Name: combustion chemistry of fuels: quantitative speciation data obtained from an atmospheric high-temperature flow reactor with coupled molecular-beam mass spectrometer
Uploaded: 2018-02-19T14:00:00
Description: Watch this Scientific Journal Video about Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectr

The experiments were carried out in the mass spectrometry department at the Institute of Combustion Technology, Deutsches Zentrum f&#252;r Luft- und Raumfahrt (DLR) in Stuttgart, Germany. The work was also supported by the Helmholtz Energy-Alliance &#34;Synthetic Liquid Hydrocarbons&#34;, the Center-of-Excellence &#34;Alternative Fuels&#34; and the DLR project &#34;Future Fuels&#34;. The authors wish to thank Patrick Le Clercq and Uwe Riedel for fruitful discussions on jet fuels.

1. Setup of the molecular beam mass spectrometer (MBMS) and flow reactor system
<ol>
	<li>Heat oven to designated start temperature, which is the highest temperature in designated measurement series. For typical conditions of Jet A-1 with &#934;=1, total oxidation is observed below 850 &#176;C (~1,100 K). The choice of proper starting temperatures depends on the chemical nature of the investigated fuel and the stoichiometry (&#934;).</li>
	<li>Prepare Time-of-Flight (TOF) spectrometer for intermediate species detection...

