Investigation of agricultural residues pyrolysis behavior under inert and oxidative conditions

Three samples of biomass including rice straw, corn straw and corncob were analyzed by using TG–MS analyzer. The relevance of the oxidizing versus inert atmosphere to the conversion of Chinese typical agricultural residues are discussed and analyzed. Firstly the effect of oxygen concentration on three biomass conversion pathway is discussed. Secondly the releasing temperature and quantities of major non-condensable gases and tar components are analyzed, and finally the kinetic parameters is calculated and compared.The results show that the oxygen concentration and fuel type play an important role in biomass conversion pathway. All the detected non-condensable gases are favored by oxidative conditions for three samples. With the increase of oxygen concentration, all the condensable gases except H₂ are released over narrower temperature ranges under oxidizing conditions. All the tar components mainly evolve within 300–700 °C, with the increase of oxygen concentration, these major tar components show different features: except that benzene and phenol quickly decreases, other tar components basically changes moderately. The Coats and Redfern integral method is used for kinetic modeling, and Malek method is adopted to select the proper mechanism function. Most of experimental data can be simulated by F1 mechanism model. For the first temperature range of all samples, the values of the activation energy and of the reaction order are lower compared to the case of inert pyrolysis.     

Thermal inactivation of alkali phosphatases under various conditions

The thermal inactivation of alkali phosphatases from bacteria Escherichia coli (ECAP), bovine intestines (bovine IAP), and chicken intestines (chicken IAP) was studied in different buffer solutions and in the solid state. The conclusion was made that these enzymes had maximum stability in the solid state, and, in a carbonate buffer solution, their activity decreased most rapidly. It was found that the bacterial enzyme was more stable than animal phosphatases. It was noted that, for ECAP, four intermediate stages preceded the loss of enzyme activity, and, for bovine and chicken IAPs, three intermediate stages were observed. The activation energy of thermal inactivation of ECAP over the range 25–70°C was determined to be 80 kJ/mol; it corresponded to the dissociation of active dimers into inactive monomers. Higher activation energies (∼200 kJ/mol) observed at the initial stage of thermal inactivation of animal phosphatases resulted from the simultaneous loss of enzyme activity caused by dimer dissociation and denaturation. It was shown that the activation energy of denaturation of monomeric animal alkali phosphatases ranged from 330 to 380 kJ/mol depending on buffer media. It was concluded that the inactivation of solid samples of alkali phosphatases at 95°C was accompanied by an about twofold decrease in the content of β structures in protein molecules. Original Russian Text ? L.F. Atyaksheva, B.N. Tarasevich, E.S. Chukhrai, O.M. Poltorak, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 2, pp. 391–396.     

Thermal isomerization of 3,3-dimethylcyclopropene under adiabatic-compression conditions

The thermal isomerization of 3,3-dimethylcyclopropene under adiabatic-compression conditions at 660–850 K occurs in two independent directions with the formation of isopropylacetylene and isoprene; kinetic parameters for each of these routes were obtained. The formation of products of the gem-dimethylvinylcyclopropanation of olefins during their copyrolysis with 3,3-dimethylcyclopropene is not observed, apparently because of the occurrence of isomerization of 3,3-dimethyl-cyclopropene in the gas phase at 660–850 K without the participation of gemdimethylvinylcarbene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2008–2010, September, 1989.The authors thank A. I. Ioffe and N. V. Volchkov for participation in the discussion of the obtained results.     

Empirical model of slow pyrolysis of hardwood chips

Applied Biochemistry and Biotechnology - The thermal decomposition of mixed hardwood chips was investigated by pyrolyzing 1-kg samples at atmospheric pressure in an electrically-heated batch...     

