We have previously reported an experimental investigation on synthesis of acetic acid directly from CH4 and CO2 via dielectric-barrier discharge. In this work, a DFT study was conducted using three hybrid DFT methods in order to understand the mechanism of such direct synthesis. It suggests that the synthesis is via two pathways with CO 2 and CO as key intermediates. The energy requirement with CO 2 pathway is much less than that with CO. The methyl radical formation and the dissociation of CO2 are two limiting steps for the synthesis of acetic acid directly from CH4 and CO2.

Ni-Fe/La2O3 catalyst prepared by a glow discharge plasma treatment following calcinations thermally exhibits higher activity and selectivity compared to the Ni-Fe/La2O3 prepared conventionally. At the same reaction temperature, the CH4 conversion, CO selectivity and H2 selectivity obtained from the plasma prepared Ni-Fe/La2O3 are 5-9%, 4-7% and 9-15% higher than those from the conventional Ni-Fe/La2O3 catalyst, respectively. At the same methane conversion, the reaction temperature with the plasma prepared Ni-Fe/La2O3 is at least 100 C lower than that with the conventional Ni-Fe/La2O3.

A density functional theory (DFT) study has been conducted in this work to investigate the reaction mechanism of synthesis of oxygenates and higher hydrocarbons from methane (CH4) and carbon dioxide (CO2), using cold plasmas. The main dissociation routes of the reactants were analyzed. The feasibility of the formation of various products, including syngas, higher hydrocarbons, and oxygenates, was discussed. The DFT study confirmed that the major obstacle of the synthesis is the dissociation of the reactants CH4 and CO2. After the cold plasma has supplied the necessary energy for the dissociation of CH4 and CO2, syngas, higher hydrocarbons, and oxygenates can be then easily produced. The present DFT study also demonstrates that the plasma synthesis will normally lead to a formation of a mixture of syngas, higher hydrocarbons, and oxygenates.

A novel Pd/HZSM-5 catalyst was prepared first by glow discharge plasma treatment followed by calcination thermally. Such prepared catalyst shows a higher activity and an enhanced stability for methane combustion. The XRD characterization and XPS analysis confirm that the plasma preparation leads to a better preparation of PdO active species over the HZSM-5 support. Especially, a plasma-enhanced acidity has been achieved upon the FT-IR analysis. The enhanced acidity plays an important role in stabilizing the dispersed PdO active species on the zeolite support.