RO2 and QOOH Chemistry in Dimethylether Combustion

Lead Research Organisation: University of Leeds
Department Name: Sch of Chemistry


Dimethylether (DME, CH3OCH3) has considerable potential as an alternative clean fuel. It has energy densities similar to current biofuels such as ethanol, is compatible with existing engine technologies, burns with low NOx and soot emissions and can be distributed via available LPG networks. However, relatively little is known about the 'low temperature' (500 - 900 K) combustion of DME; combustion in this temperature range is particularly important in newer engine technologies such as HCCI (homogeneously charged compression ignition). This proposal seeks to characterise the mechanisms of DME combustion providing useful information to the academic combustion community and industrial collaborators. The proposal is matched to EPSRC priorities in energy research.

There have been a number of previous studies on low temperature DME oxidation, but no previous study has been able to observe radical intermediates directly or to be free from potential complications of reactions on surfaces. In the current proposal we will use a novel high temperature (up to 900 K), high pressure (up to 5 atm) turbulent flow tube providing a wall-less reactor suitable for studying radical reactions on time scales of up to several hundred milliseconds. The flow tube will be directly interfaced to a low pressure fluorescence cell for radical detection and a time-of-flight mass spectrometer for detection of the proposed products from chain propagation and chain branching reactions (e.g. CO and formaldehyde).

Our experiments will probe the competition between chain propagation (controlled oxidation) and chain branching (explosive oxidation) as a function of temperature and pressure. Observation of radicals and stable products, in conjunction with the use of isotopically labelled precursors, will allow us to determine the molecular mechanism of DME oxidation.

The experimental results will be combined with theoretical calculations carried both at the University of Leeds and Argonne National Laboratory (Drs Klippenstein and Harding) to give a full picture of the mechanism and allow us to extrapolate our results to wider ranges of temperature and pressure. The impact of the work will be assessed in conjunction with Dr Henry Curran (Director, Centre for Combustion Chemistry, University of Galway) via updated kinetic models of DME combustion and comparison with end-product studies from shock tubes or engine simulations.

The work has obvious practical and commercial implications and we are working with Ford and the International DME Association (IDA, and through to IDA to organisations such as Volvo Technologies and Rolls Royce) to enhance the impact of EPSRC investment.

Planned Impact

Impact is fully integrated into this project. Dimethyl ether (DME) has good potential for use as a future fuel. The objective of the project is to better understand the very poorly characterised, but vitally important issues around DME autoignition. For coventional engines an understanding of the combination of fluid mechanics and heat release has been sufficient to drive the development of engine design, however, for newer technologies such as homogeneous charge compression ignition (HCCI), the chemistry of autoignition is central to our understanding of processes such as engine knock and performance under a range of conditions. Understanding the chemistry of DME chain branching will therefore have significant impact to engine design and the viability of DME as a fuel of the future.

Impact is classified by EPSRC under four major headings: Knowledge, People, Economy and Society (
Knowledge - Knowledge generation is a major component of this project and in addition to dissemination through appropriate conferences and journal publications, we will be running workshops with industrial collaborators to facilitate direct transfer into industry. Collaborators include Ford and the International DME Association, and through the IDA links to companies such as Volvo Technologies and Total; Curran has collaborations with Rolls Royce turbines. The updating of chemical models of DME combustion ensures that the detailed chemical understanding developed through experiments, ab initio and master equation calculations is presented in a format that will be useful for applications. It is important to note that knowledge transfer is a two way process and workshops run during the early part of the project will be a way for collaborators to provide input and help shape all aspects of the project.
People - ROQOCO will provide multidisciplinary training to the PDRA and encourage them to interact with other academics in the programme and external collaborators, providing well trained and motivated researchers equipped for careers in research and/or industry.
Economy - ROQOCO will contribute significantly to our understanding of DME combustion and hence there is the potential for significant impact on the uptake of DME as a viable fuel. As DME can be efficiently synthesised from natural gas (or biomass), the UK could benefit significantly in the medium to long term.
Society - Energy provision and security is a major societal issue. Having DME is a viable transportation or electricity generating fuel that can be produced from either renewable sources (biomass, hence with potential to reduce CO2 emissions) or relatively stable supplies of natural gas, widens the spectrum of fuels available in the future and this can only enhance stability of supply.


