Technologies for the synthesis of ethylene and propylene from natural gas

Abstract

Different technologies for the synthesis of ethylene and propylene from natural gas are considered. The simplest ethylene synthesis method is the oxidative condensation (or dimerization) of methane (OCM process), but the implementation of this method is discouraged by a low ethylene yield. Among the relatively simple methods for the synthesis of ethylene (together with acetylene) immediately from methane are thermooxidative pyrolysis (TOP process) and pyrolysis in the presence of chlorine (Benson process), whose disadvantages are a high temperature and a great number of by-products. A wide range of processes for the synthesis of ethylene and propylene with a small amount of butylenes are based on the intermediate synthesis of syngas from methane and its further use for the direct synthesis of lower olefins or products for subsequent catalytic pyrolysis to lower olefins, such as methanol (methanol-to-olefins (MTO) and methanol-to-propylene (MTP) processes), dimethyl ether, and liquid fuel (Fischer–Tropsch method). The methyl chloride-to-olefins (MCTO) process consisting of the synthesis of methyl chloride via the oxidative chlorination of methane and the catalytic pyrolysis of methyl chloride differ from these three-stage processes in the absence of the syngas production stage. The direct oxidation of methane to methanol and the homologyzation of methanol to ethanol with further dehydration of ethanol to ethylene are also considered.