| 摘要 |
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, CO2 and H2, 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, CO2 and H2 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.
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