In many chemical processes such as cracking and dehydrogenation of hydrocarbons on solid catalyst, the activity of catalyst gradually decreases as the reaction proceeds. These decreases are often caused by deposition of a carbonaceous substance (coke) which is formed by reactions parallel or consecutive to the main reaction. Fouled catalyst may be regenerated by burning off the carbonaceous product, usually with air.
In this paper, the mechanisms of coke formation are studied for dehydrogenation of n-butane over alumina-chromia catalyst, and the rate of reaction and of catalyst fouling are determined. The effects of catalyst fouling on the overall efficiency of fixed bed reactors are analyzed with an analogue computer. The concept of the average activity (the fraction of effective catalyst to the total amount of catalyst) is proposed as a satisfactory index in deciding the end point of the reaction period for regeneration.