PROCESS FOR PREPARING AN ALKENE

Abstract

A process for the preparation of an alkene from an oxygenate comprising contacting a reactant feedstream comprising at least one oxygenate reactant and water with a supported heteropolyacid catalyst at a temperature of at least 170° C., wherein the process is initiated using a start-up procedure comprising the following steps: (i) heating the supported heteropolyacid catalyst to a temperature of at least 220° C.; (ii) maintaining the heat-treated supported heteropolyacid catalyst of step (i) at a temperature of at least 220° C. for a time sufficient to remove bound water from the heteropolyacid component of the supported heteropolyacid catalyst; (iii) under an anhydrous atmosphere, reducing the temperature of the heat-treated supported heteropolyacid catalyst of step (ii) to a temperature below 220° C.; and (iv) contacting the supported heteropolyacid catalyst of step (iii) with the reactant feedstream at a temperature of at least 170° C.

Claims

1-15. (canceled)

16. A process for the preparation of an alkene from an oxygenate, the process comprising contacting a reactant feedstream comprising at least one oxygenate reactant and water with a supported heteropolyacid catalyst at a temperature of at least 170° C., wherein the process is initiated using a start-up procedure comprising the following steps: (i) heating the supported heteropolyacid catalyst to a temperature of at least 220° C.; (ii) maintaining the heat-treated supported heteropolyacid catalyst of step (i) at a temperature of at least 220° C. for a time sufficient to remove chemically bound water from the heteropolyacid component of the supported heteropolyacid catalyst; (iii) under an anhydrous atmosphere, reducing the temperature of the heat-treated supported heteropolyacid catalyst of step (ii) to a temperature below 220° C.; and (iv) contacting the supported heteropolyacid catalyst of step (iii) with the reactant feedstream at a temperature of at least 170° C.

17. A process for the preparation of an alkene from an oxygenate, the process comprising contacting a reactant feedstream comprising at least one oxygenate reactant and water with a supported heteropolyacid catalyst at a temperature of at least 170° C., wherein the process is initiated using a start-up procedure comprising the following steps: (i) heating the supported heteropolyacid catalyst to a temperature of at least 220° C.; (ii) maintaining the heat-treated supported heteropolyacid catalyst of step (i) at a temperature of at least 220° C. for a time sufficient to remove chemically bound water from the heteropolyacid component of the supported heteropolyacid catalyst; (iii) under an anhydrous atmosphere, reducing the temperature of the heat-treated supported heteropolyacid catalyst of step (ii) to a temperature below 220° C.; (iv) contacting the supported heteropolyacid catalyst of step (iii) with a reactant feed comprising the oxygenate component of the reactant feedstream and no water at a temperature of at least 170° C.; and (v) whilst maintaining a temperature of at least 170° C., adding water to the reactant feed of step (iv) to form the reactant feedstream.

18. Process according to claim 17, wherein a partial pressure of the oxygenate component in the reactant feed of step (iv) is at most 2 MPa.

19. Process according to claim 16, wherein prior to step (i), the supported heteropolyacid catalyst is treated by heating the supported heteropolyacid catalyst to a temperature of at least 220° C. and passing steam over the heated supported heteropolyacid catalyst, followed by heating the steam-treated supported heteropolyacid catalyst to a temperature of at least 220° C. under an anhydrous atmosphere.

20. Process according to claim 17, wherein prior to step (i), the supported heteropolyacid catalyst is treated by heating the supported heteropolyacid catalyst to a temperature of at least 220° C. and passing steam over the heated supported heteropolyacid catalyst, followed by heating the steam-treated supported heteropolyacid catalyst to a temperature of at least 220° C. under an anhydrous atmosphere.

21. Process according to claim 16, wherein step (i) is performed under an anhydrous atmosphere, and during step (ii), steam is passed over the heated supported heteropolyacid catalyst followed by maintaining the catalyst at a temperature of at least 220° C. under an anhydrous atmosphere.

22. Process according to claim 17, wherein step (i) is performed under an anhydrous atmosphere, and during step (ii), steam is passed over the heated supported heteropolyacid catalyst followed by maintaining the catalyst at a temperature of at least 200° C. under an anhydrous atmosphere.

23. Process according to claim 19, wherein the supported heteropolyacid catalyst has previously been employed in a process for the preparation of an alkene from an oxygenate.

