TG-MS analysis for studying the effects of fire retardants on the pyrolysis of pine-needles and their components

Thermogravimetry-mass spectrometry (TG-MS) was used to study the effect of the inorganic salts (NH₄)₂SO₄ and (NH₄)₂HPO₄, active substances of many commercial forest fire retardants, on the pyrolysis of Pinus halepensis needles and their main components (cellulose, lignin and extractives). These salts seemed to affect the pyrolysis of cellulose by increasing significantly the char residue, decreasing the pyrolysis temperature and changing the composition of the evolved gases, that is, increasing levoglucosenone and decreasing oxygen containing volatile products. (NH₄)₂SO₄ seemed to have negligible effect on the pyrolysis of lignin, while (NH₄)₂HPO₄ increased the char residue and decrease the relative contribution of guaiacols in the evolved gases. No effects of the inorganic salts on the extractives were observed. Finally, the inorganic salts seemed to affect the pyrolysis of pine-needles, mainly the cellulose component, but the effects were not as intense as in the pyrolysis of cellulose.     

Bildung siliciumorganischer Verbindungen. 77. Zur Bildung von Carbosilanen aus Methylsilanen

Formation of Organosilicon Compounds. 77. Formation of Carbosilanes from Methylsilanes The products formed by pyrolysis of me₃SiH, me₂SiH₂, and meSiH₃ are reported. Sime₄ and the mentioned methylsilanes were reacted in a plasma, and the products are compared to those of the pyrolysis. The pyrolysis of me₃SiH and me₂SiH₂ essentially yields the same groups of carbosilanes which are accessible by thermal decomposition of Sime₄, if the range is restricted to compounds with 4 Si atoms at most. Cylic carbosilanes are the main products of the pyrolysis of me₃SiH, and amoung these, 1,3,5-trisilacyclohexanes and 1,3,5,7-tetrasilaadamantanes are preferrently formed. From me₂SiH₂ above all linear compounds as 1,3-disilapropanes are obtained. This is attributed to the chosen experimental procedure in which they not subject to further reaction. In the pyrolysis of meSiH₃ a yellow solid is formed besides little amounts of meH₂Si? SiH₂me. Compared to the compounds formed by pyrolysis of Sime₄, the carbosilasen obtained from me₃SiH and me₂SiH₂ possess more SiH substituents. Also the decomposition of Sime₄ in a plasma preferrently yields carbosilanes, mainly linear compounds with 2 or 3 Si atoms.     

水城褐煤热解的气体产物析出特征及甲烷的生成反应类型研究

利用傅里叶红外光谱仪研究了煤中主要官能团的分布,利用热重-质谱联用（TG/MS）在10℃/min的条件下研究了水城褐煤的热解行为,获得了煤热解主要挥发分气体（H₂、CH₄、H₂O、CO、CO₂）生成的速率曲线。采用分峰拟合的方法将甲烷的生成速率曲线分解为五个峰,通过化学动力学分析,结合煤的结构特性、热解特性及其他挥发分气体的生成特征,认为甲烷的生成主要由一个脱吸附过程和四个化学反应组成。     

Continuous high-temperature fluidized bed pyrolysis of coal in complex atmospheres: Product distribution and pyrolysis gas

This study is devoted to investigating the continuous coal pyrolysis in a laboratory fluidized bed reactor that fed coal and discharged char continuously at temperatures of 750–980 °C and in N₂-base atmospheres containing O₂, H₂, CO, CH₄ and CO₂ at varied contents. The results showed that the designed continuous pyrolysis test provided a clear understanding of the coal pyrolysis behavior in various complex atmospheres free of and with O₂. The effect of adding H₂, CO, CH₄ or CO₂ into the atmosphere on the tar yield was related to the O₂ content in the atmosphere. Without O₂ in the atmosphere, adding H₂ and CO₂ decreased the pyrolysis tar yield, but the tar yield was conversely higher with raising the CO and CH₄ contents in the atmosphere. In O₂-containing atmospheres, the influence from varying the atmospheric gas composition on the product distribution and pyrolysis gas composition was closely related to the oxidation or gasification reactions occurring to char, tar and the tested gas.     

