The differences in the yield, parameters and carbon isotopes of light hydrocarbons obtained by two collection methods

Summary In this study, two liquid hydrocarbon collection methods were used to collect light hydrocarbons generated from the cracking of crude oil in closed system, and the characteristics of the products collected were compared. Relative to the liquid nitrogen direct freezing collection (LNDF) method, the traditional liquid hydrocarbon collection (TLH) method can cause the yield loss of 10%-75% of light hydrocarbons, especially low carbon number light hydrocarbons (such as nC6, nC7, benzene, toluene, and 3-methylhexane). Because the TLH method can lead to various degrees of loss for different compounds in light hydrocarbons, it can also lead to the deviation of some light hydrocarbon parameters representing oil-oil correlation, indicating the maturity of crude oil and reflecting secondary alteration of crude oil. In addition, the δ13C values of nC6, nC7, benzene, toluene and 3-methylhexane collected by TLH method are heavier. These compounds with heavier δ13C values are the ones that have suffered the most yield loss in the TLH method. Therefore, the LNDF method can more accurately reflect the yield, parameters and carbon isotopes of light hydrocarbons in closed system pyrolysis.