Process for the production of para-xylene

Abstract

A reforming process using a medium pore zeolite under conditions to facilitate the conversion of C 8 paraffinic compounds to para-xylene is provided. Para-xylene is produced at greater than thermodynamic equilibrium concentrations using the process.

What is claimed is: 
     
         1 . A process for producing para-xylene comprising the steps of:
 (a) providing a C 8  containing feedstock, which contains at least 10 wt. % C 8  paraffinic hydrocarbons, to a reforming reaction zone that contains a reforming catalyst comprising ZSM-5 having a silica to alumina molar ratio of at least 200, and a crystallite size of less than 10 microns;   (b) contacting the C 8  containing feedstock under reforming reaction conditions in the reforming reaction zone to produce para-xylene and meta-xylene in a para-xylene to meta-xylene weight ratio of at least 0.9; and (c) separating the para-xylene from the meta-xylene.   
     
     
         2 . The process of  claim 1 , wherein step (a) comprises providing the C 8  containing feedstock to the reforming reaction zone that contains a reforming catalyst comprising silicalite. 
     
     
         3 . The process of  claim 1 , wherein step (a) comprises providing the C 8  containing feedstock to the reforming reaction zone that contains a reforming catalyst comprising a medium pore zeolite having a silica to alumina molar ratio of at least 200, a crystallite size of less than 10 microns and an alkali content of less than 5000 ppm. 
     
     
         4 . The process of  claim 3 , wherein step (a) comprises providing a C 8  containing feedstock to a reforming reaction zone that contains a reforming catalyst comprising a medium pore zeolite having a silica to alumina molar ratio of at least 200, a crystallite size of less than 10 microns, an alkali content of less than 5000 ppm and in the range of between 0.1 wt. % and 1 wt. % of platinum, rhenium, or combinations thereof. 
     
     
         5 . The process of  claim 1 , wherein step (b) further comprises producing para-xylene and meta-xylene in the weight ratio of at least 1.0. 
     
     
         6 . The process of  claim 1 , wherein step (b) further comprises producing para-xylene and meta-xylene in the weight ratio of at least 1.1. 
     
     
         7 . The process of  claim 1 , wherein step (b) further comprises producing para-xylene and meta-xylene in the weight ratio of at least 1.2. 
     
     
         8 . The process of  claim 1 , wherein step (b) comprises contacting the C 8  containing feedstock under reforming reaction conditions, including a pressure of between 0 psig to 350 psig, a temperature of between 800° F. to 1100° F., and a flow rate of between 0.1 hf −1  to 20 hf −1  LHSV. 
     
     
         9 . The process of  claim 1 , wherein step (c) comprises separating the para-xylene from the product stream and further recovering a para-xylene depleted product stream. 
     
     
         10 . The process of  claim 9 , further comprising recycling the para-xylene depleted product stream to the reforming reaction zone. 
     
     
         11 . The process of  claim 9 , wherein step (c) comprises separating the para-xylene from the product stream by crystallization. 
     
     
         12 . The process of  claim 1 , wherein the Z5M-5 has a silica to alumina molar ratio of at least 500. 
     
     
         13 . A process for producing para-xylene comprising the steps of:
 (a) contacting a hydrocarbonaceous feed wherein at least 50 wt. % of said feed boils above 550° F., in a first reaction zone comprising a hydrocracking catalyst under hydrocracking conditions to form an effluent;   (b) separating the effluent into at least a C 8  containing fraction comprising at least 10 wt. % C 8  paraffinic hydrocarbons;)   (c) providing the C 8  containing fraction to a second reaction zone;   (d) contacting the C 8  containing fraction under reforming reaction conditions with a reforming catalyst comprising a medium pore zeolite having a silica to alumina molar ratio of at least 200, a crystallite size of less than 10 microns and an alkali content of less than 5000 ppm in a second reaction zone to produce a product stream comprising para-xylene and meta-xylene wherein the para-xylene to meta-xylene ratio is at least 0.9; and   (e) separating the para-xylene from the product stream.   
     
     
         14 . The process of  claim 13 , wherein the hydrocracking conditions comprise a temperature of between 450 to 900° F., a pressure between 500 to 5000 psig, a LHSV between 0.1 to 3015 and a hydrogen circulation rate between 2000 to 5,000 standard cubic feet per barrel. 
     
     
         15 . The process of  claim 13 , further comprising the step of recovering a para-xylene depleted product stream. 
     
     
         16 . The process of  claim 15 , further comprising the step of recycling the para-xylene depleted product stream to the second reaction zone. 
     
     
         17 . The process of  claim 13 , wherein the reforming reaction conditions include a pressure of between 0 psig to 350 psig, a temperature of between 800° F. to 1100° F., and a flow rate of between 0.1 hr −1  to 20 hr −1  LHSV. 
     
     
         18 . The process of  claim 13 , further comprising generating hydrogen from the second reaction zone. 
     
     
         19 . The process of  claim 18 , wherein the hydrogen is recycled to the first reaction zone.