Preparation Of Novel Carbon-based Solid Acid Catalysts And The Application In Hydrolysis Of Cellulose

The contradiction between the growing demand for energy and the diminishing supply of mineral resources energy have driven scientists to focus on the development and application of renewable and green energy resources.Biomass resources have attracted much attention as a green and renewable resource.Specifically,lignocellulose becomes the most potential alternation to fossil resource,due to its many advantages,such as various sources,tractability,cheapness and renewability.Lignocellulose is mainly composed of cellulose.For better utilization of lignocellulose,the key step is the degradation of cellulose into monosaccharides via chemical or biological methods.Hydrolysis of cellulose with the assistance of liquid acid catalyst could hardly prevent by-products in process,corrosions in equipment and pollutions into environment.Hydrolysis catalyzed by biological enzyme,suffered from time-consuming of the reaction and instability of the enzyme.While,solid acid catalyst might solve the above problems and becomes a promising catalyst in hydrolysis of cellulose.Therefore,in this dissertation,several novel carbon-based solid acid catalysts were developed by testing different modifying techniques and applying the techniques to different raw cellulose materials.The relationship between the adsorption properties and the catalytic activities of newly prepared catalysts on cellulose were also studied.Take sucralose as a carbon-base,a novel carbon-based solid acid catalyst contained adsorbed group-Cl and the catalytic active group-SO3H,was developed.The newly developed catalyst was characterized by FTIR,XRD,SEM and so on.The relationship between the adsorption properties and the catalytic activity of newly developed catalysts on cellulose were also studied.The yield of glucose was 55.0%,when IL-treated micro-crystalline cellulose was hydrolyzed into glucose by SUCRA-SO3H containing-Cl groups.And that was much high than 49.0%,when the same substrate was hydrolyzed by SUCRA-SO3H without-Cl groups.Besides,better adsorption capacity for the model substrate cellobiose was obtained by the catalyst containing-Cl groups other than the Cl-free one.The trend was also consistent with the changes in catalytic activity.The characterization results suggested that the carbon structure was in amorphous and the particles was some 20?m in size.The results also confirmed the successful attachment of both-Cl group and-SO3H group.The apparent activation energy of the hydrolysis reaction catalyzed by SUCRA-SO3H was 94 kJ/mol,which was remarkable lower than that of liquid acid sulfuric acid(170-180 kJ/mol).To facilitate the separation of solid acid catalysts from the completed reaction system,a novel magnetized carbon-based solid acid catalyst containing adsorbed and catalytic groups was developed by introducing magnetic particles such as ferric oxide.The newly developed catalyst was characterized and the magnetism and the catalytic activity of newly developed catalysts were also studied.The saturation magnetization increased from 0.35 emu/g to 2.62 emu/g and finally reach the summit,when the addition of ferric chloride upregulated from 1 g/L to 6 g/L.Considering the relationship between the saturation magnetization and hydrolysis efficiency of the model substrate cellobiose,the optimum ferric chloride concentration would be 4 g/L,cause the hydrolysis efficiency would not be compromised by the addition of magnetic particles at this level.The highest yield of glucose was 32.0%at 90? in the hydrolysis of IL-treated micro-crystalline cellulose.The characterization results suggested that the carbon structure was in amorphous,surface in coarse and the particles was some 100 ?m in size.The results also confirmed the successful attachment of both-Cl group,-SO3H group as well as magnetic particle ?-Fe2O3.An ionic liquid modified carbon-based solid acid catalyst was developed by introducing the di-ethylenetriamine hydro-chloride ionic liquid to the surface of a newly prepared carbon precursor containing-COOH and-SO3H functional groups.The adsorption capacity for cellobiose increased by 13.3%,compared to catalyst without ionic liquid modified.The yield of glucose increased from 42.5%to 52.1%at 120? in the hydrolysis of IL-treated micro-crystalline cellulose.The trend was also consistent with the changes in absorption activity.The characterization results suggested that the carbon structure was in amorphous.The results also confirmed the successful attachment of both-OH group,-COOH group,-SO3H group as well as di-ethylenetriamine hydro-chloride ionic liquid functional group.To further reduce the cost and simplify the preparation process,a broad range of natural lignocellulose sources were tested as the raw materials to prepare a set of carbon-based solid acid catalyst,by the process including pre-treating with hydrochloric acid and subsequently carbonization and sulfonation.Finally,a novel set of carbon-based solid acid catalyst,contained adsorbed group-Cl and the catalytic active group-SO3H,were developed.Compared to Bagasse-SO3H and MCC-SO3H,catalyst Corn-SO3H,using corn straw as raw material,got higher hydrolysis efficiency when set cellulose as the substrate.Because Corn-SO3H had a higher specific surface area and thus was benefit to the diffusion of the substrate among the catalyst.The highest yield of glucose was 63.3%at 120? after 16 h in the hydrolysis of IL-treated micro-crystalline cellulose,when the corn straw was pre-treating with 20 wt%hydrochloric acid.For more effective utilization of lignocellulose,four types of carbon-based solid acid catalysts containing both adsorbed and catalytic groups were developed,by testing different modifying techniques and applying the techniques to different raw cellulose material.This study also provided a new sight for the design of solid acid catalyst for cellulose hydrolysis.