Synthesis and Evaluation of a Novel Cassava-Based Starbon-Type Mesoporous Catalyst

Abstract

Mesoporous materials are well suited as supports for heterogeneous catalysis because they facilitate the access and mobility of large molecules, thereby improving yields across a range of chemical reactions. Among these, mesoporous carbons can be advantageously synthesized from biobased sources and further functionalized for use as acid catalysts in esterification reactions. This work focuses on the production of an esterification catalyst based on starch-derived mesoporous carbon (Starbon), using cassava starch as the raw material, and compares its performance with that of a conventional corn starch-based (Hylon VII) Starbon. The catalysts were prepared via gelatinization in water, retrogradation, solvent exchange with t-butanol, freeze-drying, and carbonization of expanded starch at 450 °C, followed by sulfonation with sulfuric acid. The resulting cassava-derived Starbon exhibited a surface area of 263 m2/g and a mean pore diameter of 8.1 nm, comparable to those of commercial corn-based material (271 m2/g and 14.5 nm). The catalysts were evaluated in the batch esterification of stearic acid with isopropyl alcohol, and their performance was compared with that of several commercial homogeneous (H2SO4, p-toluenesulfonic acid, methanesulfonic acid) and heterogeneous (Amberlyst 15, Amberlyst 35) catalysts. Despite performing below homogeneous catalysts, cassava-based Starbon outperformed all heterogeneous catalysts, reaching an apparent turnover frequency of 0.2 mol·s–1·H+ Equiv–1 and a final conversion of 24% after 5 h. Postreaction acidity measurements indicated that the catalyst is chemically stable; however, it suffers from mechanical instability. This is likely due to the high amylopectin content in cassava starch, which hinders the formation of a robust and stable porous structure.