Another alternative is CO methanati

Another alternative is CO methanation (eqn (1)) carried out in the presence of excess CO2 (Fig. 1(B)). Methanation of CO has the advantages that the reactants are already presentfor this reaction (CO and H2) in the reformates, and that the produced CH4 can be recycled as a heating fuel for the reforming unit. High selectivity for CO methanation is important in the elimination of CO by methanation, otherwise simultaneous CO2 methanation (eqn (2)) and reverse water gas shift reaction (RWGS reaction, eqn (3)) can give rise to extremely large consumption of produced H2 as well as run away of the methanation reactor due to the highly exothermic nature of the CO2 methanation reaction. To obtain a wideoperating temperature window for selective CO methanation, suitable catalysts must be developed that carry out CO methanation at low temperatures and do not favor CO2 methanation and RWGS reaction at high temperatures.