Professor Eric Kennedy

© 2018 Published by Elsevier Inc. on behalf of The Combustion Institute. This study investigates the formation of polychlorinated dibenzo- p -dioxins and polychlorinated dibenzofurans (PCDD/F) in oxidation of 4,4' -dichlorobiphenyl (4,4' -DCB) under gas phase conditions over a temperature range of 400-800 °C. The experiments involved an isothermal flow reactor equipped with a sample collection system to adsorb PCDD/F. We coated the walls of the reactor, made of high purity quartz, with boric oxide to remove catalytic effects and employed the gas chromatography-ion trap mass spectrom- etry (GC-ITMS) to quantitate PCDD/F. Trace analysis by GC-ITMS identified all four MCDF and up to fiv e DCDF isomers, of which 3,7-DCDF constitutes the dominant species, formed directly from 4,4' -DCB. MCDD and DCDD appeared at lower concentration, generated from condensation of chlorophenoxy and chlorobenzenes. Our results show significant differences from the measurements of the thermal decomposition of polychlorinated biphenyls (PCB) performed in sealed ampoules, indicating strong surface effects present in earlier studies. Gas-phase reactions ( > 600 °C) lead to selective formation of a small number of lower-chlorinated pollutants, whereas reactive surfaces, as evident from literature, engender catalytic (but non-selective) appearance of a large number of higher-chlorinated and toxic chloroaryl congeners, even at temperature of less than 300 °C. Results from the density functional theory (DFT) calculations indicate that, majority of the detected congeners of PCDF arise from the oxidative transformation of the parent 4,4' -DCB; i.e., not from the commonly suggested precursors of chlorinated phenols and benzenes. Our findings have significant importance to understanding the emission of PCB and PCDD/F in combustion processes.

© 2018. Mechanisms of pyrolysis of several representative cyclodiene pesticides, viz., dieldrin, aldrin and isodrin, have been studied by quantum chemical techniques and dieldrin and isodrin have been subjected to experimental pyrolysis investigation. Comparison is made with earlier studies on another cyclodiene - endosulfan. Cyclodienes which are initially produced by Diels-Alder condensation of hexachlorocyclopentadiene (HCCP) and a substrate, initially decompose by retro Diels-Alder reaction back into HCCP and the substrate, both of which undergo further reaction. In the case of dieldrin, pyrolysis is initiated at 673 K and the substrate, norbornadiene oxide, further decomposes to produce CO and benzene which are observed experimentally. Above ~800 K hexachlorocyclopentadiene undergoes rapid Cl bond fission and Cl atoms abstract H atoms from dieldrin forming HCl and lead to four different types of dieldrin radicals, just one of which can undergo a sequence of reactions of modest energy barriers to lead to the major observed high temperature products, pentachlorostyrene, hexachlorostyrene and polychlorinated benzenes. In contrast to other cyclodienes, pyrolysis of isodrin which is initially produced by Diels-Alder condensation of hexachloronorbornadiene and cyclopentadiene does not undergo initial retro Diels-Alder decomposition, instead undergoing an intramolecular rearrangement to a "birdcage" structure which eventually decomposes to HCl and aromatic soot precursors. A simple relationship between the rate constants for retro Diels-Alder decomposition and Cl fission of HCCP is discussed to evaluate whether cyclodiene-contaminated soils might be remediated via thermal desorption.

© 2015 Elsevier B.V. The effect of methane on the conversion of HFC-134a (CF3CH2F) in a dielectric barrier discharge non-equilibrium plasma reactor was examined. Reactions were conducted in an argon bath gas and in the absence of oxygen and nitrogen. The products of the reaction include H2, HF, CHF3, CH2F2, C2H6, C3H8, C2H3F, CHF2CHF2, C2H4F2, C3H7F as well as a polymeric solid deposit. The polymeric materials are predominantly fluorine containing random copolymers, which can be categorised as fluoropolymers, constituted from various functional groups including CF3, CF2, CHF, CHF2, CH2F, CH2and CH3. While the presence of methane in the feed stream reduces the conversion level of CF3CH2F, it also modifies the polymer architecture. The addition of 1.25% methane with 12.5% CF3CH2F in an argon bath gas at 100cm3min-1feed rate reduces the conversion of CF3CH2F from 74.5% to 46.8% and increases the formation of HF from 1500µmolh-1to 2640µmolh-1. The effect of methane addition on the electrical discharge and the reaction pathways are discussed.

