from: hydroxides of alkali metals or alkaline earth metals; secondary or tertiary amines; quaternary ammonium salts; ammonium hydroxide (NH.sub.4OH), urea.

10. Process for the production of alkenols according to claim 9, wherein said base is selected from aqueous solutions of: ammonium hydroxide (NH.sub.4OH), triethylamine, tetrapropylammonium hydroxide.

11. Process for the production of alkenols according to claim 1, wherein said catalyst based on cerium oxide has a specific surface area ranging from 0.5 m.sup.2/g to 250 m.sup.2/g.

12. Process for the production of alkenols according to claim 1, wherein said catalyst based on cerium oxide is used in the form of an extrudate, optionally containing conventional binders.

13. Process for the production of alkenols according to claim 1, wherein said diol is bio-1,3-butanediol derived from the fermentation of sugars.

14. Process for the production of alkenols according to claim 1, wherein said diol is bio-1,3-butanediol derived from the fermentation of sugars derived from guayule or thistle, including discards, residues or waste arising from said guayule and/or thistle or the processing thereof.

15. Process for the production of alkenols according to claim 1, wherein said process for the production of alkenols is carried out at a pressure ranging from 0.05 bara to 50 bara.

16. Process for the production of alkenols according to claim 1, wherein said process for the production of alkenols is carried out using a Weight Hourly Space Velocity (WHSV), which is a ratio between the weight of the diol fed in one hour and the weight of catalyst based on cerium oxide, said ratio being measured in h.sup.1, ranging from 0.5 h.sup.1 to 20 h.sup.1.

17. Process for the production of 1,3-butadiene comprising bringing at least one of the alkenols obtained with the process of claim 1, into contact with at least one catalyst, under suitable conditions for the dehydration of said at least one alkenol.

18. Process for the production of 1,3-butadiene according to claim 17, wherein said catalyst is selected from solid acid catalysts.

19. Process for the production of alkenols comprising: providing a catalyst based on cerium oxide by a process including: providing at least one cerium containing compound; providing a first addition of at least one base; wherein said at least one cerium containing compound and said at least one base are mixed to form a reaction mixture at a pH of at least 9.0; allowing said reaction mixture to react until decreasing to a pH of about 4.0; providing a second addition of said base such that said reaction mixture reaches a pH of 9.0; allowing said reaction mixture to react until a precipitate is formed and recovered to form said catalyst based on cerium oxide; and dehydrating 1,3-butanediol in a presence of said catalyst based on cerium oxide and a diluent at a process temperature ranging from 300 C. to 430 C. to produce alkenols, said diluent being selected from: inert gas, or from a compound having a boiling point greater than or equal to 50 C. and a melting temperature of less than or equal to 40 C.; said dehydrating being carried out as follows: in the case in which the diluent is selected from said inert gas, at a molar ratio between diol and diluent of at least 0.5; in the case in which the diluent is selected from said compound having a boiling point greater than or equal to 50 C. and a melting temperature of less than or equal to 40 C., at a molar ratio between diol and diluent ranging from 0.4 to 100.

20. Process for the production of alkenols according to claim 19, wherein said diol is bio-1,3-butanediol derived from the fermentation of sugars.

21. Process for the production of alkenols according to claim 19, wherein said diol is bio-1,3-butanediol derived from the fermentation of sugars derived from guayule or thistle, including discards, residues or waste arising from said guayule and/or thistle or the processing thereof.

22. Process for the production of alkenols according to claim 19 wherein said base is selected from: hydroxides of alkali metals or alkaline earth metals; secondary or tertiary amines; quaternary ammonium salts; ammonium hydroxide (NH.sub.4OH), urea.

23. Process for the production of alkenols according to claim 22 wherein said cerium containing compound is cerium nitrate.

