GB609238A - Catalytic reforming process - Google Patents

Abstract

Reforming catalysts comprise compounds of elements of the left-hand columns of Groups 5 and 6, particularly oxides or sulphides of V, Cr, Mo, and W, alone or on alumina, silica, oxides of Mg, Zn, Zr, Ti, or Th, and acid-treated clays. These may be prepared by impregnating the support with solution of the metal compounds or precipitating the support in their presence, followed by calcining; by co-precipitating and calcining; or by fusing salts of the supporting material and the active compounds, e.g. aluminium and chromium sulphates, and treating with a reducing gas to obtain the oxides.ALSO:A reforming process comprises subjecting a substantially saturated gasoline, and an olefinic gasoline fraction boiling at least largely above 120 DEG C. in admixture, and with hydrogen in a ratio of 0.5-15 moles. per mole. of hydrocarbon, to the action of a reforming catalyst at a pressure above 30 atmos. and a temperature of 400-650 DEG C., the olefinic fraction being admixed to the saturated gasoline in the proportion of 1 volume of the former to at least one of the latter, and such that a preponderance of saturated hydrocarbons over olefins is maintained and there is a net production of hydrogen. A straight run gasoline or fraction thereof may be mixed with a thermally cracked gasoline or fraction containing at least 5 per cent of olefins or with olefin polymers. The saturated gasoline comprises at least 50 per cent by volume of the mixture while the olefinic fraction consists of hydrocarbons boiling above 120 DEG C. The preferred conditions are 400-600 DEG C. and 55-100 atmos. or more. Suitable catalysts are compounds of the elements in the left-hand columns of Groups 5 and 6, particularly oxides or sulphides of V, Cr, Mo and W, alone or on alumina, silica, oxides of Mg, Zn, Zr, Ti or Th, and acid-treated clays. These may be prepared by impregnating the support with solutions of the metal compounds or precipitating the support in their presence, followed by calcining; by co-precipitating and calcining; or by fusing salts of the supporting material and the active compound, e.g. aluminium and chromium sulphates, and treating with a reducing gas to obtain the oxides. The active oxide may comprise less than 10 per cent of the composite. The sulphur content of the feed stocks may be reduced by a pretreatment with nickel-tungsten sulphide or chromium oxide under conditions giving appreciable hydrogen production. The preheated charge is fed at a liquid hourly space velocity of 0.1-10 and a mass velocity of above 5 mg./sq. cm./sec. The products are cooled, and may be treated in a series of separating zones at lower pressure and higher temperature to separate gases which are recycled, and liquid products which are subjected to a stabilizing fractionation. Part of the liquid may be used to extract light hydrocarbons from the gases before their recycle while entrained gasoline is recovered from the gases by oil treatment in an absorber. Hydrogen is introduced only at the beginning of the run or its use may be avoided by pressuring the plant with a gaseous hydrocarbon fraction and processing a naphthenic fraction until a sufficient quantity of hydrogen is obtained. The olefinic fraction may be introduced at a plurality of points along the path of the saturated fraction and hydrogen through the reaction zone. A fluidized catalyst may be used or a dense moving mass which is continuously recycled. In examples: (1) the catalyst is 9 per cent Cr2O3 and 91 per cent Al2O3, an the charge consists of a fraction of B.R. 120-205 or 150-205 DEG C. separated from a thermally cracked gasoline and mixed with varying proportions of straight run gasoline. Reaction is effected at 520 DEG C., 68 atmos., a space velocity of 0.95, and a hydrogen molar ratio of 4 : 1. The liquid product is blended with the separated lower boiling fraction of the thermally cracked gasoline; (2) comparative results are given of the reforming of a straight run naphtha with various portions of a cracked distillate using alumina-chromia at 500 DEG C., 68 atmos., and space velocity 4. Specifications 549,963 and 579,766 are referred to.