GB732189A - Process for the catalytic reforming of gasoline hydrocarbons - Google Patents

Abstract

A gasoline range hydrocarbon feed containing paraffins and naphthenes is reformed by subjecting it with hydrogen in the presence of a fixed bed of catalyst comprising alumina, combined halogen, and platinum or palladium to an elevated temperature and pressure at which hydrocracking of paraffins and dehydrogenation of naphthenes occurs, a halogen or halogen compound reactable with alumina being introduced during the reaction in such an amount that the hydrocracking activity of the catalyst is increased. The catalyst may initially be free of halogen, the halogen content being furnished by introducing halogen or halogen compound at the conditions of reforming. Preferred feeds are straight run or natural gasolines or naphtha fractions. Halogen or halogen compounds specified are chlorine, bromine, hydrogen chloride, bromide, and fluoride, ammonium chloride, mono- and trichloracetic acids, carbon tetrachloride, chloroform, tert. butyl chloride and fluoride, cyclohexyl and isopropyl fluorides, and dichlordifluormethane. They may be added alone or with the feedstock, continuously or intermittently. The amount required can be determined for a multiple adiabatic reactor system by measuring the total temperature drop when a satisfactory product is obtained with fresh catalyst and adding halogen compound in amount to maintain this constant. If the heat capacity of the reacting mixture is varied, the product of heat capacity and total temperature drop is kept constant. The amount of halogen compound is usually equivalent to less than 0.5 g. halogen/kg. hydrocarbons and may be controlled to restore lost hydrocracking activity to maintain this constant or maintain hydrocracking and dehydrogenating activity in balance. Lowering of hydrocracking activity by addition of water or compounds liberating it can be compensated for by addition of halogen compound. Reforming conditions are: temperature 400-540 DEG C., pressure 3.5-80, preferably at least 15 atmos., weight hourly space velocity 0.2-40, hydrogen charge 0.5-15 mols./mol. hydrocarbon. The catalyst may be prepared by mixing colloidal platinic sulphide with a slurry of precipitated alumina to which hydrogen fluoride or chloride or ammonium chloride has been added, drying, and calcining or reducing prior to use. The platinum content is usually 0.05-1.5, and the halogen content less than 3 per cent by weight. In an example, a straight run naphtha is reformed with and without added tert. butyl chloride. An amount of 0.1-0.2 c.c. per litre of feed is suitable, an increase to 0.5 c.c. causing carbon to deposit unless the hydrogen partial pressure is increased.