Hydrothermal co-liquefaction has the potential to improve biocrude yield. To investigate the influence of various types of biomass on co-liquefaction with municipal sewage sludge (MSS), experiments on MSS with three kinds of model feedstocks (soy oil, soy protein, and starch) were carried out. Reaction temperatures of 300, 320, and 340 °C proved to be the appropriate reaction temperatures for the highest biocrude yield for soy oil, soy protein, and starch, respectively. A synergistic effect on the biocrude yield of co-liquefaction was proved, and starch showed the highest synergistic effect with a 57.25% increase in biocrude yield, while soy oil only presented a slight synergistic effect. Thermal gravimetric analysis (TGA) results suggested that co-liquefaction with soy oil increased the light oil fractions in biocrude by 20.81%, but protein and starch led to more heavy oil fractions. Gas chromatography-mass spectrometry (GC-MS) indicated that co-liquefaction with protein or starch produced more cyclic compounds in the biocrude, while almost no new components appeared from co-liquefaction with soy oil.
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 ofChlorellaand 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.