Patent GB-472538-A (GB)
Title: Improvements in the manufacture and production of aromatic hydrocarbon compounds of low boiling point
Filed: 1936-02-18
Abstract: Aromatic hydrocarbons of low boiling point are produced from liquid or solid bituminous materials, such as coals, tars, mineral oils, asphalts or their distillation residues, by the following process. The bituminous material or a fraction thereof is subjected to destructive hydrogenation, and the portion of the products boiling above 250 DEG  C. is, in either order, (a) dehydrogenated, and (b) treated with a halide having a splitting action or with an oxidizing agent at a raised temperature, whereby side chains are removed; finally, the product is cracked.  The destructive hydrogenation products may be freed in known manner from paraffin wax and asphalt before further treatment; the separated asphalt may be subjected to destructive distillation and the distillate added to the destructive hydrogenation product before or after the latter is cracked.  The dehydrogenation may be effected at 350--600 DEG  C. and atmospheric, reduced or raised pressure in the presence of a catalyst.  Specified dehydrogenation catalysts are metals of the platinum group, silver, magnesium, zinc, aluminium, silicon, titanium, tin, lead, vanadium, chromium, molybdenum, tungsten, uranium, manganese, iron, nickel, cobalt, and rare earth metals, preferably in the form of mixtures of their compounds; the catalysts may be applied to carriers, or they may be suspended in the material to be treated and led through the reaction vessel.  Halogens, hydrogen halides, non-metallic halides or acids may be used in association with the catalysts.  The dehydrogenation may be effected in the presence of hydrogen, and other gases or vapours, e.g. steam, nitrogen, oxides of carbon, methane or water gas, may also be added; when hydrogen is present, the preferred catalysts are the oxides or sulphides of the metals of the 5th or 6th periodic group, with or without other metal compounds, and when sulphides are used a volatile sulphur compound, such as hydrogen sulphide, is preferably added.  The dehydrogenation may be effected in stages at increasing temperatures and varying pressures. Dehydrogenation may also be effected (a) by passing the material with air or oxygen over copper at 350 DEG  C., (b) by heating the material with sulphur or another reagent capable of combining with hydrogen, e.g. selenium, tellurium, nitrogen oxides or dilute nitric acid, (c) by halogenating the material and then removing hydrogen halide, or (d) by distilling the material in the presence of a metal such as sodium.  The treatment for the removal of side chains may be effected (a) by heating the material to 50--300 DEG  C. with aluminium chloride, boron fluoride, ferric chloride or titanium chloride, with or without hydrochloric acid, or (b) by treating the material at 50--150 DEG  C. with potassium permanganate or chromic acid.  The cracking stage is effected at a higher temperature than the dehydrogenation stage, suitably at 400--700 DEG  C. and atmospheric or raised pressure, and preferably in the presence of a catalyst; specified catalysts are ferrosilicon or other metal containing silicon, active carbon, which may be impregnated with a metal salt solution, or metal halides or finely divided metals in association with acids or organic halogen compounds.  Cracking is preferably effected in the presence of a small proportion of hydrogen, and other gases or vapours, e.g. nitrogen, carbon dioxide or steam, may also be present.  In the example, a fraction of coal destructive hydrogenation products boiling at 250--350 DEG  C. is led with hydrogen under 300 atm. pressure first over tungsten sulphide at 340 DEG  C. and then at 370 DEG  C. over active carbon which has been impregnated with molybdenum and cobalt salts and after-treated with hydrogen sulphide under pressure; the dehydrogenated product is freed from crystalline hydrocarbons and then heated to 150 DEG  C. with aluminium chloride, and finally passed, with addition of hydrogen, at 530 DEG  C. over a catalyst comprising molybdic acid, zinc oxide and magnesia. Specification 435,254 is referred to.  The Provisional Specification refers to the treatment of destructive hydrogenation products of resins, and states that the removal of side chains may be effected simultaneously with the dehydrogenation at a temperature up to 1000 DEG  C.ALSO:Aromatic hydrocarbons of low boiling point are produced from liquid or solid bituminous materials, such as coals, tars, mineral oils, asphalts or their distillation residues, by the following process.  