<ol>
	<li>Moore, R. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofuel+blending+reduces+particle+emissions+from+aircraft+engines+at+cruise+conditions.">Biofuel blending reduces particle emissions from aircraft engines at cruise conditions.</a> Nature. 543 (7645), 411-415 (2017).</li><li>Braun-Unkhoff, M., Kathrotia, T., Rauch, B., Riedel, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=About+the+interaction+between+composition+and+performance+of+alternative+jet+fuels.">About the interaction between composition and performance of alternative jet fuels.</a> CEAS Aeronautical Journal. 7 (1), 83-94 (2016).</li><li>Egolfopoulos, F. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+and+challenges+in+laminar+flame+experiments+and+implications+for+combustion+chemistry.">Advances and challenges in laminar flame experiments and implications for combustion chemistry.</a> Prog Energ Combust. 43, 36-67 (2014).</li><li>Lynch, P. T., Troy, T. P., Ahmed, M., Tranter, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+combustion+chemistry+in+a+miniature+shock+tube+with+synchrotron+VUV+photo+ionization+mass+spectrometry.">Probing combustion chemistry in a miniature shock tube with synchrotron VUV photo ionization mass spectrometry.</a> Anal Chem. 87 (4), 2345-2352 (2015).</li><li>Pelucchi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+experimental+and+kinetic+modeling+study+of+the+pyrolysis+and+oxidation+of+n-C3C5+aldehydes+in+shock+tubes.">An experimental and kinetic modeling study of the pyrolysis and oxidation of n-C3C5 aldehydes in shock tubes.</a> Combust. Flame. 162 (2), 265-286 (2015).</li><li>Hanson, R. K., Davidson, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+laser+absorption+and+shock+tube+methods+for+studies+of+combustion+chemistry.">Recent advances in laser absorption and shock tube methods for studies of combustion chemistry.</a> Prog Energ Combust. 44, 103-114 (2014).</li><li>Sung, C. -. J., Curran, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+rapid+compression+machines+for+chemical+kinetics+studies.">Using rapid compression machines for chemical kinetics studies.</a> Prog Energ Combust. 44, 1-18 (2014).</li><li>Kohse-H&#246;inghaus, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cover+Picture:+Biofuel+Combustion+Chemistry:+From+Ethanol+to+Biodiesel.">Cover Picture: Biofuel Combustion Chemistry: From Ethanol to Biodiesel.</a> Angw Chem Int Edit. 49 (21), 3545 (2010).</li><li>K&#246;hler, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=1-,+2-+and+3-Pentanol+combustion+in+laminar+hydrogen+flames+-+A+comparative+experimental+and+modeling+study.">1-, 2- and 3-Pentanol combustion in laminar hydrogen flames - A comparative experimental and modeling study.</a> Combust. Flame. 162 (9), 3197-3209 (2015).</li><li>Li, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Study+of+a+Fuel-Rich+Premixed+Toluene+Flame+at+Low+Pressure.">Experimental Study of a Fuel-Rich Premixed Toluene Flame at Low Pressure.</a> Energ Fuel. 23 (3), 1473-1485 (2009).</li><li>Yang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+combustion+intermediates+in+isomeric+fuel-rich+premixed+butanol-oxygen+flames+at+low+pressure.">Identification of combustion intermediates in isomeric fuel-rich premixed butanol-oxygen flames at low pressure.</a> Combust. Flame. 148 (4), 198-209 (2007).</li><li>Reuter, C. B., Won, S. H., Ju, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flame+structure+and+ignition+limit+of+partially+premixed+cool+flames+in+a+counterflow+burner.">Flame structure and ignition limit of partially premixed cool flames in a counterflow burner.</a> P Combust Inst. 36 (1), 1513-1522 (2017).</li><li>Reuter, C. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+study+of+the+dynamics+and+structure+of+self-sustaining+premixed+cool+flames+using+a+counterflow+burner.">Experimental study of the dynamics and structure of self-sustaining premixed cool flames using a counterflow burner.</a> Combust. Flame. 166, 125-132 (2016).</li><li>Bufferand, H., Tosatto, L., La Mantia, B., Smooke, M. D., Gomez, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+and+computational+study+of+methane+counterflow+diffusion+flames+perturbed+by+trace+amounts+of+either+jet+fuel+or+a+6-component+surrogate+under+non-sooting+conditions.">Experimental and computational study of methane counterflow diffusion flames perturbed by trace amounts of either jet fuel or a 6-component surrogate under non-sooting conditions.</a> Combust. Flame. 156 (8), 1594-1603 (2009).</li><li>Lefkowitz, J. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chemical+kinetic+study+of+tertiary-butanol+in+a+flow+reactor+and+a+counterflow+diffusion+flame.">A chemical kinetic study of tertiary-butanol in a flow reactor and a counterflow diffusion flame.</a> Combust. Flame. 159 (3), 968-978 (2012).</li><li>Dryer, F. L., Haas, F. M., Santner, J., Farouk, T. I., Chaos, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interpreting+chemical+kinetics+from+complex+reaction-advection-diffusion+systems:+Modeling+of+flow+reactors+and+related+experiments.">Interpreting chemical kinetics from complex reaction-advection-diffusion systems: Modeling of flow reactors and related experiments.</a> Prog Energ Combust. 44, 19-39 (2014).</li><li>Zhao, H., Yang, X., Ju, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+studies+of+ozone+assisted+low+temperature+oxidation+of+dimethyl+ether+in+a+flow+reactor+using+molecular-beam+mass+spectrometry.">Kinetic studies of ozone assisted low temperature oxidation of dimethyl ether in a flow reactor using molecular-beam mass spectrometry.</a> Combust. Flame. 173, 187-194 (2016).</li><li>O&#223;wald, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combustion+of+butanol+isomers+-+A+detailed+molecular+beam+mass+spectrometry+investigation+of+their+flame+chemistry.">Combustion of butanol isomers - A detailed molecular beam mass spectrometry investigation of their flame chemistry.</a> Combust. Flame. 158 (1), 2-15 (2011).</li><li>Herrmann, F., O&#223;wald, P., Kohse-H&#246;inghaus, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometric+investigation+of+the+low-temperature+dimethyl+ether+oxidation+in+an+atmospheric+pressure+laminar+flow+reactor.">Mass spectrometric investigation of the low-temperature dimethyl ether oxidation in an atmospheric pressure laminar flow reactor.