GB775961A - Hydrogenative reforming of gasoline and other naphtha fractions - Google Patents

Abstract

Hydroforming of naphtha or gasoline is effected in several stages in the presence of a platinum catalyst having strong hydrogenatingdehydrogenating activity, in the initial stage there being absent the combination of alumina and gaseous halogen or halide, and in a subsequent stage only there being present with the platinum catalyst an alumina carrier and a minor amount of gaseous halogen or halide mixed with the stream of naphtha and hydrogen, whereby the initial stage is more favourable for hydrogenation than isomerization and the subsequent stage more favourable for isomerization. Platinum on alumina may be used in the initial stage and halogen added only to the effluent passing to the subsequent stage. Alternatively, aromatics formed in the initial stage may be separated, and the residual product only passed with halogen to the subsequent stage, the isomerized product then being recycled to the first stage preferably with fresh naphtha. The amount of halogen is generally at least 0.001 per cent by weight of the naphtha, and preferably 0.005-0.1, using catalysts containing up to 1 per cent Pt on activated alumina. Pressures may be higher in an initial stage or stages and lower in a subsequent stage or stages. Thus, with a C6-C8 charge, initial hydrogen partial pressure is not less than 400, e.g. 450-500 p.s.i., and pressure in a final stage is not above 300, e.g. 250 down to 150 p.s.i. With higher boiling fractions, higher pressures may be used. With cuts boiling over a range of more than 100 DEG F., the final stage pressure should be at 25 per cent less than that of the first stage. Temperatures are in general 850-1050 DEG F., liquid hourly space velocities 0.5-10, and hydrogen to oil molar ratio 3-10, being the same or different in the stages. The feed may be fractionated into higher and lower boiling fractions which are treated in separate series of reactors under different reaction conditions or the higher fraction may by-pass the initial stage subsequent stages. Naphthas of B.R. 180-400 DEG F. are preferably cut at about 260-300 DEG F. In an alternative method of operation, a carrier other than alumina, such as silica gel, activated carbon or other non-acidic carrier having little or no cracking activity is used in the initial stage. Hydrogen-rich gas from the final reactor may then be recycled to the initial one even if halogen is present.