红外光谱法研究重质油分子的轻度热转化

为了从分子水平快速经济地分析重质油在热转化过程中的变化规律，利用四种模型化合物萘、四氢萘、十氢萘和正庚烷组成的混合体系来模拟重质油及其热转化缩合产物分子的基本组成，研究其红外吸收特性与平均分子参数（亚甲基和甲基的数目之比 N CH2/NCH3、芳氢率faH、芳香环系氢碳原子比NHar/NCar等）的关系。将重质油焦化重蜡油馏分进行轻度热转化，利用不同强度的系列溶剂将热转化产物的重质馏分顺序分离成系列溶剂族组分，将这些族组分进行红外分析。结果表明，混合物系列模拟体系的〖ＷＴＢＸ〗f〖ＷＴＢ１〗aH同其红外吸收在2750cm－1～3100cm－1的3000cm－1～3100cm－1强度分率（S3000~3100/S2750~3100）之间存在良好的线性关系，同时NCH2/NCH3 同2920cm－1和2960cm－1处的吸光度比值A2920/A2960之间也存在良好的线性关系。依据这些关系式可以合理解释重质油分子在热转化过程中分子结构的变化规律。随着重质油热转化的进行，NCH2/NCH3 饱和烃分子先增大后减小，芳香性族组分分子则持续降低；faH或NHar/NCar芳香性族组分分子呈现升高的趋势。

Characterization of molecular change of heavy oil under mild thermal processing using FT-IR spectroscopy

In order to quickly and economically obtain the information of molecular changes occurring in heavy oils during thermal processing, simulated mixtures of heavy oils and their pyrolyzed products were prepared from four model compounds, i.e., naphthalene, tetralin, decalin, and nheptane. FT-IR absorption characteristics and average molecular parameters of the mixtures were correlated; the molecular parameters included the number ratio of methylene to methyl (NCH2/NCH3), hydrogen aromaticity (faH), atomic ratio of hydrogen to carbon of the aromatic sheet (NHar/NCar), etc. Considering heavy coker gas oil (HCGO) as a heavy oil feedstock, HCGO was thermally processed in an autoclave and its gas oil fraction (GOF) was separated into group fractions and analyzed by FT IR. The results show that the simulated mixtures show good linearity between faH and the absorption area ratio of the bands at 2750cm－1～3100cm－1 to 3000cm－1～3100cm－1 (S3000~3100/S2750~3100), and so doesNCH2/NCH3 and absorbance ratio of the bands at 2920cm－1～2960cm－1 (A2920/A2960). These correlations could be useful tools for illustrating molecular changes occurring in heavy oil during thermal processing. As the processing proceeds, the NCH2/N１CH3 of the saturate molecules increases first and then declines, in sharp contrast to that of the aromatic molecules, which shows a consistent decline. As far as faH or NHar/NCar is concerned, however, the aromatic molecules show a rising trend. The chemistry behind these phenomena is also discussed in some detail.