Method of treating noble metal and alumina catalysts with hydrogen and hydrogen halide

摘要

Platinum group metal on alumina catalysts are activated or reactivated in the presence of iron by treatment, in the substantial absence of hydrocarbons and carbon, with a gaseous mixture of hydrogen and hydrogen halide, the hydrogen halide partial pressure being not more than 15 per cent of that necessary for the formation of iron halide at the prevailing conditions. The halide content of the catalyst is increased to 0.05-2 per cent and preferably to an equilibrium value of about 0.4-0.5 per cent by weight of chloride (or an equivalent quantity of other halide) for each 50 square metres per gram of alumina surface. The process prevents poisoning of the catalyst with iron halide formed by reaction of hydrogen halide with iron present in the apparatus or in filling materials. The treatment may be used in catalyst preparation or after oxidative regeneration of the catalyst. Temperatures of 700-1000 DEG F. and pressures of 1-40 atmospheres are suitable for the treatment. The process may include a preliminary treatment with hydrogen alone, or a subsequent treatment with hydrogen alone to remove halide above the equilibrium amount. Graphs are provided showing the equilibrium hydrogen chloride partial pressure at various temperatures and pressures. Examples describe the treatment of chlorine-containing platinum on alumina catalyst which has been used in the reforming of naphthas; after regeneration with an oxygen-containing gas to remove coke, the catalyst is treated with hydrogen containing specified small amounts of hydrogen chloride.