The bituminous material or a fraction thereof is subjected to destructive hydrogenation, and the portion of the products boiling above 250 DEG  C., is, in either order, (a) dehydrogenated and (b) treated with halide having a splitting action or with an oxidizing agent at a raised temperature, whereby side-chains are removed; finally the product is cracked.  The destructive hydrogenation products may be freed in known manner from paraffin wax and asphalt before further treatment; the separated asphalt may be subjected to destructive distillation and the distillate added to the descructive hydrogenation product before or after the latter is cracked.  The dehydrogenation may be effected at 350--600 DEG  C. and atmospheric reduced or raised pressure in the presence of a catalyst.  Specified dehydrogenation catalysts are metals of the platinum group, silver magnesium, zinc, aluminium, silicon, titanium, tin, lead, vanadium, chromium, molybdenum tungsten, uranium manganese, iron, nickel, cobalt, and rare earth metals, preferably in the form of mixtures of their compounds the catalysts may be applied to carriers, e.g. activated acid-neutralized lignite coke, or they may be suspended in the material to be treated and led through the reaction vessel. Halogens, hydrogen halides, non-metallic halides or acids may be used in association with the catalysts.  The dehydrogenation may be effected in the presence of hydrogen, and other gases or vapours, e.g. steam, nitrogen, oxides of carbon, methane or water gas, may also be added; when hydrogen is present, the preferred catalysts are the oxides or sulphides of the metals of the 5th or 6th periodic group, with or without other metal compounds, and when sulphides are used a volatile sulphur compound, such as hydrogen sulphide, is preferably added.  The dehydrogenation may be effected in stages at increasing temperatures and varying pressures.  Dehydrogenation may also be effected (a) by passing the material with air or oxygen over copper at 350 DEG  C., or (b) by heating the material with sulphur or another reagent capable of combining with hydrogen, e.g. selenium, tellurium, nitrogen oxides or dilute nitric acid, or (c) by halogenating the material and then removing hydrogen halide, or (d) by distilling the material in the presence of a metal such as sodium.  The treatment for the removal of side chains may be effected (a) by heating the material to 50--300 DEG  C. with aluminium chloride, boron fluoride, ferric chloride or titanium chloride, with or without hydrochloric acid, or (b) by treating the material at 50--150 DEG  C. with potassium permanganate or chromic acid.  The cracking stage is effected at a higher temperature than the dehydrogenation stage, suitably at 400--700 DEG C. and atmospheric or raised pressure, and preferably in the presence of a catalyst; specified catalysts are ferrosilicon or other metal containing silicon, active carbon, which may be impregnated with a metal salt solution, or metal halides or finely divided metals in association with acids or organic halogen compounds.  Cracking is preferably effected in the presence of a small proportion of hydrogen, and other gases or vapours, e.g. nitrogen, carbon dioxide or steam, may also be present.  The portion boiling below 250 DEG  C. of the original destructive hydrogenation product may be subjected again to destructive hydrogenation, as described in Specifications 281,298, 302,253, [both in Class 32], and 354,181, to increase the yield of aromatic hydrocarbons.  In the example, a paste of coal and heavy oil is subjected to destructive hydrogenation at 460 DEG  C. and 400 atmos. after addition of specified proportions of tin oxalate and chlorine; the fraction of the products boiling at 250--350 DEG C. is led with hydrogen under 300 atmos. pressure first over tungsten sulphide at 340 DEG  C. and then at 370 DEG  C. over active carbon which has been impregnated with molybdenum and cobalt salts and after-treated with hydrogen sulphide under pressure; the dehydrogenated product is freed from crystalline hydrocarbons and then heated to 150 DEG  C. with aluminium chloride, and finally passed, with addition of hydrogen, at 530 DEG  C. over a catalyst comprising molybdic acid, zinc oxide and magnesia.  Specification 435,254 also is referred to.  The Provisional Specification refers to the treatment of destructive hydrogenation products if resins, and states that the removal of side chains may be effected simultaneously with the dehydrogenation at a temperature up to 1000 DEG  C.