Method for selectively producing propylene by catalytically cracking an olefinic hydrocarbon feedstock

Abstract

The invention provides a method for converting an olefinic hydrocarbon feedstock to propylene comprising: contacting a hydrocarbon feedstock under catalytic cracking conditions with a catalyst comprising a catalyst selected from the group consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ELAPO catalysts, ELASPO catalysts, rare earth exchanged catalysts from any of the preceding groups, and mixtures thereof, under cracking conditions to selectively produce propylene. The invention further provides a method for stabilizing a catalyst to steam from the foregoing group by ion exchange with a rare earth metal. A catalyst has enhanced stability as used herein when treated with a rare earth metal or metals in a concentration effective to provide a catalyst which exhibits a higher conversion of a hydrocarbon feedstock to propylene than does an equal quantity of an untreated sample of the same catalyst under the same conditions following exposure of each catalyst to steam for a period of at least 10 hours.

We claim:  
     
         1 . A method of converting an olefinic hydrocarbon feedstock to a high propylene content product comprising: contacting a hydrocarbon feedstock under catalytic cracking conditions with a catalyst comprising a catalyst selected from the group consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and ElASPO catalysts, under cracking conditions to selectively produce propylene.  
     
     
         2 . The method of  claim 1  wherein the selectivity produces a propylene to butylene ratio of at least 2:1 or a propylene to ethylene of at least 4:1.  
     
     
         3 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock consists essentially of hydrocarbons boiling within the range of 18° to 220° C. (65° F. to 430° F.).  
     
     
         4 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock consists essentially of hydrocarbons boiling in the range of 18° to 148° C. (65° F. to 300° F.).  
     
     
         5 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock comprises from about 10 wt % to about 70 wt % olefins.  
     
     
         6 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock comprises from 20 wt % to 70 wt % olefins.  
     
     
         7 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock comprises from about 5 wt % to about 35 wt % paraffins.  
     
     
         8 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock comprises from about 10 wt % to about 30 wt % paraffins.  
     
     
         9 . The method of  claim 1  wherein the olefinic hydrocarbon feedstock comprises from about 10 wt % to about 25 wt % paraffins.  
     
     
         10 . The method of  claim 1  wherein the catalyst is contacted in the range of 400° C. to 700°.  
     
     
         11 . The method of  claim 1  wherein the catalyst is contacted at a WHSV of 1 to 300 hr −1 .  
     
     
         12 . The method of  claim 1  wherein the catalyst is contacted at a pressure of 0.1 to 30 atm. absolute.  
     
     
         13 . The method of  claim 1  wherein the catalyst comprises a catalyst selected from the group consisting of SAPO-11, SAPO-17, SAPO-31, SAPO-34, SAPO-35, SAPO-41, SAPO-44, MeAPO-11, MeAPO-31, MeAPO-41, MeAPSO-11, MeASPO-31, MeASPO-41, MeASPO-46, ElAPO-11, ElAPO-31, ElAPO-41, ElAPSO-11, ElAPSO-31 and ElASPO-41.  
     
     
         14 . The method of  claim 1  wherein the catalyst is prepared by a method which comprises ion exchanging the catalyst with a solution comprising an alkaline earth metal ion or a rare earth metal ion.  
     
     
         15 . The method of  claim 1  wherein the catalyst is exchanged against a solution comprising a rare earth metal ion selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof  
     
     
         16 . The method of  claim 9  wherein the rare earth metal ion comprises lanthanum.  
     
     
         17 . The method in  claim 1  wherein the hydrocarbon feed is cracked over the catalyst at reactor temperatures of from about 400-700° C., pressures of from about 0.1 atmosphere to about 30 atmospheres absolute, and weight hourly space velocities of from about 0.1 hr −1  to about 100 hr −1 .  
     
     
         18 . In a method for catalytic cracking of an olefinic hydrocarbon feed to produce a light olefin containing product, the improvement which comprises mixing a catalyst selected from the non zeolitic catalyst group consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and ElASPO catalysts with a second cracking catalyst in a quantity sufficient to increase propylene content in the light olefin product while decreasing either ethylene or butylene when the product composition obtained with the mixed catalyst is compared to the product composition obtained with the second catalyst alone under the same reaction conditions.  
     
     
         19 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock consists essentially of hydrocarbons boiling within the range of 18° to 220° C. (65° F. to 430° F.).  
     
     
         20 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock consists essentially of hydrocarbons boiling in the range of 18° to 148° C. (65° F. to 300° F.).  
     
     
         21 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock comprises from about 10 wt % to about 70 wt % olefins.  
     
     
         22 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock comprises from 20 wt % to 70 wt % olefins.  
     
