Primary Gaseous Products Research Articles

Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield

The thermal decomposition of coal was the essential step of many reactions, thus it was widespread concerned. In order to investigate the behaviors and kinetics of coal pyrolysis, coal samples which obtained from Ningdong coalfield of China were pyrolyzed with a tubular furnace in argon atmosphere at the heating rate of 5 K min−1. The primary gaseous products including CH4, H2, N2, CO, CO2, C2H4 and C2H6 were quantified using a gas chromatogram. It can be seen that with the temperature increasing, the yields of H2 and CO increased, while the others decreased. In order to produce possibly much tar, the optimal temperature was 923 K. The characteristic of pyrolysis kinetics was determined by thermo gravimetric analysis measurement. The Coats–Redfern and Flynn–Wall–Ozawa methods was used to obtain kinetic parameters. The activation energy range of 50–200 kJ mol−1 was determined.

Renewable fuels from pyrolysis of Dunaliella tertiolecta: An alternative approach to biochemical conversions of microalgae

The cultivation of microalgae as a feedstock for renewable fuels is widely touted as a way to sequester CO2 while negating food versus fuel competition for land. However, the widespread industrial use of microalgae for biofuels has yet to reach a critical stage based on lipid extraction alone. One alternative to the transesterification of microalgae for liquid fuel production is to use thermochemical conversion techniques. In the present work, we demonstrate that Dunaliella tertiolecta can be converted to biofuels via pyrolysis at temperatures significantly lower than terrestrial biomasses. The primary gaseous pyrolysis products were CO2, H2O, CH4, alcohols, aldehydes, organic acids and phenols. The iso-conversional distributed activation energy model was used to calculate the kinetic parameters, showing average activation energy of 243.3 kJ/mol, with a peak in activation energy at mass fraction conversions between 0.45 and 0.65. However, the substantial amount of pyrolysis gases evolved at low temperatures (between 280 and 320 °C), suggests that pyrolysis at higher temperatures, and especially to completion, might not be necessary to optimize pyrolytic production of biofuels from microalgae.

Hypercapnia Suppresses the HIF-dependent Adaptive Response to Hypoxia

Molecular oxygen and carbon dioxide are the primary gaseous substrate and product of oxidative metabolism, respectively. Hypoxia (low oxygen) and hypercapnia (high carbon dioxide) are co-incidental features of the tissue microenvironment in a range of pathophysiologic states, including acute and chronic respiratory diseases. The hypoxia-inducible factor (HIF) is the master regulator of the transcriptional response to hypoxia; however, little is known about the impact of hypercapnia on gene transcription. Because of the relationship between hypoxia and hypercapnia, we investigated the effect of hypercapnia on the HIF pathway. Hypercapnia suppressed HIF-α protein stability and HIF target gene expression both in mice and cultured cells in a manner that was at least in part independent of the canonical O2-dependent HIF degradation pathway. The suppressive effects of hypercapnia on HIF-α protein stability could be mimicked by reducing intracellular pH at a constant level of partial pressure of CO2 Bafilomycin A1, a specific inhibitor of vacuolar-type H(+)-ATPase that blocks lysosomal degradation, prevented the hypercapnic suppression of HIF-α protein. Based on these results, we hypothesize that hypercapnia counter-regulates activation of the HIF pathway by reducing intracellular pH and promoting lysosomal degradation of HIF-α subunits. Therefore, hypercapnia may play a key role in the pathophysiology of diseases where HIF is implicated.

Synthesis and Characterization of Carbon Nanospheres Obtained by Hydrothermal Carbonization of Wood-derived and Other Saccharides

