Cracking catalysts acid theory

The experimental evidence for the second hypothesis was the observed increase of the cracking rate of alkanes after addition of small amounts of alkenes to the feed. Both early theories assumed the continuation of the cracking reaction by intermolecular transfer of the charge from the products to fresh starting molecules, that is like an ionic chain mechanism with the catalyst acting only as an initiator. The problem was further clouded by the fact that two types of acid centres exist on the surface, the Br0n-... 

Ethylene (Ethene or Elayl), H2C CH2 mw 28.05 colorless, flammable, dangerous to handle gas with characteristic sweet odor and taste sp gr 0.975 (air = 1.0), mp —169.4°, bp —103.8°, flash p —136°C explosive limits in air, % by vol, lower 3.0 upper 34.0 si sol in w, more in ale sol in eth. Ethylene is a major component of petroleum refinery gas from cracking units, and is sometimes recovered therefrom by distillation or other means. Some pure ethylene is produced by passing hot ethanol vapors over a catalyst, such as activated alumina (Ref 4). Its laboratory prepn consists of heating ethanol in definite proportions with sulfuric acid of certain concns. By using a 90% acid and 90% ale, ethylene can be produced in a regular stream at a yield of 84 to 85% of theory (Ref 2). 

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