In-Situ Catalytic Pyrolysis of Oil Shale Using Cu@Zeolite Catalyst and Kinetics Analysis

The in-situ catalytic conversion technology has been regarded as a versatile approach to developing oil shale due to the advantages of environmental protection and being able to exploit the deep formations, while the high conversion temperature and low oil recovery are the key deficiencies that hinder the progress of the commercialized operation. In this study, a novel Cu@4A zeolite nano-catalyst for oil shale in-situ conversion was synthesized by the combination of the wet impregnation method and high-temperature calcination. The catalyst can enter the pore throat and pyrolyze the kerogen at a lower temperature, exhibiting favorable catalytic performance toward oil shale. The functional groups, micro-morphology, crystal structure information, elements valence state, and the thermostability of the prepared catalyst were characterized through FT-IR, SEM, XRD, XPS, and TGA techniques, results are consistent with the expected design. The effects of Cu@4A zeolite nano-catalyst on the hydrocarbon yields and kinetics were investigated, and results show that the oil and gas yields increased by 7.61% and 19.69% after adding 1% Cu@4A catalyst; the activation energy of the oil shale sample decreased from 190.73 to 147.9512 KJ/mol, and the hydrocarbon conversion is proportional to the mesh number of oil shale, the optimal heating rate is 10 °C/min. The possible explanation for its favorable catalytic performance can be that the kerogen and asphalt in oil shale would firstly decompose into macromolecule aromatic hydrocarbons via the β-cleavage of the carbenium ions over the Brønsted acidic sites of the prepared catalyst, then followed by the dehydrocyclization, oligomerization, and aromatization. The introduction of Cu can increase the quantity of Lewis acid sites on the framework of catalysts, leading to more hydrogen transfer reactions between catalyst and organics, achieving the high-efficiency catalysis of oil shale.