Para-xylene production process employing in-situ catalyst selectivation

Abstract

A catalytic process for the selective production of para-xylene comprises the step of reacting an aromatic hydrocarbon selected from the group consisting of toluene, benzene and mixtures thereof with a feed comprising carbon monoxide and hydrogen in the presence of a selectivated catalyst. The process includes a catalyst selectivation phase and a para-xylene production phase. In the catalyst selectivation phase, the aromatic hydrocarbon and the feed are contacted with the catalyst under a first set of conditions effective to increase the para-selectivity of said catalyst. In the para-xylene production phase, the aromatic hydrocarbon and said feed are contacted with the catalyst under a second set of conditions different from the first set of conditions effective to selectively produce para-xylene.

1 . A diffusionally restricted catalyst, wherein the catalyst comprises a molecular sieve and has been treated with carbon monoxide at conditions effective to increase the diffusional resistance of the catalyst such that the catalyst has a Diffusion Parameter, D/r 2 , for 2,2-dimethylbutane of less than 100, when measured at a temperature of 120° C. and a 2,2-dimethylbutane relative pressure of 0.013.  
     
     
         2 . The catalyst of  claim 1  wherein the catalyst has a Diffusion Parameter, D/r 2 , for 2,2-dimethylbutane of less than 5, when measured at a temperature of 120° C. and a 2,2-dimethylbutane relative pressure of 0.013.  
     
     
         3 . The catalyst of  claim 1  wherein the catalyst has a Diffusion Parameter, D/r 2 , for 2,3-dimethylbutane of less than 1000, when measured at a temperature of 120° C. and a 2,3-dimethylbutane relative pressure at 120° C. of 0.012.  
     
     
         4 . The catalyst of  claim 1  wherein the catalyst has a Diffusion Parameter, D/r 2 , for 2,3-dimethylbutane of less than 600, when measured at a temperature of 120° C. and a 2,3-dimethylbutane relative pressure at 120° C. of 0.012.  
     
     
         5  The catalyst of  claim 1 , wherein the catalyst has been treated with a mixture of carbon monoxide and hydrogen.  
     
     
         6  The catalyst of  claim 1 , wherein the catalyst has been treated with a mixture of carbon monoxide, hydrogen and at least one of benzene and toluene.  
     
     
         7  The catalyst of  claim 1 , wherein the molecular sieve has a constraint index of 1 to 12.  
     
     
         8  The catalyst of  claim 1 , wherein the molecular sieve is ZSM-5.  
     
     
         9  The catalyst of  claim 1  and also including one or more catalytically active metals and/or metal oxides.  
     
     
         10 . The catalyst of  claim 1  and comprising ZSM-5 and chromium and zinc oxides.  
     
     
         11 . The catalyst of  claim 1  and further including an inorganic oxide material as a binder, support and/or filler.  
     
     
         12 . A process for the selective production of para-xylene comprising the steps of reacting an aromatic hydrocarbon selected from toluene, benzene and mixtures thereof with a feed comprising carbon monoxide and hydrogen in the presence of a diffusionally restricted catalyst which comprises a molecular sieve and which has been treated with carbon monoxide at conditions effective to increase the diffusional resistance of the catalyst such that the catalyst has a Diffusion Parameter, D/r 2 , for 2,2-dimethylbutane of less than 100, when measured at a temperature of 120° C. and a 2,2-dimethylbutane relative pressure of 0.013.  
     
     
         13 . The process of  claim 12  wherein the catalyst has a Diffusion Parameter, D/r 2 , for 2,2-dimethylbutane of less than 5, when measured at a temperature of 120° C. and a 2,2-dimethylbutane relative pressure of 0.013.  
     
     
         14 . The process of  claim 12  wherein the catalyst has a Diffusion Parameter, D/r 2 , for 2,3-dimethylbutane of less than 1000, when measured at a temperature of 120° C. and a 2,3-dimethylbutane relative pressure at 120° C. of 0.012.  
     
     
         15 . The process of  claim 12  wherein the catalyst has a Diffusion Parameter, D/r 2 , for 2,3-dimethylbutane of less than 600, when measured at a temperature of 120° C. and a 2,3-dimethylbutane relative pressure at 120° C. of 0.012.  
     
