Highly selective production of green syngas by methanol decomposition over steam activated Ni/NaX zeolite catalyst

Abstract

Production of syngas from green energy carrier methanol is of great significance to reform the traditional industry of synthetic chemistry. In this paper, we propose the strategy to tune the catalytic behavior of Ni-based catalyst for highly selective methanol decomposition into green syngas by combining the nano-confined effect of zeolite and the regulatory effect of steam on the structure of Ni/NaX zeolite catalyst. The optimal Ni/NaX zeolite catalyst achieves the H₂ selectivity of 98.8 %, the H₂/CO molar ratio of 2, high coking resistance and superior stability at 340 °C. The coexistence of mesopores and micropores in NaX zeolite and the strong metal-support interaction are considered as factors for the elevated catalytic performance. An optimal fraction of Ni⁰, Ni²⁺ and Ni³⁺ in Ni/NaX zeolite catalyst is found to significantly contribute to the catalyst's high selectivity and activity. Steam acts as promoter that tunes catalytic behavior of Ni/NaX zeolite catalyst. With the presence of steam, the amount of both Lewis and Brønsted acids decreases, and the coke deposition reduces. This also accelerates the desorption of CO, enhances activity and inhibits both the methanation and Boudouard reaction. The current work provides a new idea for developing effective catalysts and optimizing reaction processes.