The effect of citric acid on the catalytic activity of nano‐sized MoS₂ toward sulfur‐resistant CO methanation

Abstract

In this work, a facile hydrothermal route was used to prepare nano-sized MoS 2 catalyst. The effect of citric acid during the MoS 2 preparation process on the catalytic activity of sulfur-resistant CO methanation was investigated. It was found that citric acid played an adverse role on the catalytic activity of MoS 2 toward sulfur-resistant CO methanation. However, CO methanation performance turned out to be better when NH 2 OH⋅HCl as a reductant was removed during the catalyst preparation process. The X-ray diffraction (XRD) and infrared spectroscopy (IR) were performed to discuss the possible mechanism for the effect of citric acid towards CO methanation performance.

Examination of Tunable Edge Sites and Catalyst Deactivation in the MoS2-Catalyzed Methanation of Syngas

“…The reaction over MoS 2 -B5 delivered a higher conversion rate of CO (5.46 h –1 ) than over other catalysts. This value is higher than that (2.86 h –1 ) reported for the reaction over unsupported MoS 2 at a higher reaction temperature (500 °C) . Moreover, the CO conversion rate presents an increasing trend with the increase of the TU amount (B1 → B5, Figure b).…”

“…This value is higher than that (2.86 h −1 ) reported for the reaction over unsupported MoS 2 at a higher reaction temperature (500 °C). 36 Moreover, the CO conversion rate presents an increasing trend with the increase of the TU amount (B1 → B5, Figure 5b). The reaction over all of the catalysts generated methane as the primary hydrocarbon product (ca.…”

“…For the sulfur-resistant methanation of syngas using Mo-based catalysts, MoS 2 is usually considered as the active phase in the existing literature. − There is a consensus that the catalytic active sites are located at the edges of MoS 2 (rather than at the inactive basal plane). A number of studies on the structure–reactivity correlation in MoS 2 -catalyzed hydrogenation reactions have demonstrated that the extent of edge sites exposed can significantly impact the activity and selectivity. − Investigations of the morphology and edge structure of MoS 2 by scanning tunneling microscopy and transmission electron microscopy (TEM) have shown that the number of active edge sites can be tuned by the grain morphology (e.g., size and shape). − Hence, considering the anisotropic nature of layered MoS 2 , decreasing the layer stacking and slab length was effective to generate smaller grains with a higher degree of edge-site exposure. MoS 2 prepared by solvent thermal synthesis using ethylene glycol as the solvent shows smaller particle sizes with increased exposure of the active edge sites than that with water, which promoted anthracene hydrogenation .…”

“…3–5 layers) have been achieved via hydrothermal synthesis using PVP as the surfactant . Considering the layer-stacking structure of bulk MoS 2 with active sites located on the edge, the shape of MoS 2 particles is another crucial parameter in determining the exposure of active edge sites. , Li et al reported that the synthesis of MoS 2 nanoflowers using NH 2 OH·HCl as the reductant and citric acid as the chelating agent could deliver more edge sites, which facilitated the methanation of syngas. Li et al, studying the effect of the Co-doped MoS 2 morphology on the catalytic performance in hydrodesulfurization (HDS), found that MoS 2 rods exhibited a higher HDS activity and stability than MoS 2 belts due to more active-site exposure.…”

Effect of DBD Plasma Treatment on Activity of Mo‐Based Sulfur‐Resistant Methanation Catalyst

“…Therefore, the more uniformly MoS 2 is dispersed on the carrier, the more active sites are exposed, leading to better catalytic reactivity. [47] The results of XPS (Figure 7) and Raman (Figure 8) characterization techniques showed that the catalyst treated by DBD plasma exposes more unsaturated coordination Mo species and S species. It was also observed by EDX-mapping (Figure 5) that the catalyst treated by plasma was more dispersed on the support.…”