环己醇催化脱水制环己烯WO3/MxOy催化剂的研究

分别以SiO₂、γ-Al₂O₃和TiO₂为载体，偏钨酸铵为WO₃前驱体，等体积浸渍法制得WO₃质量分数为12%的WO₃/SiO₂、WO₃/γ-Al₂O₃和WO₃/TiO₂三种催化剂，考察了环己醇脱水制备环己烯的催化剂活性和选择性。采用X 射线衍射、N₂吸附、NH3程序升温脱附和CO₂程序升温脱附等手段对催化剂进行表征，并与催化活性、选择性及稳定性关联。结果表明，催化剂平均孔径大，有利于降低反应物和产物的内扩散阻力，可提高环己醇转化率和环己烯选择性；孔径大小相近的前提下，酸中心量大有利于脱水反应的进行，可提高环己醇转化率；催化剂表面碱强度大、碱中心数多，有良好的抗积炭性能，因而催化剂的稳定性较好。负载WO₃质量分数为12%的WO₃/TiO₂催化剂在反应温度170 ℃和环己醇空速2.7 h^-1的条件下，环己醇转化率可达100%，环己烯选择性可达97%以上，具有良好的稳定性。

Study on WO3/MxOy catalyst for dehydration of cyclohexanol to cyclohexene

WO₃/SiO₂, WO₃/γ-Al₂O₃ and WO₃/TiO₂ catalysts with 12%wt WO₃ content were prepared by the impregnation method, using SiO₂, γ-Al₂O₃ and TiO₂ respectively as the support and ammonium metatungstate as the precursor. Catalytic behaviors of the catalysts for dehydration of cyclohexanol to cyclohexene were tested in a fixed bed reactor. The catalysts were characterized by XRD, N₂ adsorption, NH₃-TPD and CO₂-TPD. The results indicated that larger average pore diameter favored internal diffusion of cyclohexanol and cyclohexene and consequently increased conversion of cyclohexanol and selectivity to cyclohexene. More acid sites favored dehydration reaction and conversion of cyclohexanol. Higher surface base strength and more base sites inhibited coke formation and hence improved the catalytic stability. Cyclohexanol conversion of and selectivity to cyclohexene of 100% and 97%, respectively, were attained over 12%WO₃/TiO₂ catalyst at LHSV of 2.7 h^-1 and 170 ℃.