Method of production of light olefins in catalytic cracking units with energy deficiency

Abstract

The present invention relates to a method of production of light olefins, with the objective of maximizing the production of propylene and in particular ethylene by the use of a special catalyst containing high-silica zeolite, whose composition also includes a dehydrogenating metal, so as to generate light olefins and appreciable deposition of coke on the catalyst. Gains in selectivity for light olefins are observed, and at the same time the energy deficiency of catalytic cracking in petrochemical operations with light hydrocarbons is minimized, avoiding problems due to the need to burn heating oil in the catalyst regenerating section to make up for the energy deficit of the converter.

1 . A method for the production of olefins in a catalytic cracking unit with energy deficiency that comprises:
 1) supplying a stream of hydrocarbons to a reactor of a fluid catalytic cracking unit;   2) promoting contact between the stream of hydrocarbons and a heated catalyst, whose composition comprises at least one dehydrogenating metal;   3) allowing vapour-phase reactions to occur to obtain a mixture of hydrocarbons, steam and coked catalyst;   4) separating the coked catalyst from products resulting from the reactions;   5) directing the coked catalyst to a steam rectification section;   6) directing rectified coked catalyst to a heating section, to allow combustion of coke deposited on the catalyst and the burning of torch oil, with a stream of air, and to obtain a heated catalyst capable of supplying the process with energy;   7) returning the heated catalyst to the feed of the reactor to begin the cracking process again;   8) directing the hydrocarbon stream generated to a separating and fractionating section, for separating the products obtained.   
     
     
         2 . A method according to  claim 1 , characterized in that said reactor is a reactor with ascending or descending flow. 
     
     
         3 . A method according to  claim 1 , characterized in that a stream of water or of steam is introduced into said reactor. 
     
     
         4 . A method according to  claim 1  characterized in that a pressure between 100 kPa and 500 kPa is applied in said reactor. 
     
     
         5 . A method according to  claim 1 , characterized in that said stream of hydrocarbons, provided for feeding the catalytic cracking unit, is a stream of hydrocarbons, preferably light hydrocarbons, with Ramsbottom carbon residue less than 1.5% w/w. 
     
     
         6 . A method according to  claim 1 , characterized in that said stream of hydrocarbons, provided for feeding the catalytic cracking unit, comprises a stream of naphtha, diesel or kerosene or other effluent from the distillation of petroleum or from delayed coking units, hydrocracking units, hydrofining units or other refining units. 
     
     
         7 . A method according to  claim 1 , characterized in that said catalyst contains between 0% and 60% w/w of solid acid, between 0% and 50% w/w of alumina, between 0% and 40% w/w of silica and the remainder kaolin. 
     
     
         8 . A method according to  claim 7 , characterized in that said solid acid comprises a zeolite, modified or not with a dehydrogenating metal, from the pentasil family, optionally as ZSM-5, ZSM-8 and ZSM-11, of the ferrierite type, of the mordenite type or a mixture of said zeolites. 
     
     
         9 . A method according to  claim 1 , characterized in that said catalyst contains between 1.0% and 15% w/w of dehydrogenating metal. 
     
     
         10 . A method according to  claim 9 , characterized in that said dehydrogenating metal comprises a metal or a combination of metals with dehydrogenating power, said metals preferably comprising nickel, iron, manganese, cobalt, molybdenum and/or gallium. 
     
     
         11 . A method according to  claim 1 , characterized in that said step (3) above is carried out at a reaction temperature between 550° C. and 750° C., a catalyst/feed ratio between 10 and 50 and uses of an amount of steam relative to the feed of between 0.2:1 and 1:1. 
     
     
         12 . A method according to  claim 1 , characterized in that said mixture of hydrocarbons generated is a mixture of hydrocarbons, preferably light hydrocarbons, that contains at least 6% w/w of ethylene relative to the mass of the feed and/or in that the amount of coke generated is at least 4% w/w relative to the mass of the feed. 
     
     
         13 . A method according to  claim 1 , characterized in that said catalyst is regenerated at a temperature between 650° C. and 750° C. 
     
     
         14 . A method according to  claim 1 , characterized by the introduction of rapid cooling or quench in an intermediate section of the reactor. 
     
     
         15 . Method for the production of light olefins in catalytic cracking units with energy deficiency that comprises:
 1) supply of a stream of hydrocarbons to a reactor of a fluid catalytic cracking unit;   2) promotion of contact between the stream of hydrocarbons and a heated special catalyst, whose composition includes at least one dehydrogenating metal;   3) making it possible for vapour-phase reactions to occur in defined operating conditions, for obtaining a mixture of hydrocarbons, steam and coked catalyst;   4) separation of the coked catalyst from the products resulting from the reactions;   5) directing the coked catalyst to a steam rectification section;   6) directing the rectified coked catalyst to a heating section, to permit combustion of the coke deposited on the catalyst and the burning of torch oil, with a stream of air, and to obtain a heated catalyst capable of supplying the process with the necessary energy;   7) returning the heated catalyst to the feed of the reactor to begin the cracking process again;   8) directing the hydrocarbon stream generated to a separating and fractionating section, for separating the products obtained.