Houdry process cracking cycle

Various dehydrogenation processes have been developed but the Houdry process is the most extensively used. In this process, butane is passed over a catalyst of 15-20% chromia on activated alumina at an initial temperature of 620-650°C and a pressure of 20 kPa (0.2 atmosphere). After 7-15 minutes the temperature falls and the catalyst becomes coked the feed is then switched to a fresh reactor. The coke is burnt off the spent catalyst which is thus reactivated and re-heated ready for the next cycle. Butadiene is recovered from the product gas by the methods described above. Butane is the major source of butadiene in the USA at present. However, this route is becoming less important as the amount of butadiene available from naphtha and gas oil cracking increases. 

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