PROCESS FOR THE ACTIVATION OF OXIDISED CATALYSTS

Abstract

The present invention relates to a process for the liquid phase activation of catalysts. Such activated catalysts have particular utility in hydrogenation of aldehydes to alcohols. As such, the present invention relates to a process for the hydrogenation of aldehydes to alcohols in the presence of a catalyst which has been activated in accordance with the first aspect of the present invention.

Claims

1. A process for the activation of a catalyst comprising: (a) providing a reactor comprising a solid catalyst which is to be activated by reduction; (b) supplying a liquid feed stream and a reducing agent to the reactor; (c) operating the reactor such that the reducing agent causes activation of the catalyst; (d) recovering a liquid stream and a gas stream from the reactor; and wherein, the peak water concentration in the liquid stream recovered in step (d) is substantially maintained at less than 1.5 wt % by one or more of: controlling the water concentration of the liquid feed stream supplied in step (b); controlling the rate of recovery of the liquid stream recovered in step (d); and, removal of water produced within the reactor.

2. The process according to claim 1, wherein at least a portion of the liquid stream recovered in step (d) may be recycled and supplied to the reactor in step (b).

3. The process according to claim 1, wherein the liquid stream recovered from the reactor in step (d) can be subject to a treatment and then reused (recycled) alongside the liquid feed stream to be fed to the reactor in step (b).

4. The process according to claim 3, wherein said treatment comprises a drying process.

5. The process according to claim 1, wherein the reactor provided in step (a) is that in which the subsequent reaction to be catalyzed is to be carried out, such that the catalyst activation process is performed in situ.

6. The process according to claim 1, wherein the catalyst to be activated is a copper containing catalyst.

7. The process according to claim 1, wherein the liquid feed stream fed to the reactor in step (b) is a product produced in the subsequent reaction in which the catalyst will be used.

8. The process according to claim 7, wherein the liquid feed stream is an alcohol or alkane.

9. The process according to claim 8, wherein the liquid feed is an alcohol.

10. The process according to claim 9, wherein the liquid feed is butanol.

11. The process according to claim 1, wherein the liquid feed stream has a water concentration of 0.1 wt % or less.

12. The process according to claim 1, wherein the reducing agent is a gaseous reducing agent.

13. The process according to claim 12, wherein the reducing agent is hydrogen and wherein the reducing agent may be added to the reactor continuously or in pulses.

14. The process according to claim 1, wherein the initial concentration of reducing agent may be from about 2 mol % to about 100 mol %.

15. The process according to claim 1, wherein the concentration of reducing agent increases to a final concentration of about 100 mol % during the activation process.

16. The process according to claim 1, wherein the liquid feed stream and the reducing agent may be supplied separately or they may be combined before being fed to the reactor.

17. The process according to claim 2, wherein the recycle stream is supplied directly to the reactor or combined with one, or both, of the liquid feed stream and the reducing agent before being supplied to the reactor.

18. The process according to claim 1 carried out in the presence of an inert gas.

19. The process according to claim 1, wherein the process is carried out at a temperature between an initial ambient temperature to a about 200° C.

20. The process according to claim 19, wherein the process is carried out at a temperature between about 130° C. to about 180° C.

21. The process according to claim 1, wherein the process temperature may be increased by heating the liquid feed stream.

22. The process according to claim 1, wherein the process temperature may be increased by heating the recycle stream where present.

23. The process according to claim 1, wherein a positive total gas pressure is provided during the activation process.

24. The process according to claim 1, wherein the flow of the liquid stream over the catalyst is from about 5 to about 150 m.sup.3/m.sup.2h.

25. The process according to claim 1, further comprising an initial catalyst wetting process.

26. The process according to claim 25, wherein the wetting process employs a wetting liquid which is the same as the liquid feed stream which will be supplied in step (b) of the subsequent activation process.

27. The process according to claim 24, wherein following the wetting process, any water present is removed by purging the reactor such that the water content is less than about 1.5 wt %.

28. The process according to claim 1, wherein there is an initial warm up at the start of the activation process, and any water present is removed by purging the reactor to maintain the water concentration at less than about 1.5 wt %.

29. A process for hydrogenating an aldehyde comprising contacting an aldehyde with hydrogen in the presence of a catalyst activated in a process according to claim 1.

