Zeolite NaX supported nickel catalyst for highly-selective synthesis gas production by H2O enhanced methanol decomposition

Methanol decomposition for simultaneous waste heat utilization and synthesis gas production is a "one stone two birds" scheme for chemical industry. A rational design of Ni/NaX zeolite catalysts for highly selective methanol decomposition is reported in this work, with the aim to solve the problems of low selectivity, coke deposition and metal sintering. In Ni/NaX, Ni atoms highly disperse in the structure of NaX zeolite. The presence of H2O in reactant not only enhances the activity to methanol decomposition by enhancing the adsorption of CH3OH and CH3O groups and the desorption of CO on the internal surface of Ni/NaX, but also results in the high selectivity and anti-coke ability by inhibiting side reactions. The optimal catalyst (0.05-Ni/NaX-500) achieves the YH2 of 61.72% and 97.22% at 340 °C and 400 °C, relatively high stability, and high anti-coke ability with the presence of H2O in reactant. Besides, the catalysts exhibit high selectivity to H2 and CO, and the H2/CO molar ratio in the products maintains the stoichiometric value of 2. The yield of CO2 is lower than 0.31% at reaction temperature lower than 340 °C. The coexistence of Ni0, Ni2+ and Ni3+ in the catalyst can promote the redox processes by redox couples of Ni3+↔Ni0, Ni2+↔Ni0, and Ni3+↔Ni2+.