全二维气相色谱-飞行时间质谱分析焦化柴油中饱和烃的分子组成

建立了全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)分析柴油馏分中饱和烃的分子组成的方法。结合谱库检索、质谱图解析、沸点与分子结构关系和全二维谱图特征,定性(或归类)了焦化柴油饱和烃组分中1057个化合物单体,其中正构烷烃排列规律性最强,一环~三环环烷烃按照极性和沸点的差异呈瓦片状分布在其上方。另外,还准确区分了在一维气相色谱上共流出的正构烷基环己烷和正构烷基环戊烷,以及正构 α 单烯烃。根据质谱采集的总离子流色谱图,采用峰面积归一化法得到了饱和烃组分的碳数分布结果,并将该方法应用于研究不同类型柴油馏分饱和烃的分子组成特点。结果表明,催化裂化和焦化柴油馏分饱和烃组分的化合物类型和分布各不相同。分子组成分析能为油品加工工艺机理的研究提供方法支持。

Molecular composition of saturated hydrocarbons in diesels by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry

An analytical method for separation and identification of the saturated hydrocarbons in diesels at molecular level by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOF MS)was established. The saturated hydrocarbons were pre-separated from diesel samples by solid phase extraction before GC×GC-TOF MS analysis. More than 1000 individual compounds (including paraffins, naphthenes and olefins) in coker diesel were tentatively identified based on NIST library search, mass spectrum resolution, boiling point distribution law and separation characteristics. Normal paraffins showed great regularity and could be identified easily through the relative position with pristane and phytane. The cyclic alkanes arranged above paraffins with the increasing number of rings. The normal alkyl cyclohexanes and cyclopentanes were well distinguished due to the difference of their polarity. Normal α -olefins which were often neglected in the past were also identified. With the support of the above-introduced identification, the distribution by structural type and carbon number were presented using peak area normalization. This analytical method was successfully used to investigate the molecular composition of saturated fractions in different diesel samples. All the results indicated that the molecular compositions of saturates in catalytic cracking diesel and coker diesel were significantly different because of the processing mechanism. This method provided technical support for the characterization of saturated hydrocarbons in diesels and the investigation of processing mechanism.