Carbon nanospheres were synthesized by hydrothermal carbonization (HTC) of four different carbon sources: xylose, glucose, sucrose, and pine wood derived saccharides. The obtained carbon nanospheres were characterized for particle morphology and size, and surface functional groups. Morphological and structural differences among these saccharides derived HTC carbons were clearly observed. Scanning electron microscopy images of carbon nanospheres from HTC of xylose showed uniform spherical particles with diameters around 80 nm, while carbon nanospheres obtained from glucose, sucrose, and pine-derived saccharides had particle size in the range of 100-150 nm, 300-400 nm, and 50-100 nm, respectively. Carbon dioxide and carbon monoxide were primary gaseous phase products during the HTC process. In addition, methane, propane, hydrogen, and benzene were detected in the gas phase. Citation: Yan, Q., Li, R., Toghiani, H., Cai, Z., and Zhang, J. (2015). Synthesis and Characterization of Carbon Nanospheres Obtained by Hydrothermal Carbonization of Wood-derived and Other Saccharides. Trends in Renewable Energy, 1(2), 119-128. DOI: 10.17737/tre.2015.1.2.0012

Co-pyrolysis of pine sawdust and lignite in a thermogravimetric analyzer and a fixed-bed reactor

Co-pyrolysis characteristics of lignite and pine sawdust were studied in a TGA and a fixed-bed reactor. The effects of pyrolysis temperature and blending ratio on the yield and composition of pyrolysis products (gas, tar, and char) were investigated. TGA experiments showed that pine sawdust decomposition took place at lower temperatures compared to lignite. With increasing the pine sawdust content in the blend, the DTG peaks shifted towards lower temperatures due to synergetic effect. In fixed-bed experiments, the synergetic effect increased the yield of volatile matter compared to the calculated values. The major gases released at low temperatures were CO2 and CO. However, hydrogen was the primary gaseous product at higher temperatures. During co-pyrolysis, concentrations of benzene, naphthalene, and hydrocarbons in the tar decreased, accompanied by an increase in phenols and guaiacol concentrations. With increasing pyrolysis temperature, the OH, aliphatic CH, CO, and CO functional groups in char decomposed substantially.

Plasma–Catalyst Synergy During Methanol Steam Reforming in Dielectric Barrier Discharge Micro-plasma Reactors for Hydrogen Production

Non-thermal plasma is an effective technology that produces hydrogen from methanol by plasma reforming. In this study, hydrogen was produced via methanol steam reforming in a dielectric barrier discharge micro-plasma reactor filled with a Cu/Al2O3 catalyst. Comparative experimental results obtained using the reactor with and without catalyst are reported. The methanol conversion and hydrogen yield with the activated catalyst were 17.89 and 21.86 % higher than those without the catalyst. The primary gaseous products changed from H2 and CO to H2 and CO2 after adding the Cu/Al2O3 catalyst. Methanol conversion increased with the discharge frequency and input power and decreased with an increase in the liquid feed rate. Methanol conversion reached 78.48 % over the Cu/Al2O3 catalyst at a 1.0 steam-to-carbon ratio, an 18.00 ± 0.05 kHz discharge frequency, 18.70 W of input power, 10.0 mL/min Ar flow rate and 0.0165 mL/min liquid feed rate. A plausible mechanism for hydrogen generation during steam–methanol reforming using the plasma–catalyst synergy effect is presented.

Urea degradation by electrochemically generated reactive chlorine species: products and reaction pathways.

This study investigated the transformation of urea by electrochemically generated reactive chlorine species (RCS). Solutions of urea with chloride ions were electrolyzed using a bismuth doped TiO2 (BiOx/TiO2) anode coupled with a stainless steel cathode at applied anodic potentials (Ea) of either +2.2 V or +3.0 V versus the normal hydrogen electrode. In NaCl solution, the current efficiency of RCS generation was near 30% at both potentials. In divided cell experiments, the pseudo-first-order rate of total nitrogen decay was an order of magnitude higher at Ea of +3.0 V than at +2.2 V, presumably because dichlorine radical (Cl2(-)·) ions facilitate the urea transformation primary driven by free chlorine. Quadrupole mass spectrometer analysis of the reactor headspace revealed that N2 and CO2 are the primary gaseous products of the oxidation of urea, whose urea-N was completely transformed into N2 (91%) and NO3(-) (9%). The higher reaction selectivity with respect to N2 production can be ascribed to a low operational ratio of free available chlorine to N. The mass-balance analysis recovered urea-C as CO2 at 77%, while CO generation most likely accounts for the residual carbon. In light of these results, we propose a reaction mechanism involving chloramines and chloramides as reaction intermediates, where the initial chlorination is the rate-determining step in the overall sequence of reactions.

