Sustainable Valorization of Palm Fatty Acid Distillate into Green Diesel Using Ni–Co Catalysts Supported on Zeolite from Kaolin Waste under Solvent- and Hydrogen-Free Conditions

The use of low-cost, nonedible feedstocks has proven to be a promising route for catalytic deoxygenation reactions aimed at producing diesel-like hydrocarbons. In this study, palm fatty acid distillate, a byproduct of crude palm oil refining, was converted into green diesel via thermal and catalytic deoxygenation using zeolite-supported Ni, Co, and NiCo catalysts (10 wt % metal, synthesized from kaolin residue). The reactions were carried out at 250-350 °C for 30 min without solvent or hydrogen. The process was evaluated using thermogravimetric analysis, and kinetic parameters were estimated via the Coats-Redfern method. Both the thermal and catalytic routes yielded 60-65% organic liquid products, with 77-83% hydrocarbons in the C₈-C₁₇ range. The catalytic route resulted in high yields of diesel-range hydrocarbons (C₁₅-C₁₇), with 86% for NiZ, 75% for CoZ, and 65% for NiCoZ, whereas the thermal route reached only 45%. Thermodynamic evaluation further demonstrated that cobalt-based catalysts enhanced deoxygenation selectivity while limiting secondary cracking. This study presents a sustainable and scalable approach. This study presents a sustainable and scalable approach for converting industrial waste into high-quality green diesel using waste-derived catalysts under mild, hydrogen-free conditions.