24. Process according to claim 20, wherein the supported heteropolyacid catalyst has previously been employed in a process for the preparation of an alkene from an oxygenate.

25. Process according to claim 21, wherein the supported heteropolyacid catalyst has previously been employed in a process for the preparation of an alkene from an oxygenate.

26. Process according to claim 22, wherein the supported heteropolyacid catalyst has previously been employed in a process for the preparation of an alkene from an oxygenate.

27. Process according to claim 16, wherein in step (i), the supported heteropolyacid catalyst is heated to a temperature of at least 240° C.

28. Process according to claim 17, wherein in step (i), the supported heteropolyacid catalyst is heated to a temperature of at least 240° C.

29. Process according to claim 16, wherein in step (ii), the heat-treated supported heteropolyacid catalyst of step (i) is maintained at a temperature of at least 240° C.

30. Process according to claim 17, wherein in step (ii), the heat-treated supported heteropolyacid catalyst of step (i) is maintained at a temperature of at least 240° C.

31. Process according to claim 16, wherein in step (ii), the heat-treated supported heteropolyacid catalyst of step (i) is maintained at a temperature of at least 220° C. for at least one hour.

32. Process according to claim 17, wherein in step (ii), the heat-treated supported heteropolyacid catalyst of step (i) is maintained at a temperature of at least 220° C. for at least one hour.

33. Process according to claim 16, wherein the at least one oxygenate reactant in the reactant feedstream is an alcohol and/or alcohol derivative.

34. Process according to claim 17, wherein the at least one oxygenate reactant in the reactant feedstream is an alcohol and/or alcohol derivative.

35. Process according to claim 33, wherein the at least one oxygenate reactant in the reactant feedstream is ethanol and/or diethyl ether.

36. Process according to claim 34, wherein the at least one oxygenate reactant in the reactant feedstream is ethanol and/or diethyl ether.

37. Process according to claim 16, wherein the supported heteropolyacid catalyst is a supported silicotungstic acid catalyst.

38. Process according to claim 17, wherein the supported heteropolyacid catalyst is a supported silicotungstic acid catalyst.

39. Process according to claim 37, wherein the supported heteropolyacid catalyst is a supported 12-tungstosilicic acid catalyst.

40. Process according to claim 38, wherein the supported heteropolyacid catalyst is a supported 12-tungstosilicic acid catalyst.

41. Process according to claim 16, wherein the process for the preparation of an alkene from an oxygenate is performed at a temperature in the range of from 180° C. to 270° C.

42. Process according to claim 17, wherein the process for the preparation of an alkene from an oxygenate is performed at a temperature in the range of from 180° C. to 270° C.

43. Process according to claim 16, wherein the process for the preparation of an alkene from an oxygenate is performed at a pressure in the range of from 0.1 MPa to 4.5 MPa.

44. Process according to claim 17, wherein the process for the preparation of an alkene from an oxygenate is performed at a pressure in the range of from 0.1 MPa to 4.5 MPa.

Description

EXAMPLES

[0079] The following examples were all performed in a micro-reactor having an internal diameter of 15 mm, a length of 69 cm, and having a 5 mm (outside diameter) thermowell inserted in the reactor in the axial direction. The thermowell inserted in the reactor contained four thermocouples with the first being placed in a pre-heat zone where the liquid feed is vapourised, and the other three being placed in the catalyst bed. The pressure of the process was controlled by a pressure control valve (PCV) with all vapours exiting the reactor passing to the low pressure side of the PCV. A portion of the exit gas was directed to a GC for on-line analysis of the products.

[0080] The catalyst used in the examples was silicotungstic acid (ex. Nippon Inorganic Chemicals) supported on CariAct (trademark) Q15 silica pellets (ex. Fuji Silysia) at a concentration of 275 g/kg silicotungstic acid.

[0081] In all the examples, approximately 2.7 g of the above catalyst which is equivalent to a bulk volume of 5 cm.sup.3, was loaded into the reactor. The catalyst was also mixed with an inert diluent of Davicat (trademark) A372 (also known as G57) silica (2.7 g, which was of 0.25 to 0.5 mm diameter). The diluent was used to fill the voids between the catalyst particles allowing good interaction of the reactants with the catalyst (i.e. no channelling).

Example 1 and Comparative Example A

[0082] For the following examples, the reactant feedstream detailed in Table 1 was used.

