Catalyst for steam cracking reactions and related preparation process

Abstract

Catalyst for steam cracking reactions consisting of pure mayenite having the general formula: 12CaO.7Al 2 O 3 having an X-ray diffraction spectrum as indicated in Table I, obtained with a preparation process comprising the following steps: dissolution of salts containing calcium and aluminum with water; complexing of the dissolved salts by means of polyfunctional organic hydroxyacids; drying of the solution resulting from the complexing in order to obtain a solid precursor product; calcination of the solid precursor product at a temperature ranging from 1300 to 1400° C. for at least two hours.

1 . A catalyst for steam cracking reactions characterized in that it consists of pure mayenite having the general formula:  
       12CaO.7Al 2 O 3    
       with an X-ray diffraction spectrum as indicated in Table I.  
     
     
         2 . A process for the preparation of the catalyst according to    claim 1   , characterized in that it comprises the following steps: 
 dissolution of salts containing calcium and aluminum with water;    complexing of the dissolved salts by means of polyfunctional organic hydroxyacids;    drying of the solution resulting from the complexing in order to obtain a solid precursor product;    calcination of the solid precursor product at a temperature ranging from 1300 to 1400° C. for at least two hours.    
     
     
         3 . The process according to    claim 2   , wherein the calcination is effected at a temperature ranging from 1330 to 1370° C. for at least 5 hours.  
     
     
         4 . The process according to    claim 2   , wherein the salts containing calcium are selected from calcium acetate and calcium nitrate.  
     
     
         5 . The process according to    claim 2   , wherein the salt containing aluminum is aluminum nitrate.  
     
     
         6 . The process according to    claim 2   , wherein the polyfunctional hydroxyacid is citric acid.  
     
     
         7 . The process according to    claim 2   , wherein the molar ratio polyfunctional hydroxyacids/salts containing calcium and alumina ranges from 1.5 to 1.  
     
     
         8 . A process for the production of light olefins by means of the steam cracking reaction of hydrocarbon charges selected from naphtha, kerosene, atmospheric gas oil, vacuum gas oil, alone or mixed with each other, in the presence of a catalyst according to    claim 1   , operating at a temperature ranging from 720 to 800° C., at a pressure ranging from 1.1 to 1.8 absolute Ate. and for a contact time ranging from 0.07 to 0.2 sec.  
     
     
         9 . The process according to    claim 8   , wherein the naphtha is virgin naphtha.