Influence of the interaction of components on the pyrolysis behavior of biomass

There has been much interest in the utilization of biomass-derived fuels as substitutes for fossil fuels in meeting renewable energy requirements to reduce CO₂ emissions. In this study, the pyrolysis characteristics of biomass have been investigated using both a thermogravimetric analyzer coupled with a Fourier-transform infrared spectrometer (TG-FTIR) and an experimental pyrolyzer. Experiments have been conducted with the three major components of biomass, i.e. hemicellulose, cellulose, and lignin, and with four mixed biomass samples comprising different proportions of these. Product distributions in terms of char, bio-oil, and permanent gas are given, and the compositions of the bio-oil and gaseous products have been analysed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC). The TG results show that the thermal decomposition of levoglucosan is extended over a wider temperature range according to the interaction of hemicellulose or lignin upon the pyrolysis of cellulose; the formation of 2-furfural and acetic acid is enhanced by the presence of cellulose and lignin in the range 350-500 °C; and the amount of phenol, 2,6-dimethoxy is enhanced by the integrated influence of cellulose and hemicellulose. The components do not act independently during pyrolysis; the experimental results have shown that the interaction of cellulose and hemicellulose strongly promotes the formation of 2, 5-diethoxytetrahydrofuran and inhibits the formation of altrose and levoglucosan, while the presence of cellulose enhances the formation of hemicellulose-derived acetic acid and 2-furfural. Pyrolysis characteristics of biomass cannot be predicted through its composition in the main components.     

Effects of temperature and holding time during torrefaction on the pyrolysis behaviors of woody biomass

Torrefaction is the thermal treatment techniques performed at relatively low temperature (<300 °C) in an inert atmosphere, which aims to improve the fuel properties attractively. In this study, woody biomass (Leucaena leucocephala) was torrefied at various temperatures and holding times and the pyrolysis behaviors of the torrefied wood were examined in detail by using TG-MS technique. It was found that the carbon content and the calorific value of the torrefied leucaena increased significantly when temperature and holding time during the torrefaction increased. From the TG-MS analysis, the pyrolysis behaviors of the torrefied leucaena were significantly different from those of the raw leucaena. The char yield at 800 °C for the torrefied leucaena was increased when increasing the holding time during the torrefaction. On the other hand, the tar yield during the pyrolysis decreased significantly with the increase in the holding time during the torrefaction. Through the results from the TG-MS analysis, it was concluded that the structure of leucaena was changed by the torrefaction at temperature below 275 °C and the cross-linking reactions occurred during the pyrolysis resulting in increase in char yields and decrease in tar yields. It was also suggested that the longer the holding time during the torrefaction, the more the cross-linking reactions proceed during the pyrolysis. The results obtained from the study provide the basic information for the pyrolyser and/or gasifier design by using torrefied biomass as a fuel.     

基于TG-FTIR的生物质催化热解试验研究

运用热重－傅里叶红外光谱联用技术(TG-FTIR),以麦秸为研究对象,探讨催化与非催化条件下生物质的热解挥发分析出特性,分析研究热解温度、催化剂种类对生物质热解主要析出产物的影响。通过热重TG和DTG曲线,获得了相关热解特性参数及动力学参数。结果表明,添加NiO和CaO存在两个失重峰,并促进麦秸热解反应进行,降低表观活化能,其中NiO对提高热解析出产率作用更显著。通过红外光谱对热解产物实时测量的分析表明,CO与CO2的析出与失重峰基本一致,而CH4的析出滞后于前两者。添加NiO和CaO有利于减少热解产物中的CO2的浓度,促进挥发分产物CO、CH4的生成。其中CaO更有利于生物质在温度800℃以下的热解性能改善,而NiO在800℃以上具有更好的催化作用。     

TG-FTIR analysis of switchgrass pyrolysis

Switchgrass is a high yielding perennial grass that has been designated as a potential energy crop. One method of converting switchgrass to energy is by thermochemical conversion to syngas. This requires that the rate of thermal decomposition of switchgrass and the rate of production of components of the syngas be quantified. Ground switchgrass was pyrolyzed at heating rates of 10–40 °C/min in a thermogravimetric analyzer coupled to a Fourier Transform infrared spectrometer. The amount of gases (ppm) that were volatilized during the duration of experiment was quantified. The pyrolysis process was found to compose of four stages: moisture evaporation, hemicellulose decomposition, cellulose decomposition and lignin degradation. The peak temperature for hemicellulose (288–315 °C) and cellulose degradation (340–369 °C) increased with heating rate. FTIR analysis showed that the following gases were given off during the pyrolysis of switchgrass: carbon dioxide, carbon monoxide, acetic acid, ethanol, and methane.     

