Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/79986
Type: Artigo de periódico
Title: H3PO4- and H2SO4- treated niobic acid as heterogeneous catalyst for methyl ester production
Author: de Pietre, MK
Almeida, LCP
Landers, R
Vinhas, RCG
Luna, FJ
Abstract: 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.
Subject: Acidic treatment
Niobium catalysts
Transesterification/esterification
Surface treatment
Country: Holanda
Editor: Springer
Rights: fechado
Identifier DOI: 10.1007/s11144-009-0143-9
Date Issue: 2010
Appears in Collections:Unicamp - Artigos e Outros Documentos

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