| In order to balance the supply and demand of global energy,as well as reduce environmental pollution and carbon emissions,the development of green and renewable energy sources was launched across the world for promoting the transformation of energy structure.Among world's primary energy consumption,biomass energy is the world's fourth largest energy source after coal,oil and natural gas.As one of the most important biomass resource,oils and fats can be hydrolyzed to large amounts of free fatty acids,which are considered as an ideal raw material for large-scale production of fatty alcohols and liquid hydrocarbons in industry.This thesis emphasizes on the design and preparation of bimetallic carbon-based catalyst and the value-added transformation of fatty acids:1)fatty acids to long-chain hydrocarbon including alkanes and olefins without solvent;2)fatty acids to fatty alcohols in the methanol-water media.Using lauric acid as a model substance,the characterization and evaluation of the catalytic system,optimization of reaction conditions and exploration of catalytic active center are systematically studied.The concrete progress of this paper is as follows:First,PtZn/NC catalyst was synthesized via in-situ pyrolysis approach with ZIF-8 as nitrogen-doped carbon template,and it displayed outstanding catalytic activity for the decarboxylation/decarbonylation of lauric acid into long-chain alkane/alkene without solvents.The means of loading metal,the calcination temperature and atmosphere showed significant effect on the structure,morphology and catalytic activity of as-synthesized catalysts.PtZn/NC obtained after pyrolysis(900?,1 h,N2 atmosphere)of Pt clusters dispersed on ZIF-8,which was achieved by reducing H2PtC16 with NaBH4 aqueous solution before pyrolysis step,exhibited outstanding decarboxylation/decarbonylation activity of lauric acid.The core structure of the above-mentioned catalyst was bulk PtZn alloy with the average size of 3.2 nm but the shell surface of the particle was rich in Pt revealed by EDS-line-scanning results.The changes during the carbonization process of PtZn/NC catalyst were analyzed based on the TGA and FR-IR results.Combined with the parallel reaction results,the core-shell PtZn alloy was responsible for the high activity and selectivity of undecane/undecene.The optimum conditions for the preparation of long-chain hydrocarbon from lauric acid without solvent were obtained:1 wt%theoretical Pt loading,5 mg catalyst,360?,30 min.Meanwhile,the total selectivities to undecane and undecene was up to 96.6%under the conditions.Moreover,the reusability of PtZn/NC was studied and the main reason for the slightly decreased catalytic activity revealed by XRD was the decline of alloy's crystallinity.Finally,through changing the type of metal precursor,PdZn/NC catalyst was successfully prepared and showed incredible selectivity to undecane and undecene,which greatly proved the superiority of this preparation method for bimetallic carbon-based catalyst.Second,Cu-Co active center was screened for in-situ hydrogenation of lauric acid in methanol-water media among different unsupported bimetallic catalysts synthesized by co-precipitation method.Bimetallic CuCo/C catalysts with tannin as a sacrificial carbon-template were designed and prepared by in-situ calcination method under H2 atmosphere.Among the methanol-water media,Cu/C showed high selectivity to lauryl alcohol but low catalytic activity.In comparsion,Co/C exhibited good catalytic activity but too strong deoxygenation activity.Surprisingly,both dehydrogenation of methanol-water and in-situ hydrogenation of lauric acid were catalyzed efficiently by CuCo/C due to a cooperative effect of Cu and Co.The calcination temperature significantly influenced the carbonization degree of CuCo-Tannin complex and the upcoming catalytic activity.It was found that the CuCo/C calcined at 500? in H2 displayed superior activity towards the production of lauryl alcohol.The structure and properties of CuCo/C were identified by H2-TPR,XRD,Raman spectra and TEM characterizations.According to the reaction results,the coexisting of metallic Cu and metallic Co nanoparticle partially embedded into amorphous carbon with high surface area and hierarchical structure were the key catalytic active sites.In addition,the synergistic catalytic effect between Cu and Co favors the preparation of lauryl alcohol.The reaction conditions for the preparation of lauryl alcohol from lauric acid in methanol-water media were optimized.Under 0.5 ml water,50 mg methanol,15 mg CuCo4/C caltalyst with Cu/Co molar ratio of 1/4 and total theoretical metal loading of 10 wt%,the conversion of luaric acid and the yield of the lauric alcohol can reach 79.1%and 62.3%respectively at 330?for 3 h.Moreover,the reusability of CuCo4/C catalysts were investigated and the main reason for the slight decrease of catalytic activity revealed by XRD is the partial transformation of cubic Co to hexagonal Co and the falling phenomenon of partial Cu particles under severe hydrothermal conditons. |
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