“…Other drawbacks, such as severe reaction conditions and necessity of handling and feeding solids, also led to the replacement of most coal-to-acetylene processes by alternative routes, such as partial oxidation of methane and pyrolysis of hydrocarbons (e.g., methane, ethane and propane) by heating or in electric arc. [3] Depending on the feedstock and reaction conditions, the product streams contain only certain percentage of C 2 H 2 and the commonly seen gaseous co-products include ethylene (C 2 H 4 ), carbon dioxide (CO 2 ), carbon monoxide (CO) and hydrogen (H 2 ). The C 2 H 2 can be obtained as a separate product by absorption from the gas stream using organic solvents (e.g., N-methylpyrrolidone or dimethylformamide) or through the highly energy-intensive cryogenic distillation processes, and the crude C 2 H 2 also contains various impurities, such as ammonia (NH 3 ), hydrogen sulfide (H 2 S), hydrogen cyanide (HCN), phosphine, arsine and etc, which are usually removed by scrubbing and other gas clean-up operations.…”