</a> P Combust Inst. 34 (1), 771-778 (2013).</li><li>Li, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+and+kinetic+modeling+study+of+tetralin+pyrolysis+at+low+pressure.">Experimental and kinetic modeling study of tetralin pyrolysis at low pressure.</a> P Combust Inst. 34 (1), 1739-1748 (2013).</li><li>O&#223;wald, P., K&#246;hler, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+atmospheric+pressure+high-temperature+laminar+flow+reactor+for+investigation+of+combustion+and+related+gas+phase+reaction+systems.">An atmospheric pressure high-temperature laminar flow reactor for investigation of combustion and related gas phase reaction systems.</a> Rev Sci Instum. 86 (10), 105109 (2015).</li><li>O&#223;wald, P., Whitside, R., Sch&#228;ffer, J., K&#246;hler, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+experimental+flow+reactor+study+of+the+combustion+kinetics+of+terpenoid+jet+fuel+compounds:+Farnesane,+p-menthane+and+p-cymene.">An experimental flow reactor study of the combustion kinetics of terpenoid jet fuel compounds: Farnesane, p-menthane and p-cymene.</a> Fuel. 187, 43-50 (2017).</li><li>Kathrotia, T., Naumann, C., O&#223;wald, P., K&#246;hler, M., Riedel, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetics+of+Ethylene+Glycol:+The+first+validated+reaction+scheme+and+first+measurements+of+ignition+delay+times+and+speciation+data.">Kinetics of Ethylene Glycol: The first validated reaction scheme and first measurements of ignition delay times and speciation data.</a> Combust. Flame. 179, 172-184 (2017).</li><li>Hansen, N., Cool, T. A., Westmoreland, P. R., Kohse-H&#246;inghaus, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+contributions+of+flame-sampling+molecular-beam+mass+spectrometry+to+a+fundamental+understanding+of+combustion+chemistry.">Recent contributions of flame-sampling molecular-beam mass spectrometry to a fundamental understanding of combustion chemistry.</a> Prog Energ Combust. 35 (2), 168-191 (2009).</li><li>Qi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combustion+chemistry+probed+by+synchrotron+VUV+photoionization+mass+spectrometry.">Combustion chemistry probed by synchrotron VUV photoionization mass spectrometry.</a> P Combust Inst. 34 (1), 33-63 (2013).</li><li>Biordi, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+beam+mass+spectrometry+for+studying+the+fundamental+chemistry+of+flames.">Molecular beam mass spectrometry for studying the fundamental chemistry of flames.</a> Prog Energ Combust. 3 (3), 151-173 (1977).</li><li>K&#246;hler, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Speciation+data+for+fuel-rich+methane+oxy-combustion+and+reforming+under+prototypical+partial+oxidation+conditions.">Speciation data for fuel-rich methane oxy-combustion and reforming under prototypical partial oxidation conditions.</a> Chem Eng Sci. 139, 249-260 (2016).</li><li>O&#223;wald, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+flame+chemistry+tracing+by+imaging+photoelectron+photoion+coincidence+spectroscopy.">In situ flame chemistry tracing by imaging photoelectron photoion coincidence spectroscopy.</a> Rev Sci Instum. 85 (2), 025101 (2014).</li><li>O&#223;wald, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combustion+Chemistry+of+the+Butane+Isomers+in+Premixed+Low-Pressure+Flames.">Combustion Chemistry of the Butane Isomers in Premixed Low-Pressure Flames.</a> Zeitschrift f&#252;r Physikalische Chemie. 225, 1029 (2011).</li><li>Schenk, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detailed+mass+spectrometric+and+modeling+study+of+isomeric+butene+flames.">Detailed mass spectrometric and modeling study of isomeric butene flames.</a> Combust. Flame. 160 (3), 487-503 (2013).</li><li>Li, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+benzene-formation+paths+in+a+fuel-rich+cyclohexane+flame.">Multiple benzene-formation paths in a fuel-rich cyclohexane flame.</a> Combust. Flame. 158 (11), 2077-2089 (2011).</li><li>Bierkandt, T., Hemberger, P., Osswald, P., Kohler, M., Kasper, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+in+m-xylene+decomposition+under+fuel-rich+conditions+by+imaging+photoelectron+photoion+coincidence+spectroscopy.">Insights in m-xylene decomposition under fuel-rich conditions by imaging photoelectron photoion coincidence spectroscopy.</a> P Combust Inst. 36 (1), 1223-1232 (2017).</li><li>Taatjes, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enols+Are+Common+Intermediates+in+Hydrocarbon+Oxidation.">Enols Are Common Intermediates in Hydrocarbon Oxidation.</a> Science. 308 (5730), 1887-1889 (2005).</li><li>Li, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+experimental+study+of+the+rich+premixed+ethylbenzene+flame+at+low+pressure.">An experimental study of the rich premixed ethylbenzene flame at low pressure.</a> P Combust Inst. 32 (1), 647-655 (2009).</li><li>Yuan, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comprehensive+experimental+and+kinetic+modeling+study+of+ethylbenzene+combustion.">A comprehensive experimental and kinetic modeling study of ethylbenzene combustion.</a> Combust. Flame. 166, 255-265 (2016).</li><li>Hansen, N., Skeen, S. A., Michelsen, H. A., Wilson, K. R., Kohse-Hoinghaus, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flame+experiments+at+the+advanced+light+source:+new+insights+into+soot+formation+processes.">Flame experiments at the advanced light source: new insights into soot formation processes.</a> J Vis Exp. (87), e51369 (2014).</li><li>Qi, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isomeric+identification+of+polycyclic+aromatic+hydrocarbons+formed+in+combustion+with+tunable+vacuum+ultraviolet+photoionization.">Isomeric identification of polycyclic aromatic hydrocarbons formed in combustion with tunable vacuum ultraviolet photoionization.</a> Rev Sci Instum. 77 (8), 084101 (2006).</li><li>Hansen, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2D-imaging+of+sampling-probe+perturbations+in+laminar+premixed+flames+using+Kr+X-ray+fluorescence.">2D-imaging of sampling-probe perturbations in laminar premixed flames using Kr X-ray fluorescence.</a> Combust. Flame. 181, 214-224 (2017).</li></ol>

