Catalytic Upgrading of Vacuum Residue over Metal-Loaded Iraqi Kaolin Using a Fixed-Bed Reactor

The catalytic upgrading of vacuum residue (VR) is constrained by the high cost, diffusional limitations, and rapid deactivation of conventional zeolite-based catalysts due to severe coking. Addressing this, we developed novel, low-cost, and coke-resistant catalysts utilizing naturally abundant Iraqi kaolin. A composite support comprising 80 wt.% Iraqi red kaolin and 20 wt.% white kaolin was synthesized via thermal activation at 800 °C and acid leaching. This support was subsequently impregnated with transition and rare-earth metals (Ni, Co, Ce) at 3–40 wt.% loadings, and comprehensively characterized using XRD, BET, SEM-EDX, and XPS. Catalytic performance was evaluated during VR upgrading in a fixed-bed batch reactor at 450 °C. Among the formulations, the 20 wt.% Ce-loaded catalyst (MKRW-800A@Ce20%) exhibited superior efficiency, achieving 80.15% VR conversion, 61.04% liquid yield, and minimal coke formation (3.81 g) compared to Ni and Co counterparts. This enhanced activity is attributed to synergistic effects of improved surface acidity, textural accessibility, and the Ce3+/Ce4+ redox couple, which promotes selective cracking while suppressing coke precursors. These findings provide new insights into the rational design of natural clay-based catalysts, establishing Ce-modified metakaolin as a viable, sustainable alternative to zeolites for industrial heavy-oil processing.