Thermogravimetry/mass spectrometry study of woody residues and an herbaceous biomass crop using PCA techniques

The devolatilization behaviour of pine and beech wood from carpentry residuals and an herbaceous product from an energy plantation (artichoke thistle) was investigated by thermogravimetry/mass spectrometry (TG/MS). The effect of three pre-treatments, hot-water washing, ethanol extraction and their combination, was also studied. Principal component analysis (PCA) was employed to help in the evaluation of the large data set of results. The characteristics of the thermal decomposition of the herbaceous crop are considerably different from that of the woody biomass samples. The evolution profiles of some characteristic pyrolysis products revealed that the thermal behaviour of wood and thistle is still considerably different after the elimination of some of the inorganic ions and extractive compounds, although the macromolecular components of the samples decompose at similar temperatures. With the help of the PCA calculations, the effect of the different pre-treatments on the production of the main pyrolysis products was evidenced.     

Correlation between heating values and thermogravimetric data of sewage sludge, herbaceous crops and wood samples

The thermal behaviours of a sewage sludge sample, woody (black locust, poplar and willow) and herbaceous (energy grass and wheat straw) biomass as well as mixed (sewage sludge and black locust in ratios 1:1 and 1:3) samples were compared under inert and oxidative atmosphere. The thermogravimetric experiments of each sample demonstrate that the beginning temperature of decomposition is similar in inert and oxidative atmospheres, i.e. the primary bond scissions are not affected by the atmosphere. Nevertheless, oxygen increases the decomposition rate and the volatile evolution of all samples at higher temperatures. Thermogravimetry/mass spectrometry (TG/MS) experiments have been performed to determine the mass loss of the samples and the formation of volatile products as a function of temperature in inert atmosphere. Wood and herbaceous biomass samples evolved various organic products (aldehydes, ketones, acids, furan derivatives, etc.) beside water and gaseous products. Sewage sludge released mainly water, carbon oxides, methane, hydrogen, hydrocarbons, ketones, acids as well as sulphur- and nitrogen-containing products. High heating value and low heating value of the samples have been determined by a bomb calorimeter. Principal component analysis (PCA) has been used to find statistical correlation between the data. The results unambiguously support the correlation between the thermogravimetric parameters (e.g. DTG_max) and the heating values of the samples.     

Thermal degradation of wood treated with guanidine compounds in air: Flammability study

Wood has been treated with guanidine phosphate, guanidine nitrate, guanidine carbonate and guanidine chloride to impart flame retardancy. The samples were subjected to differential thermal analysis (DTA) and thermogravimetry (TG) from ambient temperature to 800°C in air to study their thermal behaviors. From the resulting data, kinetic parameters for different stages of thermal degradation were obtained following the method of Broido. For the decomposition of wood and flame retardant wood, the activation energy was found to decrease from 116 to 54 kJ mol^–1; the char yield was found to increase from 5.6 to 34.9%, LOI from 18 to 41.5, which indicated that the flame retardancy of treated wood was improved. Effects of the different compounds on the degradation and flammability of wood have also been proposed.This revised version was published online in November 2005 with corrections to the Cover Date.     

The effect of alkaline pretreatment on the thermal decomposition of hemp

The goal of this study was to clarify the effect of alkaline pretreatments on the thermal decomposition and composition of industrial hemp (Cannabis sativa L.) samples. Thermogravimetric/mass spectrometric measurements (TG/MS) have been performed, on untreated, hot water washed, and alkali-treated hemp samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. Principal component analysis (PCA) has been used to find statistical correlations between the data. Correlations have been obtained between the parameters of the thermal decomposition and the alkali ion content as well as the altered chemical structure of the samples. The differences in the thermal behavior of the samples are explained by the different K⁺ and Na⁺ contents and the changed structure of the hemicellulose component of the samples due to the pretreatments. The more alkali ions remain in the hemp samples after the alkali treatment, the more ash, char and lower molecular products are formed during thermal decomposition.     

Thermal degradation of wood treated with flame retardants

Wood, one of the most flammable materials, was treated with various compounds containing nitrogen, phosphorus, halogens, and boron. For a study of flame retardance from the standpoint of thermal degradation, the samples were subjected to thermogravimetry (TG), differential thermal analysis (DTA) and differential thermogravimetry (DTG) in nitrogen to determine if there were any characteristic correlations between thermal degradation behaviors and the level of flame retardance. From the resulting data, kinetic parameters for different stages of thermal degradation are obtained using the method of Broido. The energies of activation for the decomposition of samples are found to be from 72 to 109 kJ mol^–1. For wood and modified wood, the char yields are found to increase from 10.2 to 30.2%, LOI from 18 to 36.5, which indicates that the flame retardance of wood treated with compounds is improved. The flame retardant mechanism of different compounds has also been proposed.     

Thermogravimetric and kinetic methods to date wood finds. First results

Fresh (larch and fir, in its white and red varieties) and ancient wood samples (dating respectively to the 13th, 15th and 17th centuries) were subjected to thermogravimetric analysis (TG and DTG). The resulting thermogravimetric data were then used to construct archeometric curves for the wood varieties tested. In a preliminary approach, it was attempted to correlate the onset temperature of the thermogravimetric step corresponding to cellulose decomposition with the age (expressed in centuries) of the samples, although the results obtained were anything but brilliant. More encouraging results were obtained by examining the relationship between wood sample age and the value of the (percent cellulose/percent lignin) ratio computed from the thermogravimetric data. Lastly, a procedure for processing data obtained from the TG curves was applied to a kinetic analysis of the processes that take place when wood samples are subjected to a temperature regime with a constant heating rate, obtaining values for the activation energy of the TG step corresponding to the decomposition of cellulose. Also using these data it was attempted to construct archeometric curves, obtaining results that varied quite significantly according to the wood species tested.     

Relation Between Thermal Decomposition of Medicinal Herbs and their Non-Metals Concentration

The studies on the concentration of total nitrogen, phosphorus, sulphur, chlorine, iodine and boron as well as on the thermal decomposition of commercial raw plant materials used in medicine were performed. The 50 independent samples of herbs originating from 25 medicinal plant species collected in 1986–92 were analysed. The content of non-metallic elements was determined spectrophotometrically after previous mineralization of plant sample. The thermal decomposition was performed using the derivatograph with the application of 100 mg samples and heating rate of 5°C min⁻¹. In order to obtain more clear classification of the analysed plant materials principal component analysis (PCA) was applied. Interpretation of PCA results for two databases (non-metals and thermoanalytical data sets) allows to state, that samples of herbs from the same plant species in majority of cases are characterized by similar elemental composition and similar course of their thermal decomposition. In this way the differences in general chemical composition of medicinal plants raw materials can be determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal degradation of silane crosslinked unplasticized PVC

The thermal decomposition behaviour of rigid PVC, crosslinked using bis(γ-trimethoxysilylpropyl)amine as crosslinking agent has been studied. Different thermal stabilizers (tin and lead based) have been used with different crosslinking agent concentrations, and the influence of these factors on the decomposition behaviour in inert atmosphere studied. Results obtained have shown that the main effect of aminosilane is an advance of the first stage of the PVC degradation (i.e. the dehydrochlorination process). Moreover, samples with different concentrations of silane, and at different stages of their processing (i.e. after milling, pressing, crosslinking) have also been used in order to elucidate the influence of these factors on their thermal behaviour. A quantitative kinetic model has been developed and the corresponding kinetic constants have been obtained by modelling the experimental thermogravimetric data. The kinetic parameters obtained have revealed a reduction in the apparent activation energy of the hydrogen chloride loss process, which has shown to be markedly dependent on the thermal stabilizer used.     

SVD-based principal component analysis of geochemical data

Principal Component Analysis (PCA) was used for the mapping of geochemical data. A testing data matrix was prepared from the chemical and physical analyses of the coals altered by thermal and oxidation effects. PCA based on Singular Value Decomposition (SVD) of the standardized (centered and scaled by the standard deviation) data matrix revealed three principal components explaining 85.2% of the variance. Combining the scatter and components weights plots with knowledge of the composition of tested samples, the coal samples were divided into seven groups depending on the degree of their oxidation and thermal alteration. The PCA findings were verified by other multivariate methods. The relationships among geochemical variables were successfully confirmed by Factor Analysis (FA). The data structure was also described by the Average Group dendrogram using Euclidean distance. The found sample clusters were not defined so clearly as in the case of PCA. It can be explained by the PCA filtration of the data noise.     

Co-firing of biomass with coals

The combustion of coal and coal/fir (Abies bornmulleriana) wood blends at the proper ratio (20, 40, 50 wt%) was investigated with thermogravimetric analysis (TG). The influence of biomass blends on thermal and kinetic behavior of coal was studied under non-isothermal conditions. The activation energy of the samples was evaluated with the Ozawa–Flynn–Wall model which compares the combustion of these biowastes with coal under non-isothermal conditions. Our research found that blending influences activation energy of coal; moreover, activation energy related to 50 wt% blend was more similar to pure wood combustion than to coal combustion. Therefore, the activation energy profile shifted from 80.6 to 169.3 kJ/mol. The average reaction order of the samples ranged from 0.13 to 0.35.     

预氧化聚铝碳硅烷纤维的热分解动力学及其机理

利用热重分析仪(TGA)对预氧化聚铝碳硅烷(PACS)纤维进行了热动力学研究, 用改良的Coats-Redfern法计算了动力学参数, 用Doyle法计算了理论失重值, 并根据FT-IR, XRD和SEM对其热分解的机理进行了分析. 结果表明, 在热分解反应的主要阶段, 预氧化纤维的反应活化能低于PACS纤维, 氧的引入有利于纤维的热分解; 快速升温有利于预氧化PACS纤维的热分解. 在初始分解阶段, 主要为低分子量的PACS和H₂O的逸出, 同时≡Si—H键之间以及≡Si—H与≡Si—CH₃键发生了脱氢、脱CH₄反应, 从而导致交联程度的增加; 随热分解温度进一步的提高, 分子的有机侧基急剧热解, 分解产物从有机物转变为存在部分微晶的无机结构; 热分解温度继续提高, 纤维结构进一步完善, 1300 ℃左右, β-SiC晶粒大小约为2～4 nm左右, 纤维具有较好的性能.     

The pyrolysis process of wood biomass samples under isothermal experimental conditions—energy density considerations: application of the distributed apparent activation energy model with a mixture of distribution functions

This work deals with the isothermal pyrolysis of Pine and Beech wood samples and kinetic studies, using the thermo-analytical technique, at five different operating temperatures. Pyrolysis processes were investigated by using the distributed apparent activation energy model, which involves the complex mixture of different continuous distribution functions. It was found that decomposition processes of wood pseudo-components take place in different conversion areas during entire pyrolyses, whereby these areas, as well as the changes in apparent activation energy (E _a) values, are not the same for softwood and hardwood samples. Bulk density (Bden) and energy density (ED) considerations have shown that both biomass samples suffer from low Bden and ED values. It was concluded that pyrolysis can be used as a means of decreasing transportation costs of wood biomass materials, thus increasing energy density. The “pseudo” kinetic compensation effect was identified, which arises from kinetic model variation and wood species variation. In the current extensive study, it was concluded that primary pyrolysis refers to decomposition reactions of any of three major constituents of the considered wood samples. Also, it was established that primary reactions may proceed in parallel with simultaneous decomposition of lignin, hemicelluloses and cellulose in the different regions of wood samples, depending on the operating temperature. It was established that endothermic effects dominate, which are characterized with devolatilization and formation of volatile products. It has been suggested that the endothermic behavior that arises from pyrolyses of considered samples may indicate the endothermic depolymerization sequence of cellulose structures.     

TG studies of a composite solid rocket propellant based on HTPB-binder

Thermal decomposition kinetics of solid rocket propellants based on hydroxyl-terminated polybutadiene-HTPB binder was studied by applying the Arrhenius and Flynn-Wall-Ozawa's methods. The thermal decomposition data of the propellant samples were analyzed by thermogravimetric analysis (TG/DTG) at different heating rates in the temperature range of 300-1200 K. TG curves showed that the thermal degradation occurred in three main stages regardless of the plasticizer (DOA) raw material, the partial HTPB/IPDI binder and the total ammonium perchlorate decompositions. The kinetic parameters E _a (activation energy) and A (pre-exponential factor) and the compensation parameter (S _p) were determined. The apparent activation energies obtained from different methods showed a very good agreement. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition kinetics of potassium iodate

The rate and kinetics of the thermal decomposition of potassium iodate (KIO₃) has been studied as a function of particle size, in the range 63?C150???m, by isothermal thermogravimetry at different temperatures, 790, 795, 800 and 805?K in nitrogen atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of all samples of KIO₃ at all temperatures studied. The isothermal decomposition of all samples of KIO₃ was subjected to both model-fitting and model-free (isoconversional) kinetic methods of analysis. It has been observed that the activation energy values are independent of the particle size. Isothermal model-fitting analysis shows that the thermal decomposition kinetics of all the samples of KIO₃ studied can be best described by the contracting cube equation.     