Description

EXAMPLE 1

Preparation of a Catalyst Based on Cerium Oxide in the Presence of a Base

(1) A solution of 87 g of cerium nitrate hexahydrate (99.9% Acros; product code 218695000; CAS Number 10294-41-4) in 420 g of water was prepared by vigorous stirring, at room temperature (25 C.), in a 1 liter beaker equipped with a magnetic stirrer bar. With vigorous stirring being maintained, 77 g of a 15% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared by diluting the 30% commercial aqueous solution (Carlo Erba, 30% RPE-ACS ammonia solution; product code 419941, CAS Number 1336-21-6), were added to the resultant solution over a period of 25 minutes by means of a peristaltic pump, with pH being monitored by way of a Hamilton LIQ-GAS combined glass laboratory pH electrode connected to a EUTECH Instruments pH1500 pH meter. On completion of the addition of said solution, a suspension having a pH equal to 9.0 was obtained. Vigorous stirring of the mixture was continued for 64 hours. Subsequently, with vigorous stirring being maintained, a further 34 g of 15% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared as described above, were added to the resultant suspension, having a pH equal to 4.0, over a period of 10 minutes by means of a peristaltic pump, a suspension having a pH equal to 9.0 being obtained. The suspension was vigorously stirred for a further 24 hours, at the end of which period the pH was remeasured and found to be equal to 8.9, and a precipitate was obtained. The resultant precipitate was filtered, washed with 500 ml of water, and subsequently dried in an oven at 120 C. for 2 hours. After drying, the resultant solid was calcined for 6 hours at 1000 C. The XRD spectrum of the solid obtained after calcination revealed the formation of a catalyst based on crystalline cerium oxide (identified by comparison with reference card 04-008-6551 present in the PDF-4 database which has already been mentioned above). The resultant catalyst based on cerium oxide had a BET specific surface area, determined as mentioned above, equal to 4 m.sup.2/g.

EXAMPLE 2

Preparation of a Catalyst Based on Cerium Oxide in the Presence of a Base

(2) A solution of 870 g of cerium nitrate hexahydrate (99% Aldrich; product code 238538; CAS Number 10294-41-4) in 4200 g of water was prepared by vigorous stirring, at room temperature (25 C.), in a glass beaker equipped with a magnetic stirrer bar. The resultant solution was transferred into a glass reactor equipped with an anchor stirrer and stirring was maintained for 15 minutes. With stirring being maintained, 790 g of an aqueous 15% ammonium hydroxide (NH.sub.4OH) solution, previously prepared by diluting the 28%-30% commercial aqueous solution (Aldrich 28%-30% NH.sub.3 Basis ACS reagent; product code 221228, CAS Number 1336-21-6), were added to the resultant solution over a period of 3 hours by means of a peristaltic pump, with pH being monitored by way of a Metrohm glass pH electrode (6.0248.030) connected to a Metrohm 691 pH meter. On completion of the addition of said solution, the pH of the suspension was equal to 9.0, stirring was continued under the same conditions for 64 hours, at the end of which period the pH was found to be equal to 4.3. Subsequently, with stirring being maintained, a further 90 g of a 15% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared as described above, were added to the resultant suspension over a period of 25 minutes by means of a peristaltic pump, a suspension with a pH equal to 9.0 being obtained. The suspension was vigorously stirred for a further 24 hours, at the end of which period the pH was remeasured and found to be equal to 8.8, and a precipitate was obtained. The resultant precipitate was filtered, washed with about 10 liters of water, and subsequently dried in an oven at 120 C. for 2 hours. After drying, the resultant solid was calcined for 6 hours at 600 C.

(3) The XRD spectrum of the solid obtained after calcination revealed the formation of a catalyst based on crystalline cerium oxide (identified by comparison with reference card 04-008-6551 present in the PDF-4 database which has already been mentioned above). The resultant catalyst based on cerium oxide had a BET specific surface area, determined as mentioned above, equal to 19 m.sup.2/g.

