沙特常压渣油超临界流体萃取分馏宽馏分中含硫化合物的分子表征

Molecular characterization of sulfur-containing compounds in the wide fractions of Saudi Arabia atmospheric residue by supercritical fluid extraction fractionation

采用超临界流体萃取分馏(SFEF)装置,将沙特中质原油常压渣油(SZAR)按照分子大小和极性强弱进行多级萃取分馏,得到四个宽馏分和一个萃余残渣。考察了四个宽馏分沸程分布、密度、残炭值、黏度、相对分子质量、硫和氮含量以及结构族组成等基本性质均随萃取压力的变化趋势。采用甲基衍生化作用使含硫化合物转化为含有极性的甲基硫盐,结合正离子模式下的电喷雾(ESI)电离源的傅里叶变换离子回旋共振质谱(FT-ICR MS)分析各馏分中所包含的含硫化合物的分子组成。结果表明,超临界萃取分馏技术可以将馏分按照分子大小进行分离,且对于非烃类化合物具有富集作用。各个馏分中含量最高的均为包含一个硫原子的S1类化合物,且二苯并噻吩(DBE=6)类含量最高。馏分越重,S1、S2类化合物含量越高、种类越繁多、且缩合程度更高,包含的更多的大分子含硫化合物。

Saudi Arabia atmospheric residue（ SZAR） was subjected to supercritical fluid extraction fractionation（ SFEF） and separated into four extractable fractions and an un-extractable end-cut. The SFEF subfractions were subjected to the simulated distillation analysis,gel permeation chromatography（ GPC） for their molecular weight distributions, and open column liquid chromatography for their saturates, aromatics, resins, and asphaltenes（ SARA） compositions,by high-temperature gas chromatography（ GC）. The density,carbon residue value,viscosity,and sulfur and nitrogen content along with the extraction pressure were determined.Sulfur compounds in wide fractions were converted to methylsulfonium salts,which were characterized by positive-ion electrospray ionization（ ESI） and Fourier transform ion cyclotron resonance（ FT-ICR） mass spectrometry（ MS）. The results indicated that the mass range and maximum peak intensity of the SFEF subfraction are increased as the SFEF subfraction becomes heavier. The molecules in various SFEF subfractions are separated by their polarity and molecular weight. The highest level in the various fractions is referred to S1 class species and meanwhile,benzothiophene turns to be the dominant heteroatom compounds. Compared with the lighter fractions,heavier fractions have higher contents of S1 and S2 class species,wider range,higher molecular weight,and more aromatic cores.