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The Active Nature of Crystal MoS2 for Converting Sulfur-Containing Syngas

Chang Liu,Xue-Ying Cui,Yong-Hong Song,Min-Li Zhu,Zhao-Tie Liu,Zhong-Wen Liu

Graphical Cutting edge : The bulk MoS 2 with varied crystallite sizes was investigated for the catalytic hydrogenation of CO, and a hexagonal-prism-shaped model was developed to describe the nature of different active sites on the MoS 2 crystallite. The CO conversion decreased in the order of rim sites > edge sites ≫ basal sites, and the highest activity over the bulk MoS 2 with smallest particles was ascribed to the highest exposure of the rim sites. Molybdenum disulfides are attractive sulfur-tolerant catalysts suitable for the direct conversion of sulfur-containing syngas, which avoids the expensive step of the deep desulfurization. However, the catalytic activity of MoS 2 -based catalysts is relatively low. To improve the activity, previous works have focused on modifying MoS 2 with various promoters and supports, but the structural aspects are largely overlooked. In this work, we investigated the active nature of the MoS 2 -based catalysts for the catalytic hydrogenation of carbon monoxide. Thus, the bulk MoS 2 with varied crystallite sizes was synthesized by the hydrothermal and the thermal decomposition methods. The catalysts before and after catalytic tests were characterized by in-situ X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscope techniques. The CO hydrogenation under low-temperature methanation conditions (The syngas with a H 2 /CO=2 and 40.0 ppm H 2 S, T=360 °C, and P=2 MPa) was applied to evaluate MoS 2 as a catalyst for converting syngas. The catalytic results indicate that the MoS 2 with smaller crystallite sizes exhibited a higher CO conversion. By correlating the structural propriety with the catalytic activity, a hexagonal-prim-shaped model was developed to describe different sites on the MoS 2 crystallite. Based on this model, the activity of different active sites on the bulk MoS 2 for CO hydrogenation decreased in the order of rim sites > edge sites ≫ basal sites. The highest catalytic activity over the bulk MoS 2 with smallest particles was attributed to the highest exposure of the rim sites.