Pd掺杂Fe催化剂上邻甲酚加氢脱氧理论研究

应用密度泛函理论计算研究了邻甲酚在催化剂Fe(211)表面上的吸附活化行为和加氢脱氧反应性能。在此基础上，探究了过渡金属Pd掺杂以及表面水对Fe催化剂活性和产物选择性的影响。结果表明，邻甲酚通过苯环与催化剂表面发生吸附相比于通过羟基与表面相互作用更具能量优势，有利于活化苯环及C_Ar—O键。Fe(211)表面上邻甲酚脱羟基生成甲苯比其脱甲基生成苯酚更具动力学优势。Pd掺杂减弱了邻甲酚的吸附能，但其使邻甲酚C_Ar—O键断裂再加氢生成甲苯的活化能垒降低。Pd掺杂能够促进H₂分子解离，增大表面H^*覆盖度，降低关键表面物种的吸附热，最终提高邻甲酚加氢脱氧速率。因此，Pd掺杂Fe催化剂对邻甲酚加氢脱氧生成芳烃表现出较好的活性和选择性。H₂O^*参与能够进一步降低邻甲酚脱羟基活化能垒，促进产物甲苯的生成。

Theoretical Study on Hydrodeoxygenation of o-Cresol Over Pd-Doped Fe Catalyst

Adsorption behavior and hydrodeoxygenation property of o-cresol on Fe(211) surface were studied with density functional theory calculations. In addition, effect of Pd doping and participation of surface water on the activity and selectivity of Fe catalyst were further investigated. Experimental results showed that o-cresol adsorbed on the catalyst surfaces through benzene ring is stabler than -OH groups interacting with catalyst surfaces, and thus the former has advantage to activate both benzene ring and C_Ar—O bond. It was also found that, on Fe(211) surface, toluene formation via dehydroxylation was kinetically more favorable than phenol formation via demethylation, and thus this causes higher selectivity for aromatic products. Doping Pd can reduce energy barriers of o-cresol hydrodeoxygenation, and thus help C_Ar—O cleavage and subsequent hydrogenation to produce toluene, although it can lead to weak adsorption of o-cresol on Fe(211). In the presence of Pd dopant, hydrogen molecules can be easily dissociated, and thus increase surface H^* coverage and reduce adsorption energies of key surface species. Therefore, Pd doping can increase o-cresol hydrodeoxygenation reaction rate. Calculation results suggest that Pd-doped Fe catalyst exhibits good activity and selectivity for toluene production; H₂O^* can participate H-transfer process and further decrease hydrodeoxygenation reaction barriers, and improve toluene product selectively.