Construction Of Supported Novel Metal Catalysts And Application Of Biomass Oil Hydrogenation

With the large consumption of fossil energy and the increasing environmental problems,the efficient use of renewable biomass resources has received extensive attention.Biomass is the only renewable carbonaceous resource on the earth and a valuable source of renewable liquid fuels and chemicals.By developing an effective biomass liquid fuel method,the amount of fossil fuel used can be effectively reduced,which plays an extremely important role in improving the environment.Hydrogenation is usually the final step in the synthesis of various biomass liquid fuels.At present,the conversion of biomass oil into alternative clean energy by hydrotreating has gradually attracted the attention of more and more researchers,and the role of the catalyst is becoming increasingly indispensable.Therefore,the search for high performance catalysts for the hydroconversion of different biomass oils has become the focus of current work.Precious metal/acid bifunctional catalysts have been successfully used in the chemical industry for nearly half a century,and the excellent hydrogenation performance has also been reported in large numbers.The interaction between acid and metal has been well understood in the basic science.However,in this catalytic system,there are many factors affecting the performance of the catalyst,such as the loading of the metal,the particle size of the metal,the distribution of the metal,and the choice of the carrier.This paper analyzes the factors affecting the performance of the catalyst in detail,and clarifies how the synergy between the acid center and the metal center in the bifunctional catalyst changes the catalytic mechanism and leads to unique catalytic performance.By studying the reaction behavior of different biomass oil model compounds in the hydroconversion process,the principle and specific method of metal/acid bifunctional catalyst design were broadened,and the catalytic reaction mechanism and the synergistic effect of metal/acid were investigated.In this research,a series of different metal/acid bifunctional catalysts were prepared,such as Pt-A/Pt@SOD,Pt/Al-MCF,Pt-A/Z,and so on.Some of the catalysts were prepared by colloidal deposition during the loading of metal Pt.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),nitrogen adsorption/desorption(BET),and pyridine-infrared(py-FT-IR)were used for characterizing the structure and morphology of the catalyst.The model compounds of the cracking products of biomass oil were selected as raw materials to explore the reactivity and life of the catalyst in the process of hydrodeoxygenation and hydroisomerization,and to establish the relationship between the reaction raw materials,the bifunctional catalyst and the catalytic performance.The main research contents and conclusions were as follows.(1)Firstly,the hydrogenation reaction of three kinds of typical terpenoid compounds(geranol,nerolidol,geranylacetone)was studied over the industrial common catalyst Pt/Al2O3.The results showed that the coexistence of branched carbon skeleton,carbon-carbon double bond and oxygen-containing functional group made the catalyst have higher activity in the hydrogenation of terpenoids.The mild acidic catalyst Pr/Al2O3 was still too active during the reaction,and polycondensation occured.The reaction produced by-products of the long carbon chain.Therefore,a carrier having a milder acidity and a better diffusion property was selected to construct a catalyst suitable for the hydrogenation of terpenoids.The mesoporous material MCF was successfully prepared and characterized by hydrothermal synthesis.The bifunctional catalyst Pt/Al-MCF-n was synthesized by different Al concentration grafting and colloidal deposition methods.It was found that Pt/Al-MCF-20 had an appropriate acidity and acted on the hydrogenation process of geranylacetone to completely deoxidize it with high stability and no side reactions.(2)The catalyst Pt@SOD was synthesized by hydrothermal method,and a layer of alumina was coated on the surface of the catalyst by hydrolysis of aluminum isopropoxide to form a catalyst with a core-shell structure,Al2O3/Pt@SOD.The Pt particles were immersed in the catalyst by an equal volume impregnation method to obtain a bifunctional catalyst Pt-A/Pt@SOD.The two catalysts were used for the hydrogenation experiment of naphthalene,which was doped with 3000 ppm of benzothiophene.It was found that under the action of the catalyst Pt-A/Pt@SOD,the product was basically decahydronaphthalene,and the selectivity of decalin remained above 75%after 20h.In summary,the catalyst Pt-A/Pt@SOD has excellent sulfur resistance and good catalytic performance.(3)Alumina and zeolite molecular sieve ZSM-5 were selected and was synthesized as the composite carrier by physical mixing.The noble metal Pt was impregnated on Al2O3 and ZSM-5 by effectively controlling the impregnation conditions,and two kinds of catalysts Pt-Z/A and Pt-A/Z with different metal distributions were obtained.Through characterization analysis,it was found that the catalyst sample had a regular structure,the specific surface area was close,and the Pt nanoparticles were uniformly dispersed in the pores.The catalyst was used in the hydrodeoxygenation experiment of eugenol.It was found that under the catalysis of Pt-A/Z,the deoxidation rate reached 100%,and the selectivity of hydrocarbon was close to 100%.The catalyst Pt-Z/A was essentially deactivated after 20 h and the deoxidation rate was reduced to 20%.(4)Pt nanoparticles prepared by PVP gel method were used to prepare three kinds of catalysts Pt@PVP-Z,Pt@PVP-A and Pt@PVP-AZ by equal volume impregnation method.A comparative experiment of eugenol hydrodeoxygenation was carried out together with Pt-A/Z,which had excellent catalytic performance in the above experiment,and the influence of the position of metal and acid on the catalytic performance was further explored.It was found that in the process of hydrodeoxygenation of high concentration eugenol solution(30 wt.%),the activity sequence of the catalyst was:Pt-A/Z>Pt@PVP-AZ>Pt@PVP-A>Pt@PVP-Z.Under the action of the catalyst Pt-A/Z,the conversion of the reaction reached 77.27%,the selectivity of the hydrocarbon compound was as high as 53.63%,and no by-product formation.By adjusting the distribution of the catalyst in the reaction bed,three different catalytic systems were designed to verify the catalytic performance of the three catalysts in the process of hydrodeoxygenation of eugenol.The study found that the distance between metal and acid was not "the farther the better".in the Pt-A+Z system,the conversion rate of eugenol was only 32.80%,and the selectivity of hydrocarbon compounds was only 29.54%.In the designed catalytic system,the Pt-A/Z catalyst still showed the best catalytic performance.(5)The lifetime and activity of the catalyst Pt-A/Z were investigated under conditions of deep hydrogenation.Experiments showed that after 500 h,the catalyst Pt-A/Z still maintained the optimal catalytic performance,the conversion rate was close to 100%.The Pt-A/Z catalyst is used in a real bio-oil of lignin depolymerization for hydrodeoxygenation.Through GC-MS analysis of the product,it was found that the product is mostly a C7-C10 naphthenic compound,which can be used as a mixed component of biofuels,indicating that the catalyst Pt-A/Z has high practical application value.