Patent GB-565225-A (GB)
Title: Improved process for the production of toluene
Filed: 1943-04-22
Abstract: Toluene is produced by separating from a petroleum distillate rich in naphthenes, a fraction of B.R. 200-300 DEG  F., subjecting this to catalytic reforming, separating fractions of B.R. 200-250 and above 250 DEG  F., catalytically cracking the latter fraction, segregating from the product a fraction of B.R. 200-250 DEG  F., combining the 200-250 DEG  F. fractions from the reforming and the cracking steps, extracting with a preferential solvent for aromatics, treating the extract with sulphuric acid to remove unsaturated hydrocarbons, and fractionating to obtain substantially pure toluene.  Catalytic reforming is defined as a heat treatment above 500 DEG  F. in presence of a catalyst of a hydrocarbon oil consisting essentially of naphthenic hydrocarbons boiling within the gasoline range to give a product of higher aromaticity.  It may be effected in the presence of gases rich in hydrogen, the conditions being such that there is no overall net consumption or a net production of free hydrogen. Suitable reforming conditions are a temperature of 850-1050 DEG  F., pressure slightly above atmospheric up to 500 lbs./sq. in., rate of feed 0.1-3 vols. liquid oil per vol. of catalyst per hr. with 500-5000 c. ft. hydrogen-containing gas per barrel of oil and a catalyst comprising alumina in various forms with an oxide or sulphide of a metal of Groups 4, 5, 6 or 8, especially Mo, Cr, W, V, Co or Ni.  The cracking operation may be effected with an alumina-silica catalyst at 850-1250 DEG  F., increased pressure up to 300 lbs./sq. in., and rate of feed of 0.1-4 vols. liquid oil/vol./hr. or with aluminium chloride, and preferably a volatile chlorine compound such as hydrogen chloride, at 250-400 DEG  F., up to 100 lbs./sq. in., with a contact time of about 10 secs. up to 2-3 mins. The solvent extraction of the 200-250 DEG  F. fractions may be in the liquid phase, the fractions being mixed with, for example, liquid SO2 at 0 to -60 DEG  F. and washed in counter-current with a paraffinic hydrocarbon of substantially different boiling point such as a pentane or a heavy naphtha or light kerosene whereby the non-aromatics in the extract obtained can be separated by fractionation.  Alternatively, the hydrocarbon fractions may be in vapour phase and extracted with a solvent which remains in liquid phase, e.g. phenol, cresol, cresylic acid, a -naphthylamine, diethylene glycol, furfural, dimethylphthalate, aniline or dichlorethyl ether.  Where the fractions have a high olefine content they may be acid treated prior to the extraction.  The toluene is separated from the extract while other hydrocarbons may be recycled. When hydrogen is used in the reforming stage, it is separated from the product and recycled, if desired after scrubbing to remove light hydrocarbons, and at least part of that produced in the reforming reactions may be supplied to the cracking stage.  Cracking products boiling above 250 DEG  F. may be recycled.  Fixed catalyst beds may be used in the catalytic conversions or "fluid catalyst operation" wherein the catalyst is suspended in oil vapours or other gases and the mixture circulated in the same way as a fluid.