An investigation into the conversion of specific carbon atoms in oleic acid and methyl oleate to particulate matter in a diesel engine and tube reactor

The paper is concerned with particulate formation from the fuels oleic acid and methyl oleate. In particular the paper reports, quantitatively, the propensity of individual carbon atoms in these two molecules in being converted to particulate. The conversion of individual carbon atoms to particulate was traced by 'labelling' individual carbon atoms in those two fuel molecules with isotopic carbon-13 (C) and then measuring how many of the labelled atoms was found in the particulate. This allowed the measuring of the conversion rates of individual fuel carbon atoms to particulate. In the case of oleic acid, three carbon atoms were selected as being particularly relevant to particulate formation, and C labelled. One of the carbon atoms was double bonded to the oxygen atom on the carboxylic acid group; and the other two were part of the oleic acid molecule alkyl chain and double bonded to each other. In the case of the methyl oleate, one carbon atom was C labelled. This was the carbon atom that was double bonded to one of the oxygen atoms of the ester group. Experimental results are presented for particulate matter (PM) formed in a laminar flow tube reactor, and also in a direct injection compression ignition engine. The tube reactor has been used for the pyrolysis of oleic acid and methyl oleate at 1300 °C, under oxygen-free conditions and at air-fuel equivalence ratios (λ) of 0.1, and 0.2. Samples of PM were also collected from the compression ignition engine at an intermediate engine load. Isotope ratio mass spectrometry (IRMS) has been used to determine the relative abundance of C in the initial fuel and in the resulting PM. Significant differences in the relative conversion rates of individual carbon atoms are reported; a negligible contribution to PM from the carbon atom directly bonded to two oxygen atoms was found in both the engine and reactor. The labelling technique used in this paper requires low quantities of C labelled molecules to enrich otherwise unlabelled oleic acid; enrichment is at volumetric concentrations typically less than 0.7% (v/v). In addition, emissions data from the engine and tube reactor, including unburned hydrocarbons, CO, CO, NO, and PM size and number distributions measured by differential mobility spectrometer, are also presented

Isotopic Tracers for Combustion Research

This review article deals with the use of isotopic tracers in the field of combustion science. A number of researchers have reported the use of isotopic techniques, which have been employed to solve a wide range of combustion problems. Radioactive and stable isotopes have been utilized as tracers, including isotopes of carbon (13C and 14C), oxygen (18O), and deuterium (D). One of the main applications has been to quantitatively determine the propensity of a molecule in a mixture, or specific atom within a molecule, to form pollutant emissions. Tracer studies have also been used for the elucidation of combustion reaction pathways, and kinetic rate constant determination of elementary reactions. A number of analytical techniques have been used for isotope detection; and the merits of some of the different techniques are discussed in the context of combustion research. This article concludes by exploring emerging methods and potential future techniques and applications

The influence of fuel molecular structure on particulate emission investigated with isotope tracing

This thesis is concerned with the formation of particulate matter, a topic of scientific and practical importance due to the toxicity of particulate emissions from automotive and other combustion sources. At present, fuels are predominantly derived from fossil sources, but as production technology improves, biofuels and synthetic fuels are expected to emerge as scalable long-term sources of liquid fuels. Efforts are being made to ensure that this next-generation of fuels is cleaner burning than the last. In order to inform the production and processing of cleaner burning fuels, more needs to be known about how molecular structure influences the formation of pollutant emissions. This thesis presents research that has been carried out in order to better understand the role of functional group chemistry on the conversion of carbon atoms in the fuel to the particulate matter (PM). In particular, the propensity of individual molecules or carbon atoms within molecules to form PM is reported quantitatively. To this end, a technique using carbon-13 (13C) labelled fuel molecules was used so to track the labelled carbon atoms in the fuel to PM. The technique required only very low levels of 13C enrichment, and isotope ratio mass spectrometry equipment (IRMS) was used as a means of 13C detection. Samples of particulate matter were formed using a tube reactor, and also in a compression ignition diesel engine. The tube reactor was designed and commissioned in order to study the pyrolysis of various fuel molecules under well-controlled, homogenous conditions. The contribution to PM of a number of molecules containing various functional groups was assessed, including: alcohols, esters, aromatics, double bonded carbon atoms, a ketone, and a carboxylic acid. Tests were conducted using single-component fuels, and blended in a binary mixture with n−heptane. The results show that the contribution of carbon atoms within molecules to PM, is not equal, but depends on the local molecular structure. For example, oxygenated molecules significantly reduced the contribution to PM of the carbon atoms directly attached to oxygen. The thesis presents one of only a handful of investigations that have been published on the conversion of specific carbon atoms of various molecules to soot and particulate. It advances the field of study by providing data for validation, at the sub-molecular level, for chemical kinetic models of soot formation, and advances fundamental understanding of how fuels convert to soot and particulates

