Products distribution and gas release in pyrolysis of thermally thick biomass residues samples

The pyrolysis of thermally thick (approximately 75 g) biomass residues samples (i.e. brewer spent grains, fibreboard and coffee beans waste) has been investigated in an in-house designed and fabricated macro-TGA both by rapid sample introduction at reactor temperatures from 600 to 900 °C and by applying a constant heating rate of 10 K/min. The composition of the product gas is determined by simultaneous online use of a micro-GC and a FTIR analyser. The product yields (liquid, char and gas) and the gas composition show a clear dependence on temperature and heating rate. The main gas products are CO₂, CO, CH₄, H₂, C₂H₂, C₂H₆ and C₂H₄. The results show that a rise in temperature leads to increasing gas yields and decreasing liquid and char yields. Lower heating rates favour liquid and char yields. The release patterns of the gaseous species are also greatly affected by the temperature history of the sample.     

Influence of some minerals on the cellulose thermal degradation mechanisms

The influence of different inorganic salts (MgCl₂, ZnCl₂, NiCl₂ and H₂PtCl₆) on the primary mechanisms of cellulose thermal degradation has been conducted by using thermogravimetric (TG-DTG) and pyrolysis-mass spectrometry (Py-MS) analysis at low heating rate (10°C min-1) from ambient temperature to 500°C. The results clearly demonstrate that the used salts influence the primary degradation mechanisms. Furthermore, we can assume that some inorganic salts could be considered as specific catalysts and some others as inhibitors. MgCl₂ promotes selectively initial low temperature dehydration as observed both by TG and Py-MS. ZnCl₂ strongly changes the thermal behaviour of impregnated sample. The maximum mass loss rate temperature is shifted to lower temperature and on the basis of our results we can conclude that ZnCl₂ acts as catalyst in all primary degradation mechanisms. NiCl₂ and H₂PtCl₆ do not modify significantly the cellulose thermal behaviour but change the composition of both produced gases and liquids suggesting that these minerals catalyse some secondary reactions.     

Thermo-kinetics study of orange peel in air

Thermal degradation of orange peel was studied in dynamic air atmosphere by means of simultaneous TG-DSC and TG-FTIR analysis. According to the obtained thermal profiles, the orange peel degradation occurred in at least three steps associated with its three main components (hemicellulose, cellulose and lignin). The volatiles compounds evolved out at 150–400 °C and the gas products were mainly CO₂, CO, and CH₄. A mixture of acids, aldehydes or ketones C=O, alkanes C–C, ethers C–O–C and H₂O was also detected. The E _α on α dependence reveled the existence of different and simultaneous processes suggesting that the combustion reaction is controlled by oxygen accessibility, motivated by the high evolution low-molecular-mass gases and volatile organic compounds. These results could explain the non-autocatalytic character of the reactions during the decomposition process.     

基于Py-GC联用的煤快速热解实验研究

采用居里点裂解仪-气相色谱仪(Py-GC)联用的方法研究了4种煤的快速热解特性,分析了挥发分主要气相产物及其析出规律.结果表明,大于等于50%的挥发分在热解初期(t ≤ 2 s)释放,采用箔片装载方式的居里点裂解仪完全热解1 mg煤样需要10 s;挥发分主要气相产物中,各气体组分的生成量(mmol/g_coal)顺序为H₂ > CH₄ > CO > CO₂ > C2(C₂H₆、C₂H₄)> C3(C₃H₈、C₃H₆);挥发分释放量随热解温度的升高而增加,相同热解条件下,次烟煤挥发分的释放率高于贫煤和无烟煤;H₂和CH₄的生成量依赖于热解温度,热解温度越高,H₂和CH₄的生成量越多;CO和CO₂的生成量不仅与热解温度相关,而且与煤中的氧含量紧密相关,氧含量越高的煤热解生成的CO和CO₂越多;C2和C3气体的生成量相对于其他气体很少,体积占挥发分气相产物的5%.     