30. The process for the hydrogenation of an aldehyde to the corresponding alcohol in accordance with claim 29, wherein the catalyzed reaction is performed in situ in the same reactor vessel as the activation process.

31. The process for the hydrogenation of an aldehyde to the corresponding alcohol in accordance with claim 29, wherein the activation process comprises: (a) providing a reactor comprising a solid catalyst which is to be activated by reduction; (b) supplying a liquid feed stream and a reducing agent to the reactor; (c) operating the reactor such that the reducing agent causes activation of the catalyst; (d) recovering a liquid stream and a gas stream from the reactor; and wherein, the peak water concentration in the liquid stream recovered in step (d) is substantially maintained at less than 1.5 wt % by one or more of: controlling the water concentration of the liquid feed stream supplied in step (b); controlling the rate of recovery of the liquid stream recovered in step (d); and, removal of water produced within the reactor is performed and then following activation of the catalyst, the reactor and/or catalyst bed temperature is adjusted to a temperature suitable for carrying out the hydrogenation of the aldehyde to the corresponding alcohol, including switching the liquid feed stream of step (b) of the activation process to the desired aldehyde feed stream for the hydrogenation reaction.

32. A process for the hydrogenation of an aldehyde to the corresponding alcohol in accordance with claim 29, wherein the aldehyde is selected from butyraldehyde, valeraldehyde, 2-ethyl hexenal, 2-propyl heptenal, iso-nonyl aldehyde and detergent range aldehydes.

33. Use of a catalyst activated in accordance with claim 1 in a hydrogenation reaction.

Description

[0062] The present invention will now be described, by way of example, with reference to the accompanying figures in which:

[0063] FIG. 1 is a schematic diagram of the process of the present invention;

[0064] FIG. 2 is a schematic diagram of an alternative arrangement of the process of the present invention.

[0065] It will be understood by those skilled in the art that the drawings are diagrammatic and that further items of equipment such as feedstock drums, pumps, vacuum pumps, compressors, gas recycling compressors, temperature sensors, pressure sensors, pressure relief valves, control valves, flow controllers, level controllers, holding tanks, storage tanks and the like may be required in a commercial plant. Provision of such ancillary equipment forms no part of the present invention and is in accordance with conventional chemical engineering practice.

[0066] As illustrated in FIG. 1, a liquid feed stream is fed in line 1 to reactor 2 containing a catalyst. Gaseous reducing agent is fed in line 3 to the reactor 2. As illustrated the liquid stream and the gaseous reducing agent are fed separately. However, alternatively, they may be combined before being fed to the reactor 2.

[0067] A gaseous purge will be removed in line 4 and liquid stream is removed in line 5. During the activation process the peak water concentration in the steam recovered in line 5 will be substantially maintained at less than 1.5 wt %. Where the stream is found to have a peak water content equal to or above 1.5 wt %, the water content of the stream added to the reactor in line 1, or the rate of removal of liquid stream 5 may be adjusted to achieve the required peak water content. Additionally, or alternatively, water may be removed from the reactor in a liquid and/or gas purge.

[0068] An alternative arrangement is illustrated in FIG. 2. As in FIG. 1, a liquid feed stream is fed in line 1 to reactor 2 containing a catalyst. Gaseous reducing agent is fed in line 3 to the reactor 2. As illustrated the liquid feed stream and the gaseous reducing agent are fed separately. However, alternatively, they may be combined before being fed to the reactor 2. A gaseous purge will be removed in line 4 and liquid stream is removed in line 5.

[0069] In this alterative arrangement, the liquid stream recovered in line 5 is separated with a recovery stream removed in line 6. The remainder of the liquid stream is pumped for treatment using pump 7 via line 8 to a heat exchanger 9 before being recycled to the reactor 2 in line 10. In the illustrated arrangement, the stream recycled in line 10 is mixed with the liquid feed stream 1 before they are added to the reactor 2. However, it will be understood that the recycle stream 10 may be fed directly to the reactor or it may be combined with the gaseous reducing agent or both the gaseous reducing agent and the liquid feed stream.

[0070] Generally, the recycle stream will be cooled in the heat exchanger 9 before being recycled to the reactor 2 in line 10. However, where appropriate the heat exchanger may be used to heat the recycle stream. For example, heating may be required during start-up of the activation process.

[0071] As described above there are various options which may be used in the process of the present invention. To aid understanding one example of the activation process of the present invention is set out below. However, it will be understood that this example is simply to assist in understanding and is not limiting.

