Pyrolysis Behavior Of Cellulose Research Articles

Effects of cellulose, hemicellulose and lignin on biomass pyrolysis kinetics

In order to investigate interactions among biomass components on pyrolysis kinetics, pyrolysis experiments of individual components, synthetic biomass (designed by Design-Export software) and natural biomass (rice husk and corn straw) were conducted on a thermogravimetric analyzer (TGA). The results revealed that the pyrolysis behavior of cellulose is sharp, which is with low pyrolysis reaction order (1.38), high activation energy (168.61 kJ/mol) and high pre-exponential factor (3.50E+12/s). The pyrolysis behavior of hemicellulose and lignin is slower but more complicated, both with high pyrolysis reaction order (2.30, 1.51), low activation energy (126.31, 87.21 kJ/mol), and low pre-exponential factor (9.67E+09, 2.59E+05 /s). Comparison of the experimental and calculated kinetics of synthetic samples confirmed that interactive effects on pyrolysis kinetics exist in the co-pyrolysis process. In particular, the presence of lignin inhibited the pyrolysis reaction rate of synthetic biomass, and cellulose played the dominant role in the activation energy and frequency factor. The pyrolysis reaction order was strongly influenced by hemicellulose owing to its abundant and complex branched chains. The predicted model was also established for calculating kinetic parameters of natural biomass with known proportions of three components. The predicted results were consistent with the experimental ones, validating the effectiveness of the prediction model.

TG-FTIR for kinetic evaluation and evolved gas analysis of cellulose with different structures

In this study, the effect of structural characteristics of cellulose on its pyrolysis behavior was investigated. The structure of crystalline cellulose was altered by ball milling (BM) pretreatment, resulting in decreases in crystallinity and degree of polymerization. The initial pyrolysis temperature of BM-cellulose decreased, as well as the temperature at which maximum weight loss rate was achieved. Moreover, BM-cellulose was observed to produce more solid residue. The pyrolysis process was fitted by n-order reaction model. The global activation energy of Un-treated cellulose (228.3–270.6 kJ/mol) was higher than that of BM-cellulose (166.8–187.0 kJ/mol). TG-FTIR experiment showed that BM-cellulose yielded more CO2 and H2O than Un-treated cellulose. This research provided a comprehensive analysis of the effects of structural characteristics of cellulose on the pyrolysis behavior of cellulose.

Pyrolysis behavior of cellulose in a fixed bed reactor: Residue evolution and effects of parameters on products distribution and bio-oil composition

Significant discrepancies of cellulose pyrolysis behavior in a micro-scale pyrolyzer and that in a large-scale reactor hinder the industrial application of those findings obtained from the former reactor. In this work, the pyrolysis behavior of cellulose in a fixed bed reactor was investigated, especially the residue evolution and the effects of temperature, material thickness and carrier gas flow rate on the products distribution and bio-oil composition. And a possible pathway for the cyclopentanones formation was proposed and competing reactions during cellulose pyrolysis with the consideration of heat and mass transfer effect were analyzed. It was found that high temperature promoted the cellulose decomposition and favored the cellulose to produce furfural, cyclopentanones and light linear compounds (such as acetic acid, hydroxy actaldehyde), and relative low temperature (<450 °C) and thicker material thickness (>2 mm) favored the dehydration of cellulose to yield levoglucosenone and furans compounds, and fast carrier gas flow rate declined the yield of most compounds but favored the recovery of levoglucosan. The findings of present study, to some extent, could provide guidance on process optimization of cellulose pyrolysis in a large-scale reactor to produce desired chemicals.

Thermogravimetric characteristics and kinetics of sawdust pyrolysis catalyzed by potassium salt during the process of hydrogen preparation

Pyrolysis experiments of sawdust with KOH and K2CO3 catalysts were carried out under different heating rate in nitrogen atmosphere using thermogravimetric analyzer. The distributed activation energy model (DAEM) was used to analyze pyrolysis kinetics of sawdust. The results showed that both KOH and K2CO3 had strong catalytic effect on sawdust pyrolysis, which reduced the pyrolysis temperature of sawdust and increased the yield of char. There was only one main peak in DTG curve, which means that the pyrolysis behavior of cellulose and hemicellulose in sawdust was greatly changed. The catalytic performance of KOH was found to be more excellent in sawdust pyrolysis. Also KOH could catalyze the pyrolysis of sawdust at low temperature. The kinetic analysis results showed that the two kinds of catalysts could reduce the activation energy of sawdust pyrolysis and maintain a similar catalytic trend, but KOH had a more stable catalytic performance.

Influence of torrefaction on the characteristics and pyrolysis behavior of cellulose

The influence of torrefaction on cellulose structural characteristics and the resulting pyrolysis behavior was investigated in this study. Torrefaction reduced O/C ratio in cellulose and increased its high heating value. The crystallinity of cellulose increased slightly first and then decreased sharply with the increase of torrefaction temperature, which could be ascribed to competitive degradation between crystalline region and amorphous region, as indicated by 13C CP/MAS NMR analysis. Besides, the cleavage of β-1,4-glycosidic bond and the dehydration of hydroxyl were the major reactions occurring in torrefaction. Avrami-Erofeev model was found to be the most suitable kinetic reaction model for explaining the thermogravimetric weight loss during the pyrolysis of the raw and torrefied cellulose. A distributed activation energy model based on Avrami-Erofeev model was subsequently used to reveal the pyrolytic kinetics. It was found that the changes in cellulose structure influenced the kinetic parameters greatly. Torrefaction also changed pyrolytic product distribution. The yields of furfural, alicyclic ketones and anhydrosugars increased while that of 5-hydroxymethyl-furfural decreased as torrefaction temperature increased.

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.

Logistic distributed activation energy model – Part 2: Application to cellulose pyrolysis

The pyrolysis behavior of cellulose has been investigated by using thermogravimetric analysis (TGA). The non-isothermal TGA data obtained at different heating rates have been analyzed simultaneously. Pattern Search Method has been proposed for the estimation of the model parameter values. Predicted values from the logistic distributed activation energy model have been compared with the experimental data and the results have indicated that the model describes the kinetic behavior of cellulose pyrolysis very well. The mean value and standard deviation of the logistic activation energy distribution for cellulose pyrolysis are found to be 258.5718 kJ mol(-1) and 2.6601 kJ mol(-1), the reaction order is 1.1101 and the k(0) is 1.6218×10(17) s(-1).