Thermal degradation of pentaerythritol phosphate alcohol

Intumescent material, 2,6,7-trioxa-1-phosphabicyclo-[2,2,2]-octane-4-methanol phosphate (PEPA), is synthesized and characterized using FTIR, ¹HNMR and ¹³CNMR. The degradation properties of PEPA are studied by employing TG and TG?CMS technique. The activation energies for the degradation process of PEPA are calculated by using TG curves obtained from multiple heating rates (Friedman, Kissinger?CAkahira?CSunose and Flynn?CWall?COzawa methods). The degradation that is occurring in the temperature region 307?C366?°C has the highest activation energy. Eventhough the calculated activation energies for the degradation differ depending on the approximation method employed, the trend in variation of activation energy for degradation is similar. Single ion monitoring technique proved the evolution of H₂O, CO/C₂H₄, HCHO, C₂H₅OH/HCOOH and trace amounts of C₂H₇O₃P and C₄H₉O₄P from the degrading PEPA. The thermal conductivity and stability of the char formed during the TG analysis are also discussed.     

TG-FTIR study on thermal degradation in air of some new diazoaminoderivatives

The study on the thermal behavior of some new diazoaminoderivatives was aimed to follow the structure-thermal stability-degradation mechanism correlation by means of the TG-FTIR technique and formation enthalpies. The TG-DTG-DTA curves reveal the thermal degradation in air (30–900 °C) to show two ranges as a function of temperature (time), where the gaseous species resulting by degradation are eliminated: the first, an endothermic one which is identical to that under nitrogen atmosphere and the second, an exothermal one. As made evident by the identification of the individual gaseous species by their characteristic absorbances as well as those obtained by TG-FTIR the compounds C₂H₂, H₂C = NH, SO_2, NH_3, CO₂, H₂O, HCl are eliminated in the first domain while CO₂, SO₂, H₂O in the second, which afforded the advancement of the most probable degradation mechanism.     

Evolution of gaseous products from biomass pyrolysis in the presence of phosphoric acid

Slow pyrolysis experiments of China fir (Cunninghamia lanceolata) wood were performed in a vertical tubular furnace at various heating rates. The raw material was pretreated by impregnation with phosphoric acid solutions of various concentrations for given times. The evolution of the gaseous products CO, CO₂, H₂ and CH₄ was analyzed online by using gas spectrometry to investigate the effect of phosphoric acid on the pyrolytic gaseous products of biomass. The addition of phosphoric acid was shown to significantly reduce the pyrolysis temperature necessary for the production of CO, CO₂ and H₂ gases, and the pyrolysis variables exerted an influence on the amount of the gases released. Moreover, phosphoric acid appreciably depressed the CO, CO₂ and CH₄ production, and promoted H₂, especially when a higher heating rate was employed. This suggested that phosphoric acid catalyzed both the primary thermal decomposition of biopolymers and the secondary reactions that took place among the pyrolytic vapor products.     

The character of interactions of CO,H<Subscript>2</Subscript>, and CH<Subscript>3</Subscript>OH with the surface of γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Cu-Zn oxide catalyst

The thermal desorption of CO, H₂, and CH₃OH from the surface of Katalco-58 industrial catalyst for the synthesis of methanol and γ-Al₂O₃ was studied. Weak interaction of the gases with the surface of samples was observed over the temperature range 75–400°C. The desorption of the gases obeyed the second-order Wigner-Polyani equation. The desorption energies of the gases were calculated. The mechanism of dimethyl ether synthesis was studied.     

Mixed-potential-type propylene sensor based on stabilized zirconia and oxide electrode

By using an oxide sensing electrode, a stabilized zirconia-based sensor was developed for the selective detection of hydrocarbons at high temperature. Among the 14 kinds of oxides tested, CdO was found to be best suited for the sensing electrode of a tubular device, giving selective and quick response to propylene (C₃H₆) in air at 600°C. The emf value of the device was almost linear to the logarithm of C₃H₆ concentration in the range 50–800 ppm. The cross-sensitivities to other gases, such as CH₄, C₂H₄, C₂H₆, C₃H₈, H₂, CO, NO and NO₂, were small or insignificant. Furthermore, a compact planar device, which required no reference gas, was also fabricated. The C₃H₆ sensitivity of the planar device was found to be hardly influenced by a change in oxygen concentration in the sample gas in the range 2–21 vol.%. A sensing mechanism involving mixed potential was confirmed based on the measurements of polarization curves.     