TABLE-US-00001 TABLE 1 Liquid Feed Ethanol (% wt) 33.00 Diethyl ether (% wt) 65.50 Water (% wt) 1.50 Feed Rate Livid Feed Rate (g/min) 0.377 Nitrogen (g/min) 0.1150

[0083] In example 1, a fresh catalyst was heated to a temperature of 250° C. under a flow of nitrogen (20 barg: 0.115 g/min) and maintained at 250° C. under the nitrogen stream for 2 hours. The temperature was then reduced to 180° C., and the pressure was reduced to 3 barg. Once the temperature of the catalyst was at 180° C. and the pressure was at 3 barg, the reactant feedstream detailed in Table 1 was introduced to the reactor at a pressure of 3 barg and these conditions were maintained for 36 hours. The temperature was then increased to 240° C. and the pressure was increased to 30 barg over one hour and the reactor was maintained under these conditions. The performance of the catalyst in the preparation of ethylene from the reactant feedstream detailed in Table 1 is provided by the product composition after 98 hours on stream recorded in Table 2 below.

[0084] In comparative example A, a fresh catalyst was heated to a temperature of 180° C. under a flow of nitrogen (20 barg: 0.115 g/min) and maintained at 180° C. under the nitrogen stream for 30 minutes. The reactant feedstream detailed in Table 1 was then introduced to the reactor at a pressure of 20 barg and these conditions were maintained for 2 hours. The temperature was then increased to 240° C. and the pressure was increased to 30 barg over ten minutes and the reactor was maintained under these conditions. The performance of the catalyst in the preparation of ethylene from the reactant feedstream detailed in Table 1 is provided by the product composition after 85 hours on stream recorded in Table 2 below.

TABLE-US-00002 TABLE 2 Ethylene Ethane C.sub.4* Acetaldehyde Space (ppmw (ppmw (ppmw Time on on on Yield ethylene ethylene ethylene Example (g/l/hr) product) product) product) 1 973 330 4137 997 A 877 600 3384 1912 *Hydrocarbons containg four carbon atoms, primarily butenes.

[0085] As can be seen from the results presented in Table 2, the concentration of ethane present in the product composition when the process was started using the process of the present invention is significantly lower than comparative example A, wherein the process was started up without subjecting the catalyst to a temperature of at least 220° C. prior to introduction of the reactant feedstream.

Example 2 and Comparative Example B

[0086] In example 2, a fresh catalyst was heated to a temperature of 250° C. under a flow of nitrogen (20 barg: 0.115 g/min) and maintained at 250° C. under the nitrogen stream for 2 hours. The temperature was then reduced to 180° C., followed by a reduction of the pressure to 3 barg. Once the temperature of the catalyst was at 180° C. and the pressure was at 3 barg, ethanol was added to the nitrogen to form an ethanol feedstream which was introduced to the reactor at a pressure of 3 barg (ethanol feed rate: 0.362 g/min; nitrogen feed rate: 0.115 g/min) and these conditions were maintained for 17 hours. The temperature and pressure were then increased to 240° C. and 20 barg and maintained under these conditions for 26 hours. The ethanol feedstream was replaced by the reactant feedstream detailed in Table 1 and the reactor pressure was increased to 30 barg. The reactor was maintained under these conditions and the performance of the catalyst in the preparation of ethylene from the reactant feedstream detailed in Table 1 is provided by the product composition after 87 hours on stream recorded in Table 3 below.

[0087] In comparative example B, a fresh catalyst was heated to a temperature of 250° C. under a flow of nitrogen (20 barg: 0.115 g/min) and maintained at 250° C. under the nitrogen stream for 2 hours. The temperature was then reduced to 170° C. Once the temperature of the catalyst was at 170° C., steam was introduced to the reactor at a pressure of 3 barg (water feed rate: 0.059 g/min; nitrogen feed rate: 0.051 g/min) and these conditions were maintained for 19 hours. The water feed to the reactor was gradually replaced by an ethanol feed over a 2 hour period (ethanol feed rate: 0.402 g/min; nitrogen feed rate: 0.050 g/min). The temperature and pressure were then increased to 240° C. and 30 barg over a period of one hour, during which time, the ethanol feedstream was replaced by the reactant feedstream detailed in Table 1. The reactor was maintained at 240° C. and 30 barg and the performance of the catalyst in the preparation of ethylene from the reactant feedstream detailed in Table 1 is provided by the product composition after 90 hours on stream recorded in Table 3 below.