[0072] Activation Process for an Aldehyde to Alcohol Hydrogenation Catalyst

[0073] A commercially available oxidised copper containing catalyst with a chromium promoter, known to be suitable for hydrogenation of aldehyde ethyl propyl acrolein (EPA, 2-ethyl hexenal), is loaded into a reactor (the reactor also being suitable for the performance of the hydrogenation of the aldehyde to its corresponding alcohol). The catalyst is a solid heterogenous catalyst provided as a catalyst bed in the reactor.

[0074] Prior to the catalyst being rendered in a form suitable to act as a catalyst for the aldehyde conversion reaction it is necessary that the oxidized catalyst be activated by means of reduction. In accordance with the present invention the activation may be advantageously performed utilizing a hydrogen gas as a reducing agent whilst providing an inert liquid feed stream; in this case the liquid feed stream is “dry” butanol (99+%) with a water content below 0.1 wt %. The liquid feed stream acts as a heat sink for the exothermic reduction of the copper containing catalyst to avoid the problems associated with overheating. However, accumulated water levels as low as 2.5 wt % have been found to adversely affect the final activity of the catalyst for its intended use, and in accordance with the present invention control of the activation process water levels, as observed in the recovered liquid stream, is advantageous.

[0075] Once the catalyst bed has been loaded into the desired reactor a catalyst wetting procedure is employed as an initial step, prior to commencing the catalyst activation process. “Dry” butanol is fed into the reactor as the catalyst wetting liquid. As such in this example the butanol is utilised as both the wetting liquid, and later, as the activation liquid feed stream. In alternative arrangements, the wetting liquid and activation liquid feed stream may vary. A positive pressure is maintained in the reactor to ensure that the liquid remains in its liquid state. Suitably a pressure of between 0.1 and 0.4 MPa is achieved by supplying nitrogen as an inert gas stream. A wetting liquid recycle loop is established, and sufficient butanol is fed into the reactor to allow the catalyst to be wetted and to fill the pipes, vessels and pump of the wetting liquid recycle loop; once sufficient wetting liquid is provided introduction of further wetting liquid is stopped. It is not necessary that the wetting liquid be recycled through the reactor during the wetting process, however, in the present example this was carried out to ensure that wetting liquid flows through the catalyst bed and achieves adequate wetting in a good time.

[0076] During the wetting procedure, a sample of the recirculating wetting liquid is removed and the concentration of any water present in the liquid is analysed for. In the case that the concentration of water present is unacceptably high the removal of water is necessary. Reduction of the water concentration to less than 1.5 wt % (if necessary), prior to beginning the activation process is suitable, and in the present case a reduction to 1.5 wt % was achieved by the introduction of fresh butanol feed into the reactor, whilst recycle of the butanol used for the wetting procedure continues via the recycle loop.

[0077] Once the catalyst has been fully wetted, and the level of water in the recirculating wetting liquid is reduced to less than 1.5 wt % the activation process may begin.

[0078] Throughout the wetting process inert nitrogen gas has been fed into the reactor to establish a positive pressure, and this positive pressure is maintained for the activation process which follows. Hydrogen, which will act as the reducing agent, is now introduced to the nitrogen gas stream up to a level of 30 mol % of the total nitrogen gas stream. Once the reducing agent is introduced to the reactor the temperature of the catalyst bed in the reactor should be monitored. Initially, the temperature of the catalyst bed is raised via heating of the butanol passing through the recycle loop which is reintroduced into the reactor, alongside any further butanol liquid feed stream which may be introduced to the reactor. The heating of the catalyst bed is controlled to provide a maximum temperature increase of 5° C. per hour. In this way, localized overheating of the catalyst in the catalyst bed may be avoided. Heating is continued until a temperature of about 130° C. is achieved, which is the initial temperature at which activation is established for the copper containing catalyst. Once activation is in progress the temperature of the catalyst bed is to be maintained at about 130° C. by the exothermic nature of the reduction reaction, and by heating and/or cooling the butanol recycle stream as necessary. More especially, where a temperature rise of more than 20° C. is observed then the recycled butanol stream should be cooled. Throughout this activation procedure the butanol stream removed from the reactor for recycling is sampled and monitored for water concentration. When the water concentration of the stream removed from the reactor approaches 1.5 wt % then the rate of introduction of fresh butanol in the liquid feed stream and the rate of removal of the butanol from the reactor are adjusted up until the water concentration is maintained at below 1.5 wt %. The introduction of hydrogen can also be reduced or ceased to prevent any more water being produced in the reactor which will allow the water concentration to be reduced when feeding in fresh liquid feed whilst removing some butanol from the reactor.

