Esterification of oleic acid using 12-tungstophosphoric supported in flint kaolin of the Amazonia

In this study, 12-tungstophosphoric acid was supported in different proportions, 20, 40 and 60 wt%, using as a matrix of the Amazon kaolin flint and century (commercial kaolin) via impregnation in aqueous solution (HCl 0.1 and 0.5 mol L−1) and acetonitrile. Before the impregnation, kaolin were subjected to a leaching acid in order to increase surface area and acidity. For characterization of the catalysts, FT-IR, XRD and XRF were employed. The FT-IR analysis showed that there was no decomposition of the HPW Keggin structure during material preparation. However, in the presence of HCl 0.1 mol L−1, it was not possible to conclude that the impregnation was due to the low intensity of the absorptions for the HPW; for the spectra with acetonitrile and HCl 0.5 it was possible to observe them. The XRF and XRD data confirmed these results. The catalysts were tested in the esterification reaction using molar ratio alcohol: acid equal to 30 at 100 °C for 2 h in a PARR 4348 reactor in the presence of different alcohols. Best conversions were obtained with the use of methanol, reaching 97.21% yield, independent of HPW support. A study of reaction parameters, temperature and time with the catalyst PW(20)MFS and 20 wt% concentration of HPW in metakaolin flint (with and without acid treatment) was also conducted. It was observed that the catalyst deactivation occurred by coke formation, since leaching was about 2%.