GB743928A - Process for the reforming of hydrocarbon mixtures - Google Patents

Abstract

A normally liquid mixture containing paraffinic and naphthenic hydrocarbons boiling below 220 DEG C. is reformed by passing through a reforming zone in the presence of 0.5 to 15 mols. of hydrogen per mol. of hydrocarbon and a catalyst comprising platinum or palladium and an acid acting support under a pressure of from 3.5, preferably 13.5, to 80 atmospheres at a space velocity with the range of 0.2 to 40 parts by weight of hydrocarbon charge per hour per part by weight of catalyst and at a temperature of from 320 DEG to 540 DEG C. at which hydrocracking of paraffins tends to increse out of proportion to dehydrogenation of naphthenes, and providing water in the reforming zone in only such an amount that said increased tendency toward hydrocracking is suppressed. Water or steam may be added to the reaction zone directly or to the charging stocks. Compounds which liberate water under the reaction conditions such as oxygen, alcohols, e.g. t.-butyl alcohol, ketones, peroxides, hydroperoxides and phenols may be used in place of water and introduced with the hydrocarbon mixture. The preferred catalysts contain 0.05 to 1.5 per cent of platinum or palladium and a composite of silica, boric acid or a minor amount of halogen, e.g. 0.1 to 3 per cent by weight of fluorine and/or chlorine, with one or more of the oxides of aluminium, magnesium and the metals of Group IV (a) of the Periodic Table. Suitable acid-acting composites are specified. The catalyst may be used in a fluidized, fluidized-fixed bed, suspensoid, or moving bed operation, fixed bed operation being preferred. The hydrogen and hydrocarbon feed may be preheated to conversion temperature and passed in admixture with the requisite amount of water vapour through a plurality of adiabatic reaction zones or through tubes containing catalyst which are subjected to radiant heat. The reformate is recovered and the hydrogen is separated and recycled to the reaction zone. In a method of operation wherein hydrocracking tends to increase in the later stages of a prolonged processing period, water is introduced in the later stages in such an amount that the extent of hydrocracking is maintained constant. Water may also be introduced to suppress the tendency towards increased hydrocracking when the temperature is increased to compensate for reduced catalyst activity. In cases where the hydrocracking is insufficient relative to dehydrogenation, the partial pressure of water is increased until a predetermined proportion of hydrocracking to dehydrogenation is obtained. The amount of water to be added to the charging stock in a multiple adiabatic reactor system should be such as to maintain constant the product of the heat capacity of the reaction mixture and the sum of the temperature drops in said adiabatic reactors. The amount of water may also be regulated in response to variations in the production ratio of hydrogen to normally gaseous hydrocarbons to maintain the ratio constant. Examples are given, showing the effect of water addition with various catalysts.ALSO:Reforming catalysts comprise platinum or palladium, preferably from 0.05 per cent to 1.5 per cent thereof, and a support consisting of a commposite of silica, boric acid or a minor amount of halogen, e.g. 0.1 per cent to 3 per cent by weight of fluorine, or chlorine, or both, with one or more oxides of aluminium, magnesium and metals of the left-hand column of Group IV. Suitable composites of silica or boric acid with alumina, magnesia, zirconia and thoria are described. Natural aluminium silicates are also used. The support composite may be dried at a temperature between 125 DEG C. and 260 DEG C. and/or calcined at temperatures between 260 DEG C. and 760 DEG C. prior to adding the platinum or palladium. Platinum may be incorporated by mixing chloroplatinic acid and ammonium hydroxide to a pH of 5-10 preferably 8-10 and then commingling this mixture with the support particles. Alternatively the support may be impregnated with a solution of chloroplatinic acid and hydrogen sulphide. The resulting composite containing platinum or palladium is dried at 105 DEG C. to 260 DEG C. and calcined at 260 DEG C. to 540 DEG C.