Production of Oxygenates from CH4/CO2 Plasma Reaction Assisted by Ni/HZSM-5 Catalyst

Plasma-catalytic CH 4 /CO 2 conversion to oxygenates offers an attractive strategy for developing a sustainable and carbon–neutral society. In this study, coupling of Ni/HZSM-5 catalyst with DBD plasma is used to promote this reaction. It has been found that the catalyst preparation method, Ni loading and ground electrode of DBD reactor significantly affect the selectivity and distribution of oxygenates. The Ni/HZSM-5 prepared by solid ion-exchange method (SIE) achieved ca. 45% oxygenates selectivity. High Ni loading favors alcohols production, but inhibits acetic acid production. High loading of Ni induces strong interaction of NiO particles with HZSM-5, which creates new Lewis acid site (LAS) with stronger acidity. This is probably responsible for producing alcohols. Differently, the liquid ion-exchange method (LIE)- and SIE-prepared 1 wt% Ni/HZSM-5 catalysts, possessing abundant Brønsted acid site (BAS) and Ni 2+ species anchoring on HZSM-5 framework, exhibit a relatively high selectivity of acetic acid. Using the Al foil-DBD reactor, in stead of circulating water significantly improves the selectivity of oxygenates regardless of the employed catalysts. The increased oxygenate is mainly attributed to the improved alcohols selectivity. This probably relates with the electronic state of the CO molecule produced in the two reactors, i.e., excited state and ground state, which influence the competitive formation of alcohols and acetic acid.