Propylsulfonic acid and methyl bifunctionalized TiSBA-15 silica as an efficient heterogeneous acid catalyst for esterification and transesterification

• Propylsulfonic acid and methyl bifunctionalized TiSBA-15 material are prepared.
• As prepared TiSBA-15-Me-PrSO3H exhibits excellent catalytic activity in biodiesel production.
• Enhanced total acidity and surface hydrophobicity contribute to excellent catalytic activity.
• The TiSBA-15-Me-PrSO3H can be reused at least 3 times without loss of the activity.

Propylsulfonic acid and methyl bifunctionalized TiSBA-15 silica material, TiSBA-15-Me-PrSO3H, is prepared by a direct nonionic surfactant-templated sol–gel co-condensation approach combined with low-temperature hydrothermal treatment. The structural integrity of the incorporated propylsulfonic acid groups and terminally bonding methyl groups are studied by 13C CP-MAS NMR and 29Si MAS NMR spectroscopy, while the chemical state of Ti(IV) species in the hybrid material is tested by XPS and UV–Vis/DRS. The ordered mesostructure, morphology and porosity of as-prepared hybrid material are characterized by low-angle XRD measurements, TEM observations and nitrogen gas porosimetry measurements. As the efficient solid acid catalyst, the heterogeneous acid catalytic activity and stability of the TiSBA-15-Me-PrSO3H are evaluated by esterification of palmitic acid and transesterification of yellow horn 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 hybrid catalyst are explained by the contribution of their strong Brönsted and Lewis acidity, excellent porosity properties as well as surface hydrophobicity.

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