Fischer-Tropsch Catalyst Performance Enhancement Process

Abstract

The present invention relates to a process for treating a catalyst to improve performance, and more specifically to a process for treating a Fischer-Tropsch catalyst using a high hydrogen syngas to improve catalyst performance.

Claims

1. A process for improving performance of a Fischer-Tropsch catalyst comprising the steps of: (a) contacting the catalyst with hydrogen or syngas at a temperature in the range of from about 200 C. to about 450 C., under a pressure in the range of from about 0 barg to about 50 barg, and a GHSV in the range of from about 500 hr.sup.1 to about 5000 hr.sup.1, for a period of time of at least 1 hour to provide a reduced catalyst; (b) contacting the reduced catalyst of step (a) with syngas comprising H.sub.2:CO in a ratio in the range of from about 1:1 to about 2.1:1, in a Fischer-Tropsch synthesis reactor under a pressure in the range of from about 0 barg to about 50 barg and a GHSV of over 1000 hr.sup.1, at a temperature in the range of from about 100 C. to about 280 C.; (c) increasing the ratio of H.sub.2:CO of the syngas to a ratio of at least 3:1 at a pressure in the range of from about 30 barg to about 42 barg, for a period of time of at least 1 hour at a temperature in the range of from about 160 C. to about 250 C., and a GHSV in the range of from about 1000 hr.sup.1 to about 8000 hr.sup.1; and (d) decreasing the ratio of H.sub.2:CO of the syngas to a ratio in the range of from about 1:1 to about 2.1:1, at a GHSV in the range of from about 1250 hr.sup.1, under a pressure in the range of from about 30 barg to about 42 barg, and at a temperature in the range of from about 160 C. to about 280 C.

2. A process for improving performance of a Fischer-Tropsch catalyst comprising the steps of: (a) contacting the catalyst with hydrogen or syngas at a temperature in the range of from about 200 C. to about 450 C., under a pressure in the range of from about 0 barg to about 50 barg, and a GHSV in the range of from about 500 hr.sup.1 to about 5000 hr.sup.1, for a period of time of at least 1 hour to provide a reduced catalyst; (b) contacting the reduced catalyst of step (a) with syngas comprising H.sub.2:CO in a ratio in the range of from about 1:1 to about 2.1:1, in a Fischer-Tropsch synthesis reactor under a pressure in the range of from about 0 barg to about 50 barg and a GHSV of over 1000 hr.sup.1, at a temperature in the range of from about 100 C. to about 280 C.; (c) replacing the syngas with either pure hydrogen or a hydrogen/nitrogen mixture, at a pressure in the range of from about 30 barg to about 42 barg for a period of time of at least 1 hour at a temperature in the range of from about 160 C. to about 250 C. and a GHSV in the range of from about 1000 hr.sup.1 to about 8000 hr.sup.1; and (d) decreasing the hydrogen level and restoring a ratio of H.sub.2:CO of the syngas to a ratio in the range of from about 1:1 to about 2.1:1, at a GHSV in the range of from about 1250 hr.sup.1, under a pressure in the range of from about 30 barg to about 42 barg, and at a temperature in the range of from about 160 C. to about 280 C.

3. A process for improving performance of a Fischer-Tropsch catalyst comprising the steps of: (a) contacting the catalyst with hydrogen or syngas at a temperature in the range of from about 200 C. to about 450 C., under a pressure in the range of from about 0 barg to about 50 barg, and a GHSV in the range of from about 500 hr.sup.1 to about 5000 hr.sup.1, for a period of time of at least 1 hour to provide a reduced catalyst; (b) contacting the reduced catalyst of step (a) with syngas comprising H.sub.2:CO in a ratio of from about 1:1 to about 2:1, under a pressure in the range of from about 0 barg to about 50 barg and a GHSV of over 1000 hr.sup.1, at a temperature in the range of from about 100 C. to about 280 C.; (c) eliminating the CO from the syngas of step (b) for a period of time of at least 1 hour; and (d) reintroducing the CO to provide syngas with a ratio of H.sub.2:CO in the range of from about 1:1 to about 2.1:1, at a GHSV of about 1250 hr.sup.1, under a pressure in the range of from about 30 barg to about 42 barg, and at a temperature in the range of from about 160 C. to about 280 C.

