Normandie Univ, COBRA, UMR6014 and FR3038, Université de Rouen; INSA de Rouen; CNRS, IRCOF, 1 rue Tesnière, 76821 Mont-Saint-Aignan Cedex, France.
Analyst. 2018 Aug 6;143(16):3934-3940. doi: 10.1039/c8an00920a.
Polyalphaolefins (PAOs) are saturated alpha olefin oligomers used as a base stock oil for synthetic lubricants. The synthetic base stocks are manufactured from linear alpha olefins by catalytic oligomerization processes. The aim of this work was the characterization of different PAO grades, synthesized from different linear alpha olefins using two oligomerization processes, acid and metallocene catalyses. Negative ion atmospheric pressure photoionization (APPI) coupled with ion mobility spectrometry-mass spectrometry (IMS-MS) permitted the detection of intact PAO adducts with either chloride, bromide or iodide ions using halogenated solvents (e.g. dichloromethane, dibromomethane and diiodomethane) and toluene as the dopant. The best signal-to-noise ratio was obtained with dichloromethane. The APPI mass spectra displayed characteristic ion distributions for high viscosity PAO grades. The mass shift between two adjacent ions permitted the identification of repeating units and consequently the monomers of alpha olefins used to manufacture the PAO. For low PAO grades, the halide anion adducts were not detected as they are less stable. The IMS-MS data, as well as the correlated variables, i.e. the drift time and full width at half maximum (FWHM) of the IMS peaks, can be used to differentiate polyalphaolefins of the same grade but differently synthesized.
聚α烯烃（PAO）是用作合成润滑剂基础油的饱和α烯烃低聚物。合成基础油是通过催化齐聚工艺由线性α烯烃制造的。这项工作的目的是对使用两种齐聚工艺（酸催化和茂金属催化）从不同线性α烯烃合成的不同 PAO 等级进行表征。负离子大气压光电离（APPI）与离子淌度质谱（IMS-MS）联用，使用卤代溶剂（例如二氯甲烷、二溴甲烷和二碘甲烷）和甲苯作为掺杂剂，可以检测到与氯、溴或碘离子形成的完整 PAO 加合物。使用二氯甲烷可获得最佳的信噪比。APPI 质谱显示出高粘度 PAO 等级的特征离子分布。两个相邻离子之间的质量位移允许识别重复单元，从而确定用于制造 PAO 的α烯烃单体。对于低 PAO 等级，由于其稳定性较低，未检测到卤化物阴离子加合物。IMS-MS 数据以及相关变量，即 IMS 峰的漂移时间和半峰全宽（FWHM），可用于区分同一等级但不同合成的聚α烯烃。