A sectional approach for biomass: Modelling the pyrolysis of cellulose

We present the adaptation of the sectional model approach to the pyrolysis of cellulose, (C6H10O5)n. Cellulose is the major component of lignocellulosic biomass. Due to its longitudinal structure, cellulose is characterised by one-dimensional chains composed of a varying number of cellobiose molecules, C12H22O11. Fragments of those chains with similar mass are grouped into size classes (BINs) determined by characteristic numbers of cellobiose units. During the pyrolysis of cellulose, reaction temperatures of more than 500K (depending on the heating rate) initiate bond dissociation between cellobiose units. We have developed a new reaction scheme for the pyrolysis of cellulose based on literature models. However, we present the sectional approach as a new concept for modelling the degradation of cellulose. We propose a kinetic data set of A = 2.2 ∙ 1013 s−1 and EA = 225.9 kJ/mol for the dissociation of a single glycosidic bond. Additionally, our model includes the cellobiose devolatilisation to glucose or tars (levoglucosan) including primary gaseous products, the formation of char and water, and secondary gas-phase reactions. Our reactor simulations of cellulose pyrolysis at constant heating rates of 1, 10, 15, and 150 K/min show good agreement with two different experimental data sets.

A Rechargeable Li–O2 Battery Using a Lithium Nitrate/N,N-Dimethylacetamide Electrolyte

A major challenge in the development of rechargeable Li-O(2) batteries is the identification of electrolyte materials that are stable in the operating environment of the O(2) electrode. Straight-chain alkyl amides are one of the few classes of polar, aprotic solvents that resist chemical degradation in the O(2) electrode, but these solvents do not form a stable solid-electrolyte interphase (SEI) on the Li anode. The lack of a persistent SEI leads to rapid and sustained solvent decomposition in the presence of Li metal. In this work, we demonstrate for the first time successful cycling of a Li anode in the presence of the solvent, N,N-dimethylacetamide (DMA), by employing a salt, lithium nitrate (LiNO(3)), that stabilizes the SEI. A Li-O(2) cell containing this electrolyte composition is shown to cycle for more than 2000 h (>80 cycles) at a current density of 0.1 mA/cm(2) with a consistent charging profile, good capacity retention, and O(2) detected as the primary gaseous product formed during charging. The discovery of an electrolyte system that is compatible with both electrodes in a Li-O(2) cell may eliminate the need for protecting the anode with a ceramic membrane.

Product distributions from isothermal co-pyrolysis of coal and biomass

Co-gasification and co-pyrolysis of coal and biomass are being studied as a means to reduce the carbon footprint of an IGCC plant. Co-feeding creates many challenges in the thermochemical conversion of coal/biomass such as the variable nature of biomass feedstocks, potential nonlinear reaction rate effects during conversion and the varying composition of the products. An experimental study on isothermal co-pyrolysis of Illinois #6 coal and switchgrass was done in a drop reactor at 900°C to investigate the effects of co-feeding on pyrolysis product distributions under conditions relevant to transport gasifiers. Coal/biomass mixtures were fed to the reactor in feed ratios of 100/0, 85/15, 70/30, 50/50, and 0/100, while primary gaseous products (CO, CO2, CH4, H2 and H2O) were monitored and analyzed online. Ultimate analysis of solid and liquid products is used to track the distribution of the feedstocks’ elements and energy content into its pyrolysis products, while GC–MS and ash elemental analyses are provided to more fully characterize these products. Experimental results show that under the conditions studied, product distributions do not display any non-linear effects, and can be estimated as a mass-weighted sum of the product distributions of the pure feedstocks. This result is likely due to the higher temperatures used in this study, though it is inherently useful in the development of higher-temperature gasification systems.

