Patent GB-778821-A (GB)
Title: Cracking of heavy hydrocarbons
IPC: C10G11/16
Filed: 1955-03-28
Abstract: Heavy hydrocarbon oils containing asphaltic components are cracked by contacting the oil with a compact bed of catalyst granules at a temperature of 800 DEG -1000 DEG F. which are gravitating through a reaction zone wherein they are retained for at least 5 minutes, and supplying steam to the reaction zone in a weight-proportion at least 25 per cent of the weight of the fresh hydrocarbon feed.  Gas oil and gasoline are the primary products of the process, the formation of coke and light gases being relatively low.  Suitable catalytic materials are acid-activated clays, silica/alumina gels, clays of the kaolin and montmorillonite types which have not been activated by acidtreatment, and "spent" catalyst recovered from conventional catalytic cracking units.  After use in the present cracking process, the catalyst is purged with steam at a temperature of 900 DEG -1000 DEG F., and then regenerated by oxidative combustion in air.  In an example, a crude oil having an A.P.I. gravity of 18.4 and boiling above 850 DEG F. was cracked in the presence of a synthetic silica-alumina gel catalyst.  The catalyst temperature was held at 850 DEG F. and the oil charged thereto at the rate of one volume (as liquid) of oil per hour per volume of catalyst, together with steam amounting to about 75 per cent by weight of oil.  There were obtained 73 per cent (by weight of oil charged) of gas oil of B.R. 400 DEG -1000 DEG F., 9 per cent of liquid product boiling over 1000 DEG F., 9 per cent of gasoline, 3 per cent of gas, and 4 per cent of coke deposited on the catalyst.  The gas oil was found to be highly suitable as charge-stock for conventional catalytic cracking.  When the granules of catalyst contain more than about 400 ppm. of deposited contaminants such as nickel and/or vanadium compounds, the deleterious effect of these contaminants is "deactivated" by treatment with an agent which converts the contaminants into sulphides, fluorides, chlorides or phosphates, or by treatment with an agent selected from the group consisting of arsenic, antimony, bismuth, tin, lead, thallium, zinc, cadmium, mercury and compounds comprising such metals.  The contaminants may also be "deactivated" by treatment with a hydrocarbon gas, such as methane, ethane, ethylene, propane, propylene, butane, butylene and butadiene, at elevated temperature whereby a deposit of active carbon is formed on the contaminants.  The deactivating agent may be introduced during catalyst manufacture, or during the passage of the particles through the cracking zone; or it may be introduced in a special step carried out after regeneration of the catalyst and before its return to the cracking zone.  In an example, a crude oil is topped to remove gasoline and gas oil; and the topped crude is mixed with recycle material and passed into a gravitating bed of hot silica-alumina particles.  Steam is employed in the cracking zone and also in the purging zone.  The purged catalyst is regenerated by combustion, and the hot particles of regenerated catalyst are treated with a sulphiding gas at about 1200 DEG F. before they are returned to the cracking zone.