Encapsulation of vanadium complexes in inorganic or hybrid matrices via the sol-gel method: application to the epoxidation of allylic alcohols

Journal of the Brazilian Chemical Society

Rodolfo B. Pellegrino¹  Regina Buffon¹ 

[1] ,Universidade Estadual de Campinas Instituto de Química Campinas SP ,Brazil

关键词: vanadium;    epoxidation;    allylic alcohols;    sol-gel method;   

DOI  :  10.1590/S0103-50532004000400014

来源: SciELO

【 摘 要 】

Vanadium complexes have been encapsulated in inorganic (based on hydrolysis/condensation of tetramethylorthosilicate - TMOS) and hybrid matrices (TMOS plus a co-condensation agent) using the sol-gel method. The resulting solids were tested in the epoxidation of allylic alcohols in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant agent at 70 ºC. When the catalyst was based on [VO(salen)], the hybrid matrix led to higher initial turnover frequencies than the inorganic one for all tested alcohols (trans-3-phenyl-2-methyl-2-propen-1-ol, trans-2-hexen-1-ol, cis-2-hexen-1-ol, 1-octen-3-ol), which might be related to its higher pore diameter. Although no vanadium leaching was observed during the catalytic reactions, recycling experiments with the hybrid catalyst and trans-2-hexen-1-ol showed that some loss of vanadium took place at every Soxhlet washing (performed after every run, using CH2Cl2): a total of 1.5 wt.% after three reactions. In four successive runs, keeping the initial molar ratios, conversions decreased from 100% to 85%, 65% and 40% (in 5h).

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