渣油重组分沥青质结构分析及其对临氢热反应过程生焦的影响

Analysis of asphaltene structure and its effects on the coking behavior in the process of hydrothermal cracking

以塔河常压渣油(THAR)为原料,正己烷为溶剂分离获得重组分C6-沥青质及其脱沥青油,并将所得沥青质回调至脱沥青油中配制成不同沥青质含量的渣油,以此为原料进行了高压釜临氢热反应实验。首先利用元素分析、1H-NM R及13CNM R、GPC分子量测定、FT-IR、XRD及SEM对沥青质的分子结构参数、官能团、晶体结构及表面形貌进行了分析研究。结果表明,该沥青质芳环侧链中长链部分较少且支链化程度较高,并以甲基、乙基、丙基结构为主,其芳香度fA高达0.57,芳环缩合程度及芳香片层结构较大,且芳香环系同时存在迫位缩合和渺位缩合的结构,已经形成连接致密的高芳香度结构。鉴于沥青质结构的复杂性,考察了其含量对临氢热反应过程的影响,结果表明,随着沥青质含量的增加,渣油的转化率逐渐增加,当沥青质含量超过5.12%时,其转化率的增加以快速生成焦炭为代价。另外,渣油中长链脂碳含量f3C与轻质油收率存在一定规律性,即随着f3C增加,轻质油收率先增加后趋于平缓,而残炭值、芳香度fA与焦炭收率表现出良好的线性关系。

C6-asphaltene and deasphalted oil were obtained by using the Ta-he atmosphere residue（ THAR） as the feedstock and n-hexane as the solvent. The deasphalted oil was then mixed with C6-asphaltene to prepare the residue with different asphaltene contents for autoclave hydrothermal cracking experiments. The molecular structure parameters, functional groups, crystal structure and surface morphology of C6-asphaltene were systematically analyzed by elemental analysis,1H-NMR and13C-NMR,GPC molecular weight,FT-IR,XRD and SEM. The results showthat the aromatics in C6-asphaltene exhibit a highly branched degree and the side chains consist of mainly methyl,ethyl and propyl groups; the aromaticity（ fA） of C6-asphaltene reaches 0. 57.The aromatic ring systems have the peri- and cata-condensed structures,with high condensation degree and large aromatic slice sheets. The influence of C6-asphaltene content on its hydrothermal cracking behavior was further investigated. The result illustrate that the conversion of the residue oil is gradually increased with the increase of the asphaltene content; however,when the asphaltene content exceeds 5.12%,the increment of conversion is at the cost of the rapid coke formation. In addition,the yield of light oil increases at first and then levels off with the increase of the content of aliphatic carbon（ f3C） in long chains,whereas the carbon residue and aromaticity（ fA） showa good linear relationship with the yield of coke.