Thermal decomposition course of Eu(CH 3COO) 3·4H 2O and the reactivity at the gas/solid interface thus established

The thermal decomposition course of europium acetate tetrahydrate (Eu(CH 3COO) 3·4H 2O) was probed on heating up to 1000 °C in a dynamic atmosphere of air by thermogravimetry and differential thermal analysis. The solid- and gas-phase decomposition products were identified by X-ray diffractometry, ex- and in situ infrared spectroscopy and mass spectrometry. Results obtained showed the acetate to dehydrate stepwise at 145–283 °C, and then decompose stepwise to yield eventually cubic-Eu 2O 3 at ≥663 °C encompassing the formation of intermediate oxycarbonate (Eu 2O(CO 3) 2/Eu 2O 2(CO 3) solid products (at 347–466 °C)) and H 2O, (CH 3) 2CO and CO 2 as primary gaseous products. A considerable enhancement of the production of the primary gas phase products at 400–450 °C and the emergence of (CH 3) 2C CH 2, CH 4 and CO molecules in the gas phase are ascribed to reactions occurring at the gas/solid interface at the expense of some of the primary products. These interfacial activities impart application-worthy adsorptive and catalytic functions for the associated solid products.

Re(bipy-tBu)(CO)3Cl−improved Catalytic Activity for Reduction of Carbon Dioxide: IR-Spectroelectrochemical and Mechanistic Studies

Five Re(bipy)(CO)(3)Cl complexes were prepared and studied where bipy was 4,4'-dicarboxyl-2,2'-bipyridine (1), 2,2'-bipyridine (2), 4,4'-dimethyl-2,2'-bipyridine (3), 4,4'-di-tert-butyl-2,2'-bipyridine (4), and 4,4'-dimethoxy-2,2'-bipyridine (5). From this group, a significantly improved catalyst, Re(bipy-tBu)(CO)(3)Cl (4), for the reduction of carbon dioxide to carbon monoxide was found. The complex shows two one-electron reductions under argon, one reversible at -1445 mV (vs SCE), and one irreversible at -1830 mV. Under CO(2) the second irreversible wave displays a large catalytic enhancement in current. Diffusion coefficients were determined using the Levich-Koutecky method (1.1 × 10(-5) cm(2)/s for the neutral complex and 8.1 × 10(-6) cm(2)/s for the singly reduced species), and a second order rate constant for the electrochemical reduction with CO(2) of 1000 M(-1) s(-1) was measured. Bulk electrolysis studies were performed to measure Faradaic efficiencies for the primary gaseous products, η(CO) = 99 ± 2% in acetonitrile.

Temperature Zonal Combustion Reactor for the 15-Nitrogen and 13-Carbon Isotopic Determination of Enriched Biosynthetic Materials

A temperature distribution was imposed on a solid−gas reactor to help accomplish the 15-nitrogen or 13-carbon isotopic determination of biosynthetic materials such as algal protein-15N. The temperature zonal combustion reactor (TZCR) can operate offline from its mass spectrometer, and this reactor facilitates the stable isotopic determination of highly enriched biomaterials (>95 atom % isotope). The reactor structure is a glass pipe comprising a quartz segment, transition segments, and threaded sockets. Precise positioning of the reactor within a tubular furnace establishes a longitudinal temperature distribution that is used to drive solid−gas chemistry in distinct zones: sample, catalyst, and sorbent. The TZCR module typically includes a reactor pipe, gastight valve, sample, reactants, reactant containers, and furnace. An important advantage of TZCR-mass spectrometer is preliminary vacuum heat treatment of the crude sample to remove volatile impurities before sample combustion (enabling isotopic enrichment determination of the analyte). For the determination of 15N enrichment, sample combustion at 650 °C in oxygen was supplemented by Fe3O4 catalyst near 500 °C and Li2O at 25 °C that concertedly promoted the intrareactor depletion of CO, CO2, and H2O. As a result, the primary gaseous product was dinitrogen. After 15N sample conversion, the reactor was coupled to a quadrupole MS for product analysis (N2+ ions for 15N determination). Accordingly, uniformly enriched biomaterials were analyzed such as algal protein-15N that measured 99.0 ± 0.12 atom % 15N. By adapting the methodology for 13C determination, lyophilized algal cells-13C were determined to be 99.1 ± 0.06 atom % 13C. Stable isotope enrichments were computed by minimizing the numeric differences between theoretical and actual MS signals.