The presented combination of an atmospheric high-temperature flow reactor with a molecular-beam mass spectrometry detection system enables quantitative speciation data for a range of operating conditions. Several studies21,22,23,27 demonstrated the flexibility of the experiment starting from rich methane conditions relevant for partial oxidation phenomena (&#966; = 2.5), to investigating the co...

Understanding combustion processes in the wake of modern, low-emission fuels from renewable resources is a challenge for today&#39;s societies&#39; ecological and economic topics. They have the potential to reduce our dependence on fossil fuels, offset CO2 emissions, and have a positive impact on harmful pollutant emissions such as soot and its toxic precursors1. Combining this fast growing field with their utilization in modern combustor systems, the demand on a fundamental understanding of the governing chemical and physical processes has increased dramatically2. Even today, the complex chemical reaction networks resulting from the radical chain reactions are still not fully understood. To analyze or even control phenomena like pollutant formation or (auto) ignition processes, the detailed knowledge of chemical reaction networks is a crucial piece of the puzzle3.
To investigate and understand those chemical reaction networks, experimental and numerical approaches are mandatory. Experimentally, the combustion chemistry is typically studied by applying experiments with simplified and well controlled flow environments to target specific questions. The high complexity and dynamics of individual sub processes prevent exact reproduction of the conditions of technical combustors by the fundamental experiments, while allowing the tracking of the designated key features such as temperature, pressure, heat release, or chemical species. Early on, the need for different experimental approaches became apparent, each tackling a specific question and providing a subsequent set of information contributing to the overall global picture of the combustion chemistry. To cover the full range of conditions and gather those subsequent information sets to describe complex conditions occurring in technical systems various approaches were successfully developed. Well established techniques include:
<ul>
	<li>Shock tubes4,5,6 and rapid compression machines7. These devices provide high control of pressure and temperature over a wide range. However, the accessible reaction time and suitable analytical techniques are limited.</li>
	<li>Laminar premixed flames3,8,9,10,11 are ideal to gain high-temperature conditions in combination with a simple flow field. Since the spatial dimension of the reaction zone decreases with increasing pressure, premixed flames are typically investigated at low-pressure conditions for speciation purposes.</li>
	<li>Counterflow diffusion flames12,13,14,15 are ideal for investigating the flamelet regime in turbulent combustion. They mimic the strain due to inhomogeneities in a real turbulent flow, but are, again, highly limited in analytical speciation techniques.</li>
	<li>Various reactor experiments16,17,18 (static, stirred and plug-flow) provide access to high-pressure environments, while temperatures are typically lower compared to flame environments. Common approaches are:
	<ul>
		<li>Static reactors are widely used for e.g. pulse photolysis experiments, but are in general limited by long residence times and low temperatures.</li>
		<li>Jet-stirred reactors, i.e. gas version of a perfectly stirred reactor (PSR), rely on the efficient mixing of the gas phase and can be operated at steady state with constant residence time, temperature and pressure, making it easy to model. However, molecules have time to migrate to the hot surfaces and undergo heterogeneous reactions.</li>
		<li>Numerous flow reactor approaches are known, with the plug flow reactor (PFR) as one of the most popular approaches for describing chemical reactions in continuous, flowing systems of cylindrical geometry. Plug flow conditions at steady state are assumed with fixed residence time of the plug as a function of its position for ideal PFRs.</li>
	</ul>
	</li>
</ul>
Complementary to those valuable techniques in the field of experimental combustion kinetics, a high-temperature laminar flow reactor experiment19,20 employing the molecular beam mass spectrometry (MBMS) technique for tracing species development in detail is presented21,22 herein. Laminar flow conditions, working at atmospheric pressure and accessible temperatures up to 1,800 K are the main characteristics of the flow reactor, while the sensitive MBMS technique allows the detection of almost all chemical species present in the combustion process. This includes highly reactive species such as radicals that are not or hardly traceable with other detection methods. The MBMS technique is widely used for the detailed investigation of reaction networks in flames of conventional and modern alternative fuels, such as alcohols or ethers23,24,25 and has demonstrated to be of great value for modern kinetic model development.
Figure 1 shows the schematic of the high-temperature flow reactor with a zoomed frame of the sampling probe (A) and two pictures highlighting the overall experiment (B) and the probe setup (C). The system can be divided in two segments: first, the high-temperature flow reactor with gas supplies and vaporizer system and second, the MBMS time-of-flight detection system. In operation, the exit of the flow tube is mounted directly to the sampling nozzle of the MBMS system. The gas is sampled directly from the reactor outlet and transferred to the high-vacuum detection system. Here, ionization is performed by electron ionization with subsequent time-of-flight detection.
The reactor has a 40-mm inner diameter ceramic (Al2O3) pipe of 1,497 mm length placed in a high temperature oven (e.g., Gero, Type HTRH 40-1000). The total heated section is 1,000 mm in length. Gases are fed premixed and pre-vaporized into the reactor by a tempered flange (typically tempered to ~80 &#176;C). The highly diluted (ca. 99 vol% in Ar), laminar flowing reactant mixture passes through a known temperature profile (details on temperature characterization will be given below). Detection of the gas composition takes place at the reactor outlet as a function of the oven temperature. Measurements are performed at constant inlet mass flow, while a monotonically decreasing temperature ramp (-200 K/h) is applied to the oven in the range of 1,800 K to 600 K. Note that similar results may be obtained when distinct temperatures are measured at isothermal oven temperatures and thermal inertia is considered properly. The thermal stabilization of the system still takes some time and the temperature ramp is selected as a compromise of averaging time for a (negligible) small temperature increment and total measurement time per series. The averaging time (45 s) of the MBMS corresponds to 2.5 K. The resulting residence times are around 2 s (at 1,000 K) for the given conditions. Finally, due to the temperature reproducibility, a relative precision of the measured temperatures of &#177;5 K or better can be stated for the present reactor experiment.
Figure 2 shows the schematic of the vaporizing system, optimized to investigate even complex hydrocarbon mixtures such as technical jet fuels. All input streams are metered in high precision (accuracy &#177;0.5 %) by Coriolis mass flow meters. Vaporization of the fuel is realized by a commercial vaporizer system at temperatures up to 200 &#176;C. All supply lines with pre-vaporized fuels are preheated with temperatures of typically 150 &#176;C to prevent condensation of the liquid fuels, while avoiding thermal degradation at the same time. Complete and stable vaporization is routinely checked and may even occur at temperatures below the normal boiling point of the respective fuels. Complete evaporation was ensured by the small fuel fraction and the low partial pressure (typically below 100 Pa) needed.
The gases are sampled by a quartz cone at the centerline of the reactor exit at ambient pressures (around 960 hPa) as seen in more detail in the zoomed frame of Figure 1. The nozzle tip has a 50 &#956;m orifice, which is located roughly 30 mm inside the ceramic tube at the end of the reaction zone. Note, that the sampling location is fixed with respect to the inlet. Thermal expansion of the oven tube only takes place at the outlet, which is not mechanically connected to the sampling system resulting in a temperature independent length of the reaction segment. All reactions are immediately quenched due to the formation of a molecular beam, when gasses are expanded into high vacuum (two differential pumping stages; 10-2 and 10-4 Pa)25,26. The sample is guided to the ion source of an electron impact (EI) time-of-flight (TOF) mass spectrometer (mass resolution R = 3,000) capable of determining the exact mass of the present species in suitable precision to determine the elemental composition within a C/H/O system. The electron energy is set to low values (typically 9.5-10.5 eV) in order to minimize fragmentation due to the ionization process. Note that the diluent and reference species argon is still detectable due to the broad energy distribution of the ionizing electrons (1.4 eV FWHM). While Ar can be measured with good S/N, the low electron energy does not allow for sufficient determination of the major species (H2O, CO2, CO, H2, O2, and fuel) profiles, which are present in significant lower concentrations.
In addition to the detection by TOF, a residual gas analyzer (RGA), i.e. a quadrupole mass spectrometer, is placed in the ionization chamber to monitor the six species above with a higher electron energy (70 eV) simultaneously to the MBMS-TOF measurements.

