Catalyst system and process for conversion of a hydrocarbon feed utilizing the catalyst system

Abstract

The present invention relates to a catalyst system comprising: i. a first layer of a hydrocarbon conversion catalyst, the hydrocarbon conversion catalyst comprising: a first composition comprising a platinum group metal on a solid support; and a second composition comprising a transition metal on an inorganic support; ii. a second layer comprising a cracking catalyst; and to a process for conversion of a hydrocarbon feed utilizing this catalyst system.

Claims

1. A catalyst system comprising: i. a first layer of a hydrocarbon conversion catalyst, the hydrocarbon conversion catalyst comprising: a first composition comprising a dehydrogenation active metal on a solid support, the solid support comprising aluminum oxide, silicon dioxide, zirconium dioxide, titanium dioxide, magnesium oxide, calcium oxide, or a mixture thereof; and a second composition comprising a transition metal on an inorganic support, the inorganic support comprising silicon dioxide, a zeolite, or a mixture thereof; and ii. a second layer comprising a cracking catalyst, the cracking catalyst comprising a molecular sieve, wherein a weight ratio of the first layer to the second layer is from 50:1 to 1:20.

2. The catalyst system according to claim 1, wherein the molecular sieve is a zeolite and/or silicalite.

3. The catalyst system according to claim 2, wherein the molecular sieve of the cracking catalyst is a zeolite selected from the group consisting of ZSM-5, ZSM-11, SAPO-11, and mixtures thereof.

4. The catalyst system according to claim 1, wherein the dehydrogenation active metal is selected from the group consisting of platinum, palladium, iridium, chromium, and mixtures thereof.

5. The catalyst system according to claim 1, wherein the solid support comprises aluminum oxide, a mixture of silicon dioxide and zirconium dioxide, a mixture of magnesium oxide and aluminum oxide, or a mixture of calcium oxide and aluminum oxide.

6. The catalyst system according to claim 1, wherein the transition metal is selected from the group consisting of molybdenum, tungsten, rhenium, and mixtures thereof.

7. The catalyst system according to claim 1, wherein the second composition further comprises a mixed magnesium-aluminium oxide or a mixed calcium-aluminium oxide.

8. The catalyst system of claim 1, wherein the zeolite of the inorganic support is selected from the group consisting of ZSM-5, X-zeolite, Y-zeolite, beta-zeolite, MCM-22, ferrierite, and mixtures thereof.

9. The catalyst system of claim 1, wherein the transition metal is present in the second composition in an amount from 1 to 15 percent by weight.

10. The catalyst system of claim 1, wherein the second composition further comprises a doping agent selected from the group consisting of zinc, gallium, indium, lanthanum, and mixtures thereof.

11. The catalyst system of claim 10, wherein the doping agent is present in the second composition in an amount from 0.1 to 10 percent by weight.

12. The catalyst system of claim 1, wherein the first composition and the second composition are present as a physical mixture.

13. The catalyst system of claim 1, wherein the weight ratio of the first layer to the second layer is from 40:1 to 1:1.

14. A process for conversion of a hydrocarbon feed stream comprising a paraffin to a product stream comprising olefins, the process comprising contacting the hydrocarbon feed stream with the catalyst system according to claim 1.

15. The process according to claim 14, wherein the paraffin is selected from the group consisting of ethane, propane, butane, pentane, and mixtures thereof.

16. The process according to claim 14, wherein the process is carried out at a temperature in the range of 200−800° C.

17. The process according to claim 14, wherein the hydrocarbon feed stream contacts the hydrocarbon conversion catalyst first and the cracking catalyst second.

18. The process according to claim 14, wherein the catalyst system is pretreated by contacting the catalyst system with an inert gas, an oxidizing gas, a reducing gas, or mixtures thereof, at a temperature in the range of 250° C. to 850° C., prior to contacting with the hydrocarbon feed stream.

19. The process of claim 14, wherein the hydrocarbon feed stream comprises propane, the product stream comprises ethylene, and a selectivity to ethylene in product stream is increased, relative to a process in which the cracking catalyst of the catalyst system is absent.

