%0 Journal Article
%T Synthesis, characterization and use of Nb2O5 based catalysts in producing biofuels by transesterification, esterification and pyrolysis
%A Brand£¿o
%A Rodrigo F.
%A Quirino
%A Rafael L.
%A Mello
%A Vinicius M.
%A Tavares
%A Andr¨¦ P.
%A Peres
%A Ant£¿nio C.
%A Guinhos
%A Fl¨¢via
%A Rubim
%A Joel C.
%A Suarez
%A Paulo A. Z.
%J Journal of the Brazilian Chemical Society
%D 2009
%I Sociedade Brasileira de Qu¨ªmica, SBQ
%R 10.1590/S0103-50532009000500022
%X nb2o5/hx (x = hso4-, h2po4-, no3-) compounds were obtained from the treatment of niobium acid (nb2o5¡¤xh2o) with sulfuric, phosphoric, and nitric acids as well as nb2o5 and nb2o5¡¤xh2o have been investigated as catalysts for the transesterification, esterification and pyrolysis of vegetable oils. the compounds were characterized by thermal analysis (dta-tga), spectroscopy (drx, ft-ir and ft-raman), surface area (bet) and the acidity (ho) determined by n-butylamine titration using the hammet¡äs indicator method. it was observed that after the acid treatment both the surface area and the acidity decreased as compared to the starting nb2o5¡¤xh2o. the only exception was a higher acidity verified when nitric acid was used. among the catalyst investigated, the nb2o5/h3po4 presented the highest activity in the alcoholysis of soybean oil with different mono-alcohols (methanol, ethanol, 2-propanol, n-butanol). all tested solids seemed to stabilize the carboxylic acids formed during the pyrolysis, yielding higher acid numbers for the obtained products. finally, the use of nb2o5/h3po4 and nb2o5/h2so4 as catalysts for the esterification showed better activity than nb2o5¡¤xh2o and nb2o5.
%K esterification
%K transesterification
%K pyrolysis
%K niobium compounds.
%U http://www.scielo.br/scielo.php?script=sci_abstract&pid=S0103-50532009000500022&lng=en&nrm=iso&tlng=en