Mesoporous Tin-Triflate Based Catalysts for Transesterification of Sunflower Oil

Unimodal porous system (denoted as SnTf-MCM-41) and bimodal porosity (denoted as SnTf-UVM-7) were prepared in a two-step synthesis. The triflic acid was incorporated into previously synthesized Sn-containing porous silicas. Chemical analysis was carried out by electron probe microanalysis (EPMA), textural properties were determined by transmission electron microscopy (TEM) and from nitrogen adsorption-desorption isotherms (77 K), while structural characterization by X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) measurements. The structural characterization provided evidences on the direct interaction of triflate with incorporated tin species. The acidity of these catalysts was determined from the ammonia chemisorption measurements. The catalysts have been tested for transesterification of sunflower oil under both microwave and ultrasound activation. These experiments showed a direct reaction between the acidity of the catalysts and catalytic performances. No leaching of the triflate species or catalyst deactivation have been detected over several runs.