Professor Eric Kennedy

© 2015 Elsevier Ltd.This work has used high range imaging mass spectrometry to study a coal sample that has undergone heating with a temperature gradient. A custom made hotplate was heated to 1000°C and the coal was allowed to heat naturally through conduction to produce a large thermal gradient typical of conditions in a coke oven. The sample was quenched, sectioned and analysed using laser desorption time of flight imaging mass spectrometry (LDI-TOF-IMS) to study the molecular changes that occur within the plastic layer and in the semi-coke. The raw coal was observed to have a molecular weight range between 500 and 20,000 Da with a peak occurring at 2000 Da. The plastic layer was observed to have a prevalence for increasing 500-1000 Da structures though this formed part of the larger molecular weight range. Resolidification of the plastic layer coincided with a rise in 4000 Da structures. The semi-coke spectrum had a series of repeating peaks separated by 24 Da extending from 1000 Da to 3000 Da. This was considered evidence of broad molecular ordering. A second phenomenon was observed in the semi-coke associated with low range molecular weights (50-300 Da). This appeared as high intensity signals in a molecular range typically considered as ion fragments (being too low in size to remain in the high vacuum environment). It was speculated that these low range structures may be associated with the coking of volatile tars exiting the hot-side of the plastic layer through high temperature semi-coke. Overall, this preliminary work provides a novel methodology to study the heating impacts during coking on a molecular level.

© 2015 American Chemical Society.The reaction of CCl3F (CFC-11) with CH4 (in an argon bath gas) in a dielectric barrier discharge nonequilibrium plasma was examined. Oxygen and nitrogen were excluded from the feed stream and the reactions resulted in the production of fluorine-containing polymers, as well as a range of gaseous products including H2, HCl, HF, C2H3F, C2H3Cl, C2H2ClF, CHCl2F, CCl2F2, CH3Cl, CH2Cl2, CHCl3, and C2Cl4. The polymeric material synthesized during reaction is characterized as being non-cross-linked and random in nature, containing functional groups including CH3, CH2, CHCl, CHF, CF2, and CF3. The conversion level of CCl3F increased from 37% to 63% as the input energy density increased from 3 to 13 kJ L-1 (the applied voltage range was 14.1 to 15.2 kV, peak-peak). The electrical discharge was characterized and found to be a slight modification of filamentary discharge toward a diffuse discharge due to the presence of the relatively low concentration of CCl3F and CH4 (less than 2% each) in argon. A reaction mechanism is proposed describing the formation of gas phase, as well as polymeric products.

© 2016 Elsevier B.V.A dielectric barrier discharge non-equilibrium plasma was employed to study the reaction of HCFC-22 (CHClF2) with methane (in an argon bath gas) at atmospheric pressure and in the absence of oxygen and nitrogen. The reaction produced a fluorine-containing polymeric product, as well as gaseous species including H2, HF, HCl, CHF3, C2H3F, CH3Cl, CH2ClF, C2HClF4, CHCl2F, CH2Cl2 and CCl2F2. While the main polymeric fraction is non-crosslinked, a small portion of the solid product is crosslinked. The polymers contain a wide range of functional groups including CH3, CH2, CHCl, CHF, CHClF, CHF2, CF2 and CF3. The conversion level of CHClF2 increased from 53% to 78%, with an increment in input energy density from 3 kJ L-1 to 13 kJ L-1. A reaction mechanism is proposed explaining the formation of gaseous as well as polymeric products.

