| Efficiently converting lignocellulosic biomass into bio-oil through pyrolysis technique has been one of the most attractive research topics in recent years. Cellulose is the main composition of biomass, its pyrolysis characteristics could largely represent the entire biomass pyrolysis behavior. However, no actual consensus of cellulose pyrolysis mechanism has been reached due to primary formation of intermediate species accompanied or not with phase change phenomena in cellulose pyrolysis process. Therefore, the D-glucose which is the monomer of cellulose chain is chosen as the main object to study its pyrolysis behavior which should has great significance in better understanding the pyrolysis mechanism of lignocellulosic biomass.In this study, D-glucose, levoglucosan, hydroxymethylfurfural and D-fructose were chosen as experimental objects. In order to investgate the pyrolysis stages and characteristics of all the experimental objects, Thermogravimetric-Differential Thermal Analyzer(TG-DTA) was applied to detect both mass loss and heat flow processes. Pyrolysis volatiles released at different temperatures were transported by an Auto-injector system into Gas Chromatography and Mass Spectrometry(GC-MS) to be identified on line to investgate temperature effect on pyrolysis products distribution.Firstly, D-glucose pyrolysis was conducted on the experimental system. In its initial pyrolysis stage, D-glucose underwent violent dehydration reaction with water produced, in the meantime, D-glucose started initial decomposition with furfural and CO2 produced and its intermediate products presented in residual compounds in liquid state. Then, D-glucose came to the main pyrolysis stage and lost mass rapidly mainly with furans derivatives including furfural, furan, methyl furan, furancarboxaldehyde and levoglucosenone produced. Then, D-glucose pyrolysis came to final stage, it gradually lost mass and produced lots of aromatic species such as benzene, toluene, phenol, methylphenol, benzofuran as well as 1,4:3,6-dianhydro-α-D-glucopyranose. At 600℃ the end of experiment, the pyrolysis volatiles mainly contained 1,4:3, 6-dianhydro-α-D-glucopyranose.Secondly, levoglucosan and hydroxymethylfurfural were tested in the system. After melting into liquid phase, both of them underwent evaporation process. Then they came to main pyrolysis stage with rapid mass loss. In the last stage, they lost mass gradually and carbonized. Furfural, 2,5-furandicarboxaldehyde, and levoglucosenone were the main products of levoglucosan pyrolysis, while hydroxymethylfurfural mostly decomposed into 2,5-furandicarboxaldehyde, 5-methyl-2-furancarboxaldehyde and furfural. All the pyrolysis products in levoglucosan and hydroxymethylfurfural pyrolysis were observed in D-glucose results.In the last part, D-fructose was pyrolyzed in the system. Similar to D-glucose, fructose also dehydrated in initial pyrolysis stage without volatile produced. Pyrolysis temperature had significant effect on products distributions. In fructose main pyrolysis stage, pyrolysis volatiles mostly contained furfural, 2,5-furandicarboxaldehyde and 5-methyl-2-furancarboxaldehyde. With temperature increasing, pyrolysis products mainly consisted of dimethyl-furan, methyl-furan and 1-(2-furanyl)-ethanone. Then, at high temperature more than 400℃, aromatic species such as benzene, p-Xylene and methyl-benzofuran came out to be important products. |
