Facile synthesis of mesoporous sulfated Ce/TiO2 nanofiber solid superacid with nanocrystalline frameworks by using collagen fibers as a biotemplate and its application in esterification

Abstract

Collagen fibers, one of the most abundant biomass in the natural world, were used as the biomass template to synthesize cerium-doped mesoporous TiO₂ nanofiber (SO₄²⁻–Ce_x/TiO₂) solid acid catalysts. The physiochemical properties of the as-prepared catalysts were well characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS). The fibrous morphology of native collagen fibers were found to be well preserved in SO₄²⁻–Ce_x/TiO₂, and the acid strength and textural property of the SO₄²⁻–Ce_x/TiO₂ were adjustable by changing the doping amount of Ce and the curing temperature. The catalytic properties of as-prepared catalysts were evaluated in the esterification reactions. It was found that the SO₄²⁻–Ce_x/TiO₂ exhibited high activity under mild reaction conditions. When reacted at 90 °C for 45 min with a catalyst amount of 2 wt%, the conversion yields of ethyl acetate, butyl acetate, hexyl acetate and ethyl caproate were 99.9%, 97.06%, 94.29% and 86.75%, respectively. Additionally, the SO₄²⁻–Ce_x/TiO₂ solid acid catalyst could be reused at least 6 times without significant loss of activity, exhibiting much better reusability as compared with the SO₄²⁻–TiO₂* catalyst prepared by conventional approach.