密度泛函理论在钽化氢催化烷烃脱氢反应中的应用OA

Converting alkanes into alkenes is one of the key methods in the petrochemical field to enhance the value of raw materials.The resulting products are widely used in the synthesis of polymers,fuel additives,and fine chemicals.However,due to the inertness of the C—H and C—C bonds in alkane molecules,the direct dehydrogenation process usually requires harsh reaction conditions,and the catalytic mechanism remains unclear,which limits the design and development of efficient catalysts.In this study,density functional theory(DFT)was applied to investigate the transition state structures and reaction pathways of dehydrogenation of alkanes with different chain lengths catalyzed by tantalum-supported silica(Ta/SiO2).By calculating Gibbs free energy barriers and comparing pathways,it was found that the preferred pathway involves each alkane and the catalyst losing one hydrogen atom to form hydrogen gas,with the metal-hydrocarbon intermediate binding to the catalyst.The energy barrier for this process ranges from 147.3 to 184.1 kJ/mol.Subsequently,the metal-hydrocarbon intermediate undergoes further dehydrogenation to form the corresponding alkene while the catalyst returns to its original structure,with a lower energy barrier between 77.8 and 100.8 kJ/mol.This study clarifies the dehydrogenation reaction mechanism and preferred pathway for this catalytic system,providing a theoretical basis for the design of catalysts for alkane dehydrogenation to produce alkenes,filling the gap in the microscopic mechanistic study of this catalytic system,and offering theoretical guidance and data support for the future design of efficient and stable alkane dehydrogenation catalysts.