?.competitive Catalytical Reaction For Selective Hydrogenation And Isomerization Of Styrene Oxide ?.synthesis Of Cobalt-Based Fischer-Tropsch Catalysts By Multilayer Loading

This thesis consists of two parts,I.Competitive Catalytical reaction for Selective Hydrogenation and Isomerization of Styrene Oxide and II.Synthesis of Cobalt-Based Fischer-Tropsch Catalysts by Multilayer Loading.?.Competitive Catalytical reaction for Selective Hydrogenation and Isomerization of Styrene Oxide2-Phenylethanol is one of the most valuable material for perfume production.The Hydrogenation of styrene oxide(SO)to produce this material is the main process as well as research concentration at home and abroad.However,phenylacetaldehyde is also emerging from rearrangement and condensation reaction simultaneously as a main by-product.So how to design and prepare catalysts to inhibit these two side reactions is the only way to solve this problem.Firstly,effects of active metal species,molar ratio of supports' Si/Al and reaction conditions on the hydrogenation,heterogeneous rearrangement and condensation products during reaction were studied fully by XRD,BET,SEM,H2-TPD,NH3-TPD and other characterization measurements to relate the physicochemical properties and catalytical performance.Based on the Al2O3 support,it was found that Pd is more suitable for the selective hydrogenation than Ni and Pt metal species.Both higher conversion and 2-phenylethanol selectivity can be obtained over Pd catalyst under the mild conditions below 150?.Especially,when the reaction temperature is as low as 50?,the conversion of styrene oxide of Pdi/Al2O3 catalyst reaches at 95%,the selectivity to phenylethyl alcohol is 85 wt.%,while the selectivity to phenylacetaldehyde is less than 10 wt.%.The Pd0.5/Al2O3 catalyst for this reaction under H2 atmosphere and the isomeric reaction of styrene oxide under N2 atmosphere were further compared.It was found that the hydrogenation reaction is more favorable under low temperature(50?),while the high temperature accelerates the isomerization to phenylacetaldehyde(150?).When the reaction temperature increases to 200?,the condensation is the main reaction route.Based on the suitable Pd0.5/Al2O3 catalyst,the satisfying conversion and phenylethyl alcohol selectivity can be obtained at 150 C after optimum.By adjusting the SiO2/Al2O3 molar ratio(Si/Al)to change the acidity of the support,it was found that the catalyst rich in SiO2 is more favorable for the SO rearrangement,which promotes the formation of condensation products under higher reaction temperatures.The Pd0.5/Si0.5Al(Si/Al=0.5)catalyst was evaluated to test its stability at 150 ?.The conversion of SO was c.a.95%,and the selectivity to phenylethanol was kept at 83 wt.%.The selectivity to phenylacetaldehyde was maintained at 13 wt.%.After 40 h evaluation,this catalyst still maintained at high activity and selectivity with potential benefits for commercial application.?.Synthesis of Cobalt-Based Fischer-Tropsch Catalysts by Multilayer LoadingWith the production of petroleum decreasing,the use of Fischer-Tropsch synthesis(FTS)to produce coal-based liquid hydrocarbons has received increasing attention,which is divided into a high/medium/low temperature Fischer-Tropsch synthesis in general.The main catalysts are cobalt and iron based catalysts,among which the cobalt-based FTS catalysts show great industrial potential in a low-temperature reaction process.The main product are straight-chain alkyl and heavy hydrocarbons.However,the selectivity to methane is also very high.Based on the previous work of our research group,the multi-layer loading method was studied deeply as well as the effect of reaction conditions on catalytic performance by adding ZrO2,TiO2,ZnO to modify the surface of support and then BET,TPD,TPR,XRD to relate the physicochemical properties and catalytical performance.It has been found that different textural properties of alumina spheres cause different way for the deposition of Co3O4 in the pore or outside the alumina surface.The high specific surface area,pore size and pore volume of the alumina are more favorable to form C5+ long-chain hydrocarbons.With an appropriate amount of Zr orTi modification for the surface of Co15/Al2O3 catalyst,the hydrogenation activity is promoted because the hydrogen desorption peak moves to the low temperature.In this case,the desired C5+ selectivity increased at high CO conversion with low CH4 and CO2 productionThe Co based catalysts can also be prepared by double impregnation method,which can significantly increase the activity of FTS.The conversion of CO over Zr2-Co15/Al-D catalyst can be reached at 96%at 240?,and the C5+ selectivity can still be kept at 60 wt.%or more.It was also found that reducing the GHSV can accelerate catalytical activity and significantly increase the C5+ selectivity.Further,the reduction of H2/CO ratio in syngas also increases the CO conversion.When H2/CO ratio is 2,the methanation and water gas reaction are inhibited significantly.When the H2/CO ratio is 2.3,the CO conversion is much higher,while the methanation reaction is enhanced.Under the reaction conditions of P=2.5MPa.GHSV=1000 h-1 and H2:CO=2:1,the catalytical activity can be maintained at high value for 140 h,and the CO conversion rate can be stabilized above 60%.Simultaneously,C5+selectivity can be stabilized at c.a.83 wt.%.CH4 selectivity is only c.a.8 wt.%and CO2 selectivity is less than 2 wt.%.The effect of calcination temperature of 800 and 1000? was further studied over FTS catalysts modified by ZnO.After calcination at high temperature,the ZnAl composite oxide was obtained as a support.In this case,it is more difficult to reduce cobalt species.While it is interesting that the support calcined at 1000? is beneficial to the formation of Co3O4 particles Because this support forms a composite oxide composed of ?-Al2O3 crystal phase and intact zinc-aluminum spinel ZnAl2O4.The interaction between Co precursors and composite oxide with stable structure is not strong.The Co15/Zn3Al-1000 catalyst promotes the growth of long-chain products and decreases the water gas conversion during the FTS.