Thermal characteristics of bitumen pyrolysis

The pyrolysis behavior of bitumen was investigated using a thermogravimetric analyzer–mass spectrometer system (TG–MS) and a differential scanning calorimeter (DSC) as well as a pyrolysis-gas chromatograph/mass spectrometer system (Py-GC/MS). TG results showed that there were three stages of weight loss during pyrolysis—less than 110, 110–380, and 380–600 °C. Using distributed activation energy model, the average activation energy of the thermal decomposition of bitumen was calculated at 79 kJ mol⁻¹. The evolved gas from the pyrolysis showed that organic species, such as alkane and alkene fragments had a peak maximum temperature of 130 and 480 °C, respectively. Benzene, toluene, and styrene released at 100 and 420 °C. Most of the inorganic compounds, such as H₂, H₂S, COS, and SO₂, released at about 380 °C while the CO₂ had the maximum temperature peaks at 400 and 540 °C, respectively. FTIR spectra were taken of the residues of the different stages, and the results showed that the C–H bond intensity decreased dramatically at 380 °C. Py-GC/MS confirmed the composition of the evolved gas. The DSC revealed the endothermic nature of the bitumen pyrolysis.     

Patterns and kinetics of pyrolysis of tobacco under inert and oxidative conditions

The present work is part of a more extensive research carried out in Naples on cigarette combustion. Theoretical and modelling work highlighted the existence of a misdistribution of the gas flow across the cigarette cross-section, which results into locally variable conditions. As a consequence, oxygen-starving versus oxygen-rich conditions do establish in the pre-heat zone of the cigarette, where pyrolysis of cigarette components takes place. More specifically, oxygen-starving conditions should characterize the process of reaction front propagation in the inner part of the cigarette, close to its axis, while oxygen-rich conditions should establish at the cigarette periphery, close to the paper burn line.The present paper addresses the pattern and the kinetics of pyrolysis under inert and under oxidative conditions of three types of tobacco. The experimental work consists of non-isothermal thermogravimetric analysis at heating rates comprised between 5 and 20 °C/min and with different He–oxygen mixtures. Kinetic expressions for the rate of pyrolysis under inert and under oxidative conditions have been obtained for each ingredient investigated.Results, albeit obtained at sample heating rates smaller than those relevant to actual cigarette burning, highlight the profound differences arising under purely pyrolytic or oxy-pyrolytic conditions as regards the number of reaction steps, the rate, the temperature ranges and yields in solid versus gaseous products of thermal decomposition.The effect of inert/oxidative conditions on the chemical composition of the gaseous products of pyrolysis is discussed in a companion paper [O. Senneca, S. Ciaravolo, A. Nunziata, J. Anal. Appl. Pyrol. 78 (2007) 452].     

Thermal behavior pattern of tributyl phosphate under adiabatic conditions

Violent decomposition of Tributyl Phosphate (TBP), a widely employed extractant in the Plutonium Uranium Extraction process of nuclear fueling reprocessing plants in the presence of Nitric acid at temperatures in excess of 130 °C is a matter of concern in serious accidents including in the Savannah River (USA) and Tomsk (Russia). The thermal behavior of TBP under adiabatic conditions employing the world’s benchmark adiabatic calorimeter, the Accelerating Rate Calorimeter is examined. TBP shows multiple self heating exothermic activities with the onset of primary exotherm at 250 °C. The exothermic activity is accompanied by considerable pressure rise. The thermal decomposition of TBP is found to follow first order Arrhenius kinetic model. TBP loses about 70% of its chemical moieties as volatile matter during the exothermic decomposition. Spectroscopic methods are used to elucidate the degradation pathway.     

Thermal and pyrolysis studies of copolyesters

Random copolyesters of dimethyl terephthalate (DMT), ethylene glycol (EG), and butane-1,4-diol (BD) and the homopolyesters poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) have been subjected to degradation and pyrolysis studies. Differential thermal analysis (DTA) showed that the decomposition temperature is dependent on the percentage of EG and BD present in the copolyesters. Thermal volatilization analysis (TVA) also showed that the decomposition temperature is dependent on the percentage of EG and BD present in the copolyesters. The trend for the decomposition temperatures obtained from TVA studies for these copolyesters is similar to such other thermal properties as melting temperature T_m, ΔH_f, ΔH_c, etc. The subambient thermal volatilization analysis (SATVA) curves obtained for these polymers are also presented. The SATVA curve is the fingerprint of the total volatile products formed during the degradation in high vacuum. The isothermal pyrolysis of these materials was carried out in high vacuum at 450°C. The products formed were separated in a gas chromatograph and were subsequently identified in a mass spectrometer. The major pyrolysis products from PBT were butadiene and tetrahydrofuran, whereas those from PET were ethylene and acetaldehyde. The ratio of acetaldehyde to ethylene increases with the EG content in the copolyester, suggesting a different decomposition mechanism compared to the decomposition mechanism of PBT and PET.     

