Sulfidation of MoO 3 /γ-Al 2 O 3 towards a highly efficient catalyst for CH 4 reforming with H 2 S

• Published in: Catalysis science & technology 2021-02, Vol.11 (3), p.1125-1140
• Main Authors: Wang, Hao, Wu, Jingxian, Xiao, Zhihuang, Ma, Zhejie, Li, Ping, Zhang, Xinwei, Li, Hongying, Fang, Xiangchen
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/D0CY02226H

The process of CH 4 reforming with H 2 S is an efficient approach to H 2 production, which can not only directly convert sour natural gases without separating H 2 S from CH 4 but can also make full use of waste H 2 S, making it into high value-added products. In the present study, a MoO 3 /γ-Al 2 O 3 material was prepared and further applied to the CH 4 /H 2 S reforming process after in situ sulfidation treatment under an H 2 S/N 2 atmosphere at variable sulfidation temperatures (400−800 °C) and times (0−7 h). The reaction conversion and the H 2 production rate of sulfided catalysts were examined under the conditions of 800 °C and 1 atm with a molar ratio for CH 4 /H 2 S of 1.5 : 1 and a gas hourly space velocity (GHSV) of 15 000 h −1 . By combining various characterization techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy, the effects of sulfidation factors on the structure and the catalytic performance of the Mo-based catalyst were studied. The catalytic activity increased at first and then reduced along with increasing the sulfidation temperature and time, implying the existence of optimal sulfidation conditions, which were identified to be around 500 °C for 1 h. Both the sulfidation temperature and time have significant influences on the transformation of MoO 3 to MoS 2 and consequently affect the phase composition, the crystal size, and the texture, as well as the surface Mo valence states of the sulfurized MoO 3 /γ-Al 2 O 3 catalysts. A catalyst structural evolution mechanism during sulfidation and the subsequent reaction process were proposed, and it was speculated that two simultaneous MoS 2 formation routes, one through the MoO 2 phase and the other through the Mo 5+ O x S phase, were involved. The relationship between the catalyst structure and the catalytic performance was further established, and the edge Mo atoms were assumed to cooperate with the neighboring surface Mo sites to catalyze the reaction together.