哈萨克斯坦及俄罗斯渣油馏分中的硫化物裂解色谱分析

Analysis of sulfur species in the residua fractions of Kazakhstan and Russia crude oils by pyrolysis-gas chromatography

采用裂解气相色谱接脉冲火焰光度检测器(PY-GC-PFPD),研究了哈萨克斯坦原油及俄罗斯减压原油渣油及其馏分的裂解硫化物的组成分布。依据渣油高温裂解硫化物的主要类型:H2S、噻吩类、苯并噻吩类及二苯并噻吩类,选择噻吩、苯并噻吩(BT)和二苯并噻吩(DBT)模型化合物,考察裂解温度400℃~1000℃及时间5 s^10 s的反应产物及转化率,以证明渣油裂解硫化物基本可反映其在渣油中的结构。采用超临界流体萃取分馏,将俄罗斯和哈萨克斯坦渣油分别分割成18和19个窄馏分,在裂解温度1000℃及10 s条件下,获得了两种渣油及其馏分中H2S、噻吩、BT和DBT的含量分布,推断了渣油中硫化物噻吩类和硫醚类分布规律。

The sulfur species and their distribution in the residua of Kazakhstan and Russia crude oils were investigated by using pyrolysis-gas chromatography （PY-GC） with the pulsed flame photometric detector （PFPD）. The major sulfur-containing products from the residua pyrolysis were H2S, thiophene species, benzothiophene （BT） species and dibenzothiophene （DBT） species ; therefore, the pyrolysis of the model compounds thiophene, BT and DBT under 400 ℃ - 1 000 ℃ for 5 s - 10 s was carried out to determine the origin of sulfur species in the residua. Thiophene can easily be cracked into H2S, while BT and DBT are partially cracked into H2S. The reactivity of BT and DBT can be inhibited for pyrolysis in the blend of thiophene, BT and DBT; thus the sulfur pyrolysates can illustrate the origin of BT and DBT, while thiophene may be under estimated since it can easily be cracked. The residua of Kazakhstan and Russia crude oils were separated into 18 and 19 narrow cuts, respectively, by supercritical fluid extraction and fractionation. The sulfur species distribution for sulfides, thiophenes, BTs and DBTs in these narrow cuts and non extractable end cuts were obtained through the pyrolysis at 1 000 ℃for 10 s. As the cuts become heavier, the sulfur content in each cut increases; the relative fraction of thiophene sulfur in total sulfur content also increases, while the relative sulfide sulfur fraction decreases. Russia vacuum residue and its cuts show higher total thiophene contents than Kazakhstan vacuum residue and its corresponding cuts.