Coal pyrolysis in a fluidized bed reactor simulating the process conditions of coal topping in CFB boiler

Simulating the conditions of pyrolytic topping in a fluidized bed reactor integrated into a CFB boiler, the study was devoted to the reaction fundamentals of coal pyrolysis in terms of the production characteristics of pyrolysis oil in fluidized bed reactors, including pyrolysis oil yield, required reaction time and the chemical species presented in the pyrolysis oil. The results demonstrated that the maximal pyrolysis oil yield occurred on conditions of 873 K, with a reaction time of 3 min and in a reaction atmosphere gas simulating the composition of pyrolysis gas. Adding H₂ and CO₂ into the reaction atmosphere decreased the pyrolysis oil yield, while the oil yield increased with increasing the CO and CH₄ contents in the atmosphere. TG-FTIR analysis was conducted to reveal the effects of reaction atmosphere on the chemical species present in the pyrolysis oil. The results clarified that the pyrolysis oil yield reached its maximum when the simulated pyrolysis gas was the reaction atmosphere, but there were slightly fewer volatile matters in the pyrolysis oil than the oil generated in the N₂ atmosphere. All of these results are expected not only to reveal the composition characteristics of the pyrolysis oil from different conditions of the coal topping process but also to optimize the pyrolysis conditions in terms of maximizing the light pyrolysis oil yield and quality.     

Investigation of the evolved gases from Sulcis coal during pyrolysis under N2 and H2 atmospheres

The evolution of gases and volatiles during Sulcis coal pyrolysis under different atmospheres (N₂ and H₂) was investigated to obtaining a clean feedstock of combustion/gasification for electric power generation. Raw coal samples were slowly heated in temperature programmed mode up to 800 °C at ambient pressure using a laboratory-scale quartz furnace coupled to a Fourier transform infrared spectrometer (FTIR) for evolved gas analysis. Under both pyrolysis and hydropyrolysis conditions the evolution of gases started at temperature as low as 100 °C and was mainly composed by CO and CO₂ as gaseous products. With increasing temperature SO₂, COS, and light aliphatic gases (CH₄ and C₂H₄) were also released. The release of SO₂ took place up to 300 °C regardless of the pyrolysis atmosphere, whilst the COS emissions were affected by the surrounding environment. Carbon oxide, CO₂, and CH₄ continuously evolved up to 800 °C, showing similar release pathways in both N₂ and H₂ atmospheres. Trace of HCNO was detected at low pyrolysis temperature solely in pure H₂ stream. Finally, the solid residues of pyrolysis (chars) were subjected to reaction with H₂ to produce CH₄ at 800 °C under 5.0 MPa pressure. The chars reactivity was found to be dependent on pyrolysis atmosphere, being the carbon conversions of 36% and 16% for charN₂ and charH₂, respectively.     

Scale-up of microwave heating process for the production of bio-oil from sewage sludge

A pilot-scale microwave heating apparatus was constructed for the production of bio-oil from sewage sludge, and the effects of important microwave processing parameters and chemical additives on the quality and yield of bio-oils were investigated. It was found that bio-oil was mainly formed at the pyrolysis temperature range of 200–400 °C. A higher heating rate (faster pyrolysis) not only increased the yield of bio-oil, but also improved the quality of bio-oil according to the elemental composition and calorific values. The maximum bio-oil yield was 30.4% of organic fraction, obtained from the pyrolysis of original sewage sludge at microwave radiation power of 8.8 kW and final pyrolysis temperature of 500 °C. All of five simple additives (KOH, H₂SO₄, H₃BO₃, ZnCl₂, and FeSO₄) reduced the bio-oil yield, but the composition and property of bio-oil varied with the additive types greatly. KOH, H₂SO₄, H₃BO₃ and FeSO₄ were found to improve the quality of bio-oils remarkably according to the calorific value, density, viscosity and carbon content of bio-oils, but ZnCl₂ treatment went against that. GC–MS analysis of the bio-oils showed that, alkali treatment promoted the formation of alkanes and monoaromatics, while acid treatment favored the formation of heterocyclics, ketones, alcohols and nitriles. Compared with sulfate slat FeSO₄, chloride salt ZnCl₂ was a better catalyst for selective catalytic pyrolysis of sewage sludge. The addition of ZnCl₂ only promoted the formation reactions of a few kinds of nitriles and ketones remarkably. It is technologically feasible to produce bio-oil form microwave-induced pyrolysis of sewage sludge by optimizing pyrolysis conditions and selecting appropriate additives.     

