沥青质加氢过程中的结构组成变化

Structure changes of asphaltenes in hydroprocessing

综述了原油沥青质在加氢处理中结构组成变化的研究现状。现有的研究主要针对沥青质加氢过程中H/C原子比随加氢条件变化如何变化,S,N,V,Ni脱除状况,以及加氢处理中沥青质相对分子质量及分子结构的变化,沥青质晶体结构参数的变化。结果表明:加氢处理后沥青质C,H质量分数降低,H/C原子比且随加氢条件变化苛刻而降低。沥青质的S较易脱除,由于N,V,Ni位于沥青质芳环系中,所以难以脱除,且随着反应条件的苛刻,其质量分数增加。反应中沥青质烷基侧链变短、侧链数变少,芳环数减少,芳核缩合度增加,芳香度增加,沥青质平均相对分子质量降低,总环数增加。加氢转化后沥青质芳香层层数M减少,芳香层层间距dm和芳香层堆积高度Lc降低。通过这几方面的研究结果分析,对解决加氢处理中沥青质引起的催化剂生焦及轻质油收率低等不利影响具有重要的理论指导意义。

The research status of the changes in the elemental content and structural parameters of asphaltenes upon hydrotreatment was overviewed. Current research is aimed at the H/C atomic ratio changes over hydrogenation conditions change, the removal conditions of S, N, V, Ni, the changes of asphaltenes relative molecular mass and molecular structure, the parameters of the crystalline structure during hydrotreating. The results show that mass fraction of C, H decreases and H/C atomic ratio reduces with the strict level of hydrogenation conditions. S is easier for removal in asphahenes, but N, V and Ni are difficult to be removed for they are in the aromatic ring system and the mass fractions increase as reaction conditions are harsh. Compared with feedstock, asphaltenes from hydrotreated products are more aromatic with more aggregate rings, shorter alkyl side chains, less number of alkyl side chains and aromatic rings, apparent aggregate relative molecular mass is reduced after reaction. The crystalline parameters of asphaltenes, just like M, din, L~ reduce after hydrotreating. Through the analysis of the several aspects of research results, it has an important significance theoretical guiding to solve the adverse influence caused by asphaltenes for it is precipitated on the catalyst surface and acts as coke precursors, which in turn lead to deactivation of the catalysts during hydrotreating.