<table>
	<tbody>
		<tr>
			<td>Time-Of-Flight MBMS</td>
			<td>Kaesdorf</td>
			<td>n.a.</td>
			<td>custom design</td>
		</tr>
		<tr>
			<td>Molecular Beam Samling Interface</td>
			<td>self made</td>
			<td>n.a.</td>
			<td>custom design</td>
		</tr>
		<tr>
			<td>Laminar Flow Reactor</td>
			<td>Gero</td>
			<td>Type HTRH 40-1000</td>
			<td>custom design</td>
		</tr>
		<tr>
			<td>Quadrupole MS</td>
			<td>Hiden</td>
			<td>HAL/3F 301</td>
			<td>adapted to ionization chamber</td>
		</tr>
		<tr>
			<td>Vaporizer</td>
			<td>Bronkhorst</td>
			<td>CEM</td>
			<td>Vaporizer</td>
		</tr>
		<tr>
			<td>Mass Flow Meter</td>
			<td>Bronkhorst</td>
			<td>Mini Cori-Flow M12, M13, M14</td>
			<td>Flow Controller</td>
		</tr>
		<tr>
			<td>Jet A-1</td>
			<td>n.a.</td>
			<td>n.a.</td>
			<td>Standard Jet fuel of interest</td>
		</tr>
		<tr>
			<td>Metal syringe</td>
			<td>Hugo Sachs</td>
			<td>70-2252</td>
			<td>Fuel Supply</td>
		</tr>
		<tr>
			<td>Heating Hoses</td>
			<td>Hillesheim</td>
			<td>HMI series</td>
			<td>Gas Preheating</td>
		</tr>
		<tr>
			<td>Gas</td>
			<td>Linde</td>
			<td>Ar, O2</td>
			<td>Diluent, Oxidizer</td>
		</tr>
	</tbody>
</table>

combustion chemistry of fuels: quantitative speciation data obtained from an atmospheric high-temperature flow reactor with coupled molecular-beam mass spectrometer

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This flexible tool offers a detailed observation of chemical gas-phase kinetics in reacting flows under well-controlled conditions. The vast range of operating conditions available in a laminar flow reactor enables access to extraordinary combustion applications that are typically not achievable by flame experiments. These include rich conditions at high temperatures relevant for gasification processes, the peroxy chemistry governing the low temperature oxidation regime or investigations of complex technical fuels. The presented setup allows measurements of quantitative speciation data for reaction model validation of combustion, gasification and pyrolysis processes, while enabling a systematic general understanding of the reaction chemistry. Validation of kinetic reaction models is generally performed by investigating combustion processes of pure compounds. The flow reactor has been enhanced to be suitable for technical fuels (e.g. multi-component mixtures like Jet A-1) to allow for phenomenological analysis of occurring combustion intermediates like soot precursors or pollutants. The controlled and comparable boundary conditions provided by the experimental design allow for predictions of pollutant formation tendencies. Cold reactants are fed premixed into the reactor that are highly diluted (in around 99 vol% in Ar) in order to suppress self-sustaining combustion reactions. The laminar flowing reactant mixture passes through a known temperature field, while the gas composition is determined at the reactors exhaust as a function of the oven temperature. The flow reactor is operated at atmospheric pressures with temperatures up to 1,800 K. The measurements themselves are performed by decreasing the temperature monotonically at a rate of -200 K/h. With the sensitive MBMS technique, detailed speciation data is acquired and quantified for almost all chemical species in the reactive process, including radical species.

A typical mass spectrum of the sampled gas composition is shown in Figure 3. With the given setup of a mass resolution of approx. 3,000, species up to m/z = 260 u can be detected within the C/H/O system. After a mass calibration procedure, the peaks are integrated for each mass-to-charge (m/z) ratio with deconvolution algorithms for evaluating under-resolved signals. After background and fragmentation corrections, the signal can be quantified using the approp...

Watch this Scientific Journal Video about Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectr

Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer

An investigation of the oxidative combustion chemistry of novel biofuels, fuel components, or jet fuels by comparison of quantitative speciation data is presented. The data can be used for kinetic model validation and enables fuel assessment strategies.This manuscript describes the atmospheric high-temperature flow reactor and demonstrates its capabilities.

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This ...