TABLE-US-00003 TABLE 3 Ethylene Ethane C.sub.4* Acetaldehyde Space (ppmw (ppmw (ppmw Time on on on Yield ethylene ethylene ethylene Example (g/l/hr) product) product) product) 2 929 271 3989 987 B 943 573 8079 1712 *Hydrocarbons containing four carbon atoms, primarily butenes.

[0088] As can be seen from the results presented in Table 3, the concentration of ethane present in the product composition when the process was started using the process of the present invention is significantly lower than that of comparative example B, wherein water was present during step (iii) of the start-up procedure of the process of the present invention.

Example 3 and Comparative Example C

[0089] The reactant feedstream used in the following examples is detailed in Table 4 below.

TABLE-US-00004 TABLE 4 Liquid Feed Ethanol (% wt) 48.24 Diethyl ether (% wt) 48.20 Water (% wt) 3.56 Feed Rate Liquid Feed Rate (g/min) 0.386 Nitrogen (g/min) 0.0917

[0090] The catalyst used in comparative example C was a used catalyst whose performance in the preparation of ethylene from the reactant feedstream detailed in Table 4 is provided by the initial product composition recorded in Table 5 below (the process temperature and pressure used for preparing the initial product composition were 240° C. and 30 barg).

[0091] In comparative example C, immediately after recording the performance of the used catalyst and whilst maintaining the reaction temperature and pressure in the reactor containing the used catalyst (240° C. and 30 barg), the reactant feedstream detailed in Table 4 above was ceased and replaced with a purge stream of nitrogen for 24 hours at a temperature of 240° C. and a pressure of 30 barg (nitrogen feed rate: 0.0917 g/min). Whilst maintaining a temperature of 240° C., the pressure was reduced to 2-3 barg and steam was passed over the catalyst for 23 hours (water feed rate: 0.059 g/min; nitrogen feed rate: 0.115 g/min). After the steam had been passed over the catalyst, the water feed was stopped and replaced with the reactant feed stream detailed in Table 4 above. The pressure was increased to 30 barg and the reaction conditions were maintained for a period of 72 hours. The performance of the steam regenerated catalyst in the preparation of ethylene from the reactant feedstream detailed in Table 4 is provided by the product composition recorded in Table 5 below.

[0092] In example 3, immediately after recording the performance of the catalyst in comparative example C and whilst maintaining the reaction temperature and pressure in the reactor, the reactant feedstream was ceased and replaced with a purge stream of nitrogen for 30 minutes at a temperature 240° C. and a pressure of 30 barg (nitrogen feed rate: 0.0917 g/min). The pressure was then reduced to 2 barg for a further 5 hours. Whilst maintaining a temperature of 240° C., the pressure was increased to 3 barg and steam was passed over the catalyst for 18 hours (water feed rate: 0.059 g/min; nitrogen feed rate: 0.115 g/min). After the steam had been passed over the catalyst, the water feed was stopped and replaced with a nitrogen purge at 240° C. and 3 barg (0.115 g/min) for a period of 25 hours. The catalyst was then cooled to 180° C. under 3 barg of nitrogen. Once the catalyst had cooled to 180° C., an ethanol feedstream was introduced to the reactor and the temperature and pressure of the reactor was increased to 240° C. and 30 barg (ethanol feed rate: 0.402 g/min; nitrogen feed rate: 0.115 g/min). Once the temperature and pressure had reached 240° C. and 30 barg, the ethanol feedstream was replaced with the reactant feedstream detailed in Table 4. The performance of the regenerated catalyst in the preparation of ethylene from the reactant feedstream detailed in Table 4 is provided by the product composition recorded in Table 5 below.

TABLE-US-00005 TABLE 5 Ethylene Ethane C.sub.4* Acetaldehyde Space (ppmw (ppmw (ppmw Time on on on Yield ethylene ethylene ethylene Example (g/l/hr) product) product) product) Initial 722 954 7399 2175 C 703 750 5890 974 3 637 393 7588 744 *Hydrocarbons containing four carbon atoms, primarily butenes.

[0093] As can be seen from the results presented in Table 5, the concentration of ethane present in the product composition when the catalyst was regenerated and started using the process of the present invention is significantly lower than the initial performance of the used catalyst and the performance of the catalyst which has been regenerated in accordance with comparative example C.