Unraveling the catalytic potential of a heterometallic Zn-Ca metal-organic framework for intensified green biodiesel synthesis from waste palm oil

The diminution of fossil fuel reserves and the escalating environmental concerns have triggered a worldwide search for sustainable energy solutions. In this light, the present study explores the use of a heterometallic structured zinc-calcium metal-organic framework (Zn-Ca MOF) as a heterogeneous catalyst to address this problem. The novelty of this work lies in integrating this heterometallic Zn-Ca MOF catalyst with statistical process optimization and economic assessment for the conversion of waste palm oil into biodiesel. To optimize the transesterification process, Response Surface Methodology (RSM) based on a Central Composite Design (CCD) was employed to assess the interactive impact of key process variables, specifically methanol-to-oil molar ratio, catalyst loading, reaction temperature, and time, to maximize the production of fatty acid methyl esters (FAME). Under the optimized conditions of a methanol-to-oil ratio of 6:1, a catalyst loading of 5 wt %, a temperature of 75 °C, and a reaction time of 180 min, a remarkable biodiesel productivity of 97.34% was achieved. Catalyst reusability tests demonstrated sustained catalytic activity without decay over seven consecutive reaction cycles, while life cycle cost analysis (LCCA) confirmed the economic feasibility of the process. These findings validate that the Zn-Ca MOF is a robust, efficient, and cost-effective hetero-catalyst for sustainable biodiesel production.