© 2016 Elsevier B.V.Mineral carbonation has the potential to store billions of tonnes of CO2 safely and permanently. Enhancement of the kinetics of the formation of magnesium carbonate from magnesium-bearing silicate minerals has been the subject of numerous research studies. However, significant progress is yet to be achieved. This is, in part, due to a lack of understanding of the mechanism of the formation of magnesite in the presence of additives and under mineral carbonation conditions. In this work, an in-depth study was performed to investigate the precipitation of magnesium carbonate during single step high pressure, high temperature carbonation of thermally activated serpentine in an aqueous bicarbonate solution. Slurry samples were obtained throughout the duration of the carbonation experiments, enabling analysis of both the aqueous and solid compositions over time, providing insight into the reaction mechanism. Additionally, the effect of operating temperature on the formation of various magnesium carbonate species was examined. TGA-MS, in combination with XRD and SEM, confirmed the formation of hydromagnesite in the absence of carbon dioxide (CO2) during the reactor heat up period, owing to a reaction with the sodium bicarbonate (NaHCO3) carrier solution. Hydromagnesite was transformed to magnesite over time, with the rate of this phase transformation highly dependent on the reaction temperature. At 185¿°C all hydromagnesite converted to magnesite in a few minutes whereas at 120¿°C even after 90¿min hydromagnesite remained in the reactor. PHREEQC thermodynamic software was used to assess the observed formation of carbonate species. The model prediction was consistent with the experimental results obtained in this work.

© 2016.This article reports the results of a computational and experimental study on the thermal degradation of endosulfan, a broad-spectrum chlorinated cyclodiene insecticide. The objective of the study was to identify its decomposition pathways, and to gain an understanding of the mechanism of formation of toxic species including polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) and their precursors. We implemented pyrolysis experiments in a tubular reactor and identified the pyrolysis products and demonstrate good qualitative agreement between the experimental species measurements and quantum chemical calculations. A sampling system intercepted the gaseous products exiting the reactor which were analysed by FTIR spectroscopy and trapped (at -10°C) volatile organic compounds (VOC) generated from the thermal decomposition of endosulfan were analysed by GC/MS. Decomposition commences at about 573K in a flow reactor at a residence time of 5s. The initial primary decomposition reaction of endosulfan involves a retro Diels-Alder elimination to form hexachlorocyclopentadiene (HCCP) and 4,7-dihydro-1,3,2-dioxathiepine-2-oxide (2HDTO). Under these conditions, 2HDTO decomposes via two competing reaction channels, both eliminating SO2. At reaction temperatures of 663K and above, fission of a Cl atom results in the formation of endosulfan radical, which promotes further decomposition of endosulfan via a low barrier free radical pathway. As the temperature increases further, we observe a rise in secondary products including pentachlorocyclopentadiene (PCCP), tetrachlorostyrene (TCS) and pentachlorostyrene (PCS). At 823K, chlorinated benzene products were identified comprising pentachlorobenzene and isomers of tetrachlorobenzenes which are known precursors for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans PCDD/PCDF under oxidative conditions. Under oxidative conditions (10% oxygen), PCDD/PCDF congeners are formed, dominated by mono- to octa- chlorinated dibenzofurans and tetra- to octa- chlorinated dibenzo-p-dioxins.

© 2016 Elsevier B.V.In this contribution, the development of a process for the synthesis of potentially highly valuable polymeric products from the reaction of waste glycerol with ammonia is reported for the first time. The polymers were the result of a single step, continuous gas phase process, catalysed by an alumina-supported iron catalyst, operating under relatively mild reaction conditions. The solid product was characterised using 1D and 2D NMR spectroscopy, FTIR spectroscopy, qualitative chemical tests and elemental analysis. Characterisation revealed building blocks with unsaturated, amido and ester functionalities shaping a mixture of polymers. Nitrogen atoms were present in the main chain of the resultant polymers. NMR analyses of the polymer denotes the formation of structural defects such as unsaturation and branching; whilst the partial solubility of the polymer in solvents such as CDCl3 and THF is indicative of the formation of cross-linked structures. Insights into the mechanism of formation of these functional groups were based on the liquid and gas phase product distribution. Polymers with chain structures similar to those synthesised in this work are currently manufactured from fossil fuels and are widely used in biomedical applications not only because of their architecture but also due to their response to changes in pH and temperature.

