Preparation of efficient and recoverable organosulfonic acid functionalized alkyl-bridged organosilica nanotubes for esterification and transesterification

• Organosulfonic acid functionalized alkyl-bridged organosilica nanotubes are prepared.
• As prepared nanohybrids exhibit excellent catalytic activity in biodiesel production.
• Tubular morphology and unique textural properties positively influence the activity.
• The hybrid catalysts can be reused at least 3 times without loss of the activity.

A series of arenesulfonic or propylsulfonic acid functionalized ethane- or benzene-bridged organosilica nanotubes hybrid catalysts, Si(Ph/Et)Si-Ar/Pr-SO3H NTs, was demonstrated for the first time by a single step nonionic surfactant-templated sol–gel co-condensation approach. The pore morphologies, textual and acidic properties of as-prepared hybrid catalysts were characterized by TEM observations, nitrogen gas porosimetry measurements and acid–base titration, while the structural integrity of the incorporated organosulfonic acid groups and silica/carbon framework in the hybrid catalysts were studied by 13C CP-MAS NMR and 29Si MAS NMR. As the novel solid acid catalysts, the catalytic activity and stability of the Si(Ph/Et)Si-Ar/Pr-SO3H NTs were evaluated by esterification of palmitic acid and transesterification of yellow horn seed oil with methanol under refluxing temperature (65 °C) and atmospheric pressure. Based on the physicochemical properties and catalytic testing results, the excellent heterogeneous acid catalytic behaviors of as-prepared tubular hybrid catalysts were revealed in terms of their considerably high Brønsted acid-site density and acid strength, unique textural properties, interesting morphology as well as hydrophobic surface.

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