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 H 2 O in reactant not only enhances the activity to methanol decomposition by enhancing the adsorption of CH 3 OH and CH 3 O 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 Y H2 of 61.72% and 97.22% at 340 °C and 400 °C, relatively high stability, and high anti-coke ability with the presence of H 2 O in reactant. Besides, the catalysts exhibit high selectivity to H 2 and CO, and the H 2 /CO molar ratio in the products maintains the stoichiometric value of 2. The yield of CO 2 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+. [Display omitted] • Combination of heat utilization and syngas production via methanol decomposition. • 0.05-Ni/NaX-500 achieves the Y H2 of 97.22%, H 2 /CO ratio of 2 and high selectivity. • H 2 O enhances the adsorption of CH 3 OH and CH 3 O, and the desorption of CO. • H 2 O in reactant improves anti-coke ability by inhibiting the Boudouard reaction. • The co-existence of Ni3+, Ni2+ and Ni0 in Ni/NaX promotes the redox processes. [ABSTRACT FROM AUTHOR]