EXAMPLE 3

Preparation of a Catalyst Based on Cerium Oxide in the Presence of a Base

(4) 200 g of an approximately 30% commercial aqueous ammonium hydroxide (NH.sub.4OH) solution, (Aldrich 28%-30% NH.sub.3 Basis ACS reagent; product code 221228; CAS Number 1336-21-6) were added in a 1 liter beaker equipped with a Teflon half-moon paddle stirrer and an electrode for measuring pH [Metrohm glass pH electrode (6.0248.030), connected to a Metrohm 780 pH meter] was introduced. A solution of 200 g of cerium nitrate hexahydrate (99% Aldrich; product code 238538; CAS Number 10294-41-4) in 200 g of water was prepared in another 500 ml beaker equipped with a magnetic stirrer bar: the cerium nitrate was then dissolved by vigorous stirring at room temperature (25 C.). The resultant solution was introduced into a dropping funnel and dispensed dropwise in 6 minutes into the above-mentioned ammonium hydroxide solution present in the 1 liter beaker with constant vigorous stirring. The pH of the resultant suspension was equal to 10.1. Vigorous stirring of the mixture was continued for 3 hours, after which 200 ml of water were added and the pH was measured and found to be equal to 9.6. Vigorous stirring of the mixture was continued for a further 1.5 hours, at the end of which period a further 200 ml of water were added and the pH was measured and found to be equal to 9.5. Said suspension was vigorously stirred for 64 hours, at the end of which period the pH was remeasured and found to be equal to 4.5. Subsequently, a further 23 g of approximately 30% ammonium hydroxide (NH.sub.4OH) (Aldrich 28%-30% NH.sub.3 Basis ACS reagent; product code 221228; CAS Number 1336-21-6) were added, a pH equal to 9.0 being obtained: stirring of the mixture was continued for 6 hours, a pH equal to 8.5 being obtained. Subsequently, 16 g of approximately 30% ammonium hydroxide (NH.sub.4OH) (Aldrich 28%-30% NH.sub.3 Basis ACS reagent; product code 221228; CAS Number 1336-21-6) were added, a pH equal to 9.0 being obtained. Vigorous stirring of the mixture was continued for 17 hours, at the end of which period the pH was equal to 7.9 and a precipitate was obtained. The resultant precipitate was filtered, washed with 2 liters of water, and subsequently dried in oven at 120 C. for 2 hours. After drying, the resultant solid was calcined for 5 hours at 600 C.

(5) The XRD spectrum of the solid obtained after calcination revealed the formation of a catalyst based on crystalline cerium oxide (identified by comparison with reference card 04-008-6551 present in the PDF-4 database which has already been mentioned above). The resultant catalyst based on cerium oxide had a BET specific surface area, determined as mentioned above, equal to 49 m.sup.2/g.

EXAMPLE 4

Preparation of Alkenols by Dehydration of 1,3-Butanediol

(6) Catalytic activity tests were carried out in the experimental apparatus and using the operating methods described below.

(7) The 1,3-butanediol dehydration reaction was performed in a fixed-bed tubular reactor of AISI 316L steel, with a length of 400 mm and an internal diameter of 9.65 mm. Within the reactor, along the axis thereof, there was a well with an external diameter of 3 mm which accommodated the thermocouple for controlling temperature. The reactor was placed in an electrically heated oven capable of reaching the temperature selected for the above-stated reaction. The catalysts used in the tests were ground and then sieved to obtain the 0.5 mm to 1 mm fraction.

(8) The catalyst charge of 3 g was placed in the above-stated reactor between two layers of inert material (corundum), the catalyst bed was held in place by means of a sintered steel baffle placed on the bottom of the reactor which has a downward flow (down-flow reactor).

(9) Feed was performed from the top of the reactor, above the zone filled with inert material which acted as an evaporator and enabled the reactants to reach reaction temperature before coming into contact with the catalyst.

(10) The liquid reactants were fed by a metering pump of the type used in high-performance liquid chromatography (HPLC). The gas were fed by thermal mass flow meter (TMF). Downstream of the reactor, the products obtained were cooled in a heat exchanger and the condensed liquid was collected in glass vials by means of a series of timer-controlled valves. The uncondensed gases, on the other hand, were passed through a volumetric wet gas meter in order to measure the volume of gases produced. A small proportion of the gases was sampled in an on-line gas chromatograph (GC) for analysis. On-line analysis of the gases was performed by an Agilent HP7890 gas chromatograph (GC) with an HP-Al/S column (length 50 m; diameter 0.53 mm; film thickness 15 micron), the carrier gas used was helium flowing at 30 cm/s, the detector was a flame detector. Gas analysis was performed using an external standard with calibration curves for the individual known components.

