Improvements in the manufacture and production of hydrocarbons of low boiling point by the heat treatment of oils of high boiling point, petroleum residues, tars and the like

摘要

Refers to Specification 328,649, [Class 32], and consists in the production of hydrocarbons of low boiling point from heavy hydrocarbons, boiling substantially above 325 DEG C., without formation of undesired by-products, by splitting under pressure in the liquid phase at a temperature above 400 DEG C. in the presence of a small amount of catalyst having a splitting action, continuously withdrawing from the reaction chamber the catalyst together with the whole bulk of the resulting products, separating the catalyst and readily polymerisable substances of high molecular weight, particularly asphaltic substances, from the products and then returning to the reaction chamber a part or the whole of that fraction, free from catalyst and high molecular readily polymerisable substances, which boils above the benzine boiling range. The splitting is advantageously in the presence of small amounts of gases or vapours especially hydrogen or gases containing hydrogen, but the amount of hydrogen should be less than 100 litres per kilogram of normally liquid product leaving the reaction chamber. Suitable catalysts are compounds of groups 4--8, e.g. oxides, sulphides, phosphates and halides; they may be applied on carriers e.g. active carbon, active silica, bauxite, Florida earth or lignite coke and the amount is preferably less than 3, e.g. 0,1--2 per cent of the initial materials. Temperatures for treatment range from 400--600 DEG C., advantageously 430--520 DEG C. Pressure is above 20 atmospheres and preferably above 40, e.g. 50--1000. Initial materials especially poor in hydrogen and rich in asphalt may be pretreated with solvents, adsorption agents, or by distillation to remove asphaltic constituents. Middle oils and fractions of higher boiling point formed by the reaction may be returned to the cracking chamber or may be employed as Diesel oil, or converted to benzine by destructive hydrogenation. In an example petroleum is heated with hydrogen in a tubular preheater under a pressure of 70 atmospheres to 450 DEG C., 1 per cent of catalyst consisting of a mixture of wood charcoal with 10 per cent iron sulphide is added and the whole led through the reaction chamber from which the products are led to a hot separator where vapours and liquid constituents are separated; the latter are released from pressure and low and middle boiling constituents are distilled off from the asphaltic constituents containing the catalyst; the vapours are cooled by indirect heat-exchange with fresh initial material and condensed liquid is fractionated together with the portions distilled off from the asphaltic constituents. In a second example an oil distilled from the asphalt-containing residue of a cracking product of petroleum, from which benzine and light middle oil are separated, is preheated with hydrogen to 500 DEG C. under a pressure of 200 atmospheres and passed into a reaction chamber after adding 1 per cent of catalyst consisting of lignite coke impregnated with 2 per cent of molybdic acid. The reaction product is cooled, released from pressure, separated from catalyst by centrifuging, and then distilled.