TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The composition comprises hydrocarbon compounds containing at least 3C (less than 100 parts per million (ppm) by volume) and less than 100 ppm by volume of oxygenates and water. Preferred Components: The 2C hydrocarbon compounds are ethylene, ethane or acetylene. The effluent stream (E): comes from a methanol-to-olefins process; and contains oxygenates ( less than or equal to 1000 ppm by volume) and water ( less than or equal to 100 ppm by volume). Preferred Method: In the method, after the step (a), the compressed effluent stream (E1) is separated inside: one distillation tower T1 into an ethylene-containing composition C1 at the top of the distillation tower T1 and into a fraction H1 enriched with compounds containing at least 3C, at the bottom of the distillation tower T1; two distillation towers by (b1) separation of the compressed effluent stream (E1) inside a first distillation tower T2 into a fraction F2 at the top of the distillation tower T2 and into a fraction H2 enriched with compounds containing at least 4C at the bottom of the distillation tower T2, and (b2) separation of the fraction F2 inside a second distillation tower T3 into an ethylene-containing composition C2 at the top of the distillation tower T3 and into a fraction H3 enriched with compounds containing at least 3C, at the bottom of the distillation tower T3; or three distillation towers by: (b3) separation of the compressed effluent stream (E) inside a first distillation tower T4 into a fraction F3 at the top of the distillation tower T4 and into a fraction F4 at the bottom of the distillation tower T4, (b4) separation of the fraction F4 inside a second distillation tower T5 into a fraction F5 at the top of the distillation tower T5 and into a fraction H4 enriched with compounds containing at least 4C, at the bottom of the distillation tower T5, and (b5) separation of the fractions F3 and F5 inside a third distillation tower T6 into an ethylene containing composition C3 at the top of the distillation tower T6 and into a fraction H5 enriched with compounds containing at least 5C, at the bottom of the distillation tower T6. In the method after the step (b), the ethylene-containing composition is subjected to: an acetylene saturation; and a complementary separation step called demethanization to separate a fraction enriched with compounds lighter than ethylene from it. The process of manufacturing ethylene dichloride further comprises the pyrolysis of ethylene dichloride to produce vinyl chloride; and the polymerization of vinyl chloride to produce polyvinyl chloride. EXAMPLE - Typical composition comprised of: nitrogen gas (0.15 vol.%); methane (22.37 vol.%); carbon dioxide (less than 1 parts/million (ppm) by volume); acetylene (0.15 vol.%); ethylene (76.6 vol.%); ethane (0.73 vol.%); propylene (0.2 ppm by volume); propane (less than 0.1 ppm by volume); n-butene (less than 1 ppm by volume); n-pentene (less than 1 ppm by volume); water (less than 1 ppm by volume); and methanol (less than 1 ppm by volume).