(11) The collected liquids were characterised by means of gas chromatographic analysis using an Agilent HP6890 gas chromatograph (GC) equipped with a split/splitless injector on a Quadrex 007 FFAP column (height 25 m; diameter 0.32 mm; film thickness 1 micron), the carrier gas used was helium with a velocity of 50 cm/s, the detector was a flame detector. Determination was performed using an internal standard with calibration curves for the individual known components.

(12) The catalytic performance values shown in the following tables are expressed by calculating the conversion of 1,3-butanediol [1,3-BDO] (C.sub.1,3-BDO) and the selectivities for the various products (S.sub.i) according to the formulae shown below.

(13) $C_{1,3-\mathrm{BDO}}=\frac{{\left({\mathrm{mol}}_{1,3-\mathrm{BDO}}\right)}_{\mathrm{in}}-{\left({\mathrm{mol}}_{1,3-\mathrm{BDO}}\right)}_{\mathrm{out}}}{{\left({\mathrm{mol}}_{1,3-\mathrm{BDO}}\right)}_{\mathrm{in}}}100$$S_i=\frac{{\mathrm{mol}}_i}{{\left({\mathrm{mol}}_{1,3-\mathrm{BDO}}\right)}_{\mathrm{in}}-{\left({\mathrm{mol}}_{1,3-\mathrm{BDO}}\right)}_{\mathrm{out}}}100$

(14) The catalyst obtained as described in Example 1 (Ex. 1 cat.) in a first test, the catalyst obtained as described in Example 2 (Ex. 2 cat.) in a second test, and the catalyst obtained as described in Example 3 (Ex. 3 cat.) in a third test, ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into the reactor and subsequently pre-treated in situ, at 300 C., under a stream of nitrogen (N.sub.2).

(15) 30 g/h of 1,3-butanediol (Fluka, purity 99%) together with nitrogen (N.sub.2) in a 1,3-butanediol:nitrogen (N.sub.2) ratio equal to 1 were then fed into the above-stated reactor. The test was carried out at a space velocity relative to 1,3-butanediol (Weight Hourly Space Velocity) equal to 10 h.sup.1, at atmospheric pressure (1 bara), and at gradually rising temperatures: each sample was taken after six hours at the stated temperature.

(16) Table 1 shows the catalytic results obtained in terms of conversion (C %) and selectivity (S %), calculated as described above, at the various temperatures.

(17) TABLE-US-00001 TABLE 1 1,3- Selectivity Butanediol 3-buten- 2-buten- 1,3- conversion 2-ol 1-ol 3-buten-1-ol butadiene (C %) (S %) (S %) (S %) (S %) Ex. 1 cat. temperature ( C.) 300 16 37 25 0.0 0.1 325 33 56 39 0.0 0.0 350 70 54 39 0.2 0.0 375 93 56 37 0.6 0.0 400 98 55 29 1.2 0.0 Ex. 2 cat. temperature ( C.) 300 13 45 32 0.0 0.0 325 39 54 39 0.0 0.0 350 77 54 39 0.2 0.0 375 98 53 38 0.4 0.0 400 >99 53 31 1.1 0.0 Ex. 3 cat. temperature ( C.) 300 43 58 42 0.0 0.1 325 77 55 40 0.2 0.1 350 97 54 38 0.4 0.4 375 >99 53 32 0.9 1.2 400 >99 53 20 1.6 3.7

(18) It is evident from the data shown in Table 1 that the process provided by the present invention in which the catalysts obtained as described in Example 1 (Ex. 1 cat.), Example 2 (Ex. 2 cat.) and Example 3 (Ex. 3 cat.) were used is capable of providing elevated conversions and selectivities over a wide temperature range. It is furthermore evident that an increase in the surface area of said catalysts has no negative impact on selectivity over a broad range of temperatures and of conversions.