Thermal transformations of the supramolecular compound of cucurbit[8]uril with cobalt(III) complex {<Emphasis Type="Italic">trans</Emphasis>-[Co(en)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>]@CB[8]}Cl·17 H<Subscript>2</Subscript>O

The thermal decomposition of hydrated cucurbit[8]uril C₄₈H₄₈N₃₂O₁₆·20H₂O (CB[8]) and the inclusion compound of cucurbit[8]uril with cobalt(III) complex {trans-[Co(en)₂Cl₂]@CB[8]}Cl·17 H₂O was studied in the inert atmosphere by TG, TM, and DSC methods. The dehydration of (C₄₈H₄₈N₃₂O₁₆)·20H₂O (at 320–390 K), and the decomposition of cucurbituril itself (at 620–720 K) are accompanied by a decrease in the sample volume. The inclusion compound loses water molecules at 320–380 K; dehydration is accompanied by an increase in the sample volume. The decomposition (pyrolisis) of the anhydrous compound takes place at 620–720 K; the decomposition is forestalled by a continued increase in the sample volume with an endothermic peak (490–600 K), and only the mass loss (620–720 K) is accompanied by a decrease in the sample volume. The included guest complex does not lose amines until the decomposition process is complete; the previously observed increase in the sample volume is explained by the expansion of cavitand molecules due to a distortion of the included [Co(en)₂Cl₂]⁺ complex on heating.     

Synthesis of carbon nanofibers by catalytic pyrolysis of ethylene and methane on hydrides of intermetallic compounds of lanthanum with nickel

Carbon nanofibers were synthesized by the pyrolysis of ethylene and methane on hydrides of intermetallides LaNi_nH_x (n = 2, 3, 5; x = 0.1–4). The influence of parameters of the synthesis (temperature and the ratio of gases in an Ar: H₂: C₂H₄ (CH₄) mixture) on the structure of nanofibers thus formed was studied. Hydrides of nickel intermetallides are more efficient catalytic systems than metallic nickel. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2210–2214, October, 2005.     

Adsorption of Pure Gases and Mixtures on Porous Solids up to High Pressures

Physisorption equilibria of multicomponent gases on microporous solids like zeolites or activated carbons are considered. An overview about adsorption measurements of pure gases H₂, He, O₂, N₂, Ar, CO₂, CO, CH₄, C₂H₄ and C₂H₆ and some of their mixtures in the pressure range vacuum < p < 50 MPa at different temperatures 10^∘C–70^∘C were investigated. Also a thermodynamic formalism based on a modified van Ness method and on a new 3 parameter Isotherm equation (3-PIG) to describe the excess amount adsorbed was developed. Results are shown and discussed. Dedication to the memory of W. Schirmer.     

Comparative study on thermal degradation of some new diazoaminoderivatives under air and nitrogen atmospheres

The article is devoted to a comparative study on the thermal degradation of some new diazoaminoderivatives under both air and nitrogen atmosphere by TG-FTIR analysis. The TG–DTG–DTA curves show the thermal degradation in air to present two temperature domains: an endothermic one identical to the case of the degradation under nitrogen and an exothermic one which is not to be found under nitrogen atmosphere. The identification of the gaseous species released by degradation in air within the endothermic domain made evident the presence of the same components of the degradation in nitrogen atmosphere. In the exothermic domain of the sample degradation in air, the CO₂, H₂O, SO₂ species result by the burning of the molecular residues of the first domain. The obtained results afforded a degradation mechanism to be advanced that coincide for the endothermic domain with that of degradation under nitrogen atmosphere. Due to the importance of these compounds as possible reaction initiators and also as potentially bioactive substances (herbicides, acaricides, fungicides), the study on their thermal degradation could give useful information on the environmental impact of the degradation products resulting by the thermal processing of the plants which could possible retain these compounds, when the initial degradation temperature is exceeded.     

