Síntese e caracterização de catalisadores bifuncionais de óxidos mistos puros e sulfatados de CaO-Fe2O3-SO42, impregnados com cobre, utilizando cascas de ovo

Abstract

The present work studied the synthesis of pure and sulfated mixed oxide supports for heterogeneous catalysts seeking to improve their acid-base properties. In this way, mixed oxides of CaO-Fe2O3-SO4 2- with different molar ratios Fe2O3 /CaO = 0.5, 1.0, 1.5 and 2.0 were synthesized, identified as CF-0.5, CF-1.0, CF-1.5 and CF-2.0 and sulfated with 0.5 M H2SO4 , respectively, and impregnated with Cu. The solids were characterized by the techniques of Thermogravimetric-Differential Calorimetric Analysis (TGA-DSC), X-ray Diffraction (XRD), Temperature Programmed Desorption (TPD-NH3 and TPD-CO2), Temperature Programmed Reduction (TPR) and N2 Physisorption Analysis (BET). The TGA-DSC analysis obtained the calcination temperature of the eggshells and support, defined as 850 ºC and 650 ºC, respectively. The XRD analyses showed the production of crystalline phases of CaO and Fe2O3 , as well as the crystalline phase of iron and calcium spinel Ca2Fe2O5, as well as the phase of Fe2O3, CaSO4 and CuO. According to the TPD-CO2 results, it was possible to observe that the solids presented heterogeneous distribution of weak and strong basic sites. From the TPD-NH3 results, the solids CF-1.0 and CF-2.0 showed a higher concentration of strong acid sites. Through the TPR technique, it was observed that the catalyst CuCF-1.5 obtained reduction peaks at 385, 454 and 663 ºC, and the CuCF-0.5 reduction peak at 545 ºC, showing the reduction of the metals present at different temperatures. The BET analysis presented type III and V isotherms, and it was observed that the CF-1.5 and CuCF-1.5 solids showed specific areas of 17 and 15 m2/g, respectively, and pore diameters of 270 and 236 Å. In this sense, the synthesized precursors showed their potential use in catalytic reactions.