Sulphur distribution regularities in the liquid cracking products of oil shale from the Kashpir deposit
P. V. PANTILOV, E. B. KRIVTSOV
Institute of Petroleum Chemistry, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
Keywords: oil shale, cracking, kerogen, thiophene, benzothiophene, dibenzothiophene
Abstract
Extensive analysis of the composition (material and fractional composition, sulphur distribution over components and fractions, content of thiophene derivatives, etc.) of liquid products formed in thermal cracking of high-sulphur oil shale from the Kashpir deposit has been carried out, the effect of temperature and process duration on these parameters has been demonstrated. It has been found that the yield of liquid products at cracking temperatures of 425 and 450 °C increases with an increase in the time of thermal treatment from 40 to 100 minutes, reaching 26.40 and 23.62 wt%, respectively, due to an increase in the kerogen destruction depth. A further increase in process temperature to 475 °C intensifies secondary reactions, leading to a decrease in the yield of liquid products and the distillate fractions within them. The distribution of sulphur over distillate fractions was studied, and the predominance of benzothiophene and dibenzothiophene homologues in the diesel fraction was established. It has been shown that at cracking temperatures of 425-450 °C, an increase in process duration causes sulphur redistribution from the diesel to gasoline fraction against the background of an increasing proportion of thiophene homologues, which indicates the predominance of dealkylation and fragmentation of complex heterocyclic structures. At 475 °C, dibenzothiophene and its homologues accumulate in the residual fraction (>360 °C). The obtained data will improve the understanding of the patterns of thermal transformation of sulphur-containing structural fragments in the organic matter of high-sulphur oil shales during cracking.
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