The Study On The Test Of The Formation Mechanism Of Aromatic Hydrocarbons From The Gasoline Engine Exhaust Gas

during recent decades years, the automobile volume tenure in our country increases sharply, which is mainly the gasoline-driven cars that operate in the large and middle cities, making the environment polluted more and more seriously. However, the application of unleaded gasoline makes the aromatic hydrocarbons from the exhaust of cars increasing. As an Organics, characteristic distributes widely and is hardly to break up and has the accumulation of biology and three chronics effect (carcinogenic, monstrosity, mutation). Not only those endanger the biology and environment, but also the carcinogenic and monstrosity to human are paid more attentions. Therefore, it is necessary to investigate the discipline and mechanism of the aromatic hydrocarbons from gasoline engines, which will decrease the pollutions and is useful for the practice.This paper determined the methods for sampling, sample preparing and inspecting the benzene series and polycyclic aromatic hydrocarbons according to the usual methods and rules at home and abroad. Then we did experimentations of engine bench and sampled the exhaust of pre-catalyst and post-catalyst. At last we gained the emissions of the benzene and benzene series by the gas phase chromatography and gained the emissions of aromatic hydrocarbons by the union of gas phase chromatography and mass spectrometer. Besides, we analyze the emission principle of benzene and polycyclic aromatic hydrocarbons. We also did experimentations on the constant volume combustion device in order to investigate the principle of benzene from the gasoline combustion.From the research mentioned above, we can draw conclusions as follows:1) When the engine is working at 2600rpm with the load of 75% and 100%, TWC induces the benzene formation, while the emissions of toluene and C2-benzenes reduce. According to this , we infer that dealkylation reactions of aromatic hydrocarbons are assumed to be the major pathway leading to the formation of benzene over the TWC.2) When pre-catalyst exhaust gas temperatures are 600-800℃, with the temperature going up, the gasoline breaks up more free radicals mission, which leads to more aromatic hydrocarbons formation. As the aromatic hydrocarbons are formed by the polymerization of free radicals, the formation is decreasing with the enhancing of the number of circles, while when pre-catalyst exhaust gas temperatures are 200-600℃, aromatic hydrocarbons may be derived from the volatilization of the no completely burned gasoline.3) The benzene from the exhaust gas of gasoline is likely from the no completely burned gasoline due to the quenching effect.4) During the process of burning, the pyrogenation of gasoline produces many kinds of small molecule radicals, then it can form benzene and phenyl through a series of reactions. The small molecule radicals from breaking up not only cause the combination of benzene but also make it whither away, which process is the dominant depend on the concentration of each component.