硫酸铝钾热分解反应动力学模型

近年来,在热分析动力学研究领域内,已有许多动力学模式及相应数据处理方法来描述固相反应的最可能机理,如：aRCHAR微分法[1]Coats-Redfe积分法[2]相结合的方法和等温过程与非等过程相结合的方法[3]等。而最近Dollimore等人[4]提出了利用 TA曲线的特征来确定动力学模型的方法,从而避免了对 f(a)和 g(a)逐一尝试的麻烦。本文就是用该法来研究硫酸铝钾的热分解动力学。硫酸铝钾热分解过程虽然已有人研究[5],但其动力学则未见文献报道。1 实验部分 实验工作在美国PE公司TGA７热分析仪上完成,反应气氛为氮气,流速为40mL·min-1 ,…     

TG and Flammability Studies on Polymer Blends Containing Acrylonitrile–butadiene–styrene and Chlorinated Poly(vinyl Chloride)

The effects which an iron(III) based smoke suppressing compound have on the thermal stability of some acrylonitrile–butadiene–styrene/chlorinated poly(vinyl chloride) (ABS/CPVC) polymer blends have been investigated. Thermogravimetric analysis (TG) experiments have shown that there are three distinctive stages occurring during the thermal breakdown of these blends both when the iron compound is absent and present in the polymer formulations. The most important effect which the iron compound has when it is present in these blends is to modify the decomposition chemistry which takes place and the effect becomes more pronounced as the concentration of CPVC present in the blends increases. Other important effects are that the iron compound stabilises the blends so that mass loss is significantly reduced (by up to 50% in some cases) and the onset temperature of decomposition is raised. Flammability data generated during earlier work is supported by the TG results obtained in this work especially in the important area of smoke formation and suppression. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of methylxanthines

The thermal decomposition of theophylline, theobromine, caffeine, diprophylline and aminophylline were evaluated by calorimetrical, thermoanalytical and computational methods. Calorimetrical studies have been performed with aid of a heat flux Mettler Toledo DSC system. 10 mg samples were encapsulated in a 40 μL flat-bottomed aluminium pans. Measurements in the temperature range form 20 to 400°C were carried out at a heating rate of 10 and 20°C min⁻¹ under an air stream. It has been established that the values of melting points, heat of transitions and enthalpy for methylxanthines under study varied with the increasing of heating rate. Thermoanalytical studies have been followed by using of a derivatograph. 50, 100 and 200 mg samples of the studied compounds were heated in a static air atmosphere at a heating rate of 3, 5, 10 and 15°C min⁻¹ up to the final temperature of 800°C. By DTA, TG and DTG methods the influence of heating rate and sample size on thermal destruction of the studied methylxanthines has been determined. For chemometric evaluation of thermoanalytical results the principal component analysis (PCA) was applied. This method revealed that first of all the heating rate influences on the results of thermal decomposition. The most advantageous results can be obtained taking into account sample masses and heating rates located in the central part of the two-dimensional PCA graph. As a result, similar data could be obtained for 100 mg samples heated at 10°C·min⁻¹ and for 200 mg samples heated at 5°C min⁻¹.     

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)₄X₂, where M = Cu, X = Cl, NO₃ and CH₃COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)₄Cl₂ complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.     

Thermogravimetric analysis of wood, holocellulose, and lignin from five wood species

Thermogravimetry has been widely applied to the study of wood and cellulose materials. There is a general agreement that decomposition of hemicellulose, cellulose, and ligning take place in a relatively narrow range of temperature, partially overlapping. There is no a definitive demonstration of which thermal feature corresponds to each component. In this study, three hardwood and two softwood species were considered: Castannea sativa, Eucaliptus globulus, Quercus robur, Pinus pinaster, and Pinus sylvestris. Thermogravimetric analysis of wood powder, ethanol-extracted wood, holocellulose, and lignin, obtained from those species revealed some important differences between hardwood and softwood holocelluloses and an important role of the ethanol-extractives, which explain the different behavior observed in both kinds of wood. FTIR spectra obtained from the evolved gases helped to clarify some degradation steps.     

Influence of torrefaction on the devolatilization and oxidation kinetics of wood

Devolatilization and oxidation kinetics of torrefied wood have been studied by evaluating thermogravimetric curves measured in nitrogen and air at various heating rates. Samples consist of Norway spruce wood chips torrefied at several process temperatures and residence times. Data about untreated wood have also been obtained for comparison. Measured curves are well predicted by means of a five-reaction mechanism, consisting of three devolatilization reactions for the pseudo-components hemicellulose, cellulose and lignin and, in air, of two additional reactions for char devolatilization and combustion. The torrefaction pre-treatment only requires model modifications in the amounts of volatiles generated from the decomposition of pseudo-components, indicating that only their relative percentages and not their reactivities are modified. On the other hand, a slightly different thermal stability is found for the char generated from torrefied wood, which results in higher activation energy and lower reaction order for the oxidation step. Hence torrefaction conditions can affect the subsequent conversion characteristics of the char product.