Effects of catalysts in carbon dioxide reforming of methane via corona plasma reactions

The effects of two kinds of representative catalysts, Ni/ Al2O3 and HZSM-5 zeolite, were investigated in the CO2 reforming of CH4 via corona plasma reactions at atmospheric pressure. The catalysts showed little effect on the conversions of CH4 and CO2, and we propose that rapid free-radical processes play a main role during the plasma reactions. However, although a high-voltage electric field was used to initiate the corona discharges and many discharged particles were present within the plasma, which possibly affected the properties of the solid catalysts, Ni/Al2O3 and HZSM-5 zeolite exhibited catalytic selectivity and activity in the reactions. When the catalysts were used in the reactions, the H-2/CO ratios in the products were modified, and more hydrocarbons and oxygenates were formed. It was found that a small amount of phenol was directly synthesized in the plasma reactions when HZSM-5 zeolite was used. Thermogravimetric analyses revealed that the coke depositing over the different catalysts was of different types. It is proposed that the coke over Ni/Al2O3 mainly originated from CH4 decomposition, even though a comparative portion of the coke originated from CO disproportionation. More coke deposited over HZSM-5 zeolite than over Ni/ Al2O3, and it contained more hydrocarbons and oxygenates, simply reflecting the characteristics of the catalyst.