Transesterification of short chain esters using sulfonic acid-functionalized hybrid silicas: Effect of silica morphology

• SO3H-silica activity depends on morphology, preparation method, acid capacities.
• In presence of FFA, both transesterification and esterification reactions occur.
• Recycle of 10SBA_Ox shows no leaching and higher stability than 10Am_Ox.

Sulfonic acid-functionalized hybrid silicas with different structure (amorphous, HMS, SBA-15) were synthesized by different methodologies, with a variable amount of organic moieties (propylSO3H). The obtained catalysts, characterized by X-Ray photoelectron spectroscopy, low angle X-Ray diffraction, N2 adsorption and acid capacity measurements, were tested in the transesterification reaction of short chain esters (from hexanoic to lauric ethyl ester). The optimized reaction was carried out under mild condition in the presence of 15% mol of the corresponding organic acid in order to reproduce a typical low-grade oil. A correlation between the catalytic activity of the materials and their acid capacities was found. The propyl-sulfonic SBA-15 catalyst presented the best performance in terms of activity and structural stability with no leaching of the sulfonic groups.

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