Synergistic Ni–Zn catalysts on sustainable mesoporous aluminosilicate for deoxygenation of Calophyllum inophyllum oil: RSM optimization toward green diesel production

Bimetallic Ni-Zn catalysts supported on mesoporous aluminosilicate (AlMs) were synthesized for the deoxygenation of Calophyllum inophyllum oil (CIO) toward green diesel production. Ni and Zn at varying Ni/Zn ratios were impregnated onto AlMs prepared from cellulose and soft template mixtures. XRD analysis revealed larger NiO crystallites in the 3Ni–Zn/AlMs catalyst, whereas ZnO remained highly dispersed. The mesoporosity of aluminosilicates was evidenced from the type IV isotherm with diameters of ∼7 nm and surface areas from 267 to 287 m² g⁻¹. NH₃-TPD and H₂-TPR analysis demonstrated that Ni/Zn variation modifies the amounts of weak and medium acidity, NiO dispersion and metal–support interactions. Optimization of catalytic deoxygenation of CIO using Response Surface Methodology based on Central Composite Design (RSM–CCD) evaluates the effects of Ni/Zn ratio, reaction temperature, catalyst loading, and reaction time. Statistical analysis revealed temperature and reaction time as the dominant parameters for increasing conversion and hydrocarbon yield. The regression model and desirability analysis predicted optimal conditions at a Ni/Zn ratio of 1.374, 360 °C reaction temperature, 3 wt% catalyst loading, and 120 min reaction time produced 84.19% conversion, 47.09% hydrocarbon yield, and 83.23% selectivity toward diesel-range hydrocarbons (C15–C17). ZnO increased the dispersion of NiO acidity for selective C–O bond dissociation to green diesel hydrocarbons, facilitated the hydrogen transfer process, and suppressed excessive C-C thermal cracking.