GB954791A - Process for the preparation of vinyl chloride - Google Patents

Abstract

Vinyl chloride is prepared by pyrolysis of a vaporized hydrocarbon by injecting it into a hydrogen-rich gas, quenching the pyrolysis gas to stabilise it, purifying it to remove carbon black, tars, and unsaturated hydrocarbons containing more than two carbon atoms but not hydrogen, nitrogen, carbon monoxide, carbon dioxide and methane, passing the resulting purified acetylene and ethylene-containing gas with hydrogen chloride over mercuric chloride catalyst, separating the vinyl chloride, mixing chlorine with the residual pyrolysis gas over ferric chloride catalyst under the conditions for the synthesis of dichloroethane, separating the dichloroethane, purifying and pyrolising it to give vinyl chloride and hydrogen chloride, the latter being recycled to the first catalysis, the process being carried out under pressure of 8-10 atmospheres. The residual gas after the second catalysis may be used as the source of the hydrogen rich gas specified above. Vinyl chloride produced in the first catalysis may be separated by dissolution in dichloroethane and distilling under reduced pressure in the presence of a polymerization inhibitor e.g. phenol or hydroquinone. In the example, vaporized naphtha is injected into hot gases at 600 DEG C. under 10 atmospheres and the resulting gas quenched to stabilize the acetylene and purified by (i) oil washing to remove carbon black and tars, (ii) potassium carbonate to remove carbon dioxide and (iii) washing with kerosene to remove the C3 and C4 hydrocarbons. The purified gas and hydrogen chloride are passed over active carbon impregnated with mercuric chloride at 120 DEG C. under 10 atmospheres. The vinyl chloride produced is dissolved in dichloroethane which is subsequently degasified. Chlorine and the residual gas are mixed and passed through a steel tube under 10 atmospheres at 100 DEG C., ferric chloride being produced by the reaction of chlorine with the walls of the tube. The resulting gas is cooled under pressure to give liquid dichloroethane and the residual gas used as the source of hydrogenrich gas. Dichloroethane is pyrolysed under pressure in the presence of de-ashed activated carbon giving vinyl chloride and hydrogen chloride, which is used in the first catalysis. Ferric chloride catalyst may be impregnated on a carrier e.g. pumice, silica gel, or active carbon.