Abstract
Praseodymium (Pr)-promoted MCM-41 catalyst was investigated for the catalytic decomposition of methyl mercaptan (CH3SH). Various characterization techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption, temperature-programmed desorption of ammonia (NH3-TPD) and carbon dioxide (CO2-TPD), hydrogen temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectrometer (XPS), were carried out to analyze the physicochemical properties of material. XPS characterization results showed that praseodymium was presented on the modified catalyst in the form of praseodymium oxide species, which can react with coke deposit to prolong the catalytic stability until 120 h. Meanwhile, the strong acid sites were proved to be the main active center over the 10% Pr/MCM-41 catalyst by NH3-TPD results during the catalytic elimination of methyl mercaptan. The possible reaction mechanism was proposed by analyzing the product distribution results. The final products were mainly small-molecule products, such as methane (CH4) and hydrogen sulfide (H2S). Dimethyl sulfide (CH3SCH3) was a reaction intermediate during the reaction. Therefore, this work contributes to the understanding of the reaction process of catalytic decomposition methyl mercaptan and the design of anti-carbon deposition catalysts.
Highlights
Methyl mercaptan (CH3 SH) is one of the typical unconventional volatile organic compound (VOC) species, which exhibits high toxicity, volatility, and causticity [1,2]
People exposed to high concentrations of CH3 SH for a long time contributes to the presentation of mental illnesses [2,3]
These results suggest that the problem of deposited coke over these two types of catalysts for CH3 SH decomposition has not been resolved yet, due to the fact that the reaction mechanism of the catalytic degradation of methyl mercaptan is ambiguous
Summary
Methyl mercaptan (CH3 SH) is one of the typical unconventional volatile organic compound (VOC) species, which exhibits high toxicity, volatility, and causticity [1,2]. Nano-CeO2 and HZSM-5-based catalysts have attracted wide attention for the process of the catalytic decomposition of CH3 SH owing to their high concentration of oxygen vacancies [18] and tunable acid–base properties [19], respectively. Modified Ce0.75 RE0.25 O2−δ (RE = Sm, Gd, Nd, and La) [17,24], but the ultrashort stability was still presented for these catalysts (about 8 h TOS test) without obvious improvement These results suggest that the problem of deposited coke over these two types of catalysts for CH3 SH decomposition has not been resolved yet, due to the fact that the reaction mechanism of the catalytic degradation of methyl mercaptan is ambiguous. The reaction mechanism of eliminating methyl mercaptan was investigated in detail by product distribution results, which were detected by flame ionization detector (FID) and flame photometric detector (FPD)
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