Structure and Activity of Vanadium-Chromium Oxide Catalyst for Liquid Phase Oxidation of Acrolein

Abstract

The relations between structure and catalytic activity of vanadium-chromium oxide for the liquid phase oxidation of acrolein have been studied. The reaction was carried out in a gas sealed system and the rate of oxygen consumption was measured. The three kinds of binary oxide catalyst were prepared by calcining (at 450 C) the pastes made from different combinations of raw materials, such as NH, VOs + Cr(NO3)3 e g H20, NH4VOg3 + Cr(OH3)enH2O and V205 + Cr203, and they were denoted as V-Cr-A, V-Cr-B and V-Cr-C, respectively (Table 1). The following results were obtained. According to X-ray diffraction (Figs.2 and 3), V-Cr-C consists of only V20s and Cr20s, however, besides these oxides, there are recognized two other structures in V-Cr-A and V-Cr-B. One of these which is clarified to contain VS ion by measuring ESR (Figs.3 and 6) was denoted as Y and the other as, X. By means of DTA, etc., Y was ascertained to decompose to vanadium pentoxide, structure X and chromium orthovanadate at about 800C (Figs.5, 7 and 8). IR spectra (Figs.4. and 8) suggest. that X contqins only the bonding of -