The Research On Hydrolysis Of Cellulose With Coal-based Solid Acids As Catalysts

Cellulose as the main component of lignocellulosic biomass,is regarded as a renewable resource,which is comprised of glucose by ?-1,4-glycosidic bond.Glucose can be sued as raw material to produce bio-ethanol and important chemical products.It has great importance to ease the environment and energy issues caused by using fossil resources to produce chemicals and bunkers.The traditional methods to hydrolysis of cellulose are catalyzed by bio-enzyme and liquid acids,however,the two methods have the same shortcomings:it is hard to separate the products and the catalyst after reaction,and the complex recycling process.For these reasons,the researchers have to find new ways to cellulose hydrolysis.This thesis provides different coal-based solid acids prepared from different classes of coals which will be applied in hydrolyzing cellulose.Coal is the main body of the energy supply in China,which has the complicated structure contains amounts of benzene rings that assembled with alkyl groups and oxygenous groups(such as hydroxide radical,carboxyl,etc.).To take full advantage of these groups is not only beneficial to form carbon skeletons and active sits,but also find a new way to realize high value-added utilization for coal.The coal-based solid acids are prepared from different coals and characterized for the structures.The main contents and results are concluded as follows:1.The resulting catalysis were characterized by XRD,FT-IR and 13C NMR.It was found that the coal-based solid acids have amorphous carbon skeleton,their structures consist aromatic carbon sheets,bridge linkage,aliphatic side chains,SO3H,phenolic OH and COOH groups.2.Coal is an ideal carbon source and the coals with high coalification degree have pyknotic carbon sheets which provide the suitable active sites for HS03,as well as the carbon sheets of coals with medium and low coalification rank are much looser.The two different coalification grade coals have to carbonize to prepare coals-based solid acids with high catalytic activity and stability.The higher the coalification degree remains,the lower the carbonization temperature will be needed.3.The SO3H groups in the catalyst prepared at a low carbonization temperature have low stability,but a high carbonization temperature will form a compact structure and decrease sulfonation activity,which will be adverse to introduction of SO3H groups.4.Aliphatic side chains in coals will be still remained on the carbon precursor after carbonization as the active sits for SO3H,which can increase the sulfonation efficiency,shorten the sulfonation time and simplify preparation process,as well as the aliphatic chains can be transformed COOH for the oxidation of concentrated sulfuric acid.5.The catalyst mass-transfer property of diffusion has direct influence on cellulose hydrolysis in heterogeneous hydrolysis from the solid-solid catalysis reaction,then appropriate amounts of catalyst should be applied in cellulose hydrolysis.6.Different solid acids are used as catalyst to hydrolyze cellulose,and the result shows that coal-based solid acid has the highest catalytic activity which also demonstrate that the S03H density is not the only factor for the activity of solid acids,it is the synergistic action of SO3H,phenolic OH and COOH in hydrolyzing cellulose.7.The SO3H and small aromatic sheets can fall off from coal-based solid acids in the hydrothermic condition which reduce the catalytic activity.Datong coal-based solid acid prepared by direct sulfonation is continuing decline in catalytic activity after reusing,however,the catalytic prepared by two steps(carbonization-sulfonation)remain stable from the second use.