Mass spectrometric study of the thermal decomposition mechanism of vapors of 2,2,6,6-tetramethyl-3-iminoheptane-5-one and its copper(II) complex

Thermal conversions of vapors of ketoimine C(CH 3) 3C(NH)CH 2C(O)C(CH 3) 3 (Htmha = 2,2,6,6-tetramethyl-3-iminoheptane-5-one) and its chelate coordination compound with copper Cu(tmha) 2 is studied by in situ mass spectrometry in a vacuum and in the presence of hydrogen. Experiments are carried out under conditions close to low pressure chemical vapor deposition at the evaporator temperature of 130 °C and the reactor temperature range 130–500 °C. It is found that compounds are monomeric in the gas phase. Based on temperature dependences of the composition of primary gaseous products, the mechanism of thermal decomposition is proposed. The decomposition of ketoimine on the heated surface begins at 350 ± 10 °C and proceeds by the elimination of terminal groups. Its copper complex decomposes in two directions and yields both molecular and radical products. The latter provide the assumption that metallic copper forms as the only one solid product. The results obtained are compared with those for copper dipivaloylmethanate(2,2,6,6-tetramethylheptane-3,5-dionate).

Synthesis and thermal decomposition of freeze-dried copper–iron formates

The thermal decomposition of freeze-dried formate precursors for copper–iron oxides was investigated by means of DTA, TG, mass spectroscopy and X-ray powder diffractometry. The freeze-dried copper formate is crystalline. Its decomposition at about 200 °C releases formic acid (HCOOH) and carbon dioxide (CO 2) as main primary gaseous decomposition products beside metallic copper as a solid product. However, the decomposition of the amorphous freeze-dried iron formate starts with a dehydration process which ends up at about 200 °C. Further decomposition in several superimposed steps, between 220 °C and 330 °C, results in the delivery of: (a) HCOOH and CO 2 (with reduction of Fe(III) to Fe(II)), (b) HCOOH and CO or H 2CO and CO 2 (without reduction). Meanwhile, several secondary decomposition products are characterized by mass spectroscopy. Regarding the complex copper–iron formate, its decomposition does not reflect only some aspects of the single formates, but also an interaction between the components which lows down the decomposition temperature. Because of the intermediate formation of metallic copper, properties of the reactive homogeneous precursor are lost and the formation of the single-phase copper iron oxides requires an annealing temperature close to that of a mixed oxide technique.

Decomposition of dimethyl methylphosphonate on TiO 2(1 1 0): principal component analysis applied to X-ray photoelectron spectroscopy

The surface chemistry of dimethyl methylphosphonate (DMMP) has been studied on a TiO 2(1 1 0) surface using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). The application of principal component analysis (PCA) to the C(1s) and P(2p) XPS data showed that at least two linearly independent carbon-containing species and two linearly independent phosphorous-containing species are present on the surface between room temperature and 700 K. At room temperature, the main surface species contains intact P–OCH 3 bonds and is most likely molecularly adsorbed DMMP. Between room temperature and 700 K, the adsorbed DMMP decomposes to produce methane and H 2 as the primary gaseous products. Molecular DMMP also desorbs from the surface below 550 K. After heating to 800 K, all of the carbon is removed from the surface, whereas a single phosphorous-containing species is detected even after heating to 1000 K.

Investigation of the Pyrolytic Conversion of Poly(silylenemethylene) to Silicon Carbide

The pyrolysis of poly(silylenemethylene) (PSE), [SiH2CH2]n, a linear polycarbosilane with a regularly alternating Si−C backbone structure and a high-yield precursor to stoichiometric SiC, was investigated by using a combination of thermogravimetric analysis, evolved gas analysis, and solid-state NMR and IR spectroscopies. The observed evolution of D2 from the deuterio-derivative of PSE, [SiD2CH2]n, as the primary gaseous product in the range of ca. 250−400 °C, where cross-linking of the polymer occurs, suggests that loss of H2 from the Si is a key step in the cross-linking process. A reaction pathway is postulated for the cross-linking and pyrolysis of PSE in which both 1,1-H2 elimination and intramolecular H-transfer reactions lead to highly reactive silylene intermediates; these insert into Si−H bonds of neighboring polymer chains forming Si−Si bonds which rapidly rearrange to Si−C bonds at these temperatures to form Si−C interchain cross-links. The cross-links prevent extensive fragmentation of the pol...

