Zeólita NaP de fontes de sílica natural e residual impregnada com íons sulfatados como catalisador na esterificação de ácido oleico

Abstract

NaP zeolite synthesized by the hydrothermal method, from silica-alumina sources of heat-treated soil (rich in kaolinite) and residual silica gel, impregnated with sulfate ions was used as a catalyst in the reaction esterification of oleic acid. The precursor materials and NaP zeolite were characterized by analytical techniques: XRF, XRD, FTIR, SEM and N2 adsorption/desorption (BET and BJH methods). Esterification reactions were carried out without and with NaP zeolite (catalyst). The reaction time, oleic acid/methanol ratio and catalyst mass parameters were 5 hours, 1:5, 5 %w/w, respectively, for each reaction temperature of 80, 100, 120 and 140 °C. Chemical characterization of XRF and XRD of the calcined soil sample showed an excess of quartz (SiO2). XRD analysis of the sample of zeolitic material of interest indicated that the synthesis by the hydrothermal route was efficient in obtaining NaP zeolite. The analyzes of the FTIR spectra of the precursors agreed with the previous analytical techniques, as well as for the sample of NaP zeolite in which it confirmed the impregnation of sulfate ions, typical of acid sites distributed in the surface of NaP zeolite. The SEM images of the calcined soil sample show typical morphology of kaolinite to metakaolinite conversion and of the NaP zeolite sample with similar morphology to the literature. And the adsorption/desorption analysis of the NaP zeolite sample estimated 44 m2 g-1 of SSA typical of mesopores. The esterification reactions showed significantly higher conversion rates, mainly at 140 °C, reaching approximately 94 % of methyl oleate with catalyst and 57 % in the absence of catalyst. The thermodynamic properties indicate that esterification reactions with catalyst near and above 120 °C are spontaneous.