Xiujuan Guo

Mechanism research on cellulose pyrolysis by Py-GC/MS and subsequent density functional theory studies

The mechanism of fast pyrolysis of cellulose has been studied by using an analytical pyrolyzer coupled with a gas chromatography-mass spectrometry set-up (Py-GC/MS). The results showed that the main products comprised pyrans such as levoglucosan and levoglucosenone, furans such as furfural and 5-hydroxymethyl furfural, and linear small molecular chemicals such as acetaldehyde and 1-hydroxy-2-propanone. The compositions of products from fast pyrolysis of cellubiose and glucose were similar to that from cellulose, but with higher furan contents and lower pyran contents. Based on the experimental results, density functional theory (DFT) studies were carried out to deduce the pyrolysis mechanism of cellulose. The results showed the formation of 5-hydroxymethyl furfural from d-glucopyranose unit to be easier than the formation of levoglucosan, in agreement with the experimental results. The deduced mechanism of reaction pathways in cellulose pyrolysis provides insight into the pyrolysis behavior of cellulose and allows modification of previously proposed related mechanisms.

Properties of Bio-oil from Fast Pyrolysis of Rice Husk

Abstract Physicochemical properties of bio-oil obtained from fast pyrolysis of rice husk were studied in the present work. Molecular distillation was used to separate the crude bio-oil into three fractions viz . light fraction, middle fraction and heavy fraction. Their chemical composition was analyzed by gas chromatograph and mass spectrometer (GC-MS). The thermal behavior, including evaporation and decomposition, was investigated using thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR). The product distribution was significantly affected by contents of cellulose, hemicellulose and lignin. The bio-oil yield was 46.36% (by mass) and the yield of gaseous products was 27% (by mass). The chemicals in the bio-oil included acids, aldehydes, ketones, alcohols, phenols, sugars, etc . The light fraction was mainly composed of acids and compounds with lower boiling point temperature, the middle and heavy fractions were consisted of phenols and levoglucosan. The thermal stability of the bio-oil was determined by the interactions and intersolubility of compounds. It was found that the thermal stability of bio-oil was better than the light fraction, but worse than the middle and heavy fractions.

Influence of extractives on mechanism of biomass pyrolysis

Abstract Inert solvent was selected to extract corresponding extractives from different kinds of biomass. In this study, pyrolysis of the extractives on thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) was studied, and the influence of extractives on biomass pyrolysis was also discussed. The results indicate that extractives have distinct differences in composition and product distribution due to the different amount of guaiacyl and syringyl units in lignin component. Manchurian ash contains more methanol and methane caused by the decomposition of phenols at high temperature. Compared with raw biomass, extracted biomass has higher activation energy and release main products earlier; the yield of water, CO 2 , CO, and aldehydes increases, whereas the yield of acids and alkanes decrease.

STUDY ON CATALYTIC PYROLYSIS OF MANCHURIAN ASH FOR PRODUCTION OF BIO-OIL

Pyrolysis of Manchurian ash (Fraxinus mandshurica Rupr.) sawdust with four zeolite molecular sieve catalysts was performed on a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. Pyrolysis of pure Manchurian ash and three main components, viz. cellulose, xylan, lignin, was also carried out as reference. The four zeolite catalysts investigated in this study (viz. HZSM-5, H-β, USY and Na-Y) all catalyze the dehydration reaction, restrain the release of volatiles, and obviously promote the final residue yields. Y-type catalysts show the most evident catalytic effect, such as restraining the formation of aldehydes, acids, and ethers, and promoting that of isoalkanes and aromatics. The preferred catalyst should have both high activity for deoxygenating and selectivity for hydrocarbon production.

Mechanism of Formation and Consequent Evolution of Active Cellulose during Cellulose Pyrolysis

An intermediate product that was yellow, soluble, and solid was obtained in a high-radiation flash pyrolysis reactor. Under two different radiant heat fluxes, the yields tended to both increase initially until achieving a steady state, and then increase again with the progress of reaction. The compositional analysis of the yellow product was performed on high performance liquid chromatography (HPLC). It was indicated that the product mainly consisted of oligosaccharides, glucose, levoglucosan, methylglyoxal and so on. The compounds including oligosaccharides such as cellobiose and cellotriose, and monosaccharides such as glucose were regarded as active cellulose. Under the higher heat flux, the relative yield of the active cellulose increased initially, followed by a decreasing trend, and achieved a maximum mass fraction of 68% (w) in the soluble yellow product. The oligosaccharides with higher degree of polymerization (DP) were the primary components. Under the lower heat flux the yield of active cellulose was relatively lower, achieving a maximum of about 57% (w), and more saccharides with lower DP were contained. It was suggested that active cellulose was quite unstable at high temperature, and easily decomposed into saccharides with lower DP, even char, volatiles, and gaseous products. Finally an improved mechanism was proposed to describe the reaction route of formation and consequent evolution of active cellulose during cellulose pyrolysis.

Mechanism of Xylan Pyrolysis by Py-GC/MS

In order to investigate the decomposition behavior of hemicellulose, xylan was chosen as the representative of hemicellulose to study the fast pyrolysis on the combination system of analytical pyrolyzer and gas chromatograph coupled with mass spectrometer(Py-GC/MS). The main condensable products of xylan pyrolysis consisted of acids, aldehydes, and ketones; while gas products contained CO2, CO, CH4 and H2. Acetic acid and furfural were the most abundant products with the highest contents of 20.11% and 20.24% respectively. While furfural and acetic acid were formed competitively with residence time and temperature increases, the distribution of xylan pyrolysis products did not vary with the residence time and temperature, while the total content of several kinds of products changed a lot. According to the analysis of experimental data, a reaction pathway of xylan decomposition was deduced so as to illustrate the formation mechanism of main products.

Comparison of Pyrolysis Characteristics of degreased and synthesized Mongolian Pine

In order to study the influence of components’ cross‐interaction on biomass pyrolysis, research of degreased and synthesized Mongolian Pine (MP) was performed on a thermogravimetric analyzer coupled with a Fourier transform infrared spectroscopy (TG‐FTIR) and the fast pyrolysis device. Compared with synthesized MP, the thermal behavior of degreased MP is much closer to the original and the degreased MP produces less aldehydes, alcohols or phenols and acids due to the cross‐interactions of components. Synthesized MP has lower bio‐oil yield and higher gas production than the degreased one. And the contents of furfural, acetic acid and levoglucosan change with the kind of samples obviously due to the intense cross‐interactions of components.

Characterization and Analysis of Char Produced by Biomass Fast Pyrolysis

Pore structure properties of chars obtained by fast pyrolysis of different biomass species under different temperatures are extensively investigated. The carbon content and the calorific value of all pyrolysis chars produced are high. Pore adsorption characteristics of the chars are assigned to be a type III adsorption isotherm curve. Almost all pore diameters are larger than 2 nm, which are allocated to be macroporous and mesoporous. It is found that the pore adsorption capacity of pine pyrolysis char increases with the elevated temperature at the beginning step of pyrolysis, declining after the temperature is over 550°C. Its maximum surface area is up to 725.6 m 2 /g.