EXAMPLE 5

Preparation of a Catalyst Based on Cerium Oxide in the Presence of a Base

(19) A solution of 87 g of cerium nitrate hexahydrate (99% Aldrich; product code 238538; CAS Number 10294-41-4) in 420 g of water was prepared by vigorous stirring, at room temperature (25 C.), in a 1 liter beaker equipped with a magnetic stirrer bar. With vigorous stirring being maintained, 75 g of a 15% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared by diluting the 28%-30% commercial aqueous solution (Aldrich 28%-30% NH.sub.3 Basis ACS reagent; product code 221228, CAS Number 1336-21-6), were added to the resultant solution over a period of 25 minutes by means of a peristaltic pump, with pH being monitored by way of a Hamilton LIQ-GAS combined glass laboratory pH electrode connected to a EUTECH Instruments pH1500 pH meter. On completion of the addition of said solution, a suspension having a pH equal to 9.0 was obtained. Vigorous stirring of the mixture was continued for 64 hours. Subsequently, with vigorous stirring being maintained, a further 25 g of a 15% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared as described above, were added to the resultant suspension, having a pH equal to 4, over a period of 10 minutes by means of a peristaltic pump, a suspension having a pH equal to 9.0 being obtained. The suspension was vigorously stirred for a further 24 hours, at the end of which period the pH was remeasured and found to be equal to 8.8, and a precipitate was obtained. The resultant precipitate was filtered, washed with 500 ml of water, and subsequently dried in an oven at 120 C. for 2 hours. After drying, the resultant solid was calcined for 6 hours at 600 C. The XRD spectrum of the solid obtained after calcination revealed the formation of a catalyst based on crystalline cerium oxide (identified by comparison with reference card 04-008-6551 present in the PDF-4 database which has already been mentioned above). The resultant catalyst based on cerium oxide had a BET specific surface area, determined as mentioned above, equal to 18 m.sup.2/g.

EXAMPLE 6

Preparation of Alkenols from 1,3-Butanediol

(20) The catalyst (3 g) obtained as described in Example 5 (Ex. 5 cat.), ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into the reactor, proceeding as described in Example 4, and subsequently pre-treated in situ, at 350 C., under a stream of nitrogen (N.sub.2).

(21) 24.5 g/h of 1,3-butanediol (Fluka, purity 99%) together with nitrogen (N.sub.2) in a 1,3-butanediol:nitrogen (N.sub.2) ratio equal to 1 were then fed into the above-stated reactor. The test was carried out at atmospheric pressure (1 bara) and at a temperature of 350 C. Table 2 shows the catalytic results obtained in terms of conversion (C %) and selectivity (S %), calculated as described above, at the various reaction times: each sample was taken during the 6 hours preceding the time stated in Table 2.

(22) TABLE-US-00002 TABLE 2 1,3- Selectivity Ex. 5 cat. Butanediol 2-buten- 3-buten- 1,3- reaction time conversion 3-buten-2-ol 1-ol 1-ol butadiene (hours) (C %) (S %) (S %) (S %) (S %) 23 97 53 38 0.3 0.3 60 97 54 38 0.3 0.4 160 94 54 38 0.3 0.5 302 97 55 40 0.3 0.7 486 97 55 39 0.4 0.6

(23) It is evident from the data shown in Table 2 that the process provided by the present invention in which the catalyst obtained as described in Example 5 (Ex. 5 cat.) was used is capable of providing elevated conversions and selectivities and that said catalyst is stable even at elevated temperatures, for extended periods, despite the low diluent content [i.e. nitrogen (N.sub.2)]. It is furthermore evident that said catalyst has elevated productivity (said productivity being taken to mean the total quantity of butenols produced per unit of catalyst during the test) well above, for example, one kg of alkenols/g of catalyst, without obvious signs of deactivation.

EXAMPLE 7

Preparation of Alkenols from 1,3-Butanediol

(24) The catalyst (3 g) obtained as described in Example 5 (Ex. 5 cat.), ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into a reactor, operating as described in Example 4, and subsequently pre-treated in situ, at 350 C., under a stream of nitrogen (N.sub.2).

(25) The catalyst was then subjected to life testing using a method entirely similar to that described in Example 6 with the sole difference that water was fed as diluent instead of nitrogen (N.sub.2).

(26) 30.7 g/h of 1,3-butanediol (Fluke, purity 99%) in water in an amount of 82.5%, equivalent to a 1,3-butanediol:water ratio equal to 1, were then fed into the above-stated reactor.

(27) The test was carried out at atmospheric pressure (1 bara) and at a temperature of 350 C. Table 3 shows the catalytic results obtained in terms of conversion (C %) and selectivity (S %), calculated as described above, at the various reaction times: each sample was taken during the 6 hours preceding the time stated in Table 3.

