长链烯烃和烯烃双键位置的在线质谱测量新方法的研究及在催化脱氢反应中的应用

Long-chain olefins are important industrial chemicals, which are widely used for synthesis of linear alkylbenzene, plasticizer and fatty alcohols. Dehydrogenation of long-chain normal paraffins is the dominant method to produce olefins, while there are many by-products in the catalysis dehydrogenation processes, such as diolefins, trienes, and aromatics,etc., which are difficult to measure online by traditional instrumental analysis methods, such as GC,HPLC and GC-MS, and without simple structural characterization and quantification methods. In this proposal, we are going to build a medium vacuum pressure ion source for orthogonal acceleration time of flight mass spectrometer, and develop a direct mass spectrometry method to measure the concentration of olefins, diolefins and trienes. We will also build a new ion source, which combine single photon ionization and ozone-induced dissociation in tandem, the molecular olefin ions formed in SPI region are transferred to the O3 reaction drift tube by a quadrupole ion guide, then react with O3 molecules and produce aldehyde ions. According the m/z of olefin and aldehyde ions, the double-bond positions of long-chain olefins are precisely determined. We plan to develop a scheme to determine the double-bond positions of olefin in a mixture without prior GC separation by online calibration and the photon ionization cross section, dissociation ratio of ozonide. In the final, we will apply the method to online analyze the dehydrogenation products of long-chain paraffins in an industrial test apparatus for optimization the composition of the catalyst and the reaction parameters

长链烯烃广泛用于生产可降解烷基苯表面活性剂、增塑剂和脂肪醇等。直链烷烃的催化脱氢是生产直链烯烃的主要方法，但产物中有烯烃、多烯烃等，传统方法难以快速分析这些产物，无法确定烯烃异构体及其双键位置的信息。 我们拟用中等真空气压下的10.6 eV单光子电离质谱技术，实现对长链烯烃、多烯烃的软电离，利用分子离子的强度直接测量烯烃和多烯烃的浓度。研制一个单光子电离与O3解离反应区正交串联的新型离子源， 利用臭氧与烯烃离子之间的分解反应产生特征的醛类离子的信息，确定烯烃双键异构体的数目和浓度，同时给出其双键位置的信息。建立在线内标校正仪器参数和VUV灯光强的方法，发展利用光电离截面和O3解离反应分支比等参数，直接用质谱分析混合烯烃浓度和组成的方法，应用于长链烷烃催化脱氢产物的连续监控和分析，为优化催化剂性能，提高选择性和产率服务。

长链烯烃广泛用于生产可降解烷基苯表面活性剂、增塑剂和脂肪醇等。直链烷.烃的催化脱氢是生产直链烯烃的主要方法，但包括多种双键异构烯烃产物，利用传统方法如GC、HPLC和GC-MS难以分析。本项目开发了一个中等气压下的单光子电离质谱平台，获得了九种烯烃的光电离截面和强度vs不同浓度的线性拟合曲线，并将其与一个臭氧在线诱导解离反应装置结合，用于6种长链烯烃同分异构体的分析。该反应将烯烃在双键位置解离产生不同的醛类产物，我们研究了烯烃解离规律，考察了反应时间、O3自身氧化性对醛类的影响等因素，成功获得了每个烯烃的臭氧诱导解离产物的特征指纹谱图以及特征离子。开发了一个基于特征离子强度及其有效电离系数的定量分析算法用于准确定量混合物中各同分异构体的相对含量。利用动态在线气体制备装置模拟获得长链烷烃催化脱氢产物混合气，并最终将上述方法用于分析混合气的成分及含量，结果发现，每个烯烃组分的相对含量计算误差均小于2.5%，总的分析时间小于2 min。该结果表明，基于在线臭氧诱导解离烯烃的SPI-TOFMS法可以用于催化合成烯烃产物的在线监测中。