Patent GB-457997-A (GB)
Title: A process of treating hydrocarbon oils
IPC: C10G17/095
Filed: 1936-02-05
Abstract: Hydrocarbon oils are refined by treating while substantially in the liquid phase between 200 and 400 DEG  C. with a phosphoric acid catalyst deposited on metallurgical coke, a suitable blast furnace slag, silica gel or other carrier with similar properties, until the objectionable components are converted into innocuous substances by polymerization, cracking, isomerization and/or alkylation.  By this treatment the bromine number is reduced, the end-point of the A.S.T.M. distillation is increased, theoctane number is raised, mercaptans are converted to hydrogen sulphide and olefines, thioethers and thiophenes are converted to mer. captans, and the initial boiling point is lowered.  The process is applicable to gasoline, cracked distillate, kerosine and lubricating oil, obtained by distilling or cracking petroleum, shale and hydrogenated oils; and is particularly applicable for stabilizing cracked distillates.  The catalyst is phosphoric acid with or without other substances, catalysts or not, stable under the conditions e.g. boric acid, metal phosphates.  The carrier must be inert to phosphoric acid though it may act as activator, and must resemble metallurgical coke in surface area, number and size of pores, and compressive strength; clays, pumice and charcoal are unsuitable.  As described, coke is screened to a uniform size, from 3 inches to 6 to 10 mesh according to the installation, and impregnated with one-fourth its weight of a 50--60 per cent solution of phosphoric acid, and dried if it tends to drip. Stronger solutions up to 90 per cent may be used hot. The catalyst may be revivified after use by washing with solvent for gums, e.g. benzol-alcohol, benzol-acetone, carbon tetrachloride; or by washing with solvents for gums and phosphoric acid, e.g. acetone, methyl-ethyl ketone, di-ethyl ketone, di-ethylene oxide, ethylene glycol methyl ether, and then renewing the phosphoric acid.  The solvent and the acid may be recovered. Treatment of the hydrocarbon oil below 300 DEG  C. is suitable for stabilizing cracked gasoline, and distillates such as gasoline, Diesel fuel oil, kerosine, and lubricating oil.  Treatment above 300 DEG  C., involving cracking, is suitable for desulphurization and for improving the anti-knock value, and is applied to gaoline distillates and kerosines.  Treatment just below 300 DEG  C. improves the octane number and this effect may be increased by re-circulating a fraction of treated material with the raw material.  In one form of the process oil is treated with the catalyst first between 300 DEG  and 400 DEG  C. to convert some of the components into gum-forming substances, and then between 200 and 300 DEG  C. to convert the gum-forming substances into stable compounds.  Losses may be reduced by fractionating the raw material and treating the fractions separately.  Cracked gases containing olefines may be introduced in order to increase the yield, the anti-knock rating, and the volatility.  The yield may also be increased by removing hydrogen sulphide and mercaptans, e.g. by means of aqueous or alcoholic caustic soda, or cadmium oxide or hydroxide, before treatment.  Fractions boiling at 68--80 DEG  C., 98--112 DEG C., 120--140 DEG  C., 150--164 DEG  C., 172 to 183 DEG  C., and 192--202 DEG  C., have a high content of organic sulphur compounds and these, or fractions obtained by solvent extraction, may be treated separately or in combination above 300 DEG  C. and then desulphurized by absorption of hydrogen sulphide and mercaptans.  For more thorough removal of sulphur, hydrogen sulphide and mercaptans may be removed chemically both before and after treatment with the phosphoric acid catalyst above 300 DEG  C. The treated oil may be recirculated at about 300 DEG  C. before or after removal of mercaptans to improve its stability in storage. Distillates to be treated are freed from nitrogen compounds e.g. by treatment with a 50 per cent sulphuric acid, a fraction more volatile than pyridine being first separated and afterwards re-mixed.  In the treatment with the phosphoric acid catalyst, the time of contact is about 5 to 30 minutes.  In use the catalyst is in the form of metaphosphoric acid or a mixture of the meta- and p  pyro-acids.  The oil must not contain sufficient moisture to prevent the formation of these acids from the ortho-acid used for impregnation.  Removal of sulphur compounds after the catalytic treatment is best effected by cadmium oxide or hydroxide or other agents which do not remove acidic gum inhibitors.  Catalyst chambers are operated in series cyclically. The impregnated carrier may form a stationary bed, or it may be suspended in the oil whilst passing through a heating zone and afterwards removed by decantation or filtration.  The treatment may sometimes be effected in the vapour phase.  As described with flow diagrams (1) a cracked distillate is fractionated, the residue boiling above 115 DEG  C. is treated with sulphuric acid and re-mixed with the lighter fraction, the mixture as a whole, or after removal of fractions rich in organic sulphur, is heated in a coil furnace and treated with catalyst in two chambers, fractionated with or without steam to separate gasoline from bottoms containing polymers; gas from the first fractionation, or a condensate from this gas, is passed into the catalyst chambers; during starting up, residual oil or gasoline from a treated product is circulated through a heating coil and through the catalytic chambers; the organic sulphur concentrates are treated in the same catalyst chambers apart from the main process and at a higher temperature, and the gasoline obtained may be stabilized by treatment in the catalyst chambers during the main process; the light fraction boiling below 115 DEG  C., first separated, may be treated separately in the catalyst chambers; (2) the spent catalyst is renewed by passing acetone through the catalyst chambers, followed by gas to remove the solvent, and by phosphoric acid from sprayers; and (3) a gasoline distillate free from bases, having a low octane member and high sulphur content is sweetened and is treated in the catalyst chamber between 200 DEG  and 300 DEG  C. if poor in sulphur and rich in unsaturateds, or if rich in sulphur, it is fractionated, the low sulphur fraction (again sweetened or not) is treated in a catalyst chamber between 200 and 400 DEG  C. and the high sulphur fraction is treated in a second catalyst chamber between 300 and 300 DEG  C. the product being sweetened, and if necessary stabilized by treatment in the catalyst chamber between 200 and 300 DEG  C.; or a low octane distillate poor in sulphur may be treated like the high sulphur fraction.