ZSM-5/MgO质量比对复合催化剂物化性质及合成甲硫醇反应的影响

采用介孔碱性MgO对微孔酸性ZSM-5分子筛进行复合改性，利用液相沉淀包覆技术制备了ZSM-5/MgO复合催化剂，研究了ZSM-5与MgO质量比对复合催化剂物化性质和合成甲硫醇催化性能的影响。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面积及孔隙分析仪(BET)和化学吸附分析仪(CO₂/NH₃-TPD)等手段对不同复合催化剂的晶相组成、微观形貌、孔结构及表面酸碱性进行分析表征。结果表明：ZSM-5/MgO质量比对ZSM-5/MgO复合催化剂的物化性质和催化性能影响较大。过高或过低ZSM-5/MgO质量比制得复合催化剂中MgO结晶度都有所降低，且未形成包覆相结构；ZSM-5/MgO质量比为1/3时制得复合催化剂形成了均匀包覆相结构和微 介孔结构(总比表面积为162 m²/g，总孔体积0.46 cm³/g)，同时具有酸碱特性；在反应压力1.0 MPa、反应温度370  ℃、H2S/CH₃OH摩尔比2/1、N₂流速80 mL/min、H₂S流速4.9 mL/min反应条件下合成甲硫醇，复合催化剂表现出优越的催化性能、稳定性及寿命，CH₃OH转化率、CH₃SH选择性和CH₃SH收率分别达到90.48%、90.04%和81.47%，催化剂寿命达到18 h。与单一ZSM-5分子筛相比，复合催化剂寿命延长了7 h，CH₃SH收率提高了13.97百分点。

Effects of Mass Ratio of ZSM-5/MgO on the Physicochemical Properties and Catalytic Performance in the Synthesis of Methanethiol

ZSM 5/MgO composite catalysts were fabricated by using acidic microporous ZSM-5 molecular sieve and mesoporous alkaline MgO, based on liquid phase precipitation coating route. The effect of mass ratio of ZSM-5 to MgO on the physicochemical properties and their catalytic performance in the synthesis of methanethiol was investigated. These obtained composite catalysts were extensively characterized by the X-ray diffractometer (XRD), scanning electron microscope (SEM), specific surface area and pore analyzer (BET) and chemisorption analyzer (CO₂/NH₃-TPD) techniques to investigate their crystalline property, morphology, pore structure and surface acidity-basicity, respectively. Results indicate that various mass ratios of ZSM-5 to MgO pose significant impact on the physicochemical properties and their catalytic performance. The crystallinity and content of MgO in composite catalyst is greatly affected by the ZSM-5/MgO mass ratio. As ZSM-5/MgO mass ratio of 1/3, the homogeneously continuous coating phase and hierarchical structure (total specific surface area of 162 m²/g, the total pore volume of 0.46 cm³/g) with acidity and basicity are successfully obtained, which exhibits excellent catalytic performances, stability and reaction lifetime, with methanol conversion of 90.48%, methanethiol selectivity of 90.04%, methanethiol yield of 81.47%, and catalyst lifetime of 18 h under the conditions of reaction pressure of 1.0 MPa, reaction temperature of 370 ℃, H₂S/CH₃OH molar ratio of 2/1, nitrogen flow rate of 80 mL/min and hydrogen sulfide flow rate of 4.9 mL/min. Compared with ZSM-5 molecular sieve, the reaction lifetime of the composite catalyst is extended by 7 h and the yield of methanethiol is increased by 13.97 percentage.