Investigation of Alternative Substances for Replacing Hydrogen in Methanation

Currently, a power-to-gas technology that obtains electrolytic hydrogen from renewable energy sources, synthesizes it with carbon dioxide, and converts it to methane has received a great deal of attention. It is called methanation, but there are few studies examining alternative substances to replace the raw material of hydrogen. Since hydrogen does not exist naturally, it is important to find other substances that react with carbon dioxide. We focus on flammable gases formed in oil refineries and petrochemical plants. In this study, based on chemical equilibrium calculations of the so-called NASA-CEA, we tested several gases including flammable and nonflammable gases by reacting them with carbon dioxide. Some of them are included in flare stacks. The reactants in the present gas conversion were H2O, CH3OH, C2H5OH, NH3, CH3CN, CH3N2CH3, C3H8O (1-propanol), C3H8O (2-propanol), C2H6, C2H4, C3H8, C3H6, C3H4 (allene), C3H4 (propine), C6H5OH, (CH3COOH)2, HCOOH, HF, HCl, HBr, H2S, HNO3, and SiH4. The results show that substances with more hydrogen atoms per mol of reactant, such as C3H8, CH3N2CH3, and SiH4, can produce more synthetic methane. One more finding is that graphite due to coking increases proportionately to the number of carbon atoms in the chemical formula.