Development of Karalite catalyst for sustainable Biodiesel synthesis from Waste Cooking Oil under mild conditions

Abstract

Continuous heating of cooking oil during repeated culinary processes generates free radicals, which pose significant health risks, including incurable cancers and gastrointestinal disorders. To address this concern, this study explores the transformation of waste cooking oil into biodiesel as a sustainable alternative. However, conventional biodiesel synthesis methods are often labour-intensive, expensive, and corrosive, highlighting the need for an efficient and environmentally friendly catalytic process. The research aims to develop a highly active, stable, and reusable catalyst that overcomes the limitations of traditional methods. This study introduces Karalite, a novel nanoporous integrated framework catalyst synthesized at ambient temperature using a simple sol-gel method with diethylenetriamine as a template. Physico-chemical characterization of Karalite is performed by WAXRD, FT-IR, UV-DRS, BET, SEM, HR-TEM, TGA, and chemisorption analysis. WAXRD confirmed the formation of an integrated framework of tenorite, copper ultraphosphate, and aluminum metaphosphate. FT-IR analysis also confirmed the tenorite (650 cm⁻¹), Copper ultraphosphate (2346 cm⁻¹) and aluminium meta phosphate (730 cm⁻¹), and tetrahedral framework of PO₄^3- (1100 cm⁻¹). BET analysis confirmed the formation of four types of pore sizes 3, 4, 7, and 10 nm. TGA demonstrated its remarkable thermal stability up to 1200 °C. SEM and HR-TEM analyses revealed well-defined morphological characteristics and the d-spacing values are similar to that of XRD. UV-DRS analysis confirmed the incorporation of Cu²⁺ in the material. Karalite is applied for biodiesel synthesis and achieves a 93 % conversion and 97 % selectivity at 32 °C.