     
         16 . The process of  claim 12  wherein said reacting step is effected under conditions including a temperature of about 100 to about 700° C., a pressure of about 1 to about 300 atm. and a flow rate for the hydrocarbon feed of about 0.01 to about 100 h −1  LHSV on a liquid feed basis.  
     
     
         17 . The process of  claim 12  wherein said reacting step is effected under conditions including a temperature of about about 200 to about 600° C., a pressure of about 1 to about 200 atm. and a flow rate for the hydrocarbon feed of about 1 to about 50 h −1  LHSV on a liquid feed basis.  
     
     
         18 . The process of  claim 12  wherein the mole ratio of H 2 /CO/aromatic compound is about 0.01-10/0.01-10/0.01-10.  
     
     
         19 . A process for the selective production of para-xylene comprising the steps of reacting an aromatic hydrocarbon selected from toluene, benzene and mixtures thereof with a feed comprising carbon monoxide and hydrogen in the presence of a catalyst, wherein the process includes a catalyst selectivation phase and a para-xylene production phase and wherein: 
 (a) said catalyst selectivation phase includes the step of contacting said aromatic hydrocarbon and said feed with said catalyst under a first set of conditions effective to increase the para-selectivity of said catalyst, and    (a) said para-xylene production phase includes the step of contacting said aromatic hydrocarbon and said feed with said catalyst under a second set of conditions different from said first set of conditions and effective to selectively produce para-xylene.    
     
     
         20 . The process of  claim 19 , wherein the difference between said second set of conditions and said first set of conditions comprises a difference in the molar concentration and/or feed rate of any one of said aromatic hydrocarbon, carbon monoxide and hydrogen, in the reaction temperature and/or in the reaction pressure.  
     
     
         21 . The process of  claim 19 , wherein the temperature of said selectivation-phase is greater than the temperature of said production phase.  
     
     
         22 . The process of  claim 19 , wherein said catalyst selectivation phase occurs prior to said para-xylene production phase.  
     
     
         23 . The process of  claim 19 , wherein said catalyst selectivation phase interrupts said para-xylene production phase, and wherein said para-xylene production phase continues after said catalyst selectivation phase.  
     
     
         24 . The process of  claim 19 , wherein said catalyst comprises a first component including an acidic molecular sieve and a second component selected from the group consisting of at least one metal and at least one metal oxide.  
     
     
         25 . The process of  claim 24 , wherein at least said acidic molecular sieve has been subjected to an initial ex-situ selectivation treatment.  
     
     
         26 . The process of  claim 19 , wherein the temperature of the selectivation phase is between 100 and 700° C.  
     
     
         27 . The process of  claim 19 , wherein the temperature of the selectivation phase is between 200 and 600° C.  
     
     
         28 . The process of  claim 19 , wherein the pressure of the selectivation phase is between 1 to 300 atm.  
     
     
         29 . The process of  claim 19 , wherein the pressure of the selectivation phase is between 1 to 200 atm.  
     
     
         30 . The process of  claim 19 , wherein the flow rate of said hydrocarbon stream during the selectivation phase is between 0.01 and 100 h −1  WHSV.  
     
     
         31 . The process of  claim 19 , wherein the flow rate of said hydrocarbon stream during the selectivation phase is between 1 and 50 h −1  WHSV.  
     
     
         32 . The process of  claim 19 , wherein the feeding of the hydrocarbon stream and the gas stream during the selectivation phase is such that the molar ratio of H 2 /CO/aromatic compounds is 0.01-10/0.01-10/0.01-10 respectively.  
     
     
         33 . A process for the selectivation of a catalyst composition for the synthesis of para-xylene in a continuous reaction having a selectivation phase and a production phase comprising: 
 (i) feeding into a reactor a hydrocarbon stream comprising at least one of toluene, benzene and a mixture thereof;    (ii) feeding a gas stream comprising carbon monoxide and hydrogen into said reactor; and    (iii) contacting said hydrocarbon stream and said gas stream in said reactor in the presence of said catalyst composition;    wherein selectivation of said catalyst composition includes the step of altering for a limited period of time at least one of the molar concentration of said hydrocarbon stream in said reactor, the molar concentration of said gas stream in said reactor, the flow rate of said hydrocarbon stream, and the flow rate of said gas stream, the temperature in the reactor, and the pressure in the reactor;    whereby the selectivation of said catalyst composition does not involve interruption of the feeding of said streams and further does not involve the addition of a selectivating agent different from said hydrocarbon stream and said gas stream.