Sustainable production of biodiesel and transformation of glycerol to glycerol laurate esters over inner diameter-controlled sulfonic acid functionalized ethyl-bridged-organosilica nanotubes

Abstract

Solid acid-catalyzed biodiesel production from inedible oils offers a promising mean to reduce the cost of feedstocks and avoid the competition with edible oil market. Here we demonstrate a series of inner diameter-controlled sulfonic acid functionalized ethyl-bridged-organosilica nanotubes (Ar/PrSO3H–Si(Et)Si) by a toluene swollen mixed Pluronic surfactant micelle-templating co-condensation route for transesterification of tripalmitin or plant oils with methanol to produce fatty acid methyl esters and esterification of glycerol with lauric acid to produce mono- and di-glycerol esters. By combination of superstrong Brønsted acidity, unique hollow tubular nanostructure, excellent porosity properties and hydrophobic surface, the Ar/PrSO3H–Si(Et)Si nanotubes display higher catalytic activity as compared with acidic resin and zeolite. Additionally, the inner diameters and lengths of Ar/PrSO3H–Si(Et)Si nanotubes influence the activity obviously. The Ar/PrSO3H–Si(Et)Si nanotubes also show excellent catalytic reusability, attributing to covalent bonding of Ar/PrSO3H groups within silica/carbon framework and surface hydrophobicity of the catalysts.