| The extensive use of fossil fuels not only has brought great harm to the fragile ecological environment, but also is the source of energy conflict of today’s social. These problems have threatened the progress of human society and it is of great significance to develop renewable energy. As an extremely abundant renewable resource, biomass can alleviate the energy crisis in a very great degree in the future. Lignin, coming from biomass with a rich reserve, is the only large volume renewable feedstock to preparation of aromatic chemicals and liquid fuel in nature. However, the special structure makes lignin has physical stability and chemical inertness, resulting in difficulty in lignin using. In most cases, lignin is used as garbage which pollutes environment and wastes energy. Therefore, developing a highly efficient method of lignin depolymerization has urgent practical significance.In allusion to the current situation that lignin depolymerization system was given priority to with organic solution, this paper proposed a alkaline aqueous reaction system, which can reduce cost and the damage to operators’health. And following two experiments were carried out on this basis.1. C6o/Bi2TiO4F2 photocatalytic depolymerized lignin under visible light irradiationPhotocatalysis is a strong oxidation process. For tight structure’s lignin, the oxidation groups generated by photocatalysis can easily break it chemical bonds, result in lignin depolymerization under moderate condition. Photocatalysis under visible light irradiation can use more energy from sunlight and realize the efficiently comprehensive utilization of solar energy and biomass energy.For comparison with the catalytic activity of C6o/Bi2Ti04F2, Bi2Ti04F2 and C60/TiO2 were also studied to depolymerize lignin under visible light irradiation. Photoluminescence emission spectra and UV-vis absorption spectra of catalysts indicated that C6o/Bi2Ti04F2 possessed the strongest visible light catalytic activity., The initial solution pH, initial lignin concentration and C6o loading influencing on the yields of monomer products were studied in experiments, and the results proved that C6o/Bi2Ti04F2 had the best catalytic effect. The optimum conditions of photocatalytic depolymerization lignin by C60/Bi2Ti04F2 were initial solution pH 7, initial lignin concentration 1.25g/L and 1% C60 loading. At the same time, stability experiments of the three catalysts were also implemented to study the deactivation.2. Lignin catalytic depolymerization by rare earth oxideThe reaction of lignin catalytic depolymerization by rare earth oxide was carried out under the condition of high temperature and high pressure, which could reacted lignin with a large volume. CeO2 and La2O3 were used as catalysts to depolymerizate lignin under different temperatures in experiments. In order to analyze the performance of the catalysts, the reaction liquid was extracted by ether and ethyl acetate to get their extraction and residue. Meanwhile, the qualitative and quantitative analysis of the monomer products were implemented, and the main composition were phenol,2-methoxy-4-propylphenol,2-methoxyphenol,2-methoxy-4-ethylphenol catechol and isoeugenol.250 ℃ was the best reaction temperature for the two catalysts, which could obtain the best lignin depolymerization efficiency and the highest monomer products yield.Monomer products are molecular platform to preparation of high value-added chemicals and liquid fuel. Above two lignin depolymerization methods all achieve relatively considerable monomer product yields (the maximum total yields of the main monomer products in above two experiments are 3.65% and 6.94%), which have important significance on lignin efficient use. |
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