Research On The Effect Of Caking Propensity Of Coal On Preparation Of Carbon-based Solid Acid And Its Application In Cellulose Hydrolysis

Cellulose is the most abundant,inexpensive and renewable biomass resource on earth.Hydrolysis of cellulose produce glucose,an important platform chemical molecule,from which is able to generate many important chemicals,such as fuel ethanol and 5-hydroxymethyl furfural.It makes cellulose as the most promising alternative substance of fossil materials.Therefore,the hydrolysis of cellulose becomes a hotspot of biomass research.In recent years,cellulase and liquid acid rarely used as catalysts in cellulose hydrolysis,a novel carbon-based solid acid(CCSA)bearing sulfonic acid,carboxyl and phenolic hydroxyl groups has been regularly used in this field.It is easy to find that the feature of CCSA has some similarities with coal,a natural macromolecule,which contains the remaining groups apart from sulfonic acid groups.It makes the coal as the best raw material for the preparation of CCSA.The adhesiveness is an important technological property of caking coal,which has some significant influences on the pyrolysis process and property of caking coal.In view of this,the CCSAs were prepared from carbonization,sulfonation and oxidation of caking coal and applied into cellulose hydrolysis.The influence of caking propensity,carbonization temperature,heating rate,particle size and oxidation stages of raw materials on structure and performances of CCSAs was investigated.The structure of carbon precursors(CPs)and CCSAs were characterized by XRD and FT-IR,the density of functional groups,adsorption properties and catalytic properties have been tested by evaluating the catalytic ability of CCS A.The main results are concluded as follows:1.The caking coal derived carbon-based solid acid(CCSA)are polycyclic aromatic carbon structure with a certain degree of graphite and contain some alkyl side chains and bridge linkage,etc,its edge loaded with-SO3H,-COOH and phenolic-OH.2.The caking coal with a moderate adhesiveness and medium metamorphic grade is able to form homogeneous intermediate phase during carbonization process,which is easy to be sulfonated with concentrated sulfuric acid to form CCSA carrying higher sulfonic acid groups and total acid density and showing better adsorption and excellent catalytic hydrolysis performance of cellulose.3.The carbonization temperature has the greater effect on structure and performance of CCSA.With the increase of temperature,the structure of CCSA becomes more regular and orderly,the acidic groups density decreases,and the adsorption capacity and hydrolytic activity of catalyst have the highest point.Due to the unique characteristic of caking coal,the best carbonization temperature of CCS A is 400?.4.The heating rate has the greater effect on performance than structure of CCS A.With the decrease of heating rate,the functional groups density,adsorption properties and hydrolytic activity of CCSA reduce,namely lower heating rate is conducive to the formation of CCSA with high catalytic performance.5.The particle size of caking coal samples has obvious impact on functional group density,adsorption properties and hydrolysis activity of CCSA.Wherein,CCSA prepared from raw material of 0.15 mm-1.00 mm has a higher density of functional groups,adsorption and catalytic properties.6.The oxidation has significant effect on functional groups density and adsorption properties of CCSA.Compared with the unoxidized CCSA,the sulfonic acid density and total acid density of oxidized CCSA decrease.The oxidation greatly reduces the hydroxyl groups density,and increases carboxyl groups density.However,the adsorption performance significantly increases and CCSA shows superior performances of cellulose hydrolysis.The CCSA prepared by oxidized raw material(RM)has higher sulfonic acid group density,adsorption and catalytic properties than that of the CCSA prepared by oxidized carbon precursor(CP).7.With the increase of oxidation temperature,the-SO3H groups density gradually increases.40? is the optimum temperature of the oxidation process,at which a CCSA having good adsorption performance and excellent catalytic property of cellulose hydrolysis has been prepared.8.With the increasing proportion of the oxidizing agent,the CCSA has higher sulfonic groups density,nevertheless,the adsorption performance and catalytic property are not satisfactory.The superior ratio of sample and oxidant is 1:5,in which the sulfonic acid group density of CCSA is not high,but it shows excellent adsorption properties and better catalytic property,eventually.