Application of Clay-Based Catalysts in Co-Conversion and Co-Pyrolysis of Chlorella and Oil Shale

In this study, natural clay-like silicate minerals were used as precursors to prepare highly acid-catalytic hydrophobic catalysts. A series of sulfonic acid-functionalized attapulgite catalysts, SO3H-APG, were fabricated by the ball-milling–oxidation method. The catalytic performance in the co-liquefaction and co-pyrolysis of Chlorella and oil shale was investigated. The catalysts were analyzed using hydrophobicity evaluation, TEM, BET, FTIR, and other characterization methods. The SO3H-APG catalysts exhibited good hydrophobicity and dispensability. Sulfonation grafting improved their excellent hydrocarbon conversion activity. According to the GC–MS results, the addition of the SO3H-APG catalysts shifted the co-liquefaction products of microalgae and oil shale towards lower carbon numbers, with the majority of the products concentrated between C5 and C12, and a content of 84.9% in the range of C5–C11, while the content of products in the range of C12–C20 was only 15.1%. In the co-pyrolysis experiments, the addition of the catalysts promoted the thermal decomposition reaction. The synergistic effect between oil shale and microalgae facilitated the production of more hydrocarbon compounds with a higher H/C atomic ratio. The development of this type of catalyst provides an economically favorable approach for the co-conversion of algae and oil shale. The oil shale pyrolysis kinetic diagram shows that adding the APG clay-based catalyst significantly reduces the time for achieving the same conversion rate, especially below 300 °C, where the in situ catalytic effect is most pronounced.