© 2015 The Institution of Chemical Engineers.An increased interest in using hydrocarbons in solid oxide fuel cells for the production of power has led to research into operation on synthesis (syn) gas, a mixture of hydrogen and carbon monoxide. Hydrocarbons are typically reformed, either internally or in an external reformer prior to the fuel cell, producing syngas with various H2:CO ratios depending on the hydrocarbon used. This paper examines the effect of varying the H2:CO ratio with respect to C1 to C4 steam reforming reactions and additionally a mixture containing a higher ratio of carbon monoxide. It was found that there was no significant relationship between cell performance and H2:CO ratio when a high feed rate was employed. For low flow rates, however, the high carbon monoxide concentration resulted in a significant decrease in cell performance. It was determined that this was caused by reversible carbon deposition as opposed to a decrease in carbon monoxide reactivity.

© 2014 Elsevier B.V. All rights reserved.Nano-sized Co3O4, Fe2O3, Au/Co3O4 and Au/Fe2O3 catalysts were prepared and evaluated for catalytic combustion of lean methane-air mixtures. Characteristics and catalytic activities under dry and wet feed conditions were investigated at gas hourly space velocities up to 100 000 h-1 mimicking the typical flow and conversion requirements of a catalytic system designed to treat a ventilation air methane stream. In order to gain a better understanding of the interaction between H2O and the catalyst surface, temperature-programmed desorption of water over fresh and used samples were studied, and supported by other catalyst characterization techniques such as N2-adsorption desorption, XRD, TEM, SEM and XPS analyses. The activity measurements of the catalysts studied identify Co3O4 as the most active material. Co-precipitating gold particles with cobalt oxide or iron oxide do not enhance the activity of the catalyst, which is most likely due to blocking the active site of support by the gold particle. The presence of strong hydroxyl bonds on the catalyst surface is substantiated by TPD and XPS analyses, and is suggested to be responsible for the rapid deactivation of Fe2O3 and Au/Fe2O3 catalysts.

This journal is © the Owner Societies 2015.Density functional theory together with ab initio atomistic thermodynamics has been utilized to study the structures and stabilities of the low index CuCl surfaces. It is shown that the Cl-terminated structures are more stable than the Cu-terminated configurations, and that the defective CuCl(110)-Cu structure is more stable than the stoichiometric CuCl(110) surface. The equilibrium shape of a cuprous chloride nanostructure terminated by low-index CuCl surfaces has also been predicted using a Wulff construction. It was found that the (110) facets dominate at low chlorine concentration. As the chlorine concentration is increased, however, the contributions of the (100) and (111) facets to the Wulff construction also increase giving the crystal a semi-prism shape. At high chlorine concentration, and close to the rich limit, the (111) facets were found to be the only contributors to the Wulff construction, resulting in prismatic nanocrystals.

© 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved. The emissions of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD and PCDF) were assessed for wood impregnated with ammoniacal copper quaternary (ACQ) and copper boron azole (CBA). The two preservatives constitute the replacements for chromated copper arsenate (CCA) treatment, which is being phased out as a consequence of health concerns relating to arsenic and chromium compounds. The gaseous emission of PCDD/F from oxidative pyrolysis of CBA contained considerable amounts of PCDD/F of up to 7500 pg TE/Nm3. A large increase was also observed for the gaseous emission from smoldering of CBA following the oxidative pyrolysis, where 570 pg TE/Nm3 was detected. The ash residues of CBA remaining after the CBA emissions after oxidative pyrolysis and ensuing smoldering also showed significant propensity to yield PCDD and PCDF, resulting in 3200 ng TE/kg ash. In contrast, flaming combustion of the two treated timbers did not result in the emission of significant quantities of PCDD/F. The concentrations were quantified as 3.5 and 5.2 pg TE/Nm3 for the ACQ and CBA timber samples, and indicate no reasonable increase over that resulting from similar combustion of untreated Pinus radiata, 3.7 pg TE/Nm3. The smoldering of ACQ and CBA ash residues after flaming combustion generated PCDD/F, with the ashes containing 5.0 and 140 ng TE/kg ash, respectively. The increase in PCDD/F formation is discussed with respect to de novo formation in the ash and the influence Eof the wood preservatives.

