Study On The Formation Mechanism Of Supercritical Liquefaction Products Of Oil Shale

Because of the lack of oil reserves,oil depends on imports in China,and looking for a substitute for oil liquid fuel has an urgent need.At present,supercritical liquefaction technology has attracted more and more attention in the world due to its obvious advantages.In this paper,Fushun oil shale was used as raw material to prepare shale oil by supercritical liquefaction technology.The formation mechanism of supercritical liquefaction products was studied under different solvents（n-hexane,toluene,acetone,ethanol）.The orthogonal test method was used to explore the optimal conditions of oil shale supercritical liquefaction yield:acetone as solvent,reaction temperature 340℃,residence time 180 min,solid-liquid ratio 1 g:30 ml.Solvent type and reaction temperature are significant factors affecting shale oil yield.The formation mechanism of products during supercritical liquefaction of oil shale was further clarified through different solvents and reaction temperatures.The components of oxygen-containing compounds in shale oil are different under different solvent conditions.The increase of reaction temperature promoted the formation of ketones and inhibited the formation of esters.N-hexane was more favorable than toluene for the dissolution of oxygen-containing components.When acetone and toluene were used as solvents,cyclization and polycondensation occurred during liquefaction.The oxygen-containing structures of kerogen structure were mainly C-O and C-OH,and the ether bond and ester bond were mainly broken during liquefaction.The ether bond in the kerogen structure was completely broken in the supercritical liquefaction reaction.Due to the high content of minerals in oil shale,this paper studied the influence of minerals on liquefaction products during supercritical liquefaction.Studies have shown that the internal minerals of Fushun oil shale are mainly silicoaluminate and contain pyrite and a small amount of carbonate.With the increase of reaction temperature,the shale oil yields of the original sample,the decarbonate sample and the decarbonate-silicate sample all increased.When the reaction conditions were 360℃-30 min,the oil yields calculated according to the dry ash-free basis reached 53.8%,56.9%and 42.8%,respectively.Internal carbonates and silicates are conducive to the increase of shale oil production rate.Alkali metal and alkaline earth metal cations in carbonate inhibit the formation of alkanes.Silicate promotes hydrocarbon enrichment to low carbon number through acidic sites.Carbonate and silicate can promote and inhibit the esterification,respectively.The oxygen-containing weak bond and C-C bond of fat structure were broken during supercritical liquefaction.These two types of broken bonds form small molecules as organic sources of shale oil.