Catalytic decomposition of methane in the presence of in situ obtained ethylene as a method of hydrogen production

It is predicted that the catalytic decomposition of methane (CDM) can be a promising pro-ecological method of hydrogen production. The main drawback of this process is fast deactivation of the catalyst by the carbonaceous deposit formed on its surface. This problem can be effectively solved e.g. by methane decomposition in the presence of ethylene. However, as ethylene is expensive, an attempt was made to synthesise it in situ, in the process of oxidative coupling of methane (OCM), which was subsequently combined with the CDM process in one reactor. As OCM catalysts the sodium–calcium or lithium–magnesium oxide systems were tested, while the CDM catalyst was activated carbon. The optimum conditions of ethylene production were established and applied to conduct the combined OCM–CDM process. The combined process was found to produce hydrogen in higher yields than when only the activated carbon catalyst was used. This observation was explained by formation of catalytically active carbonaceous deposit appearing as a result of decomposition of ethylene.