The Study Of Skeletal Ni And Supported Ni For Guaiacol Hydrogenation

With the over use of fossil raw materials,resource shortages and environment pollution,the utilization of biomass resources has been paid more and more attentions.Lignin is one of the largest proportion of biomass in nature.In this dissertation,we employed catalytic hydrogenation reaction of guaiacol and its hydrolysis production as standard reaction process to systematically study the relationship between the preparation methods,reaction conditions and catalytic activity,catalyst selectivity,which indicated the direction of improving the activity of the catalyst and the selectivity of the target products.Skeletal Ni catalysts were employed for conversion of guaiacol to cyclohexanol,the effects of the reaction temperature and pressure and other reaction conditions on the products were investigated.We explore the reaction path and mechanism by tracing reflects the change of products with time.Under the optimal reaction conditions of guaiacol transformation:180°C,2.0 MPa and 10 m L H₂O for 4 h,the highest conversion rate of guaiacol was 94.3%,the highest selectivity of cyclohexanol was up to 89.4%.Three skeletal types'catalysts were employed for the hydrogenation of guaiacol to cyclohexanol.The skeletal nickel prepared by arc melting showed promising catalytic performance?the conversion rate of guaiacol is 99.7%,the selectivity is 90.3%?,the skeletal nickel prepared by mechanical alloying showed promising stability?the conversion rate of guaiacol is above 90%and the selectivity is above 80%when the catalyst was used nine times?.The catalysts have been characterized with different techniques?XRD,XPS,TEM and SEM?,the results show that the alloys prepared by quenching and arc melting are mainly composed of NiAl₃ phase and Ni₂Al₃.The alloy phase prepared by mechanical alloying are NiAl₃ and Ni2Al₃,and some NiAl alloy phase is also contained,which shows the best stability.The transformation of guaiacol was employed to study the effects of preparation methods and process parameters on catalytic performance of skeletal Ni.The preparation parameters?milling time,the type of control agent,the dosage of control agent,the temperature of heat treatment and other factors?of mechanical alloying were researched.Alloy was grinded with ball mill for 40 h with 0.4 m L ethanol as control agent and then treated at 700°C for 2 h.As a result,more Ni₂Al₃ phase was obtained and it could be further transformed in to high stable skeletal Ni.Similar to the preparation of skeletal Ni,the transformation of guaiacol was employed to study the effects of preparation methods and process parameters on catalytic performance of supported Ni catalyst which was prepared by mechanical mixing method.Supported Ni which was grinded with ball mill for 40 h with 0.4 m L ethanol as control agent and the metal loadwas 40%show promising catalytic performance,due to obvious interaction between TiO₂with Ni,it showed high catalytic activity,the conversion rate of guaiacol reach 56.8%and the selectivity of cyclohexanol reached 71.1%,the production rate of cyclohexanol reach 0.02mol_cyclohexanolg^-1_mentalh^-1,which was close to the highset compared with all reported Ni-based catalysts.