Quantification of the Fraction of Particulate Matter Derived from a Range of C-13-Labeled Fuels Blended into Heptane, Studied in a Diesel Engine and Tube Reactor

This paper presents the results of an experimental study that was carried out to determine the conversion rates to particulate matter (PM) of several liquid fuel hydrocarbon molecules and specific carbon atoms within those molecules. The fuels investigated (ethanol, n-propanol, i-propanol, acetone, and toluene) were blended in binary mixtures with n-heptane to a level of 10 mol percent. The contribution of the additive molecules to PM was quantified using a carbon-13 (13C) labeling experiment, in which the fuel of interest was enriched with 13C to serve as an atomic tracer. Measurement of the 13C/12C in the fuel and in the resulting PM was carried out using isotope ratio mass spectrometry. The fuel binary mixtures were tested under pyrolysis conditions in a tube reactor and also combusted in a direct injection compression ignition engine. In the tube reactor, samples were generated under oxygen-free pyrolysis conditions and at a temperature of 1300 °C, while the engine experiments were carried out at an intermediate load. Both in the tube reactor and in the engine it was found that, dependent on the fuel molecular structure, there were significant differences in the overall conversion rates to PM of the fuel molecules and of the “submolecular” carbon atoms. A separate experiment was also carried out in the compression ignition engine, with n-heptane as fuel, in order to determine the contribution of the engine lubrication oil to exhaust PM; the results showed that a significant portion (∼60%) of the total particulate was derived from the lubrication oil

A balance of trust in the use of government administrative data

Government departments and agencies around the world routinely collect administrative data produced by citizen interaction with the state. The UK government increasingly frames data as an ‘asset’. The potential in administrative data can be exploited by sharing and linking across datasets, but when the rhetoric of the benefits of data sharing is bound up in commercial exploitation, trustworthy motivations for sharing data come into question. Such questions are framed around two apparently conflicting public goods. The public good in re-using data to increase government efficiency and to enhance research is set against the public good in protecting privacy. Privacy is a collective as well as an individual benefit, enabling the public to participate confidently in citizen-state interactions. Balancing these public goods is challenging given rapidly evolving technology and data science. The analysis presented here draws on research undertaken by the authors as part of the Administrative Data Research Centre in England. Between 2014 and 2017, four case studies were conducted on government administrative data across education, transport, energy and health. The purpose of the research was to examine stakeholder perspectives in relation to administrative data sharing and re-use. The themes of trust, risk and consent were chosen to articulate the research questions and analysis: this article focuses on the findings related to trust. It explores the notion of trust in the collection, analysis, linkage and re-use of routinely collected government administrative data in England. It seeks to demonstrate that securing public trust in data initiatives is dependent on a broader balance of trust between a network of actors involved in data sharing and use

An overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines

Future fuels for compression ignition engines will be required both to reduce the anthropogenic carbon dioxide emissions from fossil sources and to contribute to the reductions in the exhaust levels of pollutants, such as nitrogen oxides and particulate matter. Via various processes of biological, chemical and physical conversion, feedstocks such as lignocellulosic biomass and photosynthetic micro-organisms will yield a wide variety of potential fuel molecules. Furthermore, modification of the production processes may allow the targeted manufacture of fuels of specific molecular structure. This paper therefore presents an overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines, highlighting in particular the submolecular features common to a variety of potential fuels. An increase in the straight-chain length of the alkyl moiety reduces the duration of ignition delay, and the introduction of double bonds or branching to an alkyl moiety both increase ignition delay. The movement of a double bond towards the centre of an alkyl chain, or the addition of oxygen to a molecule, can both increase and decrease the duration of ignition delay dependent on the overall fuel structure. Nitrogen oxide emissions are primarily influenced by the duration of fuel ignition delay, but in the case of hydrogen and methane pilot-ignited premixed combustion arise only at flame temperatures sufficiently high for thermal production. An increase in aromatic ring number and physical properties such as the fuel boiling point increase particulate matter emissions at constant combustion phasing