© 2014 IEEE.Nonequilibrium plasma polymerization of hydrofluorocarbon HFC-134a CF3 CH2F in argon bath gas has been studied in a dielectric barrier discharge reactor at atmospheric pressure and in the absence of oxygen and nitrogen. The reaction resulted in the formation of a polymeric solid fraction and the noncrosslinked properties of this material assisted in its characterization by solution state 13C} and 19F nuclear magnetic resonance spectroscopy. Gel permeation chromatography revealed that the polymers include low (number average molecular weight, Mn values between 900 and 3000g~mol-1 and high (Mn approximately 60000 g~mol-1 molecular weight fractions. A detailed polymerization mechanism is proposed, based on the published literature and the findings of the current investigation.

Typically, mineral carbonation comprises aqueous phase reactions involving the dissolution of naturally occurring magnesium and calcium silicate rocks, such as olivine, serpentinites and wollastonite, followed by the precipitation of magnesium and calcium carbonate minerals. In this report, we evaluated the effect of formic, acetic and DL-lactic acids on the calcium-leaching process from wollastonite between 22 C and 80 C and at atmospheric pressure. OLI Analyzer Studio 3.0 predicted equilibrium conversions of calcium and its speciation in the aqueous phase. Additionally, we measured dissolution rates, for a constant pH system, as a function of temperature for the three organic acids. All experiments involved the reaction of 17 ± 1 µm (volume mean diameter) ground rock samples with the acids in a stirred batch reactor equipped with in situ pH measurements. Inductively coupled plasma-optical emission spectrometry (ICP-OES) analysed the concentration of calcium ions in the leaching medium while scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) examined the morphology and surface chemical composition of the residual solid phase from dissolution experiments. We estimated the maximum dissolution rates of wollastonite in the limit of low but achievable pH and in the absence of diffusion limitation in pores and cracks of the SiO 2 skin. At 80 C, these rates correspond to 26(±7) × 10-5, 14(±3) × 10-5 and 17(±4) × 10-5 mol m-2 s-1 for formic, acetic and DL-lactic acids, respectively. The apparent activation energies amount to 11 ± 3, 47 ± 13 and 52 ± 14 kJ mol-1 for dissolution in formic, acetic and DL-lactic acids, respectively. These values indicate the initial diffusion limitation in the film around wollastonite particles for formic acid, and kinetic limitation for acetic and DL-lactic acids. The rates of dissolution rapidly decline for acetic and DL-lactic acids, but remain high for formic acid. The findings are altogether indicative of high performance of formic acid for extraction of Ca2+ for storing CO 2. Further experiments are needed to assess the recycling of formic acid to determine its overall suitability as a Ca2+ carrier for the weak acid process. © 2014 Elsevier Ltd. All rights reserved.

Reaction of phenol with hydrogen peroxide over H-MFI, Fe-MFI, H-BEA, Fe-BEA and TS-1 zeolite catalysts was investigated. Over H-BEA, biphenyl product was observed. It is suggested, that the larger pore size of H-BEA facilitates coupling of two phenol molecules. Two distinct reaction mechanisms are proposed for acid and redox catalysts. © 2013 Springer Science+Business Media New York.

In this paper we focus on the development of a methodology for treatment of carbon tetrachloride utilising a non-equilibrium plasma operating at atmospheric pressure, which is not singularly aimed at destroying carbon tetrachloride but rather at converting it to a non-hazardous, potentially valuable commodity. This method encompasses the reaction of carbon tetrachloride and methane, with argon as a carrier gas, in a quartz dielectric barrier discharge reactor. The reaction is performed under non-oxidative conditions. Possible pathways for formation of major products based on experimental results and supported by quantum chemical calculations are outlined in the paper. We elucidate important parameters such as carbon tetrachloride conversion, product distribution, mass balance and characterise the chlorinated polymer formed in the process. © 2014 Elsevier B.V.

