Pyrolysis of natural gas: chemistry and process concepts

Abstract

Methane can be converted directly to C 2 hydrocarbons by pyrolysis or thermal coupling. The reaction is highly endothermic and the heat must be supplied at high temperatures. Ethene, ethyne, benzene and hydrogen are the main products. Excessive carbon formation can be avoided using short reaction times and low partial pressures of methane preferably by hydrogen dilution of the feed. More than 90% selectivity of C 2 hydrocarbons may be obtained from methane. High yields of ethyne (>85%) are obtainable at extreme conditions of temperatures (> 2000 K) and short reaction times (<10 −2 s). The primary reactions during the pyrolysis of methane are now clearly defined. However, details of the later stages especially the formation of carbon (coke) are not yet fully understood. The formation of the main gas products can be described by simulation models based on elementary reactions. Pyrolysis of methane has been carried out commercially for many years. The processes differ mainly by the way heat is supplied to the reactor. At present, this technology seems to be an economical way of converting methane only under special conditions where ethyne is the desired product.