Influence of carbon number of C1–C7 hydrocarbons on PAH formation

The influence of carbon number of seven hydrocarbons (methane, ethane, propane, n-butane, i-butane, heptane and toluene) on PAH formation was investigated in a laminar tube reactor. The hydrocarbons underwent oxygen-free pyrolysis within the temperature range of 1050–1350 °C at a fixed carbon concentration of 10,000 ppm on C 1 basis. Particulate and gas phase PAHs were collected at the outlet of the reactor at pyrolysis temperature intervals of 100 °C. The particulates generated were characterised at sub-micron levels in terms of size, number and mass using a differential mobility spectrometer (DMS-500). PAHs from both the gas and particulate samples were extracted using an accelerated solvent extractor (ASE) and the extracts analysed using gas chromatography coupled to mass spectrometry (GCMS). The PAHs studied were the US EPA 16 priority PAHs with particular attention given to group B2, which are possible human carcinogens. The experimental results showed that increase in temperature of the reactor from 1050 to 1350 °C decreased the total PAH concentrations regardless of the carbon number of the hydrocarbon investigated. Increasing the carbon number of C 1 –C 7 hydrocarbons decreased the gas phase (GP) PAH concentrations at a temperature of 1350 °C, while the particulate phase (PP) PAH concentrations (as well as those of Group B2 PAHs) decreased at a temperature of 1150 °C. There was increasing and decreasing trends of total PAH concentrations with increasing carbon number of the hydrocarbons at temperatures of 1050 °C and 1350 °C respectively. Benzenoid and five-membered ring PAHs of 2–4 rings were detected in roughly similar concentrations irrespective of the carbon number of the hydrocarbon. Soot propensities, abundance of particle phase PAHs and carcinogenicity of soot particles increased substantially at a temperature of 1050 °C due to isomerisation in the case of the C 4 hydrocarbons and aromatisation in the case of C 7 hydrocarbons. PAHs from toluene and propane had the highest weighted carcinogenicities at a temperature of 1050 °C per unit volume of gas and per unit soot mass respectively. The weighted carcinogenicity (soot mass basis) decreased with increasing carbon number at temperature of 1150 °C. Potential implication of these observations is that hydrocarbons known to produce substantial particulate mass in combustion systems such as an internal combustion engines, could also have low toxicity

Risk identification and management for the research use of government administrative data

Purpose – Government administrative data have enormous potential for public and individual benefit through improved educational and health services to citizens, medical research, environmental and climate interventions and better use of scarce energy resources. The purpose of this study (part of the Administrative Data Research Centre in England, ADRC-E) was to examine perspectives about the sharing, linking and reuse (secondary use) of government administrative data. This study seeks to establish an analytical understanding of risk with regard to administrative data. Design/methodology/approach – This qualitative study focused on the secondary use of government administrative data by academic researchers. Data collection was through 44 semi-structured interviews plus one focus group, and was supported by documentary analysis and a literature review. The study draws on the views of expert data researchers, data providers, regulatory bodies, research funders, lobby groups, information practitioners and data subjects. Findings – This study discusses the identification and management of risk in the use of government administrative data and presents a risk framework. Practical implications – This study will have resonance with records managers, risk managers, data specialists, information policy and compliance managers, citizens groups that engage with data, as well as all those responsible for the creation and management of government administrative data. Originality/value – First, this study identifies and categorizes the risks arising from the research use of government administrative data, based on policy, practice and experience of those involved. Second, it identifies mitigating risk management activities, linked to five key stakeholder communities, and it discusses the locus of responsibility for risk management actions. The conclusion presents the elements of a new risk framework to inform future actions by the government data community and enable researchers to exploit the power of administrative data for public good

Influence of solvent selection and extraction temperature on yield and composition of lipids extracted from spent coffee grounds

Spent coffee grounds (SCG) are a potentially sustainable source of C16-C18 triglycerides. This study investigates known solvent extraction technologies with a wide range of solvents for lipid extraction from SCGs, and determines the effect of solvent selection and process temperature on the extraction efficiency and composition of the obtained oil. A correlation between increasing solvent boiling point, and therefore process temperature, and improved oil extraction efficiency was observed in Soxhlet extractions with a wide range of solvents. Experiments at elevated temperatures (up to 200 °C) were performed through Accelerated Solvent Extraction (ASE) and temperature increase initially improved the oil extraction efficiency when non-polar solvents were used, before decreasing it at higher temperatures. Utilization of ethanol resulted in the highest oil extraction ratio by ASE (at 165 °C), suggesting that temperature increase is more beneficial to the extraction efficiency of polar solvents. In addition, analysis of the oils was carried out to evaluate the composition of the oils extracted from SCGs using different solvents and extraction parameters. The Nuclear Magnetic Resonance (NMR) results were in agreement with the values obtained from the titrimetric determination of the free fatty acid content (FFA) of the oils in terms of the comparative trends, and also tentatively suggest that some differences in the composition of the extracted oils might be related to the type of extraction solvent used