硫对原油裂解气组成及碳同位素组成的影响

Influences of sulfur on composition of oil cracked gas and carbon isotopes

应用封闭金管-高压釜体系，对取自新疆塔里木轮古地区基本不含硫的轮古原油样品、原油加元素硫以及原油加正丙硫醇组合分别进行系列性热模拟实验；通过对比各个系列的产物产率特征及碳同位素组成特征，研究硫对原油裂解产物及烃类气体碳同位素组成的影响。结果显示，无论是硫元素还是有机硫化合物的加入，总体上轻微抑制了甲烷等烃类气体的生成，并促使H：和CO：等非烃类气体产量的增加；同时，加入的元素硫与有机硫化合物的量对反应产物的组成也有明显的影响。硫的加入对烃类气体碳同位素组成影响显著，使低温阶段生成的烃类气体碳同位素变重；尤以有机硫化合物的影响最为显著，与原油本身裂解烃类气体碳同位素相比，其对甲烷碳同位素的影响差值高达7‰，而对乙烷及丙烷碳同位素组成的影响差值也达到5‰。此外，硫对原油裂解产物组成的影响明显与硫元素的化学状态有关，有机硫化合物参与裂解反应的机理与元素硫明显不同。

A series of thermal simulation experiments were carried out with crude samples （from the Lungu area of Tarim Basin） and samples mixed with elementary sulfur or n-propyl mercaptan in a confined system of gold tube-autoclave. The influences of sulfur on cracked gas of oil and the isotope composition of hydrocarbon gas are studied through comparing the yields of experimental products and their isotope compositions in each experiment. The results show that adding sulfur or organic sulfide slightly inhibits, as a whole,the generation of methane and other hydrocarbon gas, but facilitates the production of non-hydrocarbon gases such as hydrogen and carbon dioxide. Besides, the amount of elementary sulfur or organic sulfide has an apparent effect over the composition of the products. Adding sulfur will exert a significant impact upon the carbon isotope composition of hydrocarbon gas, causing the carbon isotope generated at low temperature to be heavier. The influence of organic sulfide over the products is especially significant, resulting in a positive difference of as high as 7%0 upon the carbon isotope of methane, and 5 %0 upon that of ethane and propane. The study also suggests that the chemical state of sulfur has something to do with its influence upon the composition of oil-cracking products and that the mechanism of organic sulfide involving in cracking reaction is greatly different from that of elementary sulfur.