Homogenous gas-phase reactions in exhaust-gas tail pipes of internal combustion engines

对控制污染物排放（例如来自内燃机的NOx）、使用具有降低的气候影响的燃料以及开发更高效的发动机的日益增长的需求需要替代的后处理策略，例如将催化转化器定位成更靠近发动机。由此产生的更高的温度和压力承担了在尾管中影响排放减少的显著气相反应的可能性。例如，在选择性催化还原（SCR）系统中，NOx和NH3的摩尔比可以通过气相反应改变，导致NOx排放增加。废气组分HC/HCO/CO/NOx/O2/NH3/H2O/CO2/N2之间的均相反应几乎没有被研究，并且在尾管条件下还远未被理解。 目前的中德联合项目将研究在贫运行条件下存在NH3-SCR系统的条件下的气相反应。在发动机附近的排气管和排放控制装置的原料气体的气相反应将通过在均相气相和催化蜂窝结构的开放通道中的研究来表征、理解和建模。科学的目的是提供一个基本的了解气相反应，将发生在这些原料气体。只有这样一个基本的理解，将允许准确的那些反应混合物的特性，确实达到催化剂，从而开发现实的化学模型，并优化燃料发动机相关的后处理系统，以减少排放，降低毒性和化学危险性较小的签名。为了实现这些目标，该项目将利用合作伙伴在燃烧化学诊断、动力学分析和与氧化和燃烧相关的模型开发以及后处理策略方面的综合、互补和独特的专业知识。该项目将考虑（i）从传统汽油和柴油到目前的生物燃料和未来的电衍生燃料的燃料多样性，（ii）可变发动机运行条件，以及（iii）催化转化器更接近发动机的操作。这种巨大的条件组合是目前缺乏对近发动机原料气中气相反应的基本了解的原因。因此，识别常见的原型成分和变量（包括混合物成分和温度以及潜在的压力敏感性）至关重要。这种合作解决了严峻的挑战，这些挑战也将对中国和德国的空气质量问题产生影响。该项目将建立并扩大德国和中国集团之间业已建立的伙伴关系。

Increasing demands on the control of pollutant emissions such as NOx from internal combustion engines, the use of fuels with decreased climate impact, and the development of more efficient engines call for alternate after-treatment strategies such as positioning of catalytic converters closer to the engine. The resulting higher temperature and pressure bear the potential for significant gas-phase reactions in the tailpipe effecting the emission reduction. For instance, in a selective catalytic reduction (SCR) system, the molar ratio of NOx and NH3 could be changed by gas-phase reactions leading to increased NOx emission. Homogeneous reactions among the exhaust gas components, HC/HCO/CO/NOx/O2/NH3/H2O/CO2/N2, have barely been investigated and are far from being understood at tail-pipe conditions. The present joint Sino-German project will study gas-phase reactions for those conditions in the presence of a NH3-SCR system at lean operating conditions. Gas-phase reactions in the raw gases in the engine-near tailpipe and in emission control devices will be characterized, understood, and modelled through studies in the homogeneous gas-phase and in the open channels of catalytic honeycomb structures. The scientific aim is to provide a fundamental understanding of gas-phase reactions that will occur in these raw gases. Only such a fundamental understanding will allow the characterization of exactly those reactive mixtures that indeed reach the catalyst and thus to develop realistic chemical models, and to optimize fuel-engine-associated aftertreatment systems towards reduced emissions with decreased toxicity and chemically less hazardous signature. To achieve these goals, the project will make use of the combined, complementary, and often unique expertise of the partners regarding combustion chemistry diagnostics, kinetic analyses, and model development relevant to oxidation and combustion, and aftertreatment strategies. The project will consider (i) fuel diversity reaching from conventional gasoline and Diesel to current biofuels and to future electrically-derived fuels, (ii) variable engine operation conditions, and (iii) operation of the catalytic converter closer to the engine. This vast combination of conditions is a reason for the current lack of fundamental understanding of gas-phase reactions in the near-engine raw gases. It is thus of utmost importance to identify common, prototypical compositions and variables, including mixture components and temperature as well as potentially pressure sensitivity.This collaboration addresses acute challenges that will also have an impact on air quality issues in China and Germany. The project will build upon and expand an already well-established partnership between German and Chinese groups.