The overall goal of this experiment is to get an overview of reactive chemical species in an combustion process and investigate the combustion chemistry of technical fuels and fuel components. This method can help to answer questions in the field of combustion chemistry and pollutant formation, such as soot formation. One of the main advantages of this technique is to get an overview of the chemical species and detect even highly reactive radical species without prior knowledge.This flexible tool offers us an observation of the chemical gas-phase kinetics under well-controlled conditions. The data can be used for kinetic model validation and fuel assessment strategies. The vast range of operating conditions available for such a laminar flow reactor enables access to combustion applications that are typically not achievable by flame experiments.The schematic of the flow reactor system shows all major components. The oven is coupled to the MBMS setup with the time-of-flight, or TOF Detection System, mount the to the sampling direction and to a gas supply system. First, heat the oven to the designated start temperature, which is the highest temperature in the designated measurement series.Prepare the TOF spectrometer for intermediate species detection. Now prepare the quadrupole spectrometer for major species detection by placing it in the ionization chamber of the MBMS system and starting the software. To prepare the fuel supply system, first prepare a metal syringe for fuel supply.Then fill the metal syringe with 30 milliliters of the fuel sample. Following this, pressurize the metal syringe up to five bar by opening the valve and adding pressurized air to the system. Then heat up the vaporizer and fuel supply lines.For this experimental design, set the water cooling system to 80 degrees Celsius so that the diluted fuel cannot recondense at the coldest spot in the system, which is the temperate in that flange to the oven. Place the oven to the sampling position which is close to the plateau value of the spatial temperature profile of the oven. Next, start the diluent of choice by adding gas to the Coriolis mass flow meter.Start continuous data recording by clicking on the start buttons in the TOF and quadrupole software. Add oxygen as an oxidizer by setting the appropriate flow condition of the Coriolis mass flow meter software. Observe the incoming oxidizer as a new peak in the mass spectrum.Next, add fuel by setting the appropriate flow condition of the Coriolis mass flow meter. Check the spectre to confirm if complete oxidation is achieved and a stable carbon dioxide mass signal is observed. After the stabilization period, apply a continuous temperature decay ramp of 200 Kelvin per hour to the oven, which leads to typical measurement times of two hours per run.At a specific oven temperature during the ramp, observe a rapid change of the mass spectre with sole combustion products disappearing and small combustion intermediates appearing. With further decreasing temperature, visible intermediates become larger and larger. At cold oven temperatures, only the signal of fuel compounds and oxygen can be observed.When the final temperature is stabilized, switch off the oxidizer. Continue recording measurements and obtain fuel characterization measurements at conditions without oxidizer. Following this, switch off the fuel in the Coriolis mass flow meter software by setting the value to zero.Then stop the data recording by clicking the stop buttons in the software. For calibration issues, mount a closed chamber in front of the sampling cone. Then open the valve to the pump to evacuate the chamber.Apply binary mixtures or commercial calibration gasses for calibration. Next, start TOF software again without data recording. Adjust the pressure in the calibration chamber by a needle valve to obtain a signal intensity above the signal-to-noise ratio and below the saturation limit.Following this, start the calibration measurements and enable data recording. At each recorded temperature for each chosen species, calculate its mole fraction from the corresponding signal. Then plug the mole fraction profiles versus the oven temperature.A typical mass spectrum of the sampled gas composition is shown here. The peaks are integrated for each mass-to-charge ratio for evaluating not-fully resolved signals. Signals are plotted against the average temperature of the 2.5 Kelvin interval, resulting in a typical mole fraction versus oven temperature plot.The spatial mole fraction profiles of formaldehyde and acetylene obtained from a stoichiometric methane measurement shows agreement between the measured data and kinetic model values for the main components and intermediate species. The potential jet fuel compound, p-menthane, featuring major species profiles, is depicted here. The stoichiometry dependence of ethylene and formaldehyde, and the selected intermediate species for stoichiometric conditions are obtained.In the flow reactor setup, the oxygen and fuel profile start at a maximum at low temperatures and are consumed as the temperature increases. In depth analysis shows a similar decay for the hydrocarbon species while aromatic species show a distinct plateau region Higher mole fraction for soot precursors, propargyl radical and benzene, are measured for p-methane compared to Jet A-1 and farnesane, indicating a higher tendency to form pollutants. For farnesane, lower mole fractions for both species are measured compared to p-methane and Jet A-1 fuel.After its development, this technique paved a way for researchers in the field of future fuel design strategies to explore combustion kinetics and pollutant formation for conventional and alternative fuels and components.

combustion-chemistry-fuels-quantitative-speciation-data-obtained-from

Research

JoVE Journal

Chemistry

PTR-ToF-MS Coupled with an Automated Sampling System and Tailored Data Analysis for Food Studies: Bioprocess Monitoring, Screening and Nose-space Analysis

Proton Transfer Reaction (PTR), combined with a Time-of-Flight (ToF) Mass Spectrometer (MS) is an analytical approach based on chemical ionization that belongs to the Direct-Injection Mass Spectrometric (DIMS) technologies. These techniques allow the rapid determination of volatile organic compounds (VOCs), assuring high sensitivity and accuracy. In general, PTR-MS requires neither sample preparation nor sample destruction, allowing real time and non-invasive analysis of samples. PTR-MS are exploited in many fields, from environmental and atmospheric chemistry to medical and biological sciences. More recently, we developed a methodology based on coupling PTR-ToF-MS with an automated sampler and tailored data analysis tools, to increase the degree of automation and, consequently, to enhance the potential of the technique. This approach allowed us to monitor bioprocesses (e.g. enzymatic oxidation, alcoholic fermentation), to screen large sample sets (e.g. different origins, entire germoplasms) and to analyze several experimental modes (e.g. different concentrations of a given ingredient, different intensities of a specific technological parameter) in terms of VOC content. Here, we report the experimental protocols exemplifying different possible applications of our methodology: i.e. the detection of VOCs released during lactic acid fermentation of yogurt (on-line bioprocess monitoring), the monitoring of VOCs associated with different apple cultivars (large-scale screening), and the in vivo study of retronasal VOC release during coffee drinking (nosespace analysis).

