GB600471A - Improvements in or relating to the production of aviation gasoline - Google Patents

Abstract

A petroleum fraction is catalytically cracked or a naphtha catalytically reformed, an aromatic-rich fraction boiling within the range 200-500 DEG F. is separated, thermally cracked at at least 1200 DEG F. for a time from a few seconds to a fraction of a second, and an aromatic fraction of aviation gasoline boiling range is recovered from the products. The thermal cracking converts non-aromatics to lower boiling products, and higher boiling aromatics to benzene and toluene. The product may be acid treated to remove olefinic constituents and, if desired, fractionated to separate benzene and toluene or excess benzene may be alkylated to cumene. A high boiling feedstock such as gas oil or refined crude, may be catalytically cracked at about 800-1050 DEG F. using silica-alumina or other catalyst in a stationary or moving bed or as suspended powder. The products are fractionated to obtain a light fraction boiling up to about 200-225 DEG F. which may be worked up to a gasoline, and a fraction preferably of B.R. about 200-350 DEG F. which contains 50-80 per cent aromatics. This fraction, preferably with a diluent such as steam or hydrocarbon gases, for example steam equivalent to 80 mol. per cent of the mixture, is heated at 1200-1600 DEG F. and then quenched with water to 600-1000 DEG F. Hydrocarbons and water are condensed and the hydrocarbon layer fractionated to give a light fraction from which olefins and diolefins may be recovered, a heavy naphtha which may be used as a solvent or motor fuel or treated to recover naphthalene if present in the feed to the cracking step, and an intermediate aromatic fraction containing benzene, toluene and xylenes, for example a 145-350 DEG F. cut. This is freed from olefins with sulphuric acid, clay or fuller's earth and yields an aviation gasoline blending stock. The temperature in the thermal cracking stage should be at least equal to 1332-107.6 log. S + 10S-1,45, where S is the contact time in seconds. Alternatively, a naphtha, preferably a virgin naphtha of B.R. about 300-400 DEG F. containing more than 40 per cent naphthenes and cyclo-olefins, may be hydroformed at 850-1100 DEG F. using Group 6 oxides or sulphides, preferably molybdenum oxide on alumina, and the products fractionated as before, an intermediate fraction of B.R. 250-350 DEG or 450 DEG F. being thermally cracked, preferably with steam, quenched, and the desired aromatic fraction recovered.ALSO:A petroleum fraction is catalytically cracked or a naphtha catalytically reformed, an aromatic-rich fraction boiling within the range 200-500 DEG F. is separated, thermally cracked at at least 1200 DEG F. for a time from a few seconds to a fraction of a second, and an aromatic fraction of aviation gasoline boiling range is recovered from the products. The thermal cracking converts non-aromatics to lower boiling products, and higher boiling aromatics to benzene and toluene. The product may be acid treated to remove olefinic constituents and, if desired, fractionated to separate benzene and toluene or excess benzene may be alkylated to cumene. A high boiling feedstock such as gas oil or refined crude may be catalytically cracked at about 800-1050 DEG F. using silica-alumina or other catalyst in a stationary or moving bed or as suspended powder. The products are fractionated to obtain a light fraction boiling up to about 200-225 DEG F. which may be worked up to a gasoline, and a fraction preferably of B.R. about 200-350 DEG F. which contains 50-80 per cent aromatics. This fraction, preferably with a diluent such as steam or hydrocarbon gases, for example steam equivalent to 80 mol. per cent of the mixture, is heated at 1200-1600 and then quenched with water to 600-1000 DEG F. Hydrocarbons and water are condensed and the hydrocarbon layer fractionated to give a light fraction from which olefins and diolefins may be recovered, a heavy naphtha which may be used as a solvent or motor fuel or treated to recover naphthalene if present in the feed to the cracking step, and an intermediate aromatic fraction containing benzene, toluene, and xylenes, for example a 145-350 DEG F. cut. This is freed from olefins with sulphuric acid, clay or fuller's earth and yields an aviation gasoline blending stock. The temperature ( DEG F.) in the thermal cracking stage should be at least equal to 1332-107.6 log S+10S-1,45, where S is the contact time in seconds. Alternatively, a naphtha, preferably a virgin naphtha of B.R. about 300-400 DEG F. containing more than 40 per cent of naphthenes and cyclo-olefins, may be hydroformed at 850-110 DEG F. using Group 6 oxides or sulphides, preferably molybdenum oxide on alumina, and the products fractionated as before, an intermediate fraction of B.R. 250-350 DEG or 450 DEG F. being thermally cracked, preferably with steam, quenched and the desired aromatic fraction recovered. It may be fractionated to recover benzene and toluene or benzene in excess of specifications for aviation gasolene may be alkylated with propene and phosphoric acid at 400-500 DEG F. and 600 p.s.i. to yield cumene.