| Nitrile is an important chemical intermediate,which is widely used in medicine,agriculture,fine chemicals,rubber,functional materials,high performance polymers and other fields.The traditional process for nitrile preparation usually has many synthesis steps,harsh reaction conditions,and other problems,which is inconsistent with the concept of green and sustainable development.With alcohol as raw material,one-pot direct ammoxidation of alcohol to nitrile under the action of ammonia and oxygen has the advantages of high reaction efficiency,mild reaction conditions,and water being the only byproduct,which makes it a green route for the synthesis of nitrile.At present,the catalysts for direct ammoxidation of alcohol to nitrile is metal-based catalyst.The reaction system needs to add organic solvent,the use of organic solvent inevitably increases the production separation cost and may cause some environmental problems.Therefore,it is of great significance to develop solvent-free non-noble metal catalysts and low-cost non-metallic catalysts for the preparation of nitrile by direct ammoxidation of alcohols.In this thesis,a series of green,high efficiency and low-cost catalytic materials have been designed and prepared,and successfully applied in the direct ammoxidation of alcohols.This series of catalysts can synthesize nitrile compounds at relatively mild reaction conditions with high conversion and high selectivity.The mechanism and pathway of the direct ammoxidation reaction of alcohols were investigated,and the fundamental reason for the high activity of this series of catalysts was revealed through various physicochemical characterization.Specific research contents are as follows:(1)Ammoxidation of alcohols to nitriles over cobalt-manganese bimetallic catalyst.CoOx/MnO2 catalyst was prepared by impregnation method using MnO2 nanorods as support.The morphology and structure of CoOx/MnO2 catalyst were characterized by XRD,SEM,TEM,XPS,Raman,N2 adsorption-desorption isotherm,and NH3-TPD.The optimum reaction conditions were obtained by screening the reaction temperature,reaction time,catalyst dosage and oxygen pressure.The yield and selectivity of benzonitrile reached 85.5%and 90.2%under the optimal reaction condition(100℃,8 h)with ammonia as nitrogen source under oxygen.The interaction of Co and Mn and reaction mechanism were investigated.It was revealed that Mn species was the main active point and Co species was the co-catalyst of the reaction.The controlled experiments showed that water can accelerate the conversion of benzonitrile to benzamide and tuned the selectivity of benzonitrile and benzamide.The kinetic study shows that the oxidation of benzyl alcohol to benzaldehyde is the rate determination step for the continuous reaction.In addition,the catalytic system has good universality for the conversion of aliphatic,benzyl,allyl and heterocyclic alcohols to the corresponding nitrile.(2)Ammoxidation of alcohols to nitriles over Se,P and N doped carbonbased catalyst.Se,P,N/CN-900(Se,P,N/CN-900)tri-doped non-metallic carbonbased catalysts were prepared by simple calcination method using waste crop straw as raw material.The morphology and structure of the catalyst were characterized by XRD,SEM,TEM,XPS,Raman,FT-IR,and N2 adsorptiondesorption isotherm.The catalyst can achieve high catalytic efficiency for ammoxidation of benzyl alcohol to benzonitrile.Through the optimization of reaction conditions,the yield of benzonitrile can reach 92.7%and the selectivity is 99.5%at 120℃ and 12 h.It was found that the interaction between pyridineN/Pyrrole-N and doped Se,P,N and C was the main reason for the excellent catalytic performance.Based on the controlled experiments and kinetics,the reaction pathway is revealed.In addition,the catalytic system has good universality properties and can direct ammoxidation benzyl,allyl and heterocyclic alcohols to the corresponding nitriles. |
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