4. The process of claim 1, wherein the Fischer-Tropsch reactor is a fixed bed or tubular reactor.

5. The process of claim 1, wherein the Fischer-Tropsch reactor is a slurry reactor.

6. The process of claim 1, wherein following step (a) the catalyst is passivated prior to step (b).

7. The process of claim 1, wherein step (a) occurs within the Fischer-Tropsch synthesis reactor.

8. The process of claim 1, wherein step (a) occurs in a reactor other than the Fischer-Tropsch synthesis reactor.

9. The process of claim 1, wherein the temperature if step (b) is in the range of about 160 C. to about 240 C.

10. The process of claim 1, wherein the temperature if step (b) is in the range of about 160 C. to about 230 C.

11. The process of claim 1, wherein the catalyst is CoZnO.

12. The process of claim 1, wherein the catalyst is CoTiO.sub.2.

13. The process of claim 1, wherein the catalyst is CoMnTiO.sub.2.

14. The process of claim 2, wherein the Fischer-Tropsch reactor is a fixed bed or tubular reactor.

15. The process of claim 2, wherein the Fischer-Tropsch reactor is a slurry reactor.

16. The process of claim 2, wherein the catalyst is CoZnO, CoTiO.sub.2, or CoMnTiO.sub.2.

17. The process of claim 3, wherein the Fischer-Tropsch reactor is a fixed bed or tubular reactor.

18. The process of claim 3, wherein the Fischer-Tropsch reactor is a slurry reactor.

19. The process of claim 3, wherein the catalyst is CoZnO, CoTiO.sub.2, or CoMnTiO.sub.2.

Description

[0060] While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the processes described herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.

[0061] Brief data is provided indicating the improvement above as detailed below.

[0062] For CoTiO2, an improvement in methane selectivity was seen after 700 hours on stream (at which point the high hydrogen feed appeared, i.e., H.sub.2:CO ratio being 10:1) from 8.4% to 6.5%, remaining at 6.6% after a further 1900 hours on stream, indicating the long term benefit. A repeat later in the same run also showed the improvement from 7.4% back to 6.6%.

[0063] For CoZnO, an improvement in methane selectivity from 16.0% to 12.4% was seen.

[0064] It has been discovered that during the reactor run that CO could be removed for approximately 24 hours and continuing with hydrogen only at about 200 C. at 42 barg from the feed and then brought back on line and the performance of the catalyst was significantly better.

[0065] The catalysts were fully reduced prior to the startup and the process of the present invention is not merely a regeneration step as there is an improvement on catalyst performance beyond the initial first conditions data. The process of the present invention does not merely provide a short term benefit as the performance gains may extend for thousands of hours or the life of the run.

[0066] Table 1 shows the performance of the fixed bed catalyst at 42 barg, H.sub.2:CO in a ratio of 1.8:1, 1250 hr.sup.1 GHSV with and without the described inventive treatment. All catalysts tested were fully reduced prior to syngas introduction and the time on stream (TOS) denotes the length of time under syngas conditions. Rows A and B show the effect of the treatment on FT performance before and after the treatment, while rows C and D show the effect on catalyst performance when the treatment in not carried out. In both cases the CO conversion was targeted to 62-65% and temperature was adjusted. Both tests were studied in the first 800 hours on stream to give a fair comparison. The treatment was completed as described herein, with CO removed and reintroduced slowly in stages until the desired gas composition is achieved. The catalyst used in this example was 10% Co/1% Mn on TiO.sub.2. Improved performance has been demonstrated to remain for >3000 hrs on stream.

TABLE-US-00001 TABLE 1 Comparative test - with and without the treatment TOS/hrs Conv CH4_Set T-Appl. A Before treatment 225 64.9 8.4 198 B After treatment 800 63.7 5.6 194 C Before treatment 100 63.5 8.0 198 D After (without treatment) 700 65.4 8.3 202

[0067] Table 2 shows the performance before and after the treatment at the same applied temperature. Performance data given is at 1250 hr.sup.1 GHSV, 30 barg, H.sub.2:CO ratio of 1.8:1 using a 10% Co/1% Mn/TiO.sub.2 catalyst.

TABLE-US-00002 TABLE 2 Effect at same temperature - showing higher conversion and better selectivity Before After Difference HOS 253.16 302.44 Applied Temperature 206 206 0 Conversion 64.01 70.11 6.1 CH4 Selectivity 11.02 10.1 0.92 C5+ Selectivity 81.28 82.73 1.45 C5+ Prod 119.97 132.98 13.01

[0068] Table 3 shows the improved performance after the treatment measured at similar conversion, with lower applied temperature using a 10% Co 1% Mn TiO.sub.2 catalyst at 1250 hr.sup.1 GHSV, 42 barg, H.sub.2:CO ratio of 1.8:1.

TABLE-US-00003 TABLE 3 Effect at same conversion - showing lower applied temperature and better selectivity Before After Difference HOS 527.6 705.35 Applied Temperature 206 202 4 Conversion 64.18 64.46 0.28 CH4 Selectivity 9.14 7.78 1.36 C5+ Selectivity 83.31 85.17 1.86 C5+ Prod 126.96 126.68 0.28

[0069] Table 4 shows the use of cobalt and manganese precursors also demonstrate the effect, at 1250 hr.sup.1 GHSV, H.sub.2:CO ratio of 1.8:1 and 42 barg on a 10% Co/1% Mn TiO.sub.2 catalyst.

