Preparation Of Coal-Based Soild Acid By Lignite And Its Performance Research On Hydrolysis Of Cellulose

Cellulose is one of the most abundant natural polymer and the most important renewable resources. The hydrolysis of cellulose can effectively generate glucose, further to produce fuel ethanol, levulinic acid ester and 5-(hydroxymethyl) furfural and ethylene glycol, which is of great significance for relieving the energy crisis. Recently, the effective cellulose hydrolysis has initiated out numerous researches. Owing to the hard separation of products and catalysts after reaction and environmental pollution of the traditional enzyme and acid hydrolysis, the novel and efficient hydrolysis methods are being constantly explored by domestic and foreign researchers.In this paper, the coal-based solid acid(CSA) is prepared from Huolinhe lignite and XRD, FT-IR and TG-DTG were employed to characterize the crystalline structure, surface functional groups and thermal stability. The density of active groups was measured by acid base titrations. The influence of carbonization temperature, deashing and heating rate on the structures and the performance of heterogeneous catalytic cellulose hydrolysis were investigated by comparing the yield of reducing sugar and glucose.Results show that carbonization temperature has remarkable effect on the structure and activity performance of CSA. With rising carbonization temperature, the density of three active groups on CSA decreases gradually. The trend of catalytic activity on cellulose hydrolysis increased and then decrease with the increase of carbonization temperature, with CSA-400 having the best catalytic activity. Adsorption propertie is determined by hydroxyl density on CSA, which can be affected by the degree of aromatic carbon sheets and the density of carboxyl groups. The TOF of three active groups analysis shows that the highest activity of cellulose hydrolysis is abtained while the ratio of sulfonic acid group density, carboxyl density and hydroxyl density is 1:2.1-2.6:1.8-2.1. Hydrolytic activity is a result of the synergistic effect of a number of reactive groups.Coal sample is demineralized by HC1-HF mixed acid and coal-based solid acids(DCSA) was prepared from low ash coal. Deashing can not only enhance the density of carboxyl group and sulfonic acid group in the catalyst, but also impove the effective contact between active groups and cellulose, which in turn increases the catalytic activity. The result indicates that the yield of reducing sugar of cellulose hydrolysis increases from 40.37% to 74.08%. The ash of coal as an inert component is retained to the catalyst. The presence of ash can put impact on the attachment the reactive groups. So the ash of coal should be removed before experiment.Slow heating rate can maintain coal a long heating time in lower temperature zone, which can result in parallel and sequential condensation polymerization and high stability semi-coke. Meanwhile the aromaticity and stability of DCSA is superior to these of FDCSA. As the heating rate increases, the degree of cracking of coal is to deepen. The carboxy density on FDCSA is significantly reduced, thereby the hydrophilicity of FDCSA is decreased, which can influence the interaction between cellulose and active groups of sulfonic acid group and hydroxy. Contrast with the catalytic performance of three kinds of catalysts CSA, DCSA and FDCSA, the DCSA has the best catalytic activity on hydrolysis of cellulose.