1H-NMR评价不同重油缓和热转化过程中的相对供氢能力

Evaluation of relative hydrogen-donating abilities of different heavy oils during mild thermal conversion by 1H-NMR

以蒽为化学夺氢探针,采用1H-NMR为检测手段测定了三种典型重质渣油及其亚组分在380℃、临氮初压4 MPa、反应8 min条件下的可供氢含量,并分析了产物的甲苯不溶物、液体馏程分布以及气体组成。结果表明,本实验条件下的热反应较为缓和,渣油及组分反应前后结构变化不明显,样品体系内部主要发生渣油及组分向夺氢体（蒽）的氢转移反应。1H-NMR中化学位移在1.4~2.0的H cβ和2.5~4.7的H cα含量的变化值与化学探针法测定的实际可供氢量有较好的线性关联,可利用此两段化学位移内的氢含量评价不同重质油品在缓和热改质过程中的相对供氢能力。

The relative hydrogen-donating abilities of different heavy oils were determined by 1H-NMR. Three typical heavy residues and the corresponding subfractions were thermally treated with equal weight of chemical accepting probe （i. e. anthracene） at 380 ℃ for 8 min under the nitrogen pressure of 4 MPa; the toluene insoluble yield, gas yield and composition, and the distillation curve of liquid products were determined. The results show that the thermal reaction of samples under the testing conditions is relatively moderate with no apparent structural changes. By comparing the hydrogen distribution of samples with that of residues after reaction, it is proved that the primary reaction during the thermal process can make the hydrogen transfer from oil samples to anthracene. The reduction value of the hydrogen content of Hcβ （ chemical shift ranging from 1.4 2.0 in 1H-NMR spectrum, representing naphthenic hydrogen two positions from the aromatic ring of naphthenoaromatics） and Hcα （chemical shift ranging from 2.5 ~ 4.7 in 1H-NMR spectrum, representing hydrogen on naphthenic ring adjacent to fused aromatic ring of naphtheno-aromatic） is correlated well to the donated hydrogen content measured by chemical method. Thus it is reasonable to regard Hcβ and Hcα as the main donated hydrogen during mild thermal conversion of heavy oils, and to entatively evaluate the relative hydrogen-donating ability of heavy oil using the two tVlae protons content in 1H-NMR is acceotable.