Pyrolysis Of Hemicellulose Research Articles

Pyrolysis study of poplar biomass by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

Pyrolysis is one of the most important methods to convert biomass into biofuel, which is a potential substitute for fossil fuel. The pyrolysis process of poplar biomass, a potential biofuel feedstock, has been studied with tunable synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry (PIMS). The mass spectra at different photon energies, temperatures, and time-evolved profiles of selected species during poplar pyrolysis process were measured. Our results reveal that poplar is typical of hardwood according to its relative contents of three lignin monomeric precursors. As temperature increases from 300 to 700°C, the overall intensities of pyrolysis products decrease due to the gas-phase cracking. Observed intensities of syringyl and guaiacyl subunits of lignin in poplar at low temperature present different trends: the intensities of syringyl subunits of lignin undergo an increase firstly and then a decrease, whereas those of guaiacyl subunits of lignin show decrease continuously. Time-dependent data demonstrate that hemicellulose pyrolysis is faster than lignin in poplar. This work reports a new application of SVUV PIMS in biomass pyrolysis, which performs very well in products analysis.

Pyrolysis of olive residue and sugar cane bagasse: Non-isothermal thermogravimetric kinetic analysis

Thermal degradation and kinetics for olive residue and sugar cane bagasse have been evaluated under dynamic conditions in the presence of nitrogen atmosphere, using a non-isothermal thermogravimetric method (TGA). The effect of heating rate was evaluated in the range of 2–50 K min −1 providing significant parameters for the fingerprinting of the biomass. The DTG plot for the olive residue and sugar cane bagasse clearly shows that the bagasse begins to degrade at 473 K and exhibits two major peaks. The initial mass-loss was associated with hemicellulose pyrolysis and responsible for the first peak (538–543 K) whereas cellulose pyrolysis was initiated at higher temperatures and responsible for the second peak (600–607 K). The two biomass mainly devolatilized around 473–673 K, with total volatile yield of about 70–75%. The char in final residue was about 19–26%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. Ozawa–Flynn–Wall and Vyazovkin methods were applied to determine apparent activation energy to the olive residue and sugar cane bagasse. Two different steps were detected with apparent activation energies in the 10–40% conversion range have a value of 153–162 kJ mol −1 and 168–180 kJ mol −1 for the hemicellulose degradation of olive residue and sugar cane bagasse, respectively. In the 50–80% conversion range, this value is 204–215 kJ mol −1 and 231–240 kJ mol −1 for the cellulose degradation of olive residue and sugar cane bagasse, respectively.

Characteristics of corn stalk hemicellulose pyrolysis in a tubular reactor

Pyrolysis characteristics of corn stalk hemicellulose were investigated in a tubular reactor at different temperatures, with focus mainly on the releasing profiles and forming behaviors of pyrolysis products (gas, char, and tar). The products obtained were further identified using various approaches (including GC, SEM, and GC-MS) to understand the influence of temperature on product properties and compositions. It was found that the devolatilization of hemicellulose mainly occurred at low temperatures (<500°C), and produced large amounts of tar. A higher reactor temperature was conducive to the yield of gas products, accompanied by a reduction of tar because of the secondary cracking of volatiles. The gas components mainly consisted of CO2, CO, H2, and CH4, together with trace C2H4 and C2H6. The CO2 evolved easily and reached a relatively large yield of 129.2ml/g at 550°C, while CO and H2 were mainly released at higher temperatures (700-900°C). The tar was mainly composed of a range of oxygenated compounds, including ketones, furans, carboxylic acids, and alcohols, and their contents were influenced by the final temperature. An in-depth analysis of the properties of the products generated at different temperatures is favorable for a better understanding of the mechanism of hemicellulose pyrolysis.

The structural and thermal characteristics of wheat straw hemicellulose

The structural characteristics of hemicelluloses isolated from delignified wheat straw were investigated by ion chromatography, FT-IR and NMR. The pyrolytic characteristic and the products at different temperatures were studied by TG and pyrolysis gas chromatography and mass spectrometry (py-GC/MS). The results showed wheat straw hemicelluloses were mainly consisting of arabinoxylan and uronic acids, the typical structure of straw hemicelluloses. The TG and DTG curves suggested the mass loss of hemicelluloses mainly happened between 190 and 315 °C and formed a 24 wt.% residue at 700 °C. The result of py-GC/MS revealed that the volatile products at different temperatures varied greatly and the main products of hemicellulose pyrolysis were acetic acid, carbon oxide, 2-furaldehyde, cyclopenten-1-one derivatives and small amounts of aromatic compounds which were very useful chemicals.