利用温度跃升傅立叶变换红外原位分析技术对斯蒂酚酸碳酰肼和斯蒂酚酸氨基脲快速热解反应的研究

Flash pyrolysis of （CHZ）2TNR and （SCZ）2TNR was conducted by T-jump/FTIR spectroscopy under 0.1 MPa Ar atmosphere. The results show that eleven IR-active gas products obtained during flash pyrolysis process of the two title compounds are NO, CO, HCN, NH3, NO2, N2O, HNCO, HNO2, CO2, H2O and HCHO, of which NO and CO are the main gas products. The molar fraction of the individual product in the pyrolysis gas mixture was described as a function of time. At least some of the NO2, N2O and H2O can result from the oxidization reaction of NH3 during flash pyrolysis of （CHZ）2TNR. It can be concluded that the two compounds are not worthy of further in-depth consideration of the adoption in detonators as eco-friendly primary explosive, and should not be used as gas generation composition of automobile crash airbag system taking into account the toxicity.     

Thermal degradation and evolved gas analysis of thiourea-formaldehyde resin (TFR) during pyrolysis and combustion

Thiourea formaldehyde resin (TFR) has been synthesized by condensation of thiourea and formaldehyde in acidic medium and its thermal degradation has been investigated using TG-FTIR-MS technique during pyrolysis and combustion. The results revealed that the thermal decomposition of TFR occurs in three steps assigned to drying of the sample, fast thermal decomposition of polymers, and further cracking. The similar TG and DTG characteristics were found for the first two stages during pyrolysis and combustion. The combustion process was almost finished at 680?°C, while during pyrolysis a total mass loss of 93 wt% is found at 950?°C. The release of volatile products during pyrolysis are NH₃, CS₂, CO, HCN, HNCS, and NH₂CN. The main products in the second stage are NH₃ CO₂, CS₂, SO₂, and H₂O during combustion. In the next stage, the combustion products mentioned above keep on increasing, but some new volatiles such as HCN, COS etc., are identified. Among the above volatiles, CO₂ is the dominant gaseous product in the whole combustion process. It is found that the thermal degradation during pyrolysis of TFR produced more hazardous gases like HCN, NH₃, and CO when compared with combustion in similar conditions.     

Preparation and pyrolysis of a blended precursor possessing Ti?N and Al?N bonds

The preparation and pyrolysis of a blended precursor possessing Ti? N and Al? N bonds were investigated. The precursor was prepared by mixing (HAlN ⁱPr) _n, whose main compo‐nent was a cage‐type compound, and an aminolysis product of Ti(NMe₂)₄ with MeHNCH₂CH₂NHMe with a molar ratio of Ti:Al = 2:1. IR analysis of the products pyrolyzed under NH₃–N₂ indicated that a large proportion of the organic groups in the precursor were removed by an amine‐exchange reaction during the pyrolysis under NH₃; thus, the products contained only a small amount of carbon. On the contrary, a considerable amount of carbon was present in the product pyrolyzed under Ar. Composites consisting of AlN and an NaCl‐type compound were obtained after pyrolysis of the precursor under both NH₃–N₂ and Ar. The composition of the NaCl‐type compound depended significantly on the pyrolysis atmosphere. Copyright © 2001 John Wiley & Sons, Ltd.     

Analysis of pyrolysis products formed from ethylene-tetrafluoroethylene heterosequences of poly(ethylene-co-tetrafluoroethylene)