Thermal characterisation of Australian oil shales

There has been a significant research effort on the development of an oil industry based on Australian oil shales. However, to date the research has been based mainly on the processing aspects of oil shale. The thermal analyses of oil shales, while having been the subject of many studies, have been limited to some extent by instrumentation and analytical techniques. This paper reports on thermal analysis studies utilising traditional thermogravimetry/differential thermal analysis (TG/DTA) and differential scanning calorimetry (DSC). The application of modern thermal analysis techniques such as high resolution TG (HRTG) and modulated differential scanning calorimetry (MDSC) is also examined and compared to the traditional methods.     

Application of analytical pyrolysis for the characterisation of old inks

In the last years particular attention has been dedicated to the analysis of iron-gall inks for their effects on the degradation of paper. Mainly spectroscopic techniques devoted to the determination of iron have been studied, while a minor attention has been dedicated to the organic components.

In this study we propose THM pyrolysis as a rapid tool for the characterisation of inks organic component. The method was applied on several standards and on original samples showing that it is suitable for the characterisation of iron gall and sepia inks. Moreover, information on the organic binder may also be achieved at the same time.     

Modeling of acetylene pyrolysis under steel vacuum carburizing conditions in a tubular flow reactor

In the present work, the pyrolysis of acetylene was studied under steel vacuum carburizing conditions in a tubular flow reactor. The pyrolysis temperature ranged from 650 degrees C to 1050 degrees C. The partial pressure of acetylene in the feed mixture was 10 and 20 mbar, respectively, while the rest of the mixture consisted of nitrogen. The total pressure of the mixture was 1.6 bar. A kinetic mechanism which consists of seven species and nine reactions has been used in the commercial computational fluid dynamics (CFD) software Fluent. The species transport and reaction model of Fluent was used in the simulations. A comparison of simulated and experimental results is presented in this paper.     

The formation of Pt-Ru alloy nanoparticles in a carbon matrix under IR pyrolysis conditions

Nanosized Pt-Ru alloy and Pt₁₃Ru₂₇ intermetallic compound particles dispersed in a carbon matrix were obtained for the first time directly during the preparation of the composite. The alloying of the Pt and Ru particles occurred at IR pyrolysis intensities corresponding to temperatures above 700°C over the whole homogeneity range of solid solutions based on platinum. Metallic nanoparticles were round-shaped (the mean size 6–8 nm) and had a narrow particle-size distribution.     

The pyrolysis of cigarette paper under the conditions that simulate cigarette smouldering and puffing

The combustion properties and pyrolysis behavior of cigarette paper under the pyrolysis conditions of cigarette smouldering were investigated by micro-scale combustion calorimetry (MCC), thermogravimetric analysis coupled to Fourier transform infrared spectrometer (TG-FTIR), respectively. MCC results demonstrated that the combustion and pyrolysis behavior are influenced by heating rate obviously. TG-FTIR results illustrated that the composition of the gaseous products were mainly composed of CO₂, H₂O carbonyl compounds, CO, and methanol. Flash pyrolysis experiment in combination with high performance liquid chromatography (FPy-HPLC) was used to study the pyrolytic formation of eight carbonyl compounds (i.e., formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, crotonaldehyde, methyl ethyl ketone, and butyraldehyde) during the pyrolysis of cigarette paper under the pyrolysis conditions of cigarette puffing. Moreover, the solid char formed after the flash pyrolysis experiments were studied by X-ray photoelectron spectroscopy (XPS). It had been found that the pyrolysis temperature influenced the formation of carbonyl compounds and the composition of char greatly.     