© 2014 American Chemical Society.A dielectric barrier discharge (DBD) nonequilibrium plasma reactor was employed to polymerize CFC-12 (CCl2F2, dichlorodifluoromethane) at atmospheric pressure. The plasma polymerization of this saturated halogenated hydrocarbon was conducted in the presence of methane as reactant, in an argon bath gas and where the reaction environment was free from oxygen and nitrogen. The reaction resulted in the formation of non-cross-linked polymer product and whereby the non-cross-linked nature of the polymer enabled its characterization by solution state 13C and 19F nuclear magnetic resonance (NMR) spectroscopic analysis. The generated polymer was also analyzed by Fourier transform infrared (FTIR) spectrometry, and the spectra thus obtained were consistent with the analysis by NMR. The analyses of NMR and FTIR spectroscopy reveal the formation of fluoropolymers from the conversion of CFC-12.

This contribution assesses the dissolution behaviour of serpentinite specimens, featuring distinct stages of serpentinisation, by treating the specimens with aqueous solutions of formic acid. We have observed a marked improvement in the extraction of magnesium when the samples were finely ground and thermally conditioned before treatment with formic acid. An extraction of 42% for -25 µm particles activated at 700 °C (29% residual OH) could be obtained from the forsterite-lizardite bearing specimen whereas 66% of magnesium was leached out of the fully serpentinised antigorite mineral, which was crushed to a particle size of -53 µm and baked at 720 °C (36% residual OH). Combined results derived from FTIR and XRD indicate that heat activation between 500 and 720 °C results in a reorganisation of lizardite and antigorite to amorphised material, forsterite and silica. Unreactive enstatite forms from the amorphised material and silica once the heating temperature exceeds 800 °C. Semi-quantitative XRD analysis yields an estimate of the crystalline and non-crystalline (forsterite) fractions of the activated material, permitting approximation of relative rates of dissolution of amorphous and forsterite phases. Although FTIR provides important information on forsterite and silica formation, it cannot detect the amorphous material. Forsterite and amorphous phases alike dissolve in the weak acid but the formation of skins of the amorphous silica limits the overall magnesium yield on a laboratory time scale. The material that constitutes the skins originates from two sources: (i) silica formed in forsterisation of serpentine minerals undergoing heat treatment, and (ii) silica produced during extraction of Mg by a weak acid from amorphous and forsterite phases. Heat activation also leads to the formation of andradite and modified chlorite minerals that exhibit less solubility than forsterite and amorphous phases in weakly acidic medium.© 2014 Elsevier Ltd. All rights reserved.

This contribution reports the results of batch and semibatch experiments involving bubbling of nitrogen in aqueous solutions of magnesium bicarbonate, with and without the addition of either carbonic anhydrase (CA) or Scenedesmus alga to the solution. Precipitation of nesquehonite occurred during both an accelerated degassing of CO2 induced by sparging small nitrogen bubbles (representative diameter of 20 µm), and during slow degassing engendered by introducing large nitrogen bubbles (representative diameter of 5 mm). The response of the system during low rates of degassing closely approached quasi-thermodynamic predictions, which permitted an estimation of the level of supersaturation of nesquehonite, prior to the onset of precipitation. Small bubbles and CA significantly increased rates of degassing and indirectly the production of nesquehonite, as the rate of degassing can limit the precipitation process. The response of the system during rapid rates of degassing, prior to precipitation, was not entirely consistent with quasi-thermodynamic predictions. During precipitation, higher rates of degassing produced similar alkalisation and precipitation trends to that observed for lower rates of degassing. Our results agree with the formation of travertine deposits in nature, where the degassing of solutions enriched with inorganic carbon, and enhanced alkalisation by microorganisms, have been shown to influence carbonate formation. The results demonstrate a catalytic effect of CA on the rate limiting carbonate reactions, increasing CO2 exchange between nitrogen and water, and indirectly accelerating the precipitation of carbonates for a system controlled by rate of degassing. The results of this study have applications to large-scale storage of CO2 by mineralisation. © 2013 Elsevier Ltd. All rights reserved.

