H3PO4- and H2SO4- treated niobic acid as heterogeneous catalyst for methyl ester production

The activity of solid niobic acid treated with sulfuric acid and with phosphoric acid was tested in the catalytic esterification of oleic acid and in transesterification of soybean oil with methanol. X-ray diffraction studies revealed niobic acid treated with sulfuric acid to be an amorphous solid, while niobic acid treated with phosphoric acid presented a crystalline phase, probably due to the formation of hydrogen niobium phosphate. Among the characterization methods employed here, XPS was particularly instrumental in showing that niobium dihydrogen phosphate and niobium hydrogen sulfate moieties are the acidic active sites responsible for the catalytic effect. The latter is more active according to ammonia TPD studies. Yields as high as 78% in the esterification of oleic acid with methanol and 40% in the transesterification of soybean oil catalyzed by NbSO4 were recorded.992269280Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ

Delaminated vanadoaluminosilicate with [V,Al]-ITQ-18 structure

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This paper reports on the delamination of the layered [V,Al]-Nu-6(1) to originate the [V,Al]-ITQ-18, where vanadium and aluminum were inserted in the structure by direct synthesis. The delaminated solids were obtained directly from the basic medium used for swelling, after sonication and after acid addition. Vanadium and aluminum atoms are part of the lattice sites as confirmed by Al-27-MAS-NMR,V-51-MAS-NMR and UV-Vis spectroscopy. The extent of delamination was monitored by X-ray diffraction, N-2 adsorption-desorption isotherms and Si-29-MAS-NMR. The presence of FTIR bands in the double rings region indicates that the structural unit of the initial lamellar precursor is still preserved in the delaminated materials. The material obtained after acid addition contains V5+ in extraframework octahedral and in tetrahedral sites, the first ones are easily exchanged by sodium ions. On the other hand, the material prepared only under alkaline conditions presents only framework tetrahedral V5+. The presence of the V4+ was confirmed in the lamellar precursor by EPR but the vanadium oxidation state and localization change throughout the delamination procedure. (C) 2012 Elsevier Inc. All rights reserved.156244256Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq