Devolatilization behaviour and pyrolysis kinetic modelling of Spanish biomass fuels

The basic pyrolysis behaviour of eight different biomass fuels has been tested in a thermogravimetric analyser under dynamic conditions (5, 20 and 50 °C min^?1 heating rates) from room temperature up to 1,000 °C. Their decomposition was successfully modelled by three first-order independent parallel reactions, describing the degradation of hemicellulose, cellulose and lignin. Hemicellulose would be the easiest one to pyrolyse, while lignin would be the most difficult one. Experimental and calculated results show good agreement. The reactivity of the different biomass type functions of various thermal, kinetic and composition parameters are discussed. The effect of the heating rate on pyrolysis behaviour was studied, and a comparison between slow and fast heating rate reveals a small displacement of the DTG profiles to higher temperatures. The heating rate not only affects the highest mass loss rate temperature but also influences the mass loss rate value.     

Thermal decomposition of liebigite

Summary A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO₄ and Ca₃UO₆. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the 50°C spectrum at 3504 and 3318 cm^-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned to the υ₁ symmetric stretching modes of the (CO₃)^2- units are observed at 1094, 1087 and 1075 cm^-1 in agreement with three structurally distinct (CO₃)^2- units. At 100°C, two bands are found at 1089 and 1078 cm^-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment.     

Pyrolysis of pistachio shell as a biomass

There is an increasing concern with the environmental problems associated with the increasing CO₂, NO_x and SO_x emissions resulting from the rising use of fossil fuels. Renewable energy, mainly biomass, can contribute to reduce the fossil fuels consumption. Biomass is a renewable resource with a widespread world distribution. Pistachio is available in large quantities in Gaziantep region in Turkey. Pistachio shell has a good energy potential for exploitation through pyrolysis and gasification. This study deals with the thermal degradation characteristics of in different particle sizes pistachio shell and its kinetics. Thermal degradation analysis have been done by using a thermogravimetric analyzer from room temperature to 800°C in N₂ atmosphere at different heating rates (5, 10, 15 and 20°C min⁻¹). TG and DTG curves exhibited two distinct degradation zones. Kinetic parameters were calculated by using Coats-Redfern method and model-free isoconversional Flynn-Wall-Ozawa (FWO) kinetic method.     

Dynamic and controlled rate thermal analysis of hydrozincite and smithsonite

The understanding of the thermal stability of zinc carbonates and the relative stability of hydrous carbonates including hydrozincite and hydromagnesite is extremely important to the sequestration process for the removal of atmospheric CO₂. The hydration-carbonation or hydration-and-carbonation reaction path in the ZnO-CO₂-H₂O system at ambient temperature and atmospheric CO₂ is of environmental significance from the standpoint of carbon balance and the removal of green house gases from the atmosphere. The dynamic thermal analysis of hydrozincite shows a 22.1% mass loss at 247°C. The controlled rate thermal analysis (CRTA) pattern of hydrozincite shows dehydration at 38°C, some dehydroxylation at 170°C and dehydroxylation and decarbonation in a long isothermal step at 190°C. The CRTA pattern of smithsonite shows a long isothermal decomposition with loss of CO₂ at 226°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of zinc carbonate minerals via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. The CRTA technology offers a mechanism for the study of the thermal decomposition and relative stability of minerals such as hydrozincite and smithsonite.     

Controlled rate thermal analysis of hydromagnesite

The reaction of magnesium minerals such as brucite with CO₂ is important in the sequestration of CO₂. The study of the thermal stability of hydromagnesite and diagenetically related compounds is of fundamental importance to this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO₂. This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The dynamic thermal analysis of synthetic hydromagnesite proves that dehydration takes place in two steps at 135 and 184°C, dehydroxylation at 412°C and decarbonation at 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145°C, respectively. In the CRTA experiment both water and carbon dioxide are evolved in an isothermal decomposition at 376°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial nesquehonite structure.     

Thermal decomposition of lutetium propionate

The thermal decomposition of lutetium(III) propionate monohydrate (Lu(C₂H₅CO₂)₃·H₂O) in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy and X-ray diffraction. Dehydration takes place around 90 °C. It is followed by the decomposition of the anhydrous propionate to Lu₂O₂CO₃ with evolution of CO₂ and 3-pentanone (C₂H₅COC₂H₅) between 300 °C and 400 °C. The further decomposition of Lu₂O₂CO₃ to Lu₂O₃ is characterized by an intermediate constant mass plateau corresponding to a Lu₂O_2.5(CO₃)_0.5 overall composition and extending from approximately 550 °C to 720 °C. Full conversion to Lu₂O₃ is achieved at about 1000 °C. Whereas the temperatures and solid reaction products of the first two decomposition steps are similar to those previously reported for the thermal decomposition of lanthanum(III) propionate monohydrate, the final decomposition of the oxycarbonate to the rare-earth oxide proceeds in a different way, which is here reminiscent of the thermal decomposition path of Lu(C₃H₅O₂)·2CO(NH₂)₂·2H₂O.     

Characterization of the decomposition course of nickel acetate tetrahydrate in air

Thermogravimetry, differential thermal analysis, X-ray diffractometry and infrared spectroscopy showed that Ni(CH₃COO)₂·4H₂O decomposes completely at 500°C, giving rise to a mixture of Ni^o and NiO. The results revealed that the compound undergoes dehydration at 160°C and melts at 310°C. The water thus released hydrolyses surface acetate groups, acetic acid being evolved into the gas phase. At 330°C, the anhydrous acetate is converted into NiCO₃, releasing CH₃COCH₃ into the gas phase. The carbonate subsequently decomposes (at 365°C) to give NiO_(s), CO_2(g) and CO_(g). On further heating up to 373°C, a mixture of Ni^o and NiO is formed. Other gas-phase products were detected at 400°C, viz. CH₄ and (CH₃)₂CH=CH₂, which were formed in surface reactions involving initial gas-phase products. Non-isothermal kinetic parameters (A and ΔE) were calculated on the basis of temperature shifts experienced in the various decomposition processes as a function of heating rate (2–20 deg·min^?1).     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Thermal decomposition of Ln(C2H5CO2)3·H2O (Ln?=?Ho, Er, Tm and Yb)

The thermal decomposition of Ho(III), Er(III), Tm(III) and Yb(III) propionate monohydrates in argon was studied by means of thermogravimetry (TG), differential thermal analysis (DTA), IR-spectroscopy and X-ray diffraction (XRD). Dehydration takes place around 90?°C. It is followed by the decomposition of the anhydrous propionates to Ln₂O₂CO₃ (Ln?=?Ho, Er, Tm or Yb) with the evolution of CO₂ and 3-pentanone (C₂H₅COC₂H₅) between 300 and 400?°C. The further decomposition of Ln₂O₂CO₃ to the respective sesquioxides Ln₂O₃ is characterized by an intermediate plateau extending from approximately 500?C700?°C in the TG traces. This stage corresponds to an overall composition of Ln₂O_2.5(CO₃)_0.5 but is more probably a mixture of Ln₂O₂CO₃ and Ln₂O₃. The stability of this intermediate state decreases for the lighter rare-earth (RE) compounds studied. Full conversion to Ln₂O₃ is achieved at about 1,100?°C. The overall thermal decomposition behaviour of the title compounds is similar to that previously reported for Lu(C₂H₅CO₂)₃·H₂O.     

A Thermal Decomposition Study of Individual and Co-Precipitated Y, Ba and Cu Oxalates

Y-Ba-Cu oxalate powder with a presumed Y:Ba:Cu molar ratio of 1:2:4 was prepared by a modified co-precipitation method and its solid-phase thermal decomposition was studied from 25 to 1000°C, the major evolved gases being H₂O and CO₂. The air-dried powder contained residual moisture. It required isothermal heat treatment for elimination of the evolved gases. The melting point of the co-precipitation Y-Ba-Cu oxalate powder, determined by DSC at a heating rate of 10°C min⁻¹ was approximately 882°C in N₂, 949°C in air and about 979°C in O₂. The dependence of the sintering properties of this material upon the atmosphere and the temperature is considered. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal reactions of kaolinite with potassium carbonate

It was previously established that kaolinite reacts with K₂CO₃ on heating to form products of KSiAlO4 composition. In the present study we investigated the solid state reactions with K₂CO₃ of four kaolinites of different thermal stability. The mixtures were calcined at temperatures ranging from 400-700°C and washed before or after boiling with the remaining K₂CO₃. FTIR spectra indicated that the X-ray amorphous material formed after calcining the mixtures at 500-590°C had a SiAlO₄ tetrahedral framework. Attempts to convert the products to zeolites gave promising results. After calcining at 700°C under atmospheric pressure synthetic kaliophilite (KSiAlO₄) was obtained. These conditions are appreciably milder than previously reported for kaliophilite syntheses. Conversion to kalsilite increased with decreasing thermal stability of the original kaolinite. In similar reactions with KCl much less K was incorporated into the amorphous phase and kaliophilite was not obtained. The reactions of the four kaolinites with K₂CO₃ or with KCl were similar in trend, but differed in detail. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evolved gas analysis of coal-derived pyrite/marcasite

The products evolved during the thermal decomposition of the coal-derived pyrite/marcasite were studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR–MS) technique. The main gases and volatile products released during the thermal decomposition of the coal-derived pyrite/marcasite are water (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved product H₂O is mainly released at below 300 °C; (2) under the temperature of 450–650 °C, the main evolved products are SO₂ and small amount of CO₂. It is worth mentioning that SO₃ was not observed as a product as no peak was observed in the m/z = 80 curve. The chemical substance SO₂ is present as the main gaseous product in the thermal decomposition for the sample. The coal-derived pyrite/marcasite is different from mineral pyrite in thermal decomposition temperature. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanations have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials.     

Effective tri-metallic TiO2 supported catalyst for hydrocarbon production from carbon dioxide

The current socio-economic issues with concerns on environmental quality and global warming are attributed to high concentrations of atmospheric carbon dioxide due to extensive usage of fossil fuels. Thus, over the last two decades, comprehensive work has been reported on carbon capture and storage and catalytic conversion of carbon dioxide to hydrocarbons. Among these, the reactions with hydrocarbons to form value-added products have been in focus. In this work, an attempt was made to identify the feasibility of the reaction: carbon dioxide and steam to form hydrocarbons of fuel value. After reviewing the literature on the development of various catalysts and their mechanism, a multi-metallic catalyst supported by TiO₂ Nano-needles was explored. The reaction mechanism is expected to proceed with activated CO₂ complex and hydroxyl groups over the metal oxide catalyst. Current reported work on CO₂ and Hydrogen proceeds with activated CO₂ and protons over the catalyst. The characterization techniques mainly XPS, XRD, TGA, FESEM-EDAX, FTIR, and NMR were used to analyze the catalyst activity and to confirm the products formed. The reaction is found to yield methanol and oxygen only. However, the conversion is found to be 0.4% - 3.8% in the temperature range 350°C to 550°C. The reaction of CO₂ with hydroxyl groups from water vapor can be effective as an alternative to the reaction with protons from hydrogen.     

Research of thermal decomposition kinetic characteristic of emulsion explosive base containing Fe and Mn elements

The kinetic characteristic of thermal decomposition of the Emulsion Explosive Base Containing Fe and Mn elements (EEBCFM) which was used to prepare nano-MnFe₂O₄ particles via detonation method was investigated by means of non-isothermal DSC and TG methods at various heating rates of 2.5, 5 and 7.5°C min⁻¹respectively under the atmosphere of dynamic air from room temperature to 400°C. The results indicated that the EEBCFM was sensitive to temperature, especially to heating rate and could decompose at the temperature up to 60°C. The maximum speed of decomposition (dα/dT)_m at the heating rate of 5 and 7.5°C min⁻¹ was more than 10 times of that at 2.5°C min⁻¹ and nearly 10 times of that of the second-category coal mine permitted commercial emulsion explosive (SCPCEE). The plenty of metal ions could seriously reduce the thermal stability of emulsion explosive, and the decomposition reaction in the conversion degree range of 0.0∼0.6 was most probably controlled by nucleation and growth mechanism and the mechanism function could be described with Avrami-Erofeev equation with n=2. When the fractional extent of reaction α>0.6, the combustion of oil phase primarily controlled the decomposition reaction.     

Thermal transformations of lead oxides

Differential scanning calorimetry, differential thermogravimetry, X-ray analysis and electronic microscopic studies of thermal transformations of PbO₂ were carried out. Formation of fine dispersed (less than 100 nm) particles of α-PbO was observed at PbO₂ thermal decomposition at heating to 580°C. Reverse reaction of Pb₃O₄ formation from PbO was found at cooling and annealing at 400°C in air. At heating of α-PbO to 650°C the particle growth to 1 μm with formation of β-PbO took place. Thermal decomposition with formation of β-PbO particles with size from 0.3 to 1 μm at PbO₂ heating to 650°C was observed. Transition from PbO to Pb₃O₄ at cooling of sample heated to 650°C was not detected. Interpretation of observed phenomena from the point of view of particle size influences on the shift of α-PbO↔β-PbO phase transition temperature and on the chemical activity of phases are presented.     