Study on the pyrolytic behaviour of xylan-based hemicellulose using TG–FTIR and Py–GC–FTIR

Two sets of experiments, categorized as TG–FTIR and Py–GC–FTIR, are employed to investigate the mechanism of the hemicellulose pyrolysis and the formation of main gaseous and bio-oil products. The “sharp mass loss stage” and the corresponding evolution of the volatile products are examined by the TG–FTIR graphs at the heating rate of 3–80 K/min. A pyrolysis unit, composed of fluidized bed reactor, carbon filter, vapour condensing system and gas storage, is employed to investigate the products of the hemicellulose pyrolysis under different temperatures (400–690 °C) at the feeding flow rate of 600 l/h. The effects of temperature on the condensable products are examined thoroughly. The possible routes for the formation of the products are systematically proposed from the primary decomposition of the three types of unit (xylan, O-acetylxylan and 4-O-methylglucuronic acid) and the secondary reactions of the fragments. It is found that the formation of CO is enhanced with elevated temperature, while slight change is observed for the yield of CO 2 which is the predominant products in the gaseous mixture.

Kinetic study of wood chips decomposition by TGA

AbstractPyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C for four heating rates: 2 K min−1, 5 K min−1, 10 K min−1, and 15 K min−1. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds.

Pyrolysis of wood species based on the compositional analysis

Based on the Van Soest method, the components in Chinese fir and fast-growing poplar were quantified, and the fiber present was separated into three fractions: neutral detergent fiber, acid detergent fiber and strong acid detergent fiber. Microstructure of the fibers was investigated by a Fourier transform infrared spectrometry. Cellulose and hemicellulose both represent the characteristics of polysaccharides, while lignin has dissimilar structure. Pyrolysis of fir, poplar and the detergent fibers was carried out on a thermogravimetric analyzer coupled with FTIR spectrometry. After the removal of extractives and soluble minerals, pyrolysis of NDF shows the characteristics of the three main components. Hydrocarbons, aldehydes, ketones, acids, alcohols and others are generated due to the primary pyrolysis of hemicellulose and cellulose in single stages. Phenols and alcohols are the dominant volatiles released from pyrolysis of lignin in two successive stages, respectively.

Influence of inorganic matter on wood pyrolysis at gasification temperature

The influence of inorganic matter on the pyrolysis of Japanese cedar (Cryptomeria japonica) wood was studied at a gasification temperature of 800°C with demineralization through acid washing. Some influences on the formation of char, tar, and low molecular weight products coincided with results reported at temperatures lower than the gasification temperature. However, the carbonization behavior of the volatile products and the yield of polysaccharide fraction were not able to be explained as a sum of the pyrolysis of cellulose, hemicellulose, and lignin even after demineralization. These results suggest some interactions between wood constituent polymers other than the influence of inorganic matter.

Cellulose–hemicellulose and cellulose–lignin interactions in wood pyrolysis at gasification temperature

Cellulose–hemicellulose and cellulose–lignin interactions during pyrolysis at gasification temperature (800 °C) were investigated with various cellulose samples mixed with hemicellulose (glucomannan or xylan) or milled wood lignin. Significant interactions were observed in cellulose–lignin pyrolysis; lignin inhibited the thermal polymerization of levoglucosan formed from cellulose and enhanced the formation of the low molecular weight products from cellulose with reduced yield of char fraction; cellulose reduced the secondary char formation from lignin and enhanced the formation of some lignin-derived products including guaiacol, 4-methyl-guaiacol and 4-vinyl-guaiacol. Comparatively weak interactions were also observed in cellulose–hemicellulose pyrolysis. Finally, factors influencing the wood pyrolysis at gasification temperature are discussed.

Characteristics of hemicellulose, cellulose and lignin pyrolysis

Abstract The pyrolysis characteristics of three main components (hemicellulose, cellulose and lignin) of biomass were investigated using, respectively, a thermogravimetric analyzer (TGA) with differential scanning calorimetry (DSC) detector and a pack bed. The releasing of main gas products from biomass pyrolysis in TGA was on-line measured using Fourier transform infrared (FTIR) spectroscopy. In thermal analysis, the pyrolysis of hemicellulose and cellulose occurred quickly, with the weight loss of hemicellulose mainly happened at 220–315 °C and that of cellulose at 315–400 °C. However, lignin was more difficult to decompose, as its weight loss happened in a wide temperature range (from 160 to 900 °C) and the generated solid residue was very high (∼40 wt.%). From the viewpoint of energy consumption in the course of pyrolysis, cellulose behaved differently from hemicellulose and lignin; the pyrolysis of the former was endothermic while that of the latter was exothermic. The main gas products from pyrolyzing the three components were similar, including CO 2 , CO, CH 4 and some organics. The releasing behaviors of H 2 and the total gas yield were measured using Micro-GC when pyrolyzing the three components in a packed bed. It was observed that hemicellulose had higher CO 2 yield, cellulose generated higher CO yield, and lignin owned higher H 2 and CH 4 yield. A better understanding to the gas products releasing from biomass pyrolysis could be achieved based on this in-depth investigation on three main biomass components.

Influence of mineral matter on pyrolysis of palm oil wastes

The influence of mineral matter on pyrolysis of biomass (including pure biomass components, synthesized biomass, and natural biomass) was investigated using a thermogravimetric analyzer (TGA). First, the mineral matter, KCl, K 2CO 3, Na 2CO 3, CaMg(CO 3) 2, Fe 2O 3, and Al 2O 3, was mixed respectively with the three main biomass components (hemicellulose, cellulose, and lignin) at a weight ratio (C/W) of 0.1 and its pyrolysis characteristics were investigated. Most of these mineral additives, except for K 2CO 3, demonstrated negligible influence. Adding K 2CO 3 inhibited the pyrolysis of hemicellulose by lowering its mass loss rate by 0.3 wt%/°C, while it enhanced the pyrolysis of cellulose by shifting the pyrolysis to a lower temperature. With increased K 2CO 3 added, the weight loss of cellulose in the lower temperature zone (200–315 °C) increased greatly and the activation energies of hemicellulose and cellulose pyrolysis decreased notably from 204 to 42 kJ/mol. Second, studies on the synthetic biomass of hemicellulose, cellulose, lignin, and K 2CO 3 (as a representative of minerals) indicated that peaks of cellulose and hemicellulose pyrolysis became overlapped with addition of K 2CO 3 (at C/W = 0.05–0.1), due to the catalytic effect of K 2CO 3 lowering cellulose pyrolysis to a lower temperature. Finally, a local representative biomass—palm oil waste (in the forms of original material and material pretreated through water washing or K 2CO 3 addition)—was studied. Water washing shifted pyrolysis of palm oil waste to a higher temperature by 20 °C, while K 2CO 3 addition lowered the peak temperature of pyrolysis by ∼ 50 ° C . It was therefore concluded that the obvious catalytic effect of adding K 2CO 3 might be attributed to certain fundamental changes in terms of chemical structure of hemicellulose or decomposition steps of cellulose in the course of pyrolysis.

Volatile composition and sensory characteristics of Chardonnay wines treated with American and Hungarian oak chips

Toasted or non-toasted chips of oak woods of different geographical provenances were macerated in Chardonnay wines (4 g/l) during a period of 25 days. Oak lactones were detected in significant quantities in wines treated with American oak. Only trace amounts of oak lactones were detected in the wines treated with Hungarian oak. Toasting of the oaks increased the quantities of the compounds derived from the thermal degradation of lignin: vanillin, eugenol, guaiacol and its derivatives and the pyrolysis of cellulose and hemicellulose: furfural and 5-methyl furfural, and decreased the concentrations of the two isomers of oak lactones. The concentrations of the majority of the volatile compounds did not present statistically significant differences between 15 and 25 days. However, the wines preferred by the tasters and with maximum intensity of the sensory attributes acquired were those treated with oak chips for 25 days. Chemical and sensorial analyses of wines revealed that the effect of the toasting of oak chips on wine characteristics was greater than the type of oak used. All wines studied were positively evaluated by the panellists.

A new method to determine the composition of biomass by thermogravimetric analysis

AbstractA method for the direct determination of the cellulose and lignin content of biomass has been developed. The method assumes that negligible interactions exist between biomass macrocomponents and it is based on the analysis of thermogravimetric (TG) pyrolysis data. The TG‐weighed sum method seems to be reliable and less time consuming than conventional methods for the determination of the cellulose and lignin content. Some limitations of the macrocomponent approach in the description of biomass pyrolysis are also discussed. In particular, hemicellulose pyrolysis data are analyzed. The use of xylans as substitute materials for hemicellulose have been critically examined. The results obtained point out that the widely practiced use of xylans as substitute compounds for the simplified description of hemicellulose pyrolysis can lead to significant errors.