Ultrafast Biodiesel Synthesis via K2CO3-Supported Mg-Al Hydrotalcite Catalyst With Tailored Basicity and Mesoporous Structure

Abstract

With the increasing global energy demand and the growing prominence of environmental issues, biodiesel has garnered significant attention as a renewable, low-emission green energy source. Conventional hydrotalcite-based catalysts often suffer from insufficient basicity and limited accessibility of active sites, leading to relatively long reaction times and limited efficiency. This study synthesizes Mg-Al hydrotalcites composed of various metal salts via the co-precipitation method and employs them as supports for K2CO3 to efficiently produce biodiesel. The transesterification performance of different Mg-Al hydrotalcite catalysts was evaluated using a three-component reaction (rapeseed oil, methanol, and methyl acetate) under conditions of an oil-ester-alcohol ratio of 1:1:10, a catalyst loading of 10 wt%, and a reaction temperature of 60°C. Results indicated that Mg-Al hydrotalcite derived from acetate metal salts using K2CO3 as the precipitant achieved a high biodiesel yield of 98.79% within 15 min, which is substantially faster than most reported hydrotalcite-based reactions that typically require 30–120 min under comparable conditions. TG-DTA analysis revealed that the formation of potassium aluminum oxide after high-temperature calcination, which provides more alkaline sites as suggested by CO2-TPD profiles, is a key reason for the high catalytic activity. BET and SEM analyses showed that the catalysts possess a large specific surface area and rich pore structure, significantly enhancing the dispersion of alkaline sites. These synergistic features enable ultrafast biodiesel synthesis and provide a promising strategy for designing efficient and sustainable solid base catalysts for large-scale biofuel production.