Incorporação da zircônia sulfatada à peneira molecular MCM-41 para ser utilizada na reação de transesterificação.

Abstract

The MCM-41 molecular sieve is considered promising as a support for the petroleum refining metal oxides, adsorbents and catalysts. Heterogeneous catalysts have great potential to make viable the production of biodiesel through the transesterification reaction. The synthesis of the MCM-41 molecular sieve was performed from deionized water, cetyltrimethylammonium bromide (CTABr), ammonium hydroxide (NH4OH), ethanol and tetraethyl orthosilicate (TEOS). The zirconium oxide was obtained by the sol-gel method from zirconium oxychloride with ammonium hydroxide at room temperature, the material was activated at 550 and 700 °C, and thereafter, sulphated. The material was then activated using the calcination process at 550 and 700 ° C and sulfated. The sulfation process was carried out with a 0.5 mol.L-1 sulfuric acid solution and allowed to stand for 30 minutes, dried for 12 h at 120 ° C and calcined at 400 ° C. The process of incorporation of ZS into the MCM-41 molecular sieve was done using different mass proportions (10, 20, 30, 40 and 50%) in relation to the mass of the MCM-41 molecular sieve, by wet method. It was verified from the analyzes of X-ray diffraction, the adsorption of nitrogen (BET method) and Fourier transform infrared spectroscopy (FTIR) the crystalline and textural properties which confirmed the molecular sieve obtainment and the presence of the tetragonal and monoclinic phases of the sulfated zirconia in the mesoporous structure. The micrographs of activated zirconium oxide at 550 and 700 °C and sulphated showed dispersed particles with the presence of cracks on its surface, after the incorporation there were no modifications in the structure. The catalytic activity was evaluated by the transesterification reaction of the soybean oil via the methyl route, using all the catalysts which were synthesized. The results showed that the catalyst 50_ZS/MCM-41_550 °C showed a greater conversion of methyl esters of 81.4% with the predominant tetragonal phase. The catalyst with the zirconium oxide activated at 700 °C obtained a conversion of 83.8% to the 40_ZS/MCM-41_700 °C catalyst, with the predominant monoclinic phase. However, the ester content of the oil samples was below the value established by the National Agency of Petroleum, Natural Gas and Fuels (ANP). The density and kinematic viscosity of the catalysts under study X_ZS/MCM-41 were in the range of the established standard. The acidity index was above the specified values, confirmed by the high percentage of free fatty acids in the oil.