TABLE-US-00004 TABLE 4 Catalyst using cobalt acetate and manganese acetate as precursors. Before After After @ same conv HOS 560 640 700 Applied Temperature 201 201 199 Conversion 60.8 66.8 61.4 CH4 Selectivity 7.4 6.5 5.6 C5+ Selectivity 86.5 87.5 88.4 C5+ Prod 113 128 120

[0070] Table 5 provides an example with Cobalt on titania using a 20% Co/TiO2 catalyst at 1500 hr.sup.1 GHSV, H.sub.2:CO ratio of 1.8:1, 42 barg in a fixed bed reactor. CO feed gas was stepped out slowly to leave a hydrogen/nitrogen mixture at 42 barg. The catalyst was held under the flowing hydrogen/nitrogen atmosphere for approximately 24 hours, before the gas feed returned to FT reaction condition.

TABLE-US-00005 TABLE 5 CoTiO.sub.2 catalyst (no Mn) Before After After @ same conv Temp 202 197 5 Conversion 63 63 CH.sub.4Sel 10.2 8.21 1.99 C.sub.5+Sel 82.1 86.0 +3.9 C.sub.5+Prod 145 153 +8

[0071] Table 6 shows the improved catalytic activity is also seen on other supports, in this example zinc oxide support was used, with 10% Cobalt. Conditions for operation were 1055 hr.sup.1 GHSV, H.sub.2:CO ratio of 1.8:1 and 32 barg. The treatment involved cooling to 180 C. and a low pressure hydrogen purge of the reactor for 8 days before restarting under syngas.

TABLE-US-00006 TABLE 6 CoZnO Catalyst Pre treatment Post treatment After @ same conv Applied Temp C. 210 C. 195.5 C. 14.5 xCO 54.6% 54.3% 0.3 sCH.sub.4 18.8% 9.8% 9.0 sC.sub.5+ 72.7% 83.3% +10.6

[0072] Tables 7 and 8 show the effect of the treatment under more forcing conditions, with both cases using a 10% Co/1% Mn/TiO.sub.2 catalyst at 1500 hr.sup.1 GHSV and 3600 hr.sup.1 GHSV respectively. In both cases the CO feed was dropped out gradually and held under H.sub.2/N.sub.2 for 24 hours before the reintroduction of CO, and return to pretreatment conditions, at lower applied temperature.

TABLE-US-00007 TABLE 7 Fixed bed catalyst test Before After After @ same conv Temp 215 203 12.0 Conversion 62.6 64.1 +1.5 CH.sub.4Sel 9.3 5.5 3.8 C.sub.5+Sel 81.0 89.2 +8.2 C.sub.5+Prod 144 159 +15.0

TABLE-US-00008 TABLE 8 High productivity reactor catalyst test Before After After @ same conv Temp 219 211 8.0 Conversion 65.3 67.5 +2.2 CH.sub.4Sel 8.2 5.5 2.7 C.sub.5+Sel 80.9 87.7 +6.8 C.sub.5+Prod 362 404 +42.0

[0073] Tables 9 and 10 both used a 10% Co 2% MnTiO2 catalyst at 1250 hr.sup.1 GHSV, H.sub.2:CO ratio of 1.8:1. Table 9 shows performance is improved by means of a lower applied temperature, better selectivity or productivity. Table 10 shows the benefit at the same applied temperature. In both cases the CO feed was removed stepwise to leave a H.sub.2/N.sub.2 flowing feed over the catalyst for 24 hours before CO was reintroduced and returned to FT condition prior to the treatment.

TABLE-US-00009 TABLE 9 Increased manganese catalyst test Prior to Post After @ treatment treatment same conv Applied Temperature 206 200.5 5.5 Conv. 62.96 65.89 2.93 CH4 Sel. 9.64 7.97 1.67 C5+ Sel 81.41 84.62 3.21 C5+ Prod 118.55 128.29 9.74

TABLE-US-00010 TABLE 10 Increased manganese catalyst test Prior to Post to After @ treatment treatment same Temp Applied Temperature 206 206 0 Conv. 63.78 72.53 8.75 CH4 Sel. 9.25 7.69 1.56 C5+ Sel 81.15 84.87 3.72 C5+ Prod 119.49 141.16 21.67

[0074] The performance of the cobalt/manganese catalysts showed an increase in performance, i.e., higher conversion at same temperature and lower methane selectivity.