重芳烃组成对汽油车尾气细颗粒物浓度及特征谱的影响规律研究

The improvement of fuel quality can limit the vehicular emissions effectively at the source, which has become an important part of air pollution control in China. The heavy aromatic hydrocarbons in gasoline are closely related to the generation of fine particulate matters (PM2.5), but the content remains quite high in gasoline with the limitation of crude petroleum quality and refinery process in current China. How to optimize the composition structure of heavy aromatics is the key technology to improve gasoline quality. In view of the problem, the typical heavy aromatic components with different carbon numbers are selected first based on the detailed hydrocarbon analysis of marked gasoline samples. And five kinds of test gasoline with different composition structures of heavy aromatics are prepared using these typical components. Then typical vehicles with different fuel injection technologies are selected from Chinese market for emission tests using the five kinds of test gasoline. The fine particle concentrations in tailpipe emissions will be detected online, besides the particulate matters will be also sampled for further analysis of the source profile. Finally, an index indicating the generation potentiality of fine particulate matters will be calculated based on theoretical derivation. And the influence mechanism of heavy aromatics component structure on particle emissions will be studied with its carbon number and detail hydrocarbons based on the mathematical statistics. The outcome of this study will provide theoretical basis and technical support for the oil update from “clean gasoline” to “formulate gasoline” in China. Meanwhile, the research findings will be very important for environmental protection department in making vehicular emission control plan, especially in making scientific design, making certain control emphases and lowering the control cost.

提高油品质量可以从源头上控制汽车尾气排放，是目前我国城市大气污染防治的重要组成部分。但受原油质量和炼化工艺限制，汽油中对细颗粒物排放影响最为显著的重芳烃含量则很难再有大幅下降，如何对其组成结构进行优化将是进一步提升我国汽油品质的关键。本研究针对这一问题，首先，基于市售汽油详烃分析筛选出了不同碳数重芳烃的代表性成分，并以此调配出五种具有不同重芳烃组成结构的试验汽油；然后，选取典型技术汽油车分别添加不同试验汽油开展整车尾气排放试验，对尾气中细颗粒物浓度在线检测，同时对细颗粒物进行采样并开展源成分谱分析；最后，通过理论推导建立一种能够反映汽油细颗粒物生成潜势的指数，并采用数学统计方法探明汽油重芳烃组成对汽车尾气细颗粒物排放浓度及其特征谱的影响规律。该研究将对我国车用汽油从"清洁化"升级至"组分化"提供理论基础和技术支撑，同时对环保部门制定科学、经济、有效的机动车污染防治政策也具重要意义。

提高油品质量可以从源头上控制汽车尾气排放，是目前我国城市大气污染防治的重要组成部分，但受原油质量和炼化工艺限制，汽油中对细颗粒物排放影响最为显著的重芳烃含量则很难再有大幅下降，如何对其组成结构进行优化将是进一步提升我国汽油品质的关键。本研究针对这一问题，首先，借助中国环境科学研究院国家环境保护机动车污染控制与模拟重点实验室主导的车用燃料环保指标现状调查工作在北京市不同区域对20个加油站进行了市售汽油采样和详烃分析，分别选择甲苯、1,3-二甲基苯、1,2,4-三甲基苯、1,2-二甲基-5-乙基苯、仲戊基苯作为C7-C11不同碳数代表性成分，并以此调配出“X型”、“A型”、“V型”、“型”和“O型”等5种具有不同重芳烃组成结构的试验汽油；然后，选取GDI和PFI两种典型技术汽油车分别添加5种不同试验汽油开展整车转毂尾气排放试验，在对尾气中细颗粒物数浓度在线检测的同时，对PM2.5进行滤膜采样并对其中碳质组分、多环芳烃、水溶性离子和无机元素进行成分分析；数理统计分析发现，高碳数重芳烃组分占比越大，PM和PN排放越高，且有增加颗粒物中萘、苊烯、荧蒽和芘等高毒性PAHs趋势，说明在我国汽油中芳烃含量难以进一步下降的情况看下应进一步降低汽油中高碳数重芳烃含量占比。最后，基于受试汽油中关键组分的碳数、不饱和度和蒸气压等理化指标建立了一种能够反映汽油细颗粒物生成潜势的指数PMEI，且PMEI与PM和PN之间具有较好的相关性，相关系数R2高达0.83~0.96。该研究将对我国车用汽油从"清洁化"升级至"组分化"提供理论基础和技术支撑，同时对环保部门制定科学、经济、有效的机动车污染防治政策也具重要意义。