Theoretical Study On The Hydrogenation Of Acrolein Catalyzed By Molybdenum Carbide-based Catalyst

α,β-unsaturated alcohols have high application value in fine chemical and pharmaceutical fields.In the current process for producing unsaturated alcohols,the process for producingα,βunsaturated alcohols by selective hydrogenation ofα,βunsaturated aldehydes is widely used because of its green environmental protection and cheap raw materials,This method involves C=C bonds and C=O bonds.Generally,C=C bonds are more easily hydrogenated than C=O bonds in terms of thermodynamics and kinetics.So we need to find a suitable catalyst to control the selectivity of hydrogenation.Although precious metals have good catalytic performance,they are expensive and resources are short.Transition metal carbides have received extensive attention due to their excellent physical and chemical properties（high hardness,high melting point,strong electrical conductivity and stable chemical properties）.Mo₂C has Pt-like properties and has better selectivity to unsaturated alcohols in experimental studies.Therefore,in this study,the Mo₂C（001）surface was used as the catalyst model.The density functional theory method was used to study the mechanism of selective hydrogenation of acrolein on the surface of Mo₂C（001）,Pt/Mo₂C（001）,Ir/Mo₂C（001）and Mo₂C/γ-Al₂O₃（110）catalysts.The main contents are as follows:In this paper,Mo₂C（001）and Pt/Mo₂C（001）catalyst models are constructed.The adsorption configuration,adsorption energy,activation energy,reaction energy,bond length,and electron transfer of acrolein on the two models were studied.Bond length analysis shows that the hydrogenation of acrolein is a stretching process.Electronic analysis shows that Mo atoms take some electrons from surrounding Pt and C atoms,so the hydrogenation activity of Mo atoms around Pt atoms is enhanced,forming local active sites dominated by Pt atoms adjacent to Mo atoms.As a result,the adsorption energy of adsorbate on the surface of Pt/Mo₂C（001）is greater than that on the surface of Mo₂C（001）,and the partial reaction activation energy on the Pt/Mo₂C（001）surface is reduced,which shows high selectivity for C=O bond.The produced propenol is not easy to undergo hydrogenation reaction further and has good stability.It can be seen from the stable adsorption configuration of each adsorbate on the catalyst surface during the hydrogenation of acrolein that with the addition of H atoms,the adsorbate gradually moves away from the catalyst surface.In order to find a more suitable catalyst,Ir/Mo₂C（001）catalyst model was established and was compared with Mo₂C（001）and Pt/Mo₂C（001）catalyst models.Electron analysis results show that Ir atoms transfer electrons to Mo atoms.Compared with the adsorption energy of the adsorbate on the Mo₂C（001）and Pt/Mo₂C（001）surface.The adsorption energy of adsorbate on Ir/Mo₂C（001）surface is larger than that on Pt/Mo₂C（001）surface.The hydrogenation of acrolein on Ir/Mo₂C（001）surface has a lower activation energy to produce allyl alcohol,and the selectivity toward allyl alcohol is higher than that on Pt/Mo₂C（001）surface.After that,Mo₂C/γ-Al₂O₃（110）catalyst model withγ-Al₂O₃（110）as the carrier was constructed.Compared with the Mo₂C（001）catalyst,it is found that Mo atoms have more electrons and the adsorption energy is also larger than that on Mo₂C（001）surface,which leads to better selectivity toward propanol on Mo₂C/γ-Al₂O₃（110）.