Infrared spectroscopic determination of the gas-phase thermal decomposition products of metal-ethyldithiocarbonate complexes

Head-space analysis by gas-phase infrared spectroscopy (HAGIS) allows the facile examination of the decomposition mechanisms of the metal xanthates [metal-( O-alkyldithiocarbonates], Fe(EtOCS 2) 3, Zn(EtOCS 2) 2, Cu(EtOCS 2), Pb(EtOCS 2) 2 and Ni(EtOCS 2) 2, over the temperature range 25–120°C. These metal xanthates fall into two groups based on the generation of the primary gaseous decomposition products, CS 2, COS and CO 2. The first group, consisting of Fe(III) and Zn(II) xanthates, decompose readily, forming mostly CS 2 and COS in a constant ratio and leaving, initially, a metal-alkoxide residue. In the second group, decomposition is relatively small, generating CO 2 and COS, with the proportion of COS increasing as the temperature increases and CS 2 formation occurring only at the upper end of the temperature range. The residue is more of a metal-thioalkyl species in this case. Presumably, CO 2 is formed by re-insertion of COS into a metal alkoxide and elimination of CO 2, leaving a thioalkyl moiety. Volatile metal-xanthates are probably observed in the gas-phase, allowing examination of the changes concomitant to the vaporization of the discrete metal xanthates from network or partially associated solids.

Laser sensitized dissociation of tetramethyl germane

Tetramethyl germane was decomposed using laser sensitized photochemistry. Sulfur hexafluoride, a sensitizer, was added to gas phase tetramethyl germane and irradiated using a carbon dioxide, infrared, continnous wave laser under variable experimental conditions. The gas phase reactions were monitored before and after reaction using both Fourier transform infrared spectroscopy and gas chromatographic/mass spectral techniques. End product analysis showed that methane, ethene, and ethyne were the primary gaseous products. Germanium was identified visually as a gray solid. This laser sensitized dissociation of tetramethyl germane was optimized by a variation in irradiations and conditions such as sample pressure including sensitizer to reactant pressure ratio, laser power, and time. The yield of germane at the 1 s irradiation was 33% while at the 5 s irradiation, at 57% was observed. Both the rate of depletion of tetramethyl germane and the rate of formation of methane, ethene, and ethyne were determined at numerous irradiation times. Longer irradiation times and higher sulfur hexafluoride pressures produced higher yields. Experimental data from the time studies were used to generate simulated concentrations of reactants, reactive intermediates, and products as a function of time to a high degree of accuracy. The rate constants for the laser sensitized dissociation of tetramethyl germane using sulfur hexafluoride as a sensitizer were determined. Simulation analysis suggests that this reaction can be fit statistically to an eight-step reaction mechanism. These results are discussed and compared to similar literature studies of tetramethyl germane dissociations.

Artificial Coalification of a Fossil Wood from Brown Coal by Confined System Pyrolysis

Artificial coalification of a sample of fossil wood of lignitic rank by a confined system pyrolysis in gold tubes reveals that such a simulation only partially mimics natural coalification processes. Analysis of gaseous products by gas chromatography, liquid products by gas chromatography/mass spectrometry, and solid products by elemental analysis, quantitative solid-state 13 C NMR, and flash pyrolysis/gas chromatography/mass spectrometry allows mass balance calculations. It is clear that, for this sample, confined system pyrolysis reproduces well the natural transformations of aromatic rings, but the reactions of aliphatic structures, derived predominantly from the side-chain carbons of lignin, are not simulated by such an artificial maturation process. This partially explains the deviations from the normal van Krevelen diagram observed in most artificial maturation experiments. The primary gaseous product, CO 2 , appears to originate from carboxyl and carbonyl groups and the methane, generated during the most severe stages of thermal treatment, appears to derive from methyl substituents on aromatic rings. The main liquid products observed are phenols, alkylbenzenes, and naphthalenes, with the phenolic products predominating at low severity and the naphthalenes and alkylbenzenes at high severity.