(28) TABLE-US-00003 TABLE 3 1,3- Selectivity Ex. 5 cat. Butanediol 2-buten- 3-buten- 1,3- reaction time conversion 3-buten-2-ol 1-ol 1-ol butadiene (hours) (%) (S %) (S %) (S %) (S %) 22 88 56 39 0.3 0.1 192 90 57 39 0.3 0.1 252 92 57 39 0.4 0.2 312 93 57 39 0.4 0.1 572 96 57 39 0.4 0.2

(29) It is evident from the data shown in Table 3 that the process provided by the present invention in which the catalyst obtained as described in Example 5 was used is capable of providing elevated conversions and selectivities and that said catalyst is stable even at elevated temperatures, for extended periods, despite the low diluent content [i.e. H.sub.2O]. It is furthermore evident that said catalyst has elevated productivity (said productivity being taken to mean the total quantity of butenols produced per unit of catalyst during the test) well above, for example, one kg of alkenols/g of catalyst, without obvious signs of deactivation.

EXAMPLE 8

Preparation of Alkenols from 1,3-Butanediol

(30) The catalyst obtained as described in Example 2 (Ex. 2 cat.), ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into a reactor, operating as described in Example 4, and subsequently pre-treated in situ, at 400 C., under a stream of nitrogen (N.sub.2).

(31) 29.5 g/h of 1,3-butanediol (Fluka, purity 99%) together with nitrogen (N.sub.2) in a 1,3-butanediol:nitrogen (N.sub.2) ratio equal to 1 were then fed into the above-stated reactor. The test was carried out at a space velocity relative to 1,3-butanediol (Weight Hourly Space Velocity) equal to 10 h.sup.1, at atmospheric pressure (1 bara), and at a temperature of 400 C.

(32) Table 4 shows the catalytic results obtained in terms of conversion (C %) and selectivity (S %) at the various reaction times: each sample was taken during the 6 hours preceding the time stated in Table 4.

(33) TABLE-US-00004 TABLE 4 1,3- Selectivity Ex. 2 cat. Butanediol 2-buten-1- 3-buten- 1,3- reaction time conversion 3-buten-2-ol ol 1-ol butadiene (hours) (%) (S %) (S %) (S %) (S %) 146 >99 52 34 0.8 1.9 162 >99 53 36 0.6 1.8 246 >99 52 36 0.7 1.7 301 98 52 37 0.6 1.4

(34) It is evident from the data shown in Table 4 that the process provided by the present invention in which the catalyst obtained as described in Example 2 (Ex. 2 cat.) was used is capable of providing elevated conversions and selectivities and that said catalyst is stable for extended periods even at elevated temperatures, despite the low diluent content [i.e. nitrogen (N.sub.2)].

EXAMPLE 9

Preparation of a Catalyst Based on Extruded Cerium Oxide

(35) A solution of 870 g of cerium nitrate hexahydrate (99% Aldrich; product code 238538; CAS Number 10294-41-4) in 4200 g of water was prepared by vigorous stirring, at room temperature (25 C.), in a glass beaker equipped with a magnetic stirrer bar. The resultant solution was transferred into a glass reactor equipped with an anchor stirrer and stirring was maintained for 15 minutes. With stirring being maintained, 790 g of an aqueous 15% ammonium hydroxide (NH.sub.4OH) solution, previously prepared by diluting the 28%-30% commercial aqueous solution (Aldrich 28%-30% NH.sub.3 Basis ACS reagent; product code 221228, CAS Number 1336-21-6), were added to the resultant solution over a period of 3 hours by means of a peristaltic pump, with pH being monitored by way of a Metrohm glass pH electrode, 6.0248.030, connected to a Metrohm 691 pH meter. On completion of the addition of said solution, the pH of the suspension was equal to 9.0: stirring of the mixture was continued for 64 hours, at the end of which period the pH was equal to 4.3. Subsequently, with stirring being maintained, a further 90 g of a 15% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared as described above, were added to the resultant suspension over a period of 25 minutes by means of a peristaltic pump, a suspension with a pH equal to 9.0 being obtained. The suspension was vigorously stirred for a further 24 hours, at the end of which period the pH was remeasured and found to be equal to 8.8, and a precipitate was obtained. The resultant precipitate was filtered, washed with about 10 liters of water, and subsequently dried in an oven at 120 C. for 2 hours.

