Modified catalyst with structure type mtw, a method for its preparation and its use in a process for the isomerization of an aromatic c8 cut

Abstract

The invention concerns a catalyst comprising at least one zeolite with structure type MTW, a matrix, at least one metal from group VIII of the periodic classification of the elements, said catalyst having a mesopore volume increased by at least 10% compared with its initial mesopore volume, which is generally in the range 0.55 to 0.75 mL/g, at the end of a treatment with steam at a partial pressure in the range 0.01 to 0.07 MPa and at a temperature in the range 300° C. to 400° C. for at least 0.5 hour. The invention concerns the process for the preparation of said catalyst as well as an isomerization process employing said catalyst.

1 . A catalyst comprising at least one zeolite with structure type MTW, a matrix, at least one metal from group VIII of the periodic classification of the elements, said catalyst having a mesopore volume increased by at least 10% compared with its initial mesopore volume, which is generally in the range 0.55 to 0.75 mL/g, at the end of a treatment with steam at a partial pressure in the range 0.01 to 0.07 MPa and at a temperature in the range 300° C. to 400° C. for at least 0.5 hour. 
     
     
         2 . The catalyst according to  claim 1 , in which the steam is at a partial pressure in the range 0.04 to 0.06 MPa. 
     
     
         3 . The catalyst according to  claim 1 , in which the steam used is diluted in a neutral gas, dioxygen or in air. 
     
     
         4 . The catalyst according to  claim 1 , in which the temperature is in the range 300° C. to 380° C. 
     
     
         5 . The catalyst according to  claim 1 , in which the overall atomic ratio Si/A1 of the zeolite with structure type MTW is in the range 20 to 200, limits included, preferably in the range 20 to 100, limits included. 
     
     
         6 . The catalyst according to  claim 1 , in which the zeolite content is in the range 1% to 20% by weight with respect to the mass of the support, preferably in the range 1% to 10% by weight, the support representing the mixture of zeolite and matrix. 
     
     
         7 . The catalyst according to  claim 1 , in which the matrix is selected from clays, magnesia, aluminas, silicas, titanium oxide, boron oxide, zirconia, aluminium phosphates, titanium phosphates, zirconium phosphates, silica-aluminas and charcoal or a mixture of at least two of these compositions. 
     
     
         8 . The catalyst according to  claim 7 , in which the matrix is an alumina. 
     
     
         9 . The catalyst according to  claim 1 , in which the zeolite with structure type MTW is selected from the group formed by ZSM-12, CZH-5, NU-13, TPZ-12, Theta-3 and VS-12; preferably, the zeolite is ZSM-12 zeolite. 
     
     
         10 . A process for the preparation of a catalyst according to  claim 1 , comprising at least the following steps:
 i) using at least one zeolite with structure type MTW,   ii) preparing a support by shaping said zeolite with a matrix,   iii) depositing at least one metal from group VIII of the periodic classification of the elements onto said support or onto said zeolite, the order of carrying out said steps ii) and iii) being unimportant following said step i),   iv) bringing the catalyst obtained in step ii) or step iii), depending on the order in which they are carried out, into contact with steam at a partial pressure in the range 0.01 to 0.07 MPa, at a temperature in the range 300° C. to 400° C., for at least 0.5 hour, in a manner such that the mesopore volume of the catalyst is increased by at least 10% compared with the initial mesopore volume of the catalyst, which is generally in the range 0.55 to 0.75 mL/g.   
     
     
         11 . The preparation process according to  claim 10 , in which step ii) is followed by drying carried out at a temperature in the range 100° C. to 150° C. for a period in the range 5 to 20 hours in an oven, then by calcining carried out at a temperature in the range 250° C. to 600° C. for a period in the range 1 to 8 hours. 
     
     
         12 . The preparation process according to  claim 10 , in which step ii) for depositing the metal(s) is followed by calcining at a temperature in the range 250° C. to 600° C., for a period in the range 0.5 to 10 hours, preceded by drying at a temperature from ambient temperature to 250° C. 
     
     
         13 . The preparation process according to  claim 10 , in which the catalyst is reduced ex situ or in situ before it is used, in a stream of hydrogen at a temperature of 450° C. to 600° C., for a period of 0.5 to 4 hours. 
     
     
         14 . A catalyst which is capable of being obtained by the preparation process according to  claim 10 . 
     
     
         15 . A process for the isomerization of an aromatic cut containing at least one aromatic compound containing 8 carbon atoms per molecule, comprising bringing said cut into contact with a catalyst according to  claim 1 . 
     
     
         16 . The process according to  claim 15 , carried out at a temperature of 300° C. to 500° C., a partial pressure of hydrogen of 0.3 to 1.5 MPa, a total pressure of 0.45 to 1.9 MPa and a feed space velocity, expressed as kilograms of feed introduced per kilogram of catalyst per hour, of 0.25 to 30 h −1 . 
     
     
         17 . The process according to  claim 15 , in which the aromatic cut comprises a mixture of xylenes alone, or ethylbenzene alone, or a mixture of xylene(s) and ethylbenzene.