Description

EXPERIMENTAL RESULTS

(1) In the examples section below, the conversion of propane into olefins, preferably ethylene and butene, has been investigated using catalyst systems according to the present invention and one comparative example.

(2) For each test, the reaction zone was set up so that the cracking catalyst is placed downstream to the hydrocarbon conversion catalyst. Weight ratio of the hydrocarbon conversion catalyst to the cracking catalyst used was approximately 40:1. C3H8 was fed to contact first with the hydrocarbon conversion catalyst and then with the cracking catalyst. The reaction zone was maintained at approximately 485 to 490° C., 0.1 bar gauge, and WHSV of approximately 0.15 to 0.2 h.sup.−1. The results were measured at time on stream approximately 115-120 hours and are shown in the table below.

(3) For the hydrocarbon conversion catalyst as used in the examples, a catalyst has been utilized with a first and a second composition.

(4) The first composition containing 5 wt-% of platinum and 1.4 wt-% ytterbium on a SiO.sub.2—ZrO.sub.2 support was prepared by impregnating a solution of chloroplaiinic acid hexahydrate and a solution of ytterbium trinitrate onto powder of SiO.sub.2—ZrO.sub.2 mixture, then the resulting material was dried at 100° C. for 2 hours, followed by calcination under air at 700° C. for 3 hours.

(5) For the second composition containing 7 wt % W, 4 wt % Y-zeolitc, 9 wt % Mg—Al oxide, and balancing SiO2 was prepared by impregnating a solution of ammonium metatungstate hydrate on a mixture of SiO2 and Y-zeolite, then dried at 110° C. for 3 hours. Then the resulted material was then mixed with Mg—Al—CO3 layered double hydroxide followed by calcination under air at 550° C. for 2 hours.

(6) 1 part by weight of the first composition and 1 part by weight of the second composition were physically mixed together to form the hydrocarbon conversion catalyst.

(7) Different cracking catalyst was used in each example as follow.

(8) Example 1 (comparative): No cracking catalyst was used

(9) Example 2 (comparative): a mixture of SiO.sub.2 and Al.sub.2O.sub.3 was used

(10) Example 3: a ZSM-5 zeolite with Si/Al ratio of 500 was used

(11) Example 4: a silicalite was used

(12) Example 5: a SAPO-34 zeolite was used

(13) Example 6: a SAPO-11 zeolite was used

(14) Example 7: a β-zeolite was used

(15) TABLE-US-00001 TABLE 1 Result C3H8 Selectivity (% wt) Conversion Total Example (% wt) Olefins CH4 C2H4 C2H6 C3H6 C4H8 C4H10 C5+ Example 1 21.842 61.034 0.721 1.462 21.991 41.241 16.496 14.361 2.979 Example 2 22.353 65.496 0.867 3.302 20.870 41.910 19.052 11.570 1.230 Example 3 21.812 55.365 0.946 4.125 23.048 35.939 13.996 12.507 2.307 Example 4 21.574 47.887 1.074 3.939 24.368 30.365 11.611 17.197 4.051 Example 5 23.127 57.680 0.891 2.835 23.072 37.907 15.330 13.479 2.601 Example 6 23.028 56.044 0.978 3.283 23.354 37.236 13.916 12.453 2.559 Example 7 21.401 60.015 0.964 3.292 22.557 38.708 16.903 12.329 2.049

(16) It can be seen from the results above that when the catalyst system include zeolite or silicalite as a downstream layer, butenes selectivity was decreased while ethylene selectivity was increased comparing to when no cracking catalyst was used or a normal mixture of SiO.sub.2—Al.sub.2O.sub.3 was used as a downstream layer of the catalyst system.

(17) It can be further noticed that when ZSM-5 was used as a cracking catalyst, the increase of ethylene selectivity was highest. When β-zeolite was used, ethylene selectivity was increased but butenes selectivity was not reduced. When silicalite was used, butenes selectivity was decreased, and ethylene selectivity was increased, however, more of C5+ which is usually an undesired by-product was also produced. The features disclosed in the foregoing description and in the claims may, both separately and in any combination thereof, be material for realizing the invention in diverse forms.

(18) The features disclosed in the foregoing description and the claims may, both separately and in any combination thereof, be material for realizing the invention in diverse forms thereof.