[0079] Once the activation process has proceeded to a point at which the level of hydrogen in the inert nitrogen gas stream exiting the reactor equals 30 mol %, and the temperature of the catalyst bed has stabilised such that no temperature rise is observed, and water generation has ceased then the hydrogen concentration may be increased in 10 mol % increments to 100 mol %.

[0080] In addition, at this stage the pressure in the reactor may be increased up to no more than 1.5 MPa, and the temperature observed in the catalyst bed is now closely monitored to ensure that it does not exceed 150° C., and is substantially maintained at 130° C. Control of the catalyst bed temperature is achieved as described above. If the temperature rise in the catalyst bed is deemed to be too high then the pressure increase should be halted until the temperature of the catalyst bed stabilizes. Throughout this procedure the water concentration of the removed butanol liquid stream is sampled and the concentration of water controlled at a level of less than 1.5 wt % as described above.

[0081] When there is no temperature increased observed, and no further water generation then the temperature of the catalyst bed is increased to 150° C. in 5° C. per hour increments. Each temperature increase increment is maintained for 2 hours to allow the temperature across the catalyst bed to stabilise and avoid localized overheating. During this heating ramp the butanol recycle and feed streams are maintained and sampled to ensure no further reduction is occurring.

[0082] Once the reactor pressure has been increased, and the temperature rise has stabilized at 150° C., the water concentration in the butanol removed for recycle has stopped increasing, and no hydrogen is being consumed, then the catalyst activation is deemed to be complete.

[0083] Once the activation of the catalyst is deemed to be complete then the reactor with the activated catalyst in situ may be readied for use in the subsequent process of hydrogenation of an aldehyde feed. More especially, the temperature of the catalyst bed may be reduced via the cooling of the recycle of the butanol stream which continues to be reintroduced to the reactor. Additionally, the hydrogen gas stream may be replaced or diluted with an alternative gas stream. Suitable hydrogenation reaction conditions are known to the person skilled to the art.

[0084] Although the above example concerns a copper containing catalyst for use in hydrogenation of an aldehyde, similar activation processes can be employed to activate other oxidised catalysts.

EXAMPLES

[0085] The present invention will now be described by way of example with reference to the following Examples and Comparative Examples.

[0086] In examples 1 to 4 the reactor was charged with 250 ml catalyst (⅛″ tablets 50% CuO 50% Cr.sub.2O.sub.3) in all examples.

Comparative Example 1

[0087] A gas phase activation was performed using a stream of 1.7 mol % hydrogen in nitrogen which was passed over the catalyst at 100 NL/h and the bed temperature raised to approximately 175° C. The exotherm was followed as it moved down the catalyst bed and the temperatures stabilised after 30 hours. The hydrogen concentration was then incrementally increased to 100 mol %, before increasing the pressure from approximately 0.1 MPa to 2 MPa. The bed temperatures were reduced to 100° C. before wetting the catalyst with butanol and establishing recycle flow prior to introduction of aldehyde feed and the assessment of the catalysts activity.

[0088] In each of the following examples, the liquid phase activation procedure used is as described above with any modifications described in the example details provided below.

Comparative Example 2

[0089] In this example, the activation liquid feed was crude butanol containing 0.4 wt % water. No butanol recovery was applied and no water was removed from the reactor during the liquid phase activation process. The peak water level concentration reached was 2.55 wt. %. As such, this comparative example represents a typical known liquid phase activation method where water concentration is not controlled.

Example 3

[0090] In this example, the activation liquid feed was pure n-butanol (containing less than 0.1 wt % water) and a continuous butanol recovery rate is employed to control the concentration of water in the liquid stream. The peak water level reached was 1.27 wt %.

Comparative Example 4

[0091] Comparative Example 4 was performed to confirm the effect of increasing the water concentration. In this example, the activation liquid feed was crude butanol. Additional water was dosed in the circulating butanol prior to activation to give an initial water concentration of 3.4 wt %. No recovery of the butanol was performed to limit the water concentration. The peak water concentration was 6.29 wt %. It will be understood by the person skilled in the art that the relative volume of catalyst/liquid inventory is significantly reduced on an experimental rig, such as that used for the present examples as compared to a commercial unit, and so the dosing of additional water in this example was required to give an experimental peak water concentration close to the peak water levels seen on commercial units.

