CatPlasKin: The microkinetics of non-thermal plasma-assisted heterogeneous catalysis with application to the non-oxidative coupling of methane

甲烷是一种丰富的物质，作为化学品合成的原料具有巨大的潜力。它作为天然气的主要成分被广泛使用，但也越来越多地从可持续来源，如沼气和垃圾填埋气，以及非常规来源，如页岩气，煤层甲烷和甲烷水合物获得。此外，甲烷的100年全球变暖潜能值是二氧化碳的25倍以上，因此开发高效的甲烷利用方法以获得增值产品的必要性非常明显。在众多用途中，甲烷已被确定为生产乙烯的非常有前途的原料。后者是生产最广泛的基础化学品，例如用于聚合物，但其生产依赖于原油，产生了英国化学工业中绝大多数的二氧化碳排放。事实上，根据《京都议定书》和《英国气候变化法》，英国在减少温室气体排放方面有具体的国际和国内目标。其中11%是来自农业、废物管理和能源工业的甲烷，因此由甲烷生产乙烯可能是一种有前途的方法，对这些部门有多种好处。然而，通过热催化活化稳定的甲烷分子所需的高温，结合使用氧化剂以促进化学上有利的路线，低温等离子体与催化剂的结合最近已经成为一种有前途的技术，使催化剂能够在低温下操作。在非热等离子体中，整体气体温度与环境温度一样低，但是电子具有高能量，导致碰撞，容易破坏分子键，产生各种反应性物质，如自由基，激发态和参与后续反应的离子。这些等离子体的强非平衡特性已被证明甚至允许在环境条件下发生化学上不利的反应。能够在非氧化条件下在低温下进行甲烷直接偶联生成乙烯将带来显著的好处，从无碳氧化物的产品到大幅降低的能源需求，并将使聚合物和高辛烷值燃料的替代生产路线成为可能。将等离子体的高反应性与催化剂表面的高选择性相结合，有巨大的潜力来揭示这些好处，这可以通过使用可持续的电力来产生等离子体来进一步增强。然而，非热等离子体与催化剂之间的相互作用是一个高度复杂的现象。已经有大量的实验工作旨在了解基本的过程，但大多数机械细节尚未阐明。结合实验，理论和建模研究需要获得一个更基本的insight.Microkinetic建模提出了一种新的方法，以提高理解，并使等离子体辅助的多相催化反应系统的优化。在英国巴斯夫公司的支持和精心设计的实验计划下，该项目的新奇在于首次系统地考虑了在等离子体相中和催化剂表面发生的所有基元反应过程，并明确描述了它们之间的相互作用。该项目非常及时，涉及环境和战略与资源中心一揽子方案中与能源效率和替代燃料及化学品来源有关的专题。成功的实施将导致预测计算工具的开发，可用于加速新工艺的设计，减少实验需求和相关成本。

Methane is an abundant material that presents huge potential as a feedstock for chemicals synthesis. It is widely available as the major constituent of natural gas, but becomes also increasingly more obtainable from sustainable sources, such as biogas and landfill gas, and unconventional sources, such as shale gas, coalbed methane and methane hydrates. Moreover, it has more than 25 times higher 100-year global warming potential to that of CO2, so the need to develop efficient methane utilization methods towards value-added products is more than clear.Among many uses, methane has been identified as a very promising raw material for the production of ethylene. The latter is the most widely produced base chemical, used e.g. for polymers, but its production depends on crude oil, generating the vast majority of CO2 process emissions in the UK chemical industry. In fact, under the Kyoto Protocol and the UK Climate Change Act, UK has specific international and domestic targets for reducing greenhouse gas emissions. 11% of these are represented by methane originating from agriculture, waste management and the energy industry, hence the production of ethylene from methane can be a promising process with multiple benefits for these sectors.The high temperatures needed, though, for the activation of the stable methane molecule via thermal-catalysis, in conjunction with the use of oxidants to facilitate thermodynamically favourable routes, result in significant amounts of undesired carbon oxide by-products in the currently applied upgrading methods.The combination of non-thermal plasma with catalysis has recently emerged as a promising technology to enable catalysts to operate at low temperatures. In non-thermal plasmas, the overall gas temperature is as low as ambient, however electrons are highly energetic resulting in collisions that easily break down molecule bonds, producing various reactive species like free radicals, excited states and ions that participate in subsequent reactions. The strong non-equilibrium character of these plasmas has been shown to even allow thermodynamically unfavourable reactions to occur under ambient conditions.Being able to carry out direct methane coupling towards ethylene at low temperatures at non-oxidative conditions would present significant benefits, ranging from carbon oxides-free products to drastically reduced energy requirements and would enable alternate production routes towards polymers and high octane-number fuels. Combining the high reactivity of plasma with the high selectivity of the catalytic surface has a huge potential to unravel these benefits, which can further be enhanced by the use of sustainable electricity for the generation of the plasma.Nonetheless, the interaction between non-thermal plasma and catalysts is a highly complex phenomenon. There has been a considerable amount of experimental work aimed at understanding the underlying elementary processes, however most mechanistic details are not yet elucidated. The combination of experimental, theoretical and modelling studies is needed to gain a more fundamental insight.Microkinetic modelling is proposed as a novel approach to enhance the understanding and enable the optimisation of plasma-assisted heterogeneous catalytic reaction systems. With support from BASF, UK and a carefully designed experimental program, the novelty of the proposed project lies on the, for the first time, systematic consideration of all elementary reaction processes taking place in the plasma phase and on the catalyst surface and the explicit description of the interactions among them. The project is very timely, addressing topics in EPSRC's portfolio in relation to energy efficiency and alternative fuels and sources of chemicals. Successful implementation will result in the development of predictive computational tools that can be used to accelerate the design of new processes, reducing the needs for experimentation and associated costs.