GB840817A - Recovery of unsaturated hydrocarbons - Google Patents

Abstract

Substantially pure acetylene and pure ethylene are simultaneously recovered from a gaseous mixture obtained by the high temperature cracking of a hydrocarbon feed by passing this gaseous mixture comprising acetylene, ethylene and diacetylene through a first contact with a sufficient amount of a selective solvent to remove substantially all the diacetylene, passing the gaseous mixture through a second contact with a selective solvent of sufficient amount to absorb substantially all the acetylene and ethylene in the mixture, separating the absorbed gas from the solvent of the second contact, passing the separated gas through a third contact with a selective solvent of sufficient amount to absorb substantially all of the acetylene, withdrawing as product all of the pure ethylene passing through said third contact solvent and separating as product substantially all of the acetylene absorbed by the third contact solvent. The preferred selective solvents are dimethylformamide for the removal of the diacetylene, lean oil to dissolve the acetylene and ethylene together, and dimethylformamide for the final separation of acetylene. The cracking step may be effected in two steps, firstly as a high temperature regenerative cracking process at 1/2 atmosphere total pressure with steam dilution and temperatures ranging from 1800 DEG to 2300 DEG F. and then by conventional cracking in a tubular furnace at slightly above atmospheric pressure at 1470-1550 DEG F. Loss of acetylene at the initial adsorption may be minimized by the recycling of a small quantity of stripping gas consisting of the nearly acetylene-free residual gas produced in the system.ALSO:Substantially pure acetylene and pure ethylene are simultaneously recovered from a gaseous mixture obtained by the high temperature cracking of a hydrocarbon feed by passing this gaseous mixture comprising acetylene, ethylene and diacetylene through a first contact with a sufficient amount of a selective solvent to remove substantially all the diacetylene, passing the gaseous mixture through a second contact with a selective solvent of sufficient amount to absorb substantially all the acetylene and ethylene in the mixture, separating the absorbed gas from the solvent of the second contact, passing the separated gas through a third contact with a selective solvent of a sufficient amount to absorb substantially all of the pure ethylene passing through said third contact solvent and separating as product substantially all the acetylene absorbed by the third contact solvent. The preferred selective solvents are dimethylformamide for the removal of diacetylene lean oil to dissolve the acetylene and ethylene together, and dimethylformamide for the final separation of acetylene.