GB712033A - Improvements relating to the catalytic desulphurisation of petroleum hydrocarbons - Google Patents

Abstract

Petroleum feedstocks are desulphurized in a two-stage process comprising passing a relatively low-boiling feedstock in vapour form to an autofining zone operated at a pressure below the equilibrium pressure and passing the excess gas formed to a second desulphurization zone in which a relatively high-boiling petroleum feedstock is contacted with a sulphur-resistant hydrogeneration catalyst. Sulphur-free products are removed from both zones. In the autofining process the feedstock in admixture with hydrogen is passed over a catalyst under such conditions of temperature and pressure that dehydrogenation of naphthenes in the feedstock produces sufficient hydrogen to convert organically combined sulphur to hydrogen sulphide and to maintain the pressure in the reaction zone, the hydrogen being recycled to the reaction zone on the sole source of hydrogen thereto. The catalyst may be mixtures of oxides of cobalt and molybdenum, chemical compounds of cobalt, molybdenum and oxygen, or mixtures thereof; a specified catalyst is mixed cobalt and molybdenum oxides on alumina. The autofining process may be carried out in a static bed reaction or by using a moving bed or third catalyst. The low-boiling feedstock may be naphtha or kerosine and the high-boiling feedstock may be gas oil, wax distillate, crude oil or reduced crude. A crude oil may be fractionated to recover a fraction, which is autofined, and a residue, which is hydrofined using the excess gas from the autofining stage. The autofining zone may be operated at a temperature of 750 DEG -800 DEG F. and a pressure of 50-250 p.s.i.