Process and apparatus for cracking hydrocarbons

Abstract

The cracking of hydrocarbon fractions, for example to obtain low olefins, in particular ethylene, is performed in reaction tubes that are at least partially coated with catalyst. The catalyst can promote gasification of coke with water vapor after the water-gas reaction in CO, CO 2 and H 2 , and/or the cracking reactions. The catalyst coating can be placed directly on reaction tubes or on top of a previously applied adhesion promoter and/or auxiliary medium placed on the reaction tubes, in particular on a grid. Preferably, the catalyst coating is applied thermally, by cold-coating processes, in particular the slip process, by vapor deposition and/or,adhesion. The catalyst can promote, in particular, gasification of coke with water vapor after the water-gas reaction in CO, CO 2 and H 2 and make hydrogen, obtained during catalytic gasification, available for cracking hydrocarbons and/or as additional product. As catalyst, one based on calcium aluminate is especially suitable, preferably with a doping of alkali vanadate, in particular of potassium pyrovanadate. Cracking can be performed by, for example, steam cracking, pyrolysis, thermocatalytic cracking or steam reforming.

What is claimed is:  
     
         1 . In a process for cracking hydrocarbons, hydrocarbon mixtures or hydrocarbon fractions, the improvement wherein cracking is performed in reaction tubes coated at least partially with catalyst.  
     
     
         2 . A process according to  claim 1 , wherein said catalyst promotes gasification of coke with water vapor after the water-gas reaction in CO, CO 2 , and H 2 , promotes cracking reactions; or promotes both cracking reactions and gasification of coke with water vapor.  
     
     
         3 . A process according to  claim 1 , wherein the catalyst coating 
 is applied directly to said reaction tubes,    is applied to reaction tubes to which an adhesion promoter has been previously applied, and/or    is applied to an auxiliary medium placed in said reaction tubes.    
     
     
         4 . A process according to  claim 1 , wherein said catalyst is applied to auxiliary mediums in the form of tubular grids which are positioned within said reaction tubes.  
     
     
         5 . A process according to  claim 1 , wherein the catalyst coating is applied by a thermal process, by a cold coating process, by a vapor deposition process or by an adhesion process.  
     
     
         6 . A process according to  claim 2 , wherein the catalyst promotes gasification of coke with water vapor after the water-gas reaction in CO, CO 2  and H 2 , whereby hydrogen obtained during gasification is available for cracking of hydrocarbons; as an additional product, or both.  
     
     
         7 . A process according to  claim 1 , wherein said catalyst contains calcium aluminate.  
     
     
         8 . A process according to  claim 7 , wherein said catalyst is doped with alkali vanadate.  
     
     
         9 . A process according to  claim 8 , wherein said alkali vanadate is potassium pyrovanadate.  
     
     
         10 . A process according to  claim 1 , wherein cracking is performed by vapor cracking, pyrolysis, thermocatalytic cracking or steam reforming.  
     
     
         11 . A process according to  claim 1 , wherein the mass speed is 5-300 kg/s·m 2 .  
     
     
         12 . A process according to  claim 1 , wherein the average internal sur face load on said reaction tube,is 10-120 kW/m 2 .  
     
     
         13 . A process according to  claim 1 , wherein product gasses are quickly cooled in a cracked gas cooler or quench exchanger having catalyst-coated surfaces therein.  
     
     
         14 . In a process for cracking hydrocarbons, hydrocarbon mixtures or hydrocarbon fractions, the improvement wherein the reaction tubes of an existing cracking unit are coated with catalyst.  
     
     
         15 . In a cracking furnace for cracking hydrocarbons, hydrocarbon mixtures or hydrocarbon fractions in reaction tubes, the improvement wherein said reaction tubes are coated with a catalyst.  
     
     
         16 . In an ethylene production unit, for cracking hydrocarbons, hydrocarbon mixtures or hydrocarbon fractions in reaction tubes, the improvement wherein said reaction tubes are coated with a catalyst.  
     
     
         17 . In a steam reformer, for cracking hydrocarbons, hydrocarbon mixtures or hydrocarbon fractions in reaction tubes, the improvement wherein said reaction tubes are coated with a catalyst.  
     
     
         18 . In a cracking furnace, steam reformer, reactor, cracked gas cooler, quench exchanger, evaporator and/or heat exchanger, wherein surfaces that come into contact with carbon and/or carbon compounds during operation are coated at least partially with a catalyst to reduce or avoid coke deposits and to promote gasification of coke and/or cracking reactions.  
     
     
         19 . An apparatus according to  claim 18 , wherein the catalyst coating is applied directly on said surfaces or on an adhesion promoter layer previously applied to said surfaces and/or on an auxiliary medium placed adjacent said surfaces.  
     
     
         20 . An apparatus according to  claim 19 , wherein the catalyst coating is applied as a thermal coating, a cold coating, a vapor-deposited coating or an adhesive coating.  
     
     
         21 . An apparatus according to  claim 19 , wherein the catalyst coating contains calcium aluminate.  
     
     
         22 . A process according to  claim 21 , wherein said catalyst is doped with alkali vanadate.  
     
     
         23 . A process according to  claim 22 , wherein said alkali vanadate is potassium pyrovanadate.