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publication icon
Lockhart J (2013) Mechanism of the reaction of OH with alkynes in the presence of oxygen. in The journal of physical chemistry. A

Description Dimethylether (DME) is a potentially important fuel, useful for new HCCI engines and potentially produced from biomass. Significant uncertainties exist over the detailed mechanism of chain branching at temperatures relevant for HCCI and the potential role of Criegee intermediates (these reactive species are usually considered to be more relevant in atmospheric chemistry) in this chemistry.
Progress with the project has included
Publication of a paper on the initial step in the reaction.
Publication of papers looking at the chemistry of intermediate species. A key finding has been the role played by chemically activated species. Normally the reactivity of a compound depends on its thermal energy or temperature. Chemically activated species, which have retained energy from the previous reaction which led to their generation, react much more rapidly than would be expected from their temperature. Work has been published in the very high impact journal Science.
We have developed a new instrument for the measurement of reactions at high pressures and temperatures and this should open avenues for future research applications.
Finally, our results and publications have stimulated interest in the mechanism of DME oxidation and combustion.

Although the project only started in 2012, we have been able to build rapidly on previous work and have a paper on OH + DME close to submission and have done a substantial amount of work on Criege
Exploitation Route Interaction with the International DME Association. Discussions with Shell research (November 2015). Development of MESMER programme for prediction of the temperature and pressure dependence of reactions (several hundred downloads ( Publications, conferences - see separate output.
Sectors Energy,Environment,Transport

Description Equipment Grant associated with BioEnergy CDT at University of Leeds
Amount £110,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 11/2014 
End 06/2015
Title High pressure Reactor 
Description The techniques we had used to study elementary reactions relevant to combustion operate best at low pressures, typically below 0.5 atm, however, combustion often occurs at much higher pressures. Our new instrument (as reported in Stone et al. Rev Sci Inst 2016) allows reactions to occur at pressures of up to ~ 5 atm, but samples the radical species into a low pressure, low temperature environment for more sensitive detection. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact Allows us to explore much wider parameter space. Publications in other applications pending. Data have been reported at an Invited Talk at AGU (Dec 2016) and will be presented at the International Conference on Chemical Kinetics in Chicago in May 2017. 
Description MESMER is an open access programme to calculate the pressure and temperature dependence of pressure dependent reactions occurring over complex potential energy surfaces. Significant updates to MESMER have been incorporated during the lifetime of this grant, epitomised by our latest publication (Chem Phys Lett 2016) where we have coupled elementary reactions together and can allow for chemical activation. 
Type Of Material Improvements to research infrastructure 
Year Produced 2009 
Provided To Others? Yes  
Impact MESMER has been picked up by groups around the world. We are aware of an intercomparison exercise including MESMER which should shortly be submitted for publication. There have been several hundred downloads of the programme. 
Description Accelrys 
Organisation Accelrys
Country United Kingdom 
Sector Private 
PI Contribution On going work with the development of the MESMER programme to model the pressure and temperature dependence of reactions associated with multiple energy wells. Applications in Combustion Chemistry, Atmospheric Chemistry and in understanding fundamental physical processes, particularly energy transfer.
Collaborator Contribution Computation and programming support. Contributions to intercomparisons and publications.
Impact On going upgrades to the MESMER programme. Contributions to an intercomparison of MESMER with the MULTIWELL programme, an alternative approach to calculating temperature and pressure dependences.
Description Argonne National Laboratory 
Organisation Argonne National Laboratory
Country United States 
Sector Public 
PI Contribution Joint collaboration for a Science paper.
Collaborator Contribution Provision of theoretical calculations
Impact Publication in Science (Glowacki et al. 2012)
Start Year 2012
Description University of Oslo 
Organisation University of Oslo
Country Norway 
Sector Academic/University 
PI Contribution The collaboration involved studies of the branching ratios of OH radicals with amines relevant for the atmospheric decomposition of amines released during Carbon Capture with amine based solvents. Work at Leeds provided the experimental data.
Collaborator Contribution Prof Nielsen lead the theoretical component of this work, calculating the potential energy surfaces for the reactions and from this, the branching ratios for OH radicals with either the C-H or N-H bonds in primary and secondary amines. The results have been compared with experiment.
Impact One publication (Onel et al. JPCA 2013) includes calculations from the Oslo group. The collaboration is still on-going and we are working on a publication on the branching reactions of OH with monoethanol amine, currently the solvent of choice for Carbon Capture. Update for 2017 Submission - Collaboration is still active. On the basis of this collaboration Seakins is an external advisor to a programme led by Nielsen on the atmospheric oxidation of amines and Heard (researcher at Leeds) has been contributing experimentally to this programme. Additionally the collaboration has led to the submission of a Marie Curie Application for Early Career Researchers (Carbon Capture and the Environment H2020-MSCA-ITN-2017) in January 2017.
Start Year 2012