Thermal decomposition of the layered double hydroxides of formula Cu6Al2(OH)16CO3 and Zn6Al2(OH)16CO3

Zn-Al hydrotalcites and Cu-Al hydrotalcites were synthesised by coprecipitation method and analysed by X-ray diffraction (XRD) and thermal analysis coupled with mass spectroscopy. These methods provide a measure of the thermal stability of the hydrotalcite. The XRD patterns demonstrate similar patterns to that of the reference patterns but present impurities attributed to Zn(OH)₂ and Cu(OH)₂. The analysis shows that the d003 peak for the Zn-Al hydrotalcite gives a spacing in the interlayer of 7.59 ? and the estimation of the particle size by using the Debye-Scherrer equation and the width of the d003 peak is 590 ?. In the case of the Cu-Al hydrotalcite, the d003 spacing is 7.57 ? and the size of the diffracting particles was determined to be 225 ?. The thermal decomposition steps can be broken down into 4 sections for both of these hydrotalcites. The first step decomposition below 100°C is caused by the dehydration of some water absorbed. The second stage shows two major steps attributed to the dehydroxylation of the hydrotalcite. In the next stage, the gas CO₂ is liberated over a temperature range of 150°C. The last reactions occur over 400°C and involved CO₂ evolution in the decomposition of the compounds produced during the dehydroxylation of the hydrotalcite.     

Thermal analysis of the pyrolytic behaviors of a highly crosslinked polymer

Thermogravimetric-mass spectrometric (TG/MS) and differential scanning calorimetric (DSC) techniques were used in the characterization of oxidative and nonoxidative degradation reactions of a highly crosslinked divinylbenzene/styrene copolymer. When the copolymer was subjected to a temperature-programmed air environment, four exothermic reactions were detected. The initial small exothermic reaction, starting at ca. 125°C and reaching its maximum at ca. 180°C, was presumed to result from the decomposition of peroxides. The second exothermic reaction, which overlapped with the initial one and peaked at ca. 270°C, was attributed to oxidation with a significant amount of oxygen uptake and liberation of some gaseous products such as CO₂, styrene, benzaldehyde, ethylstyrene, and ethylbenzaldehyde. The strongest exothermic reaction took place at ca. 290–380°C and had its peak at ca. 360°C. Associated with this reaction was the generation of many gaseous pyrolysates, as given above. The exothermic reaction continued at a relatively constant rate from ca. 380°C to the maximum temperature of the experiment (500°C) with the release of only one gaseous product (CO₂). The initial exothermic reaction can be eliminated by controlled thermal decomposition of peroxides; therefore, a more thermally stable polymer can be obtained. Exothermic reactions, starting at ca. 170°C, were observed. Pyrolytic reactions in an inert gas were also studied.     

Formation of Cr(II) Species in the H2/CrO3 System. Parameter control

The thermal behaviour of CrO₃ on heating up to 600°C in dynamic atmospheres of air, N₂ and H₂ was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO₃ near 215°C (independent of the atmosphere), (ii) decomposition into Cr₂(CrO₄)₃ at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr₂O₃ at 415–490°C (significantly dependent). The decomposition CrO₃ → Cr₂(CrO₄)₃ is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr₂(CrO₄)₃ → Cr₂O₃ involves endothermic reductive deoxygenation reactions in air (or N₂) which are greatly accelerated and rendered exothermic in the presence of H₂. TG measurements as a function of heating rate (2–50°C min⁻¹) demonstrated the acceleratory role of H₂, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H₂ molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min⁻¹) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of nickel and zinc peroxotitanates to metatitanates

Methods of DTA, TG, X-ray phase analysis and IR spectroscopy were used to study the thermal dehydration and decomposition of Ni²⁺ and Zn²⁺ peroxotitanates to the corresponding metatitanates. The course of the process was established and the intermediate phases were identified. The information obtained was utilized to determine the optimum temperatures of heating the initial peroxotitanates for conversion to metatitanates with a fairly high degree of crystallinity (for ZnTiO₃ the optimum temperature is 600°C, while for NiTiO₃ it is 550°C).     

Thermal degradation of PVC cable insulation studied by simultaneous TG-FTIR and TG-EGA methods

Thermogravimetry (TG/DTG) coupled with evolved gas analysis (MS detection) of volatiles was used to characterize the thermal behavior of commercial PVC cable insulation material during heating in the range 20-800°C in air and nitrogen, respectively. In addition, simultaneous TG/FTIR was used to elucidate chemical processes that caused the thermal degradation of the sample. A good agreement between results of the methods was found. The thermal degradation of the sample took place in three temperature ranges, namely 200-340, 360-530 and 530-770°C. The degradation of PVC backbone started in the range 200-340°C accompanied by the release of HCl, H₂O, CO₂ and benzene. The non-isothermal kinetics of thermal degradation of the PVC cable insulation in the temperature range 200-340°C was determined from TG results measured at heating rates of 1.5, 5, 10, 15 and 20 K min^-1 in nitrogen and air, respectively. The activation energy values of the thermal degradation process in the range 200-340°C of the PVC cable insulation sample were determined from TG results by ASTM method. This revised version was published online in July 2006 with corrections to the Cover Date.