Conversion of glycerol to allyl alcohol was carried out over an iron on alumina catalyst. With the aim of enhancing selectivity towards the desired product and to reduce acrolein formation (a detrimental impurity in the subsequent epoxidation of allyl alcohol) the supported iron catalyst was modified using alkali metals. It was found that lithium, sodium, potassium, rubidium and caesium deposition on the catalyst surface increased allyl alcohol yield and reduced the rate of catalyst deactivation. Coincidently, acrolein selectivity decreased by up to 75% following treatment with the alkali salt.Changes in the product distribution were determined to be associated with altering the acid/base properties of the catalyst, as confirmed by isopropanol dehydration/dehydrogenation, ammonia and carbon dioxide temperature programmed desorption. The treatment was also found to influence the physical properties of the catalyst surface. A correlation between acid to basic site concentration and allyl alcohol selectivity was established. A reduction in the former value results in an enhancement in the rate of allyl alcohol formation. A reaction mechanism was developed based on the effect of iron and alkali metals catalysing the conversion of glycerol into allyl alcohol. The proposed catalyst modification technique is a straightforward method, readily applicable at a larger scale due to the simplicity of the alkali inclusion and its striking influence on the reaction selectivity. © 2014.

In this paper, we report new insights into the deactivation phenomenon of palladium based catalysts for catalytic combustion of ventilation air methane (VAM). It was found that the primary factor responsible for low temperature catalyst deactivation is the water vapour present in the feed stream. The influence of water vapour on VAM was examined by comparing the properties of fresh catalysts with catalysts following over 1000 h reaction time-on-stream. The techniques applied to characterize the catalysts included TPD, XRD, N 2-isotherm adsorption, H2-chemisorption and XPS analyses. Alternating between dry and water vapour-saturated VAM feed disclosed ca. 50% reversible drop in activity. XPS analysis suggests an absence of a palladium hydroxide phase during the initial 2 h on stream, although prolonged exposure to the reactant leads to the formation of palladium hydroxide, which appears to match the progressive deactivation of the Pd/Al2O3 catalyst. Introduction of VAM dust (a mixture of fine coal, CaCO3 and aluminosilicate particles) causes a variation in catalytic activity originating from coal-dust ignition and the effect of chloride on the surface of the catalyst. In the presence of these inhibiting agents, an average methane conversion of higher than 75% over 1100 h was achieved at reaction temperatures below 600°C. This journal is © the Partner Organisations 2014.

A continuous process for the conversion of glycerol to allyl alcohol, where ammonia or organic acids are added to the feed as sacrificial reductants, was investigated. Significant enhancement on the rate of formation and yield of the allyl alcohol is observed with some of the reducing agents examined over an alumina-supported iron catalyst. Optimising the molar ratio of the reductant relative to feed glycerol results in an increase in the yield of allyl alcohol from 9% (in the absence of additives) to 11.3% with ammonia, 15.1% with ammonium hydroxide, 17.8% with oxalic acid and 19.5% with formic acid. Moreover, the addition of other organic acids, which are produced in a typical glycerol conversion experiment, was studied. However, acetic and propanoic acids had little effect on the rate of formation of allyl alcohol. Analysis of the product distribution in the liquid and gas phases when oxalic and formic acids were added suggests a two-step process for the formation of allyl alcohol under the operating conditions of the reaction; the initial step involves the dehydration of glycerol while the second comprises the reduction of the species produced in step one. © the Partner Organisations 2014.

A central step in the low-temperature oxidation of hydrocarbons is the abstraction of H by the hydroperoxyl radical (HO2). In this study, reaction rate constants are derived theoretically for H abstraction by HO2 from the three distinct locations of H in ethylbenzene (primary, secondary and aromatic H, with H on the ortho carbon taken as an example of unreactive aromatic H) as well as for the addition of HO2 at the four possible aromatic sites. Potential energy surface is mapped out based on the results of computations performed with the composite CBS-QB3 theoretical method. Rate constants are fitted to modified Arrhenius forms in the wide temperature range of 300-2000K. The dominant channel at all temperatures is found to be H abstraction from the secondary C of the ethyl chain with a rate constant expression of k=1.28×10-24T3.70exp-5100Tcm3molecule-1s-1. Abstraction from the primary C also contributes significantly at higher temperatures (>800K) with a rate constant expression of k=2.90×10-24T3.78exp-8400Tcm3molecule-1s-1. Reasonable agreement was obtained with the limited experimental data available in the literature. Addition at the four sites of the aromatic ring and abstraction of one of the C-H aromatic bonds are relatively unimportant over the temperature range studied. We also investigate the abstraction of H from the secondary C on the ethyl chain by triplet oxygen and report the associated rate expression. The results presented herein should be useful in modelling the oxidation of alkylbenzenes at lower temperatures. © 2012.

