High dose rate electron beam irradiation of heavy alkanes in a multi-phase flow system

Abstract

A high energy electron beam (10 MeV, LINAC) was used to irradiate mineral oils in a continuous flow system to study radiation effect on large alkane hydrocarbons at constant temperatures (80 and 150 °C). Oil flows down an open channel with methane or helium bubbling from the bottom. The gas mixes with the oil but also may be reactive. Oil was irradiated with about 300–500 kGy by passing 20–30 times down the channel at 18–24 kGy per pass. Analysis by GC-FID showed 7–12% conversion in treated samples and about 60–70% product selectivity to light hydrocarbons right after the irradiation experiment. Stability of products was tested after two years and showed reduced conversion to light products. Selectivity to light products was nearly 100% and dropped to 72% after two years in sample treated with methane. Initially 63%, after aging product selectivity to lights became 46% in sample irradiated at higher temperature and reduced from 62% to 18% in sample irradiated at lower temperature. Overall conversion yields in the flow system are 4–7 molecules/100 eV higher than typical literature values for batch processing of alkanes and cycloalkanes. Irradiation with methane had higher yields and higher selectivity to lighter products compared to helium. Product selectivity to light products is 72% after two years and total yield to lights is 4.4 molecules/100 eV. Methane gas led to higher yield with no viscosity change. Product instability may cause significant economics loss in irradiation upgrading of heavy oils and needs to be addressed.