III International Conference

PP-II-150steamed until a gel formation followed by calcination in air at 400 °C. Catalystscharacteristics were studied by XRD, IR spectroscopy, Differential Dissolution and H 2 -TPR.For unpromoted CCZY samples, the solid solutions of fluorite structure are alreadyformed after calcination at 400 °C and they all contain CuO phase. According to XRD, IR andDD, the samples promoted by alumina and Cr contain highly dispersed YCuO x , Al 2 O 3 of poorcrystallinity and Cr 2 O 3 along with a solid solution of the fluorite type. Addition of aluminaand Cr leads to the significant increase of the specific surface area from 6-33 m 2 /g (CCZYsamples) up to 170 m 2 /g for CCZYA and CCZYA+Cr samples.Redox properties of the catalysts were investigated by H 2 -TPR. For all catalysts, a broadpeak with a maximum at 200-235 °C is observed in TPR spectra. The position of this peakdepends on the copper content and presence of promoters. Thus, the peak maximum shiftsfrom 232 °C for unpromoted catalysts to 209 °C for Al 2 O 3 and Cr-containing catalysts. Thispeak could be assigned mainly to reduction of Cu 2+ since the H 2 consumption increases withthe copper content. However, the ratio of H 2 consumption to Cu concentration is above 1,hence, even at this relatively low temperature partial reduction of Ce 4+ occurs as well.Moreover, for promoted samples, the increase of H 2 consumption is observed testifyingacceleration of oxygen mobility.The catalysts were tested in partial oxidation of acetone using a quartz flow reactorpacked with a catalyst (0.25-0.50 mm fraction) diluted with quartz sand. Reaction mixture of1% acetone + 0.5% O 2 , He -balance was fed through the reactor at contact time 25 ms andincreasing temperature from 25 to 880 °C with the rate 10 °C/min.The overall system of reactions which may occur during the acetone oxidation is quitecomplex. For almost all catalysts, the main tendency of product distribution is similar.Formation of CO 2 due to partial acetone oxidation is observed in the temperature range of 150to 250 °C depending on the catalyst. At 300-350 °C, H 2 and CO appear indicating thatthermal decomposition of acetone competes with the oxidation. H 2 is produced faster then COand its maximum concentration attains at lower temperatures. The steep increase of COconcentration followed by the decrease of CO 2 concentration at 600-650 °C may be attributedto the reverse water-gas shift reaction [3]. Chemical composition of the catalysts stronglyinfluences on their performance in acetone oxidation. The start temperature of hydrogen andsyngas evolution depends on the copper and alumina content, chromium additives in thecatalyst. Thus, among unpromoted CCZY catalysts, for the sample with the highest coppercontent, the maximum hydrogen concentration reaches at the lowest temperature – 790 °C.441