C-Nitroso compounds represent a class of chemical species with radical spin trapping capacity. They are widely employed to scavenge nitric oxide (NO) in biological and chemical systems and prospectively could be applied to reduce and control NO formation from important chemical processes. In this study, we examined the physicochemical properties of four ortho-substituted aromatic nitroso compounds, 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS), 4-nitrosobenzenesulfonate (NBS), 3,5-dimethyl-4-nitrosobenzenesulfonate (DMNBS), and 3,5-dichloro-4-nitrosobenzenesulfonate (DCNBS). These compounds, like most C-nitroso spin traps, exist in a monomer-dimer equilibrium, and only the monomeric form is active as a free radical spin scavenger. The influence of the aromatic ring substituent(s) on the dissociation of the dimer to give the monomer was investigated using UV-vis spectrophotometry. We describe the thermodynamic and kinetic parameters associated with the monomer-dimer equilibria, which allow us to provide a mechanistic understanding of NO trapping by C-nitroso compounds. © 2013 American Chemical Society.

This contribution aims to elucidate the chemical aspects of the autoxidation of linseed oil that may lead to self-heating and fires, especially for linseed oil doped with salts of transition metals, in the presence of an additional fuel, such as cotton. We examine the formation of peroxides, which function as important intermediates in the autoxidation reaction. In particular, we describe the relationship between the formation of peroxides and changes in the degree of unsaturation, together with other structural and compositional modifications occurring in the molecules of unsaturated fatty acid esters. Transition metal salt catalysts were found to decompose peroxides which had built up during the autoxidation reaction of linseed oil, thereby increasing the number of reactive radicals and resulting in higher product yields. Higher temperatures increased the rate of peroxide decomposition. The overall activation energy for peroxide formation corresponds to 71±1 kJ mol -1. FTIR analysis of oil film demonstrated the progressive decrease in the concentration of cis non-conjugated double bonds, formation of trans conjugated double bonds, appearance of hydroxyl groups and the broadening of the carbonyl peak. The overall rate of disappearance of double bonds follows first order kinetics with a rate constant of 0.030±0.007 h-1. © 2013 Elsevier Ltd.

This contribution compares the formation of toxic species, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) and their precursors such as polychlorobenzenes (PCBz) and polychlorophenols (PCP), during oxidation of 4-chlorobiphenyl (4-CB) in a laboratory-scale apparatus, under conditions similar to those that occur in fires and waste combustion. The experiments were conducted using two gas flow reactors made of 99.5% alumina and high purity quartz, respectively. A sampling system intercepted the gaseous products leaving the reactors, trapping the volatile organic compounds (VOC; i.e., PCBz and PCP) and PCDD/F on a XAD-2 cartridge. The analysis of VOC involved high resolution gas chromatography (HRGC) - quadrupole mass spectrometry (QMS) while HRGC - ion trap (IT) MS/MS quantitated the PCDD/F produced. For the experiments using the alumina reactor, VOC analysis revealed the formation of PCBz and PCP, commencing at temperatures as low as 400 °C. Other products included benzaldehyde, naphthalene, 3-ethylbenzaldehyde, 1-chloro-4-ethynylbenzene and benzofuran. Gaseous species such as CO, CO 2 and HCl were detected and quantitated either by Fourier transform infra-red spectroscopy (FTIR) or ion chromatography (IC). Similar products were found to form in the quartz reactor, however, their formation commenced at 500 °C, with their yields significantly lower than those found for the alumina reactor. The present measurements indicate that surface reactions govern the oxidation of 4-CB between 300 and 650 °C for the alumina reactor, and between 450 and 600 °C for the quartz reactor. At 700 °C, both reactors operate similarly, with the oxidation process dominated by the gas phase reactions. With respect to dibenzo-p-dioxins and dibenzofurans, only isomers of chlorinated monochlorodibenzofuran (MCDF) and chlorinated dichlorodibenzofuran (DCDF) were found at low temperatures (300 to 450 °C), with 3-MCDF as the dominant congener. In our system, they appear to form in gas phase reactions involving 4-CB and singlet oxygen (1Ag O2), the latter generated on the reactor walls. The present results indicate that the combustion of 4-CB in fires will be dominated by catalytic surfaces of fly ash below 600 °C, and by gas-phase kinetics above 700 °C. © 2013 International Association for Fire Safety Science.

