Development of Highly Effective Sulfonic Acid–Functionalized NR/MS Nanocomposites for Biodiesel Production

Abstract

The acidic natural rubber/wormhole-like mesostructured silica nanocomposites (NR/WMS-SO₃H) were successfully functionalized with propylsulfonic acid and arenesulfonic acid via a cocondensation method using 3-mercaptopropyl trimetho-xysilane (MPTMS) and 2-(4-chloro-sulfonylphenyl) ethyltrimethoxy silane (CSPTMS), respectively. Compared with organosulfonic acid-functionalized wormhole-like mesostructured silica (WMS-SO₃H), NR/WMS-SO₃H demonstrated increased hydrophobicity while maintaining mesoporosity and a large surface area. The catalytic performance of the synthesized solid acids was subsequently evaluated via batch esterification of palmitic acid with methanol to generate fatty acid methyl esters for biodiesel synthesis. Compared with WMS–SO3H, NR/WMS–SO₃H demonstrated superior catalytic activity, which was attributed to the synergistic interaction between the strongly acidic functional groups and surface hydropho-bicity. The NR/WMS-SO₃H catalysts demonstrated novel properties with a large surface area and high acidity and prevented hydrolysis, paving the way for further study to produce other high-value ester products via esterification since they exhibited high conversion of free fatty acids.