Poly(ethylene-co-tetrafluoroethylene) (PETFE) was pyrolyzed and the pyrolysis products formed from the ethylene-tetrafluoroethylene heterosequences were analyzed using gas chromatography/mass spectrometry (GC/MS). Major pyrolysis products were 3,3-difluoropropene (DFP), 3,3,4,4-tetrafluoro-1-butene (TFB), 1,1,2,2,3,3-hexafluorocyclopentane (HFCP), 1,1,2,2,3,3-hexafluorocyclohexane (HFCH), 1,1,2,2,3,3,4,4-octafluorocyclohexane (OFCH), and 3-trifluoromethyl-3,4,4,5,5-pentafluorocyclohexene (FMPFCH). Their formation mechanisms were proposed. Peak intensity ratios of HFCP, HFCH, and FMPFCH compared to OFCH increased as the pyrolysis temperature increased, while those of DFP, TFB, HFCP, and HFCH compared to tetrafluoroethylene decreased. Order of the relative abundances of the major pyrolysis products formed from PETFE was OFCH > HFCP > HFCH > TFB > DFP. The order may be due to the difference in bond energies of CH₂-CH₂, CF₂-CH₂, and CF₂-CF₂. Formation of the pyrolysis product through the CH₂-CH₂ bond cleavage was more favorable than those through the CF₂-CH₂ and CF₂-CF₂ ones.     

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.     

Experimental and Theoretical Study on Pyrolysis of Isopsoralen

The pyrolysis of isopsoralen was studied by synchrotron vacuum ultraviolet photoionization mass spectrometry at low pressure. The pyrolysis products were detected at different photon energies, the ratios of products to precursor were measured at various pyrolysis temperatures. The experimental results demonstrate that the main pyrolysis products are primary CO and sequential CO elimination products (C₁₀H₆O₂ and C₉H₆O). The decomposition channels of isopsoralen were also studied by the density functional theory, then rate constants for competing pathways were calculated by the transition state theory. The dominant decom-position channels of isopsoralen and the molecular structures for corresponding products were identified by combined experimental and theoretical studies.     

Synthesis of carbon nanofibers by catalytic pyrolysis of ethylene in the presence of vapors of volatile components

Catalytic pyrolysis of ethylene was carried out at 700 °C in the presence of vapors of H₂O, EtOH, NH₄OH, PCl₃, (MeO)₃P, Me₂SO₄, (MeO)₃B, and HCl. The composition of solid pyrolysis products was studied using the elemental analysis, X-ray diffraction analysis, and electron microscopy. The composition of the gaseous pyrolysis products was studied using mass spectrometry. The processes in the gas phase were characterized, and the relationship between conditions of ethylene pyrolysis and the structure of formed carbon nanofibers was revealed. The introduction of gaseous additives has a substantial effect on the formation, growth, and structure of the carbon nanofibers formed.     

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.     

Effect of manganese-based pigment catalyst on CO removal during biomass pyrolysis

A commercially available black pigment was evaluated for its potential as a CO oxidation catalyst during the pyrolysis of biomass. Characterization by X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that the pigment consisted of a mixed oxide system (Cu_1.5Mn_1.5O₄–Mn₃O₄–Fe₂O₃) with an average particle size of 30–300 nm. The as received pigment catalyst was able to completely oxidize CO to CO₂ in a 4% CO–21% O₂–He gas mixture. In this study, the effect of catalyst on CO removal was evaluated during the pyrolysis of tobacco in inert and oxidizing conditions. The experiments were carried out in a flow tube reactor, which was connected to a multi-channel gas analyzer capable of measuring CO, CO₂ and O₂ concentrations. The catalyst was able to decrease the amount of CO production by 56% during the pyrolysis of biomass (tobacco) in the presence of oxygen (21% O₂–He). Oxidation of the biomass/catalyst mixture started at a lower temperature of 260 °C as opposed to a higher temperature of 300 °C in the absence of catalyst. Experiments in thermo gravimetric analyzer and differential scanning calorimeter (TG/DSC) mass spectrometer showed evidence of two-stage oxygen consumption during the pyrolysis of biomass/catalyst mixture while pure biomass pyrolized in single-stage oxygen consumption. Based on the experimental findings, a mechanism of reaction is proposed. The results show that the manganese-based mixed oxide pigment is a promising CO oxidation catalyst for biomass pyrolysis.     