Solubility of nonpolar gases in tetrahydropyran at 0 to 30°C and 101.33 kPa partial pressure of gas

Solubility measurements of several nonpolar gases (He, Ne, Ar, Kr, Xe, H₂, D₂, N₂, CH₄, C₂H₄, C₂H₆, CF₄, and SF₆) in tetrahydropyran at the temperature range 0 to 30°C and 101.33 kPa partial pressure of gas are reported. Thermodynamic functions for the solution process (Gibbs energy, enthalpy, and entropies) at 25°C are evaluated from the experimental values of the solubility of gases as mole fraction and their variation with the temperature. Lennard-Jones 6–12 pair potential parameters for tetrahydropyran are estimated by using the scale particle theory (SPT); and experimental solubilities are compared with the calculated values using this model. Experimental solubilities of gases in tetrahydropyran and intermolecular potential parameters are compared with those obtained for the same gases in other cycloethers.     

Pure and mixed gas permeation through a composite polydimethylsiloxane membrane

A thin polydimethylsiloxane (PDMS) layer on polyethersulfone (PES) support was synthesized and pure and mixed gas permeation of C₃H₈, CH₄, and H₂ through it was measured. At first, a macroporous PES support was prepared by using the phase inversion method and characterized. Then, a thin layer of PDMS was coated over the support. Finally, permeation behavior of the synthesized composite membrane was investigated by pure and mixed gas experiments under various operating conditions. The synthesized PDMS/PES membrane showed much better gas permeation performance than others reported in the literature. Pure gas experiments showed that increase in the transmembrane pressure increases the permeability coefficient of heavier gases, C₃H₈, while decreases those of lighter ones, CH₄ and H₂. Exactly opposite behavior was observed in mixed gas experiments due to the competitive sorption and diffusion in the plasticized polymer matrix. Temperature was realized to induce similar effects on the permeability of pure and mixed gases. As expected, in rubbery membranes such as PDMS, permeability values of more condensable gases decrease with increasing temperature, whereas those of permanent gases increase. In the case of mixed gas experiments, increase in the C₃H₈ concentration in feed led to increase in the permeabilities of all the components due to the C₃H₈‐induced swelling of the PDMS film. High C₃H₈/H₂ and C₃H₈/CH₄ ideal selectivities of 22.1 and 14.7, respectively, at a transmembrane pressure of 7 atm as well as reasonable C₃H₈ separation factor (SF) values for all mixed gas experiments (in the range of 8.1–16.8) demonstrated the ability of the synthesized PDMS/PES membrane for the separation of organic vapors from permanent gases. Copyright © 2009 John Wiley & Sons, Ltd.     

Evolved gas analysis at thermal treatment of some solid fossil fuels

Coupled TG-FTIR technique was used for identification of gaseous compounds evolved at thermal treatment of six coal samples from different deposits (Bulgaria, Russia, Ukraine). The experiments were carried out under dynamic heating conditions up to 900°C at heating rates of 5, 10 or 50 K min^–1 in a stream of dry air. The emission of CO₂, H₂O, CO, SO₂, COS, methane, methanol, formic acid, formaldehyde, acetaldehyde, chlorobenzene was clearly identified in FTIR spectra of the samples studied. The formation of ethanol, ethane, ethylene and p-xylene, at least on the level of traces, was also identified. At the heating rate of 5°C min^–1 the temperature of maximum intensities of the characteristic peaks of COS was 270°C, of formaldehyde, formic acid, ethane and methanol 330°C, of SO₂, CO, acetic acid, ethylene and p-xylene 400°C and of chlorobenzene 500°C. At 10°C min^–1 and 50°C min^–1 these temperatures were shifted, respectively, by 70–300°C and 150–450°C towards higher temperatures and the respective absorption bands in FTIR spectra were, as a rule, more intensive.     