     
         23 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock comprises from about 5 wt % to about 35 wt % paraffins.  
     
     
         24 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock comprises from about 10 wt % to about 30 wt % paraffins.  
     
     
         25 . The method of  claim 18  wherein the olefinic hydrocarbon feedstock comprises from about 10 wt % to about 25 wt % paraffins.  
     
     
         26 . The method of  claim 18  wherein the selected catalyst comprises a silicoaluminophosphate selected from the group consisting of SAPO-11, SAPO-17, SAPO-31, SAPO-34, SAPO-35, SAPO-41, SAPO-44, MeAPO-11, MeAPO-31, MeAPO-41, MeAPSO-11, MeAPSO-31, MeAPSO-41, MeAPSO-46, ElAPO-11, ElAPO-31, ElAPO-41, ElAPSO-11, ElAPSO-31, and ElAPSO-41.  
     
     
         27 . The method of  claim 18  wherein the mixed catalyst is contacted in the range of 400° C. to 700° C.  
     
     
         28 . The method of  claim 18  wherein the catalyst is contacted at a WHSV of 1 hr −1  to 300 hr −1 .  
     
     
         29 . The method of  claim 18  wherein the catalyst is contacted at a pressure of 0.1 to 30 atm.  
     
     
         30 . The method of  claim 18  wherein the selected catalyst is prepared by a method which comprises ion exchanging the catalyst with an aqueous solution comprising an alkaline earth metal ion or a rare earth metal ion.  
     
     
         31 . The method of  claim 30  wherein the selected catalyst is exchanged against a solution comprising a rare earth metal ion selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof.  
     
     
         32 . The method of  claim 30  wherein the rare earth metal ion comprises lanthanum.  
     
     
         33 . The method in  claim 18  wherein the hydrocarbon feed is cracked over the catalyst at reactor temperatures of from about 400-700° C., pressures of from about 0.1 atmosphere to about 30 atmospheres absolute, and weight hourly space velocities of from about 0.1 hr −1  about 100 hr  −1 .  
     
     
         34 . A method for enhancing the stability of a silicoaluminophosphate catalyst in propylene production which comprises ion exchanging the selected catalyst with a solution which comprises a rare earth metal.  
     
     
         35 . The method of  claim 34  wherein the ion exchange is with an aqueous solution comprising a rare earth metal ion.  
     
     
         36 . The method of  claim 34  wherein the selected catalyst is exchanged against a solution comprising a rare earth metal ion selected from the group consisting of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and mixtures thereof.  
     
     
         37 . The method of  claim 34  wherein the rare earth metal ion comprises lanthanum.  
     
     
         38 . The method of  claim 22  wherein the catalyst is selected from the group consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and ElASPO catalysts and mixtures thereof.  
     
     
         39 . A method for producing propylene in a cracking process while minimizing production of butylene which comprises contacting an olefinic hydrocarbon feed with a non-zeolitic silicoaluminophosphate containing catalyst under cracking conditions to produce at least 2 times as much propylene as butylenes.  
     
     
         40 . A method according to  claim 39  wherein the process produces at least 4 times as much propylene as ethylene.  
     
     
         41 . A method according to  claim 39  wherein the catalyst is selected from the group consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and ElASPO catalysts and mixtures thereof.  
     
     
         42 . A method according to  claim 41  wherein the catalyst is a SAPO selected from the group consisting of SAPO-11, SAPO-17, SAPO-31, SAPO-34, SAPO-35, SAPO-41, SAPO-44.  
     
     
         43 . A method according to  claim 39  wherein at least 2.5 times as much propylene as butylenes is produced.  
     
     
         44 . A method according to  claim 39  wherein at least 3 times as much propylene as butylenes is produced.  
     
     
         45 . A method for producing propylene in a cracking process while minimizing production of ethylene which comprises contacting an olefinic hydrocarbon feed with a non-zeolitic silicoaluminophosphate containing catalyst under cracking conditions to produce at least 2 times as much propylene as ethylene.  
     
     
         46 . A method according to  claim 45  wherein the process produces at least 4 times as much propylene as ethylene.  
     
     
         47 . A method according to  claim 45  wherein the catalyst is selected from the group consisting of SAPO catalysts, MeAPO catalysts, MeASPO catalysts, ElAPO catalysts and ElASPO catalysts and mixtures thereof.  
     
     
         48 . A method according to  claim 45  wherein the catalyst is a SAPO selected from the group consisting of SAPO-11, SAPO-17, SAPO-31, SAPO-34, SAPO-35, SAPO-41, SAPO-44.  
     
     
         49 . A method according to  claim 45  herein at least 2 times as much propylene as butylenes is produced.  
     
     
         50 . A method according to  claim 45  wherein at least 3 times as much propylene as butylenes is produced.