(36) After having repeated the above-stated preparation for an appropriate number of batches to obtain sufficient quantities of material, the resultant solids were combined and ground in a mortar: 1905 g of powder obtained in this manner were then place in Erweka planetary mixer with an AMD model motor.

(37) The powder was dry mixed for 1 hour and the following were subsequently added dropwise in succession, 250 g of a 25% aqueous ammonium hydroxide (NH.sub.4OH) solution, previously prepared by diluting the commercial aqueous 28%-30% solution (28%-30% NH.sub.3 Basis ACS reagent Aldrich; product code 221228; CAS Number 1336-21-6), over a period of 50 minutes and 250 ml of demineralised water, likewise over a period of 50 minutes, a paste being obtained which was extruded with a Hutt extruder fitted with rollers having 2 mm holes. The resultant pellets obtained by extrusion were allowed to dry in air for two days.

(38) Subsequently, a sample of the pellets weighing 134 g was oven-dried at 120 C. for 2 hours and subsequently calcined for 6 hours at 600 C., a catalyst based on cerium oxide being obtained.

(39) The resultant catalyst based on cerium oxide had a BET specific surface area, determined as mentioned above, equal to 18 m.sup.2/g.

EXAMPLE 10

Preparation of Alkenols from 1,3-Butanediol with Catalyst Based on Extruded Cerium Oxide

(40) The catalyst obtained as described in Example 9 (Ex. 9 cat.), ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into a reactor, operating as described in Example 4, and subsequently pre-treated in situ, at 400 C., under a stream of nitrogen (N.sub.2).

(41) 28.8 g/h of 1,3-butanediol (Fluka, purity 99%) together with nitrogen (N.sub.2) in a 1,3-butanediol:nitrogen (N.sub.2) ratio equal to 1 were then fed into the above-stated reactor. The test was carried out at a space velocity relative to 1,3-butanediol (Weight Hourly Space Velocity) equal to 10 h.sup.1, at atmospheric pressure (1 bara), and at a temperature of 400 C.

(42) Table 5 shows the catalytic results obtained in terms of conversion (C %) and selectivity (S %) at the various reaction times: each sample was taken during the 6 hours preceding the time stated in Table 5.

(43) TABLE-US-00005 TABLE 5 Ex. 9 cat. Selectivity reaction 1,3-Butanediol 3-buten-2- 2-buten-1- 3-buten- 1,3- time conversion ol ol 1-ol butadiene (hours) (%) (S %) (S %) (S %) (S %) 90 >99 51 30 0.9 2.8 187 >99 53 34 1.0 2.8 283 99 52 38 0.6 1.8 348 98 52 39 0.6 1.3

(44) It is evident from the data shown in Table 5 that the process provided by the present invention in which the catalyst obtained as described in Example 9 (Ex. 9 cat.) was used is capable of providing elevated conversions and selectivities and that said catalyst is stable even at elevated temperatures and also at low diluent contents [i.e. nitrogen (N.sub.2)]. It should furthermore be noted that said catalyst performs substantially similarly to those catalysts which have not been subjected to forming operations.

EXAMPLE 11

Preparation of a Catalyst Based on Silica-Alumina

(45) 7.6 g of aluminium tri-sec-butoxide (97% Aldrich; product code 201073; CAS Number 2269-22-9) were introduced into a 500 ml, 2-necked flask. A solution of 50 g of silicic acid (99.9% Aldrich; product code 288772; CAS Number 1343-98-2) with 250 g of deionised water was then prepared by vigorous stirring in a 500 ml conical flask. Using a suitable dropping funnel, the solution was then transferred in 10 minutes into the above-mentioned flask containing the alumina precursor, while the mixture was vigorously stirred. Once addition was complete, the solution was vigorously stirred for 1 hour. After 1 hour, the temperature was adjusted to 90 C. and the solution was kept at said temperature for 1 hour. The resultant suspension was filtered and washed with 5 liters of deionised water, a precipitate being obtained which was oven-dried at 120 C. for 12 hours. After drying, the resultant solid was calcined at 550 C. in a muffle furnace for 5 hours.