Thermal self-sustainability of biochar production by pyrolysis

The pyrolysis of several agricultural and biofuel production residues (grape residues, sugarcane residues, dried distiller's grain, palm oil residues, apple pomace and forestry residue) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and two vapor residence times (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers. The thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The most promising biomass feedstocks for the sustainable production of biochar were indentified. Furthermore, this study presented the char yield in relation to the excess heat that could be obtained by combusting the gas and bio-oil coproducts of biochar production, as functions of pyrolysis temperature and vapor residence time.     

Synthesis and characterisation of strontium carboxylates formed at room temperature and under hydrothermal conditions

A novel method was developed for the synthesis of highly pure strontium complexes in high yield. Syntheses proceeded along three pathways with optimum conditions being at T?=?120–140°C, a base?:?acid ratio of 1.2 and 15?min reaction-time in an autoclave vessel. Large crystals were readily obtained within hours. The crystal structures of strontium R-glutamate hexahydrate (I) and strontium di(hydrogen S-glutamate) pentahydrate (II) were determined by X-ray powder diffraction methods at 295?K with Rietveld refinement (I: Space group P2₁2₁2₁, Z?=?4, a?=?7.3519(2), b?=?8.7616(2), c?=?20.2627(5)?Å; II: Space group P2₁, Z?=?2, a?=?8.7243(1), b?=?7.2635(1), c?=?14.6840(2)?Å, β?=?100.5414(7)°). Synthesis at room temperature provided four additional new strontium compounds that may be applicable as constituents of pharmaceutical products for the treatment of bone conditions.     

Thermal analysis of formation of ZrO2 nanoparticles under hydrothermal conditions

The formation of ZrO₂ nanoparticles during the hydrothermal treatment of zirconium oxyhydroxide has been investigated depending on the chemical and thermal history of the initial material. It has been shown that the crystallization of c(t)-ZrO₂ and m-ZrO₂ under hydrothermal conditions proceeds virtually simultaneously, and the amount of one or another polymorph depends mainly on the ratio of rates of these processes.     

Thermal characterisation of molybdenum and platinum-molybdenum catalysts

Alumina supported Mo and Pt-Mo catalysts was subject to temperature programmed reduction (TPR) using H₂ and CO. After earlier oxidation step TPR–H₂ profiles shows different surface species, which depends on the composition of the catalysts and reduction temperature. Change in reducing gas from H₂ into CO results in significant changes in catalyst system. Hydrogen causes a decrease in oxidation number of metals, while carbon monoxide reacts with chemisorbed chemicals.     

Thermal decomposition of polystyrene foam under controlled atmosphere and temperature conditions

The thermal decomposition of polystyrene foam with and without tetrabromovinylcyclohexene, at sample sizes permitting secondary reactions, was studied. The decomposition was carried out in a carefully controlled device providing high reproducibility at 823, 1023 and 1223 K, in air, in a mixture of air and nitrogen and in nitrogen. No flame source was included. The volatile products (boiling range roughly 350–750 K) were studied by gas chromatography—mass spectrometry.The study showed that the amounts of the products were dependent on the decomposition temperature and on the kind of sample. The products were very complex mixtures, containing, amongst others, monomer, oligomers, fused aromatic ring compounds, oxidized hydrocarbons and bromine-containing products. The types and amounts of the products were influenced by the atmosphere, the decomposition temperature and the type of sample.     

Thermal decomposition of nickel(II) complexes under quasi-equilibrium conditions

The stoichiometry of thermal decomposition and the relationship between the thermal parameters (quasi-equilibrium decomposition temperaturesT _D and decomposition entalpies H _D) of NiL₄(NCS)₂ complexes (L=imidazole derivatives) were studied. It was found that changes in the experimental conditions strongly influence the decomposition stoichiometry. TheT _D and H _D can be ordered in the following sequence (according toL): imidazole<2-Me imidazole<2-Et imidazole相似文献