abstract
The first immobilization of the trivacant Keggin-type polyoxometalate ([A-PW9O34](9-), PW9) to prepare a novel heterogeneous oxidative catalyst is here reported. PW9 was incorporated into the cavities of the chromium terephthalate metal-organic framework MIL-101(Cr). Characterization of the composite PW9@MIL-101 by powder X-ray diffraction, SEM-EDX, FT-IR, FT-Raman spectroscopy, N-2 adsorption-desorption isotherms and P-31 solid-state NMR confirmed that the structures of MIL-101 and the polyoxometalate anion were retained after immobilization. The composite PW9@MIL-101 revealed versatility as a heterogeneous catalyst to oxidize efficiently monoterpenes as well as to reach a complete desulfurization of a model oil containing the most refractory sulfur compounds in fuel, using in both systems acetonitrile as the solvent and H2O2 as the oxidant. Complete conversion of geraniol to 2,3-epoxygeraniol was achieved after the first 30 min at room temperature, while the total desulfurization of the model oil containing 1707 ppm of sulfur was attained after 2 h. In both systems the catalyst was recyclable for various cycles without a significant loss of activity. The stability and heterogeneity of the catalyst were confirmed by several techniques and by leaching tests.
keywords
LIQUID-PHASE OXIDATION; HETEROGENEOUS CATALYSTS; KEGGIN-TYPE; COMPLEX HETEROPOLYTUNGSTATES; DEEP DESULFURIZATION; LIMONENE EPOXIDATION; PHOSPHOTUNGSTIC ACID; POLYOXOMETALATE; H2O2; PERFORMANCE
subject category
Chemistry
authors
Granadeiro, CM; Barbosa, ADS; Ribeiro, S; Santos, ICMS; de Castro, B; Cunha-Silva, L; Balula, SS
our authors
Carlos Miguel Cardeal Enes Granadeiro
Post-Doc Fellowship
Isabel Cristina Maia da Silva Santos Vieira
Junior Researcheracknowledgements
The authors acknowledge the Fundacao para a Ciencia e a Tecnologia (FCT, MEC, Portugal) for their general financial support through the strategic project Pest C/EQB/LA0006/ 2011 (to Associated Laboratory REQUIMTE) and Operation NORTE-07-0124-FEDER-000067 - Nanochemistry, the R&D projects PTDC/CTM/100357/2008 and PTDC/EQU-EQU/121677/ 2010, and the fellowship SFRH/BPD/73191/2010 (to CG).