Proton Transfer Reaction Time of Flight Mass Spectrometry allows high-sensitivity, rapid and non-invasive analysis of volatile organic compounds. To demonstrate its potential, we give three examples: lactic acid fermentation of yogurt (on-line bioprocess monitoring), different apple genotypes (large-scale screening), and retronasal space after drinking coffee (nosespace analysis).

Proton Transfer Reaction (PTR), combined with a Time-of-Flight (ToF) Mass Spectrometer (MS) is an analytical approach based on chemical ionization that ...

Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry

A flowing microwave plasma based methodology for converting electric energy into internal and/or translational modes of stable molecules with the purpose of efficiently driving non-equilibrium chemistry is discussed. The advantage of a flowing plasma reactor is that continuous chemical processes can be driven with the flexibility of startup times in the seconds timescale. The plasma approach is generically suitable for conversion/activation of stable molecules such as CO2, N2 and CH4. Here the reduction of CO2 to CO is used as a model system: the complementary diagnostics illustrate how a baseline thermodynamic equilibrium conversion can be exceeded by the intrinsic non-equilibrium from high vibrational excitation. Laser (Rayleigh) scattering is used to measure the reactor temperature and Fourier Transform Infrared Spectroscopy (FTIR) to characterize in situ internal (vibrational) excitation as well as the effluent composition to monitor conversion and selectivity.

This article describes a flowing microwave reactor that is used to drive efficient non-equilibrium chemistry for the application of conversion/activation of stable molecules such as CO2, N2 and CH4. The goal of the procedure described here is to measure the in situ gas temperature and gas conversion.

A flowing microwave plasma based methodology for converting electric energy into internal and/or translational modes of stable molecules with the purpose ...

A Practical Guide on Coupling a Scanning Mobility Sizer and Inductively Coupled Plasma Mass Spectrometer (SMPS-ICPMS)

A large variety of analytical methods are available to characterize particles in aerosols and suspensions. The choice of the appropriate technique depends on the properties to be determined. In many fields information about particle size and chemical composition are of great importance. While in aerosol techniques particle size distributions of gas-borne particles are determined online, their elemental composition is commonly analyzed offline after an appropriate sampling and preparation procedure. To obtain both types of information online and simultaneously, a hyphenated setup was recently developed, including a Scanning Mobility Particle Sizer (SMPS) and an Inductively Coupled Plasma Mass Spectrometer (ICPMS). This allows first to classify the particles with respect to their mobility diameter, and then to determine their number concentration and elemental composition in parallel. A Rotating Disk Diluter (RDD) is used as the introduction system, giving more flexibility regarding the use of different aerosol sources. In this work, a practical guide is provided describing the different steps for establishing this instrumentation, and how to use this analysis tool. The versatility of this hyphenated technique is demonstrated in example measurements on three different aerosols generated out of a) a salt solution, b) a suspension, and c) emitted by a thermal process.

A Practical Guide on Coupling a Scanning Mobility Sizer and Inductively Coupled Plasma Mass Spectrometer SMPS-ICPMS

In this work a practical guide is provided, describing the different steps to establish the coupling of SMPS and ICPMS systems, and how to use them. Three descriptive examples are presented.

A large variety of analytical methods are available to characterize particles in aerosols and suspensions. The choice of the appropriate technique depends ...

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to the gas phase, and efficiently transferred to a detection system. Fizzy extraction takes advantage of the effervescence phenomenon. First, a carrier gas (here, carbon dioxide) is dissolved in the sample by applying overpressure and stirring the sample. Second, the sample chamber is decompressed abruptly. Decompression leads to the formation of numerous carrier gas bubbles in the sample liquid. These bubbles assist the release of the dissolved analyte species from the liquid to the gas phase. The released analytes are immediately transferred to the atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The ionizable analyte species give rise to mass spectrometric signals in the time domain. Because the release of the analyte species occurs over short periods of time (a few seconds), the temporal signals have high amplitudes and high signal-to-noise ratios. The amplitudes and areas of the temporal peaks can then be correlated with concentrations of the analytes in the liquid samples subjected to fizzy extraction, which enables quantitative analysis. The advantages of fizzy extraction include: simplicity, speed, and limited use of chemicals (solvents).

Fizzy extraction is a new laboratory technique for analysis of volatile and semivolatile compounds. A carrier gas is dissolved in the liquid sample by applying overpressure and stirring the sample. The sample chamber is then decompressed. The analyte species are liberated to the gas phase due to effervescence.

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to ...

Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental exposure in a non-invasive manner. In this work, we present a protocol to characterize the exhaled VOCs in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry (Sec-nanoESI-HRMS). The homemade Sec-nanoESI source was readily set up based on a commercial nanoESI source. Hundreds of peaks were observed in the background-subtracted mass spectra of exhaled breath, and the mass accuracy values are -4.0-13.5 ppm and -20.3-1.3 ppm in the positive and negative ion detection modes, respectively. The peaks were assigned with accurate elemental composition according to the accurate mass and isotopic pattern. Less than 30 s is used for one exhalation measurement, and it takes approximately 7 min for six replicated measurements.

A protocol for characterizing chemical composition of exhaled breath in real time by using secondary nanoelectrospray ionization coupled to high resolution mass spectrometry is demonstrated.

Exhaled volatile organic compounds (VOCs) have aroused considerable interest, since they can serve as biomarkers for disease diagnosis and environmental ...

