GB822689A - A process for the catalytic desulphurization of deasphaltized heavy sulphur-containing hydrocarbon oil fractions - Google Patents

Abstract

A process for the desulphurization of a deasphaltized heavy hydrocarbon oil fraction, of which at least 90% volume boils above 450 DEG C. and more than 20% volume boils above 500 DEG C., comprises allowing the fraction, while at least partly liquid, to flow downwardly at 10 to 100 atmospheres and 300-500 DEG C., over a fixed catalyst comprising at least one metal and/or compound thereof from each of Groups VI and VIII in the presence of an added, sulphur-containing auxiliary hydrocarbon oil of lower boiling range and in the presence of an excess of a gas containing a major proportion of hydrogen such that after cooling and removing H2S from the exit gases of the process there remains between 50 and 2000 litres gas/kg. total oil (S.T.P.). The heavy oil and the auxiliary oil may subsequently be separated by distillation with or without vacuum and/or the addition of steam. The heavy oil fraction may be obtained by applying one or more physical, thermal and/or catalytic treatments to crude petroleum, e.g. fractional, vacuum and/or steam distillation, cracking, and extraction of aromatics with polar solvents. Deasphaltizing liquids mentioned are liquefied light hydrocarbons, e.g. butane and/or propane. Auxiliary oils mentioned are kerosine, gas oil and flashed distillates. They may be straight-run distillates of crude oils or the products of one or more physical, thermal or catalytic treatments thereof. A 200-450 DEG C. fraction obtained in the catalytic cracking of heavy oils is particularly suitable. The boiling range of the auxiliary fraction may adjoin or slightly overlap that of the heavy fraction but it is preferably distinctly lower. The preferred catalysts comprise nickel and/or cobalt plus molybdenum and/or tungsten on alumina, the elements being present as metals and/or compounds with one another and/or oxygen and sulphur, particularly 5-15 wt. per cent of cobalt and molybdenum (as metals and/or compounds with each other and/or one or more of the elements oxygen, sulphur and aluminium) on alumina, wherein the atomic ratio Co:Mo is between 1:20 and 18:20. The hydrofining is operated by the trickle process wherein the liquid portion of the oil flows in a thin film over a fixed bed of catalyst. The hydrogen-containing gas may be a mixture of hydrogen and light hydrocarbons and usually contains at least 60 volume per cent, preferably more than 80%, of hydrogen. It may be passed in counter-current or parallel flow with the liquid oil and may be recycled after removal of H2S. In an example a deasphalted residue, of which 90% by volume boiled above 492 DEG C. and 85% by volume boiled above 500 DEG C. containing 2.73% wt. of sulphur is blended with a flashed distillate (350-500 DEG C.) from the same crude and desulphurized by the trickle technique over a 3.9 wt. per cent CoO/10.7 wt. per cent MoO3/81.3 wt. per cent Al2O3 catalyst at 50 kg./sq. cm., 275 DEG C., 1 kg./l./hr., and a feed rate of 550 to 570 N.T.P. litres of pure H2/kg. feed, to give a 500 l./kg. excess of H2 and 83% desulphurization. Specifications 657,521 and 665,575 are referred to.