The adsorption complex of hydrogen chloride on copper-modified ZSM-5 was studied by FTIR and theoretical calculations. The results indicate that the Cl atom of hydrogen chloride is bound to the Cu cations when adsorbed at low pressures (<1 µbar). At higher pressures, HCl adsorbs on the zeolite Brønsted acid sites as well as is hydrogen bonded to the Cu in a larger cluster. Using in situ infrared spectroscopy, we observed a sharp decrease in stretching vibrational frequency of HCl of about 700 cm-1 compared with the H-Cl stretching vibration of gaseous hydrochloric acid. The findings were supported by density functional theory cluster quantum chemical calculations. © 2013 American Chemical Society.

In recent years, the use of nitrogenous industrial explosives has come under intense scrutiny by environmental agencies due to emission of toxic fumes to the atmosphere during blasting of ammonium nitrate based explosives. Ammonium nitrate (AN) is a major ingredient in ammonium nitrate fuel oil (ANFO), and emulsion explosives, which are commonly applied in trench or surface mines blasting, and construction operations. It is well known that ammonium nitrate based explosives release toxic fumes (which contains NO and NO2 emissions) under certain blasting condition, and/or oxygen rich explosive formulations. We investigated the effect of potassium on crystal structure, and thermal behaviour of ammonium nitrate. We observed multiphase structures in co-recrystallised ammonium nitrate containing low (2-4 mol %) and high (>25 mol %) concentrations of potassium in the crystallisation solution; mol % is based only on K+ and NH4+. Co-recrystallised salts were characterise using X-ray diffraction (XRD), Scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS), Inductively coupled plasma - optical emission spectroscopy (ICP-OES), and Thermogravimetric analyser and differential scanning calorimeter (TGA/DSC). In addition, we report concentration profiles of NO during thermal analyses of corecrystallised potassium ammonium nitrates. The results obtained from thermal decomposition of the co-recrystallised potassium ammonium nitrate salts showed decrease in production of NO. and 3-5 mol % K was the optimal concentration when compared with pure AN.

© Copyright 2014 International association for fire safety science.This paper reports the ignition temperature and emissivity of heterogeneous materials characterised by high void fraction of between 0.92 and 0.94 and composed of loose particles of shredded grass and paper, planed wood, shredded plastic bags, as well as sugar and bread, with about 95 % of the particles (by mass) of less than 50 mm in size. These materials reflect a typical composition and void fraction of so-called refusederived fuels (RDF), which are obtained from municipal solid waste, then densified and combusted for energy recovery. An infrared pyrometer, with a spectral response range of 8 to 14 µm, recorded the surface temperature of the surrogate RDF, prior to the onset of the flaming combustion, in a stand alone mass loss calorimeter operated at 20 and 45 kW m-2. The overlapping spectral ranges of the pyrometer and the radiator heater necessitated the development of a practical methodology to obtain the actual surface temperature from the apparent measurements, which included the effect of the reflected radiation. In addition to surface temperatures (292 - 325 °C for 20 kW m-2 and 250 - 294 °C for 45 kW m-2), in this contribution, we estimate the actual emissivities (0.95 - 0.98) of the materials from the intensity of the reflected radiation. KEYWORDS: cone calorimeter, ignitability, piloted ignition, ignition temperature, ignition delay, ignition mechanism, heat transfer in fires, fire properties, emissivity, firepoint, biofuels.