TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: A purified carbon monoxide stream (12), a purified hydrogen stream (11), a purified methane stream (13) and a product stream comprising hydrocarbons are produced by the separation process.Partial condensation of the process stream is carried out, and vapor/liquid separation is then performed in a flash drum or rectification column.The separation of stream (4) is carried out by vapor/liquid separation in flash drum, distillation column having rectification section and stripping section, or by combined rectification and chilling process carried out using dephlegmator, distillation column with side condensers or advanced heat integrated rectifier system.Portion(s) of intermediate stream (5) is passed to a methane wash tower, and contacted with methane to give an overhead stream comprising predominantly hydrogen and a bottom stream comprising carbon monoxide and methane.The bottom stream is then passed with intermediate stream (S3) to a carbon monoxide recovery system having hydrogen stripper column and carbon monoxide purification column.The bottom stream and stream (S3) used as reflux liquid stream are passed to the hydrogen stripper column.The bottom stream from hydrogen stripper column, rich in carbon monoxide and methane, is passed to the carbon monoxide purification column, in which carbon monoxide and methane are separated as respective carbon monoxide-rich and methane-rich product streams.The streams (5, S3) are treated separately until the streams enter common carbon monoxide purification column. The stream (5) is passed to a rectification column, and contacted with reflux liquid stream comprising carbon monoxide, which is separated from the overhead stream from the rectification column to produce hydrogen-rich stream and bottom stream containing methane and carbon monoxide, with reduced quantity of hydrogen.The bottoms stream from the rectification column is passed to hydrogen stripper column to recover another hydrogen-rich stream and stream (4) rich in carbon monoxide and methane.The stream (S3) is treated to remove hydrogen, and hydrogen-rich stream and stream rich in carbon monoxide and methane are produced.The streams (4, 5) rich in carbon monoxide and methane is passed to carbon monoxide purification column.The process stream containing carbon monoxide, hydrogen, methane and hydrocarbons is derived from the product stream of autothermal cracking process for the production of olefins.Hydrocarbon-containing feedstock and oxygen-containing gas are autothermally cracked in an autothermal cracking reactor over a supported catalyst capable of supporting combustion beyond the fuel rich limit of flammability to produce a product stream comprising olefin, unreacted hydrocarbon, hydrogen, carbon monoxide, methane, and reduced quantity of acetylene, aromatic and carbon dioxide.The reaction product in the product stream is quenched with water, when discharged from the autothermal cracking reactor.Carbon dioxide is removed from the product stream.Portion(s) of product stream is separated into streams (4, 5).The stream (4) is separated into product stream comprising hydrocarbons and intermediate stream (S3) comprising carbon monoxide, hydrogen and methane.The streams (5,S3) are treated in a cryogenic separation system to separate the carbon monoxide, and optionally the hydrogen.Preferred Composition: The intermediate stream (4) contains at least 75 mol% of hydrocarbons, and intermediate stream (5) contains less than 1 mol% of hydrocarbons.The product stream produced by separation of stream (4) comprises at least 90 mol% of hydrocarbons, and intermediate stream (S3) containing less than 1 mol% of hydrocarbons.