Reforma a vapor de acetona sobre catalisadores de Ni e Co/MgAl2O4: efeito das propriedades redox dos reagentes e dos catalisadores nos caminhos de reação

Abstract

The Steam reforming of Acetone (SRA) reaction was studied on magnesium aluminate (MgAl2O4) supported nickel (Ni) and cobalt (Co) catalysts. The catalysts with 8 wt.% of Ni, Co or Ni-Co were prepared by dry impregnation and characterized with X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR) and Thermogravimetric Analysis (TGA). The catalytic tests were carried out at the molar ratio H2O/C3H6O = 6 of three ways: i) Thermal decomposition of C3H6O as a function of temperature between 523 and 973K; ii) SRA reaction as a function of temperature between 523 and 873K; and iii) SRA reaction in presence of H2 as a function of temperature. The stability tests were carried out for 4 hours at 773 and 4 hours at 873K. The thermal decomposition of acetone in homogeneous phase was significant above 923K. The SRA on reduced catalysts occur at temperatures above 773K, with conversion in a mixture of H2, CO2, CO and minor conversion to CH4 and C2H4. On Cocontaining catalysts, the SRA occurs via pyrolytic mechanism with the activation of C3H6O by cleavage of C-H bonds, followed of C-C and C-O bonds and oxidation of C formed by H2O. The Ni-containing catalyst, in the presence of H2, is active at lower temperatures (523K) than Co-containing catalysts with conversion predominantly to CH4. The results indicate that the H2 instead of C3H6O reduce of NiO on surface and the intermediates of acetone activation on reduce Ni surface is hydrogenate to CH4 at low temperatures. The thermogravimetric analysis of used catalysts demonstrate greater carbon accumulation on Ni than on Co-containing catalysts.