© 2016 Elsevier B.V. This paper presents the results of dichloromethane (DCM) decomposition to polymers utilising dielectric barrier discharge under non-oxidative reaction conditions. The conversion levels, mass balance, reaction mechanism and polymer characterisation in relation to DCM reaction are presented in this paper. Reaction pathways describing the decomposition of DCM and subsequent formation of the major products are outlined. Speculation of the mechanism of formation of CHCl3and C2HCl3are supported by quantum chemical calculations. In addition, the effect of introducing methane in the reaction feed on the conversion level of DCM and the polymer structure is also examined in this paper.

© 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.

© 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, CH2Cl2and 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, CF2and CF3. The conversion level of CHClF2increased from 53% to 78%, with an increment in input energy density from 3 kJ L-1to 13 kJ L-1. A reaction mechanism is proposed explaining the formation of gaseous as well as polymeric products.

© the Owner Societies 2016. A novel Pd supported on TS-1 combustion catalyst was synthesized and tested in methane combustion under very lean and under highly humid conditions (<1%). A notable increase in hydrothermal stability was observed over 1900 h time-on-stream experiments, where an almost constant, steady state activity obtaining 90% methane conversion was achieved below 500 °C. Surface oxygen mobility and coverage plays a major role in the activity and stability of the lean methane combustion in the presence of large excess of water vapour. We identified water adsorption and in turn the hydrophobicity of the catalyst support as the major factor influencing the long term stability of combustion catalysts. While Pd/Al2O3catalyst shows a higher turn-over frequency than that of Pd/TS-1 catalyst, the situation reversed after ca. 1900 h on stream. Two linear regions, with different activation energies in the Arrhenius plot for the equilibrium Pd/TS-1 catalyst, were observed. The conclusions were supported by catalyst characterization using H2-chemisorption, TPD, XPS analyses as well as N2-adsorption-desorption, XRD, SEM, TEM. The hydrophobicity and competitive adsorption of water with oxygen is suggested to influence oxygen surface coverage and in turn the apparent activation energy for the oxidation reaction.

© 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 CDCl3and 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 H<inf>2</inf>:CO ratios depending on the hydrocarbon used. This paper examines the effect of varying the H<inf>2</inf>:CO ratio with respect to C<inf>1</inf> to C<inf>4</inf> 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 H<inf>2</inf>: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.

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 CF3CH2F 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, Mnvalues between 900 and 3000g~mol-1and high (Mnapproximately 60000 g~mol-1molecular weight fractions. A detailed polymerization mechanism is proposed, based on the published literature and the findings of the current investigation.

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 state13C and19F 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 CO2induced 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 CO2exchange 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 CO2by 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 HO2from 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 HO2at 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, CO2and 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 (1AgO2), 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-1compared 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.

© 2015 The Authors. We present a modelling approach for the continuous aqueous carbonation of serpentinite leachate derived from carbonic acid, suitable for practical application to large-scale CO2sequestration. Experiments involved bubbling of gaseous carbon dioxide (CO2) at a partial pressure of 1 bar into an aqueous suspension of thermally activated serpentinite. Isothermal heating of the ground mineral (-53 µm) at 720 °C for a total period of 30 min resulted in a reactive mineral showing some development of forsterite from the predominantly antigorite basis, with residual hydroxyl content of 53.9 %. An Avrami-Erofe'ev solid state model was fitted to early stage dissolution data (<10 % Mg extraction) and this was used in conjunction with a kinetic formulation of the carbonate system to model continuous mineral dissolution. Dissolution over a contact time of 5 min was sufficient to produce an alkalised solution that was then degassed in a batch operation at 30°C yielding nesquehonite. X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were used to assess changes to the heat activated serpentinite prior to and following dissolution. ICP-OES analysis, and alkalinity measurements were used to estimate magnesium (Mg) and carbon elemental balances.

© 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.