Samuel Kenneth Sutrisno, Ian Mattew Yehofa Natanael, Shella Permatasari Santoso, Jindrayani Nyoo Putro, Felycia Edi Soetaredjo, Maria Yuliana, Suryadi Ismadji
Clay minerals have re-emerged as heterogeneous catalysts for biodiesel production because their layered and fibrous architectures can be engineered to control active-site accessibility, acid/base functionality, and feedstock–catalyst interactions. However, despite their widespread use, the current understanding of the structure–property–performance relationship across different clay families remains fragmented. This review provides a comprehensive and critical synthesis of recent developments (with an emphasis on the literature from 2020 to 2025) on pristine, acid/base-modified, pillared, metal-impregnated, and composite clay catalysts for transesterification and esterification reactions. Fundamental mineralogical characteristics—including layer structure, cation exchange capacity, interlayer accessibility, Brønsted/Lewis acidity, surface functionalities, and confined-space effects—are systematically linked to catalytic behavior under various reaction environments. Mechanistic pathways governing triglyceride conversion, free fatty acid (FFA) esterification, alcohol activation, and deactivation phenomena (pore blocking, fouling, leaching, structural collapse) are discussed in correlation with clay architecture. Performance evaluation encompasses reaction kinetics, tolerance to high FFA feedstocks, operational windows, and long-term stability across multiple reuse cycles. A critical comparison with conventional, biological, and emerging catalyst families—including NaOH/KOH, CaO, sulfonated carbon, ion-exchange resins, enzyme catalysts, zeolites, metal oxides, MOFs, and COFs—highlights the competitive position of clay-based catalysts in terms of cost, availability, tunability, feedstock tolerance, environmental safety, and suitability for scalable biodiesel production. The review concludes by outlining future research opportunities, including operando mechanistic studies, rational surface engineering, hierarchical porosity design, hybrid clay–MOF systems, lifecycle assessment (LCA), techno-economic analysis (TEA), and integration with green process intensification strategies. Distinct from previous reviews that mainly summarize heterogeneous catalyst classes or biodiesel yield data, this review establishes a clay-mineralogy-centered framework that links structural class, modification chemistry, active-site evolution, confined-space catalysis, feedstock tolerance, deactivation behavior, and industrial feasibility. Overall, this work presents a unified framework that links clay mineralogy to catalytic performance, providing actionable insights for the development of next-generation clay-based catalysts for scalable, sustainable biodiesel production. © 2026 Elsevier Ltd
Department of Chemical Engineering, Widya Mandala Surabaya Catholic University, Kalijudan 37, Surabaya, 60114, Indonesia