Syngas production from pyrolysis–catalytic steam reforming of waste biomass in a continuous screw kiln reactor

A two-stage continuous screw-kiln reactor was investigated for the production of synthesis gas (syngas) from the pyrolysis of biomass in the form of waste wood and subsequent catalytic steam reforming of the pyrolysis oils and gases. Four nickel based catalysts; NiO/Al₂O₃, NiO/CeO₂/Al₂O₃, NiO/SiO₂ (prepared by an incipient wetness method) and another NiO/SiO₂ (prepared by a sol–gel method), were synthesized and used in the catalytic steam reforming process. Pyrolysis of the biomass at a rapid heating rate of approximately 40 °C/s, was carried out at a pyrolysis temperature of 500 °C and the second stage reforming of the evolved pyrolysis gases was carried out with a catalytic bed kept at a temperature of 760 °C. Gases were analysed using gas chromatography while the fresh and reacted catalyst was analysed by scanning electron microscopy, thermogravimetric analysis, transmission electron microscopy with energy dispersive X-ray and X-ray photoelectron spectroscopy. The reactor design was shown to be effective for the pyrolysis and catalytic steam reforming of biomass with a maximum syngas yield of 54.0 wt.% produced when the sol–gel prepared NiO/SiO₂ catalyst was used, which had the highest surface area of 765 m² g⁻¹. The maximum H₂ production of 44.4 vol.% was obtained when the NiO/Al₂O₃ catalyst was used.     

Gas Evolution from the Pyrolysis of Jordan Oil Shale in A Fixed-bed Reactor

Jordan oil shale from El-Lajjun deposit was pyrolysed in a fixed-bed pyrolysis reactor and the influence of the pyrolysis temperature between 400 to 620°C and the influence of the pyrolysis atmosphere using nitrogen and nitrogen/steam on the product yield and gas composition were investigated. The gases analysed were H₂, CO, CO₂ and hydrocarbons from C₁ to C₄. The results showed for both nitrogen and nitrogen/steam that increase the pyrolysis bed temperature from 400 to 520°C resulted in a significant increase in the oil yield, after which temperature the oil yield decreased. The alkene/alkane ratio including ethene/ethane, propene/propane, and butene/butane ratios, can be used as an indication of pyrolysis temperature and the magnitude of cracking reactions. Increasing alkene/alkane ratio occurring with increasing pyrolysis temperature. The alkene/alkane ratio for nitrogen/steam pyrolysis atmosphere was lower than the one found under nitrogen atmosphere. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pyrolysis of Hailar lignite in an autogenerated steam agent

An in situ pyrolysis process of high moisture content lignite in an autogenerated steam agent was proposed. The aim is to utilize steam autogenerated from lignite moisture as a reactant to produce fuel gas and additional hydrogen. Thermogravimetric analysis revealed that mass loss and maximum mass loss rate increased with the rise of heating rates. The in situ pyrolysis process was performed in a screw kiln reactor to investigate the effects of moisture content and reactor temperature on product yields, gas compositions, and pyrolysis performance. The results demonstrated that inherent moisture in lignite had a significant influence on the product yield. The pyrolysis of L _R (raw lignite with a moisture content of 36.9 %, wet basis) at 900 °C exhibited higher dry yield of 33.67 mL g^?1 and H₂ content of 50.3 vol% than those from the pyrolysis of the predried lignite. It was also shown that increasing reaction temperature led to a rising dry gas yield and H₂ yield. The pyrolysis of L _R showed the maximum dry yield of 33.7 mL g^?1 and H₂ content of 53.2 vol% at 1,000 °C. The LHV of fuel gas ranged from 18.45 to 14.38 MJ Nm^?3 when the reactor temperature increased from 600 to 1,000 °C.     

H2气氛下褐煤快速热解过程中CH4逸出规律的分析

在带有输送煤样的管式反应器上进行了霍林河褐煤加压快速氢解实验,分析了H₂对煤/半焦的化学键断裂和对CH₄生成规律的影响。在加压快速氢解条件下,CH₄产率随着热解温度升高、压力的增大而增大;在50% H₂气氛下,操作压力为1.0 MPa、温度为900 ℃时,CH₄产率为8.08%,达到最大,较N₂气氛下的提高了72.5%。H₂或H·自由基诱发了芳环的开裂、侧链、脂肪链和醚键的断裂,促进了煤热解。CH₄产率的增加主要是由于外部供H的结果;热解温度低于700 ℃时,H₂对煤结构中活性基团的作用促进了煤热解,导致了CH₄产率的增加;而热解温度高于700 ℃后,煤/半焦加氢气化促进了CH₄产率的增加。