Cold Plasma Processing and Plasma Chemistry of Metallic Cobalt Surface

Plasma processing of metallic cobalt was experimentally investigated with three fluorine-containing gases, CF₄–O₂, SF₆–O₂, and NF₃ to determine the surface decontamination rate and to examine the reaction mechanism. Results show that the maximum etching rate reaches 17.12 μm/min with NF₃ gas at 420°C, while the rates are 2.56 μm/min and 1.14 μm/min with CF₄–O₂ and SF₆–O₂ gas, respectively, at the same temperature. AES analysis identified the constituent elements of the reaction products to be oxygen, fluorine, and cobalt, and XPS analysis reveals that the reaction product with all three plasma gases is very likely to be CoF₂.     

Synthesis and thermal characterization of NZP compounds Na1?xLixZr2(PO4)3 (x?=?0.00–0.75)

Sodium zirconium phosphate (NZP) composition Na_1−x Li _x Zr₂(PO₄)₃, x = 0.00–0.75 has been synthesized by method of solid state reaction method from Na₂CO₃·H₂O, Li₂CO₃, ZrO₂, and NH₄H₂PO₄, sintering at 1050–1250 °C for 8 h only in other to determine the effect on thermal properties, such as the phase formation of the compound. The materials have been characterized by TGA and DTA thermal analysis methods from room temperature to 1000 °C. It was observed that the increase in lithium content of the samples increased thermal stability of the samples and the DTA peaks shifted towards higher temperatures with increase in lithium content. The thermal stability regions for all the sample was observed to be from 640 °C. The sample with the highest lithium content, x = 0.75, exhibited the greatest thermal stability over the temperature range.     

Synthesis of formamidines from 2-amino-3-methylquinazolin-4-one and its 6-nitro derivative

The condensation of 2-amino-3-methylquinazolin-4-one and its 6-nitro derivative with dialkyl-, arylalkyl-, and heterylformamides has given the corresponding formamidines of the quinazolinone series. The details of the compounds synthesized are as follows X, R, R′, yield (%), mp (°C, ethanol), R_f (chloroform-methanol (20:1) Al₂O₃): empirical formula: H, CH₃, CH₃, 77, 238–240, 0.49, C₁₂H₁₄ON₄; H, C₂H₅, C₂H₅, 65, 208–210, 0.96, C₁₄H₁₈ON₄; H, CH₃, C₆H₅, 84, 162–164, 0.54, C₁₇H₁₆ON₄; H, (CH₂)₂O(CH₂)₂, 60, 196–197, 0.43, C₁₄H₁₆O₂N₄; H, (CH₂)₅, 6.6, 196–198, 0.4, C₁₅H₁₈·ON₄; NO₂, CH₃, CH₃, 64. 194–196, 0.83, C₁₂H₁₃O₃N₅; NO₂, C₂H₅, C₂H₅, 37, 142–144, 0.8, C₁₄H₁₇O₃N₅; NO₂; CH₃, C₆H₅, 38, 298, 0.88, C₁₇H₁₅O₃N₅; NO₂, (CH₂)₂O(CH₂)₂, 60, 148–150, 0.7, C₁₄H₁₅O₄N₅. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 680–684, September–October, 1980.     

Factors determining selectivity of ethylene conversion to butadiene over aluminosilicate catalyst

A study has been made of the influence of temperature, partial pressure of C₂H₄, and contact time on the selectivity of direct conversion of ethylene to butadiene over an aluminosilicate catalyst. A critical analysis has been made of the competing directions of C₂H₄ conversion, which determine the selectivity of C₄H₆ formation under conditions of a heterogeneous-homogeneous mechanism in carrying out the process. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of the Ukraine, 31 Nauka Prospect, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 78–82, March–April, 1997.