Different Strategies to Anchor Organotin Methoxides on Silica and Their (Re)Use as Heterogeneous Catalysts for Transesterification Reactions

AUTOR(ES)

Jesus, Roberta A. de

FONTE

J. Braz. Chem. Soc.

DATA DE PUBLICAÇÃO

16/09/2019

RESUMO

Catalysts were prepared by the heterogenization of the tributyltin(IV) methoxide (n-Bu3Sn(OMe)) and dibutyltin(IV) dimethoxide (n-Bu2Sn(OMe)2) on silica by two strategies: (i) anchoring of the organotin(IV) compounds on silica and (ii) anchoring of the organotin(IV) compounds on a silica gel functionalized with mercaptopropyl groups (SiO2–SH). The characterization results showed that, regardless of the method used to anchor the organotin species, the solids contained approximately 7-10% of Sn. The decrease or disappearance of the O–H and S–H stretching signals in the SiO2 and SiO2–SH spectra after the treatment with the organotin(IV) methoxide derivatives suggest the immobilization via O–Sn or S–Sn covalent bonds. The catalytic performance was evaluated in methanolysis of ethyl acetate, in comparison to the analogous homogeneous systems, and the order of reactivity is n-Bu2Sn(OMe)2 > n-Bu3Sn(OMe) > SiO2–SnBu2 > SiO2–S–SnBu2 > SiO2–SnBu3 > SiO2–S–SnBu3. The solids on which the organotin species were directly immobilized on activated SiO2 showed catalytic efficiencies slightly higher than those immobilized on thiol-functionalized silica. All of the solid catalysts were recovered and reused for recycling studies and characterized again after the reuse tests. A better interaction between n-Bu3Sn(OMe) and both supports was observed, as verified by the low leaching of Sn after the first catalytic reaction.

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