Preparação e atividade catalítica de Cr2O3:ZnO na reação de desidrogenação do isopropanol.

Abstract

In the literature, a synergistic increase in the catalytic activity of mixed chromium oxides and zinc in the atomic composition of 40 to 60% chromium as catalysts for the isopropanol dehydrogenation reaction and in the 1: 4 atomic composition for methanol synthesis. Baumgartner determined that the preparation method for the CuO: ZnO torque conversion of isopropanol, was the evaporation of the solvent. In the present work it was decided to study the catalytic activity of the Cr2 O3: ZnO binary in the model reaction of isopropanol dehydrogenation. The main objectives were: - Prepare catalysts by the evaporation method of the solvent of the Cr2O3: ZnO system in atomic compositions 00: 100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10 and 100: 00. - Characterize the catalyst samples by analyzing the chemical composition, specific area and diffraction of X-ray. - Evaluate the catalytic activity of the prepared samples, among which, with the catalyst of greater activity, study the influence of factors such as: catalyst mass, feed flow, reaction temperature, partial pressure of acetone in the feed and reaction time. The 40:60 atomic composition of Cr203: Zn0 showed the highest catalytic activity per gram of catalyst. An external diffusion effect was observed, which should influence the apparent activation energy value. There was a decrease in the conversion of isopropanol (from 65 to 15%), with an increase in the feed flow (8.0 to 60.0 ml / h), and an increase (from 15 to 50%) with an increase in the reaction temperature. (300 to 370 ° C). During 40 uninterrupted hours of operation the percentage conversion and selectivity remained constant. The presence of acetone, one of the products reaction, in the feeding causes a decrease in the fleece reaction city. The catalysts showed an increase in specific area, from 2 to 46 m2 / g of catalyst, with increasing the percentage of chromium. The results of the diffractograms indicated the presence of a new phase, the zinc chromite (Zn Cr204), considered an inert phase for dehydrogenation of isopropanol, and a good crystalline phase of the catalysts. Using the experimental data, a 1st order reaction was observed, according to the classic reaction order model.