Fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking

Abstract

The present invention relates to a fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking. The main technical problems to be solved are a relatively high reaction temperature, and low activities and poor selectivities of the catalyst at a low temperature, during the reaction for preparing ethylene and propylene by catalytically cracking naphtha. The technical solution of the catalyst is a composition of the chemical formula Mo 1.0 V a A b B c C d O X based on stoichiometric ratio. It has satisfactorily solved the above-mentioned problems, and is useful in the industrial production of ethylene and propylene by catalytically cracking naphtha.

1 . A fluid-bed catalyst for the preparation of ethylene and propylene by catalytic cracking, said fluid-bed catalyst comprising a support selected from at least one of SiO 2 , Al 2 O 3 , molecular sieves and composite molecular sieves, and a composition of the following chemical formula based on stoichiometric ratio:  
         Mo 1.0 V a A b B c C d O X ,  wherein A is selected from at least one element of Groups VIII, IB, IIB, VIIB, VIB, IA and IIA;    B is selected from at least one of rare earth elements;    C is selected from at least one of Bi and P;    a is from 0.01 to 0.5;    b is from 0.01 to 0.5;    c is from 0.01 to 0.5;    d is from 0 to 0.5; and    X represents the total number of oxygen atoms that meets the valances of the elements in the catalyst,    wherein the molecular sieve is at least one of ZSM-5, Y, β, MCM-22, SAPO-34 and mordenite, and the composite molecular sieve is a composite grown together from at least two molecular sieves of ZSM-5, Y, β, MCM-22, SAPO-34 and mordenite, and    wherein the amount of the catalyst support as used is from 20 to 80% by weight on the basis of the weight of the catalyst.    
     
     
         2 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, characterized in that a is from 0.01 to 0.3, b is from 0.01 to 0.3, c is from 0.01 to 0.3 and d is from 0.01 to 0.3.  
     
     
         3 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, characterized in that the element of Group VIII is selected from at least one of Fe, Co and Ni, the element of Group IB is selected from at least one of Cu and Ag, the element of Group IIB is Zn, the element of Group VIIB is selected from at least one of Mn and Re, the element of Group VIB is selected from at least one of Cr, Mo and W, the element of Group IA is selected from at least one of Li, Na and K, and the element of Group IIA is selected from at least one of Ca, Mg, Sr and Ba.  
     
     
         4 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, characterized in that the rare earth element is selected from at least one of La and Ce.  
     
     
         5 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, characterized in that the molecular sieve in the catalyst support is at least one of ZSM-5, Y zeolite, mordenite and β zeolite, and the composite molecular sieve is at least one of ZSM-5/mordenite, ZSM-5/Y zeolite and ZSM-5/β zeolite.  
     
     
         6 . A fluid-bed catalyst according to  claim 5  for the preparation of ethylene and propylene by catalytic cracking, characterized in that the silica-alumina mol ratios, SiO 2 /Al 2 O 3 , of said molecular sieve and said composite molecular sieve are from 10 to 500.  
     
     
         7 . A fluid-bed catalyst according to  claim 6  for the preparation of ethylene and propylene by catalytic cracking, characterized in that the silica-alumina mol ratios, SiO 2 /Al 2 O 3 , of said molecular sieve and said composite molecular sieve are from 20 to 300.  
     
     
         8 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, characterized in that the amount of the catalyst support as used is from 30 to 50% by weight on the basis of the weight of the catalyst.  
     
     
         9 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, characterized in that when Cr is a component of the catalyst, the ratio of Mo: Cr is 1:0.01 to 0.5 based on stoichiometric ratio.  
     
     
         10 . A fluid-bed catalyst according to  claim 1  for the preparation of ethylene and propylene by catalytic cracking, said fluid-bed catalyst being useful for catalytically cracking heavy oil, light diesel oil, light gasoline, catalytically cracked gasoline, gas oil, condensate oil, C 4  olefin or C 5  olefin.