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and cost savings through the &#34;scaling out&#34; strategy as opposed to the traditional &#34;scaling up&#34;. Herein, we report the reaction of diphenyldiazomethane with p-nitrobenzoic acid in both batch and flow modes. To effectively transfer the reaction from batch to flow mode, it is essential to first conduct the reaction in batch. As a consequence, the reaction of diphenyldiazomethane was first studied in batch as a function of temperature, reaction time, and concentration to obtain kinetic information and process parameters. The glass flow reactor set-up is described and combines two types of reaction modules with &#34;mixing&#34; and &#34;linear&#34; microstructures. Finally, the reaction of diphenyldiazomethane with p-nitrobenzoic acid was successfully conducted in the flow reactor, with up to 95% conversion of the diphenyldiazomethane in 11 min. This proof of concept reaction aims to provide insight for scientists to consider flow technology&#39;s competitiveness, sustainability, and versatility in their research.

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Flow chemistry carries environmental and economic advantages by leveraging superior mixing, heat transfer and cost benefits. Herein, we provide a blueprint to transfer chemical processes from batch to flow mode. The reaction of diphenyldiazomethane (DDM) with p-nitrobenzoic acid, conducted in batch and flow, was chosen for proof of concept.

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and ...

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables the acquisition of photoluminescence spectra covering the time regime from nanoseconds up to 0.1 s. This enables us to follow the changes in the intensity (decay) and emission of the spectra over time. Using this method, it is possible to study diverse photophysical phenomena, such as the emission of phosphorescence, and the contributions of prompt and delayed fluorescence in molecules showing thermally activated delayed fluorescence (TADF). Remarkably, all spectra and decays are obtained in a single experiment. This can be done for solids (thin film, powder, crystal) and liquid samples, where the only limitations are the spectral sensitivity of the camera and the excitation wavelength (532 nm, 355 nm, 337 nm, and 266 nm). This technique is, thus, very important when investigating the excited state dynamics in organic emitters for their application in organic light-emitting diodes and other areas where triplet harvesting is of paramount importance. Since triplet states are strongly quenched by oxygen, emitters with efficient TADF luminescence, or those showing room temperature phosphorescence (RTP), must be correctly prepared in order to remove any dissolved oxygen from solutions and films. Otherwise, no long-lived emission will be observed. The method of degassing solid samples as presented in this work is basic and simple, but the degassing of liquid samples creates additional difficulties and is particularly interesting. A method of minimizing solvent loss and changing the sample concentration, while still enabling to remove oxygen in a very efficient and a repeatable manner, is presented in this work.

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables ...

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO2, and Au/TiO2) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided.

For a continuous and scalable synthesis of noble-metal-based nanocomposites, a novel photocatalytic reactor is developed and its structure, operation principles, and product quality optimization strategies are described.

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic ...

Reducing Willow Wood Fuel Emission by Low Temperature Microwave Assisted Hydrothermal Carbonization

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative environmental impact and slag formation. The selected short rotation coppice (SRC) willow wood has a high ash content (<img alt="Equation 1" src="/files/ftp_upload/58970/58970eq1.jpg" /> = 1.96%) and, therefore, a high content of emission and slag precursors. Therefore, the reduction of minerals from SRC willow wood by low temperature microwave assisted hydrothermal carbonization (MAHC) at 150 &#176;C, 170 &#176;C, and 185 &#176;C is investigated. An advantage of MAHC over conventional reactors is an even temperature conductance in the reaction medium, as microwaves penetrate the whole reactor volume. This allows a better temperature control and a faster cooldown. Therefore, a succession of depolymerization, transformation and repolymerization reactions can be analyzed effectively. In this study, the analysis of the mass loss, ash content and composition, heating values and molar O/C and H/C ratios of the treated and untreated SCR willow wood showed that the mineral content of the MAHC coal was reduced and the heating value increased. The process water showed a decreasing pH and contained furfural and 5-methylfurfural. A process temperature of 170 &#176;C showed the best combination of energy input and ash component reduction. The MAHC allows a better understanding of the hydrothermal carbonization process, while a large-scale industrial application is unlikely because of the high investment costs.

A protocol for the emission precursor depletion from low quality biomass by low temperature microwave assisted hydrothermal carbonization treatment is presented. This protocol includes the microwave parameters and the analysis of the biocoal product and process water.

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative ...

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

The computational study of the formation and growth of atmospheric aerosols requires an accurate Gibbs free energy surface, which can be obtained from gas phase electronic structure and vibrational frequency calculations. These quantities are valid for those atmospheric clusters whose geometries correspond to a minimum on their potential energy surfaces. The Gibbs free energy of the minimum energy structure can be used to predict atmospheric concentrations of the cluster under a variety of conditions such as temperature and pressure. We present a computationally inexpensive procedure built on a genetic algorithm-based configurational sampling followed by a series of increasingly accurate screening calculations. The procedure starts by generating and evolving the geometries of a large set of configurations using semi-empirical models then refines the resulting unique structures at a series of high-level ab initio levels of theory. Finally, thermodynamic corrections are computed for the resulting set of minimum-energy structures and used to compute the Gibbs free energies of formation, equilibrium constants, and atmospheric concentrations. We present the application of this procedure to the study of hydrated glycine clusters under ambient conditions.

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

The atmospheric concentrations of weakly bound molecular clusters can be computed from the thermochemical properties of low energy structures found through a multi-step configurational sampling methodology utilizing a genetic algorithm and semi-empirical and ab initio quantum chemistry.

The computational study of the formation and growth of atmospheric aerosols requires an accurate Gibbs free energy surface, which can be obtained from gas ...