[0092] After completion of each of the activation procedures described above, the activity of the reduced catalyst was measured in a hydrogenation process test using a mixed butyraldehyde feedstock which contained >95 wt % aldehydes (n:i ratio in the range 6-12:1). The conditions for the activity tests are given in Table 1 below:

TABLE-US-00001 TABLE 1 Aldehyde Feed Rate LHSV* = 1 Inlet Temperature, ° C. 150 Peak Temperature, ° C. 168 Recycle to Feed Ratio 20:1 Vent Flow Rate, nL/h  10 *= Liquid hourly space velocity

[0093] A summary of experiments performed under these standard conditions showing the effect of observed peak water concentration during the activation process on the subsequent catalyst activity for mixed butyraldehyde hydrogenation using commercial copper-chrome catalyst are set out in Table 2. The catalyst activity is measured as the aldehyde slip during the initial period of operation at the standard conditions above.

TABLE-US-00002 TABLE 2 Peak Water During Aldehyde Activation Activation Slip Comments (wt %) (ppm) Comparative Gas Phase N/A 301 Example 1 Comparative Crude Butanol used 2.55 985 Example 2 (0.4 wt % water) Example 3 Dry Butanol— 1.27 361 Continuous Removal Comparative High Initial Water 6.29 1381 Example 4

[0094] It can therefore be seen that the catalyst activated in accordance with the processes of the present invention produced an activation which was similar in performance to that activated in gas phase activation.

[0095] Temperature programmed reaction studies support the observations of the impact of water being present in the activation process on reducing surface area which it is believed leads to the reduced activity in the subsequent aldehyde hydrogenation process. In this experiment, the effect of the presence of water in the reducing atmosphere (referred to as a “wet” atmosphere) on the copper metal area of two catalysts was investigated.

[0096] 1. A sample of a copper-chromite catalyst was reduced in a water/hydrogen/helium stream comprising 2.5 mol % water and 5 mol % hydrogen at a temperature of from ambient to 220° C. Similarly, a sample was reduced in a hydrogen/helium stream comprising 5 mol % hydrogen at a temperature of from ambient to 220° C. The copper metal areas of the sample were measured by N.sub.2O decomposition at 60° C. The obtained relative copper surface areas from reactive frontal chromatograms of N.sub.2O decomposition on samples following reduction in dry atmosphere or in wet atmosphere are shown in Table 3, below. Reduction in a “wet” atmosphere leads to a reduction in the measured copper surface area.

[0097] Table 3 shows the measured relative copper surface area from Reactive Frontal Chromatograms of N.sub.2O decomposition over the copper-chromite catalyst following temperature programmed reduction (TPR) of the sample in either an H.sub.2/He stream or a H.sub.2/H.sub.2O/He stream

TABLE-US-00003 TABLE 3 Relative Active Activation Stream Copper Surface Area 2.5 mol % H.sub.2O/5 mol % H.sub.2/He 0.7 5 mol % H2/He 1.0

[0098] 2. A sample of a copper-alumina catalyst was reduced in a water/hydrogen/helium stream comprising 2.8 mol % water and 5 mol % hydrogen at a temperature of from ambient to 220° C. Similarly, a sample was reduced in a hydrogen/helium stream comprising 5 mol % hydrogen at a temperature of from ambient to 220° C. The copper metal areas of the sample were measured by N.sub.2O decomposition at 60° C. The obtained relative copper surface areas from reactive frontal chromatograms of N.sub.2O decomposition on samples following reduction in dry atmosphere or in wet atmosphere are shown in Table 4 below. Reduction in a “wet” atmosphere leads to a reduction in the measured copper surface area.

[0099] Table 4 shows the measured relative copper surface areas from Reactive Frontal Chromatograms of N.sub.2O decomposition over a copper-alumina catalyst following temperature-programmed reduction (TPR) of the sample in either an H.sub.2/He stream or a H.sub.2/H.sub.2O/He stream

TABLE-US-00004 TABLE 4 Relative Active Copper Activation Stream Surface Area 2.8 mol % H.sub.2O/ 0.8 5 mol % H.sub.2/He 5 mol % H2/He 1.0