(46) Elemental analysis of the solid after calcination performed by WD-XRF (Wavelength dispersion X-Ray fluorescence) using a PANalytical Axios Advanced spectrometer equipped with a 4 kW X-ray tube with Rh anode, revealed the formation of a solid having an Al.sub.2O.sub.3 content equal to 3.8%.

(47) Subsequently, a part of the solid obtained as described above, designated active phase, was bound with alumina (Versal V250-UOP).

(48) To this end, 40.4 g of active phase were placed in an 800 ml beaker with 24.4 g of alumina (Versal V250-UOP). The powders were mixed mechanically, then 302 g of a 4% acetic acid solution, previously produced by diluting the >99.7% commercial aqueous solution (Aldrich >99.7% acetic acid ACS reagent; product code 320099; CAS Number 64-19-7), were added. The resultant suspension was heated to 60 C. and kept at said temperature with vigorous stirring for 2 hours. The suspension, with vigorous stirring still being continued, was then heated to 150 C., and allowed to dry at said temperature for 12 hours, a dry product being obtained which was transferred into a porcelain evaporating dish and placed in a muffle furnace to calcine at 550 C. for 5 hours.

EXAMPLE 12

Preparation of 1,3-Butadiene from Butenols

(49) The catalyst obtained as described in Example 11 was used in a dehydration test of a mixture of butenols and water.

(50) To this end, the mixtures of butenols obtained as described in Example 4 and Example 5 were combined to obtain a mixture which was distilled to obtain an aqueous solution of isomeric butenols having the composition shown in Table 6.

(51) TABLE-US-00006 TABLE 6 Composition (%) 2-Buten-1-ol 14 3-Buten-2-ol 50 3-Buten-1-ol 0.4 Water 35

(52) The catalyst obtained as described in Example 11 (Ex. 11 cat.), ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into a reactor, operating as described in Example 4, and subsequently pre-treated in situ, at 300 C., under a stream of nitrogen (N.sub.2).

(53) 27.8 g/h of the aqueous solution of isomeric butenols shown in Table 6 and 7.4 NI/h of nitrogen (N.sub.2) were then fed into the above-stated reactor.

(54) The catalytic results obtained were expressed in terms of conversion and selectivity. The calculations were performed using formulae similar to those stated above for the diol dehydration stage, taking as the starting reactant the sum of butenols present in the mixture and calculating the selectivity by taking account of the number of mol of 1,3-butadiene obtained.

(55) After 2 hours of reaction at 300 C., the reactivity values were as follows: butenol conversion (C %): 99%; selectivity for 1,3-butadiene (S %): 91%.

(56) It is evident from the data shown above that the process provided by the present invention is capable of producing mixtures of butenols which may subsequently be used in the production of 1,3-butadiene with excellent conversion (C %) and selectivity (S %) values.

EXAMPLE 13

Preparation of 1,3-Butadiene from Butenols

(57) The catalyst obtained as described in Example 11 (Ex. 11 cat.) was used in a dehydration test of a mixture of butenols and water.

(58) For this purpose, the catalyst (3 g) obtained as described in Example 11 (Ex. 11 cat.), ground and sieved to obtain the 0.5 mm to 1 mm fraction, was charged into a reactor, operating as described in Example 4, and subsequently pre-treated in situ, at 300 C., under a stream of nitrogen (N.sub.2).

(59) 27.8 g/h of the aqueous solution of butenols shown in Table 6 and 7.4 NI/h of nitrogen (N.sub.2) were then fed into the above-stated reactor.

(60) The catalytic results obtained at 400 C., stated in terms of conversion and selectivity, after 2 hours, 4 hours and 6 hours of reaction, are shown in Table 7.

(61) TABLE-US-00007 TABLE 7 Ex. 11 cat. Butenol Selectivity for reaction time conversion 1,3-butadiene (hours) (C %) (S %) 2 100 82 4 100 91 6 100 92

(62) It is evident from the data shown above that the process provided by the present invention is capable of producing mixtures of butenols which may subsequently be used in the production of 1,3-butadiene with excellent conversion (C %) and selectivity (S %) values.