Study on biomass catalytic pyrolysis for production of bio-gasoline by on-line FTIR

The pyrolysis of biomass is a promising way for production of bio-gasoline if the stability and quality problems of the bio-crude-oil can be solved by catalytic cracking and reforming.In this paper,an on-line infrared spectrum was used to study thecharacteristics of catalytic pyrolysis with the following preliminary results.The removal of C O of organic acid is more difficultthan that of aldehydes and ketones.HUSY/γ-Al_2O_3 and REY/γ-Al_2O_3 catalysts exhibited better deoxygenating activities whileHZSM-5/γ-Al_2O_3 catalyst exhibited preferred selectivities for production of iso-alkanes and aromatics.Finally,possiblemechanisms of biomass catalytic pyrolysis are discussed as well.     

钾元素对生物质主要组分热解特性的影响

采用热重-红外联用仪对松木及生物质主要化学组分半纤维素、纤维素、木质素的热解特性及钾元素对其热解特性的影响进行了研究.结果表明,半纤维素、纤维素、木质素发生热解的主要温度分别为200~350 ℃、300~365 ℃和200~600 ℃;半纤维热解产物中CO、CO₂较多;纤维素热解产物中LG和醛酮类化合物最多;木质素热解主要形成固体产物,气体中CH₄相对含量较高.三种组分共热解过程中发生相互作用使热解温度提高、固体产物增加,气体中CO增加而CH₄减少.添加K₂CO₃后半纤维素和纤维素热解温度区间向低温方向移动,固体产率提高.K对纤维素作用最明显,CO、CO₂气体与固体产物产率明显增加,醛酮类和酸类物质的产率降低;木质素受K影响相对较小,热解固体产物略有增加,挥发分中H₂O和羰基物质增加;三组分共热解减弱了钾元素的催化作用.     

Catalytic effects of six inorganic compounds on pyrolysis of three kinds of biomass

Six inorganic compounds, i.e., Na₂CO₃, NaOH, NaCl, Na₂SiO₃, TiO₂ and HZSM-5, have been investigated with regard to their catalytic effects on pyrolysis of three biomass species, i.e., pine wood, cotton stalk and fir wood by thermal analysis experiments. The results show that Na₂CO₃, NaOH, Na₂SiO₃ and NaCl made devolatilization occur at lower temperature regions in the pyrolysis of the three kinds of biomass, whereas TiO₂ and HZSM-5 made that occur at higher temperature regions in the pyrolysis of cotton stalk and had no obvious effects on pyrolysis temperatures of pine wood and fir wood. The basic catalysts NaOH, Na₂CO₃ and Na₂SiO₃ decreased the maximum weight loss rates while NaCl and HZSM-5 increased them and TiO₂ had no obvious effects on them. The four sodium compounds made pyrolysis of the three kinds of biomass more exothermic, which might be due to more char formation, whereas TiO₂ and HZSM-5 had minor effects on reaction heat. The catalytic effects in all aspects were roughly correlated with one another and their relationship with the basicity and acidity of the catalysts were preliminarily described and analyzed.     

Pre-formed activated carbon matting derived from the pyrolysis of biomass natural fibre textile waste

Low grade biomass fibre produced as a by-product from the flax and hemp industry was manufactured into a non-woven, pre-formed matting material via entanglement, layering and needling. The advantage of such a structure is that textile technology is used to form a self supporting fibre matrix, utilising the ease with which fibre can be worked. The non-woven matting was then pyrolysed and gasified with steam to produce activated carbon. The influence of pyrolysis process conditions on the production of chars and activated carbon from the pre-formed, non-woven textile matting were investigated.     

HZSM-5上生物质催化裂解的近期研究进展

概述了近期的HZSM-5对生物质和生物油催化裂解的研究进展,重点介绍了催化剂的应用、生物油提质的方法和反应机理.     

Screening acidic zeolites for catalytic fast pyrolysis of biomass and its components

Zeolites have been shown to effectively promote cracking reactions during pyrolysis resulting in highly deoxygenated and hydrocarbon-rich compounds and stable pyrolysis oil product. Py/GC-MS was employed to study the catalytic fast pyrolysis of lignocellulosic biomass samples comprising oak, corn cob, corn stover, and switchgrass, as well as the fractional components of biomass, i.e., cellulose, hemicellulose, and lignin. Quantitative values of condensable vapors and relative compositions of the pyrolytic products including non-condensable gases (NCG's) and solid residues are presented to show how reaction products are affected by catalyst choice. While all catalysts decreased the oxygen-containing products in the condensable vapors, H-ZSM-5 was most effective at producing aromatic hydrocarbons from the pyrolytic vapors. We demonstrated how the Si/Al ratio of the catalysts plays a role in the deoxygenation of the vapors towards the pathway to aromatic hydrocarbons.     

秸秆含氮模型化合物热解氮转化规律的实验研究

采用TG-FTIR联用实验系统,在氩气氛围下研究了含氮模型化合物甘氨酸酐热解失重特性以及NO_x前驱物的释放特性;研究了K、Ca、Fe金属盐对甘氨酸酐热解氮转化的影响。结果表明,在20、40、60℃/min升温速率下,NH₃、HCN、HNCO为甘氨酸酐热解的主要气相含氮产物,其中,NH₃产率最大,HCN次之,HNCO生成量最小;随升温速率增加,TG失重曲线右移,热解剩余物减少;且HCN和HNCO的产率增加,NH₃产率降低;K、Ca、Fe盐均对甘氨酸酐热解氮转化具有催化作用,其中,K、Ca有利于促进NH₃、HCN的生成,Fe对HCN的生成具有促进作用,但对NH₃的生成起到抑制作用。     

TG-FTIR Study on Corn Straw Pyrolysis-influence of Minerals

In order to study the effect of minerals on biomass pyrolysis, experiments on pyrolysis of corn straw with different pretreatment methods were performed by using a thermogravimetric analyzer（TGA） coupled with a Fourier transform infrared （FTIR） spectrometer. The pretreatment methods included water washing and acid washing. The experimental results show that acid washing can remove almost all K^＋ and 78% of Ca^2＋ , while water washing only removes most of K ^＋. The existence of K^＋ and Ca^2＋ obviously favors the formation of compounds containing carbonyl groups and CO2 , but it will decrease the yields of compounds containing C-O-C groups. However, the formation of H2O, CO and CH4 are slightly affected by the removal of inorganic ions. With regard to the structure of the metal ions-adsorbed cellulose characterized by IR analysis, it can be considered that there is an ＂ion force＂ between metal ions and cellulosic biomass. The results of thermal kinetic analysis show that this force can make the reaction activation energy of the biomass pyrolysis decrease. A new mechanism is proposed for explaining the effect of inorganic ions on cellulose pyrolysis.     

Thermogravimetric study of the pyrolysis of waste wood

A thermogravimetric study of the pyrolysis of three different types of waste wood (forest wood, old furniture and used pallets) is carried out in a TGA equipment using dynamic and isothermal techniques. Isothermal runs were carried out at two temperature levels, one between 225° and 325°C (low range) and the other, between 700° and 900°C (high range). Results show a good agreement between the kinetic parameters obtained from either dynamic or isothermal techniques. It must be remarked that the own chemical composition of each type of wood together with the compounds added to the wood for each application, play a fundamental role in the kinetic behavior of their thermal decomposition.     

应用TG-FTIR联用研究催化剂对煤热解的影响

用TG-FTIR联用技术研究了碱金属、碱土金属和过渡金属对宝日希勒褐煤和包头烟煤热解的催化作用和挥发分析出的影响。结果表明,各种催化剂对褐煤和烟煤热解的催化效果分别为Ni>Fe~Ca>K和Ca~Fe>Ni>K,K2CO3对煤的热解没有明显的催化作用。催化剂使褐煤和烟煤热解转化率增加的最大值分别为10.1％和6.4％。烟煤热解生成的CH4比褐煤的多,不同的催化剂使煤热解挥发产物CO2、H2O、CH4和CO增加的幅度不一样,催化效果与温度和煤的变质程度有关。     

Kinetic models based in biomass components for the combustion and pyrolysis of sewage sludge and its compost

In the present work, pyrolysis and combustion of the sewage sludge (fresh and composted) have been simulated using five fractions: low stability organic compounds, hemicellulose, cellulose, lignin-plastic, and inorganic compounds. Thermal behavior and kinetic parameters (pre-exponential factor and apparent activation energy) of the main components of the sludge are similar to those reported for hemicellulose, cellulose, and lignin present in lignocellulosic biomass. Comparing non-isothermal thermogravimetric analysis data obtained from fresh and composted sewage sludge, it is possible to measure the efficiency of the composting process. Most of the biodegradable matter is volatized in a temperature range from 150 °C to 400 °C. Non-biodegradable organic matter volatilizes between 400 °C and 550 °C. In both, fresh and composted sludges, oxygen presence increases the mass loss rate at any temperature, but differences between pyrolysis and combustion are focused in two clearly defined ranges. At low temperature (200–350 °C), mass loss is related with a volatilization process. At higher temperature (350–550 °C), mass loss is due to slow char oxidation (oxidative pyrolysis).     

Modeling pyrolysis kinetics of plastic mixtures

Modeling pyrolysis behavior of waste plastic mixtures is of importance for design and operation of reactors which convert these waste plastics into valuable chemicals. However, because of limited understanding of their degradation behavior even for single component plastic wastes, modeling degradation kinetics of plastic mixtures is a challenging task.In this work, we report modeling of binary and ternary mixture degradation kinetics of polyethylene terephthalate (PET), low density polyethylene (LDPE) and polypropylene (PP). A simple mixing rule approach was used with one cross-kinetic degradation parameter per each binary. Ternary kinetics were completely predictive and showed good agreement with the experimental data.     

Current technologies for analysis of biomass thermochemical processing: A review

Pyrolysis and gasification are two of the more promising utilization methods for the conversion of biomass toward a clean fuel source. To truly understand and model these processes requires detailed knowledge ranging from structural information of raw biomass, elemental composition, gas-phase reaction kinetics and mechanisms, and product distributions (both desired and undesired). The various analytical methods of biomass pyrolysis/gasification processing are discussed, including reactor types, analytical tools, and recent examples in the areas of (a) compositional analysis, (b) structural analysis, (c) reaction mechanisms, and (d) kinetic studies on biomass thermochemical processing.     

应用TG-FTIR技术研究黄土庙煤催化热解特性

用浸渍法制备过渡金属氧化物担载型催化剂MO_x/USY(M=Co、Mo、Co-Mo),用热重红外联用技术考察了MO_x/USY催化剂对黄土庙(HTM)煤热解失重特性和热解产物生成规律的影响。热重实验结果表明,MO_x/USY催化剂可使HTM煤热解的二次脱气条件更为温和,热解峰温分别提前14、23和9℃。动力学分析结果表明,MO_x/USY催化剂可降低HTM煤样热解的活化能。FT-IR研究表明,MO_x/USY催化剂可有效改善HTM煤热解产物的组成和分布,CoO_x/USY催化剂能显著提高HTM煤热解产物中高热值气体(CO、CH₄)和轻质芳烃以及脂肪烃类化合物的含量;MoO_x/USY催化剂没有明显改善HTM煤热解产物组成和分布;MoO_x-CoO_x/USY催化剂可促进CO、CH₄、轻质芳烃和脂肪烃类化合物的生成,却使热解产物的生成向高温区移动,说明USY负载的不同过渡金属氧化物对煤样热解行为和热解产物有较大影响。     

Molecular-beam mass-spectrometric analysis of lignocellulosic materials : I. Herbaceous biomass

A rapid analytical technique has been developed to qualitatively screen and quantitatively analyze biomass feedstocks for conversion into hydrocarbon fuels and chemicals. In this rapid analytical pyrolysis approach, herbaceous biomass feedstocks stored in the open without cover for 6 to 9 months were characterized using the molecular-beam mass spectrometer (MBMS). The biomass materials were pyrolyzed at 600°C and the volatile pyrolysis products were analyzed in real time by the MBMS. The mass spectral data were further analyzed by multivariate statistical techniques (Factor Analysis). The contents of nitrogen compounds, pentosans and hexosans estimated from the pyrolysis mass-spectrometric/multivariate analysis techniques correlated well with the results obtained by conventional wet chemical methods. However, lignin correlation was very weak because of the presence of microbial degradation products of biomass (humic material) that interfered with the Klason lignin analysis.

This rapid analytical technique was used to analyze various fractions of the stored biomass feedstocks. A comparison of exposed surface biomass materials and the unexposed materials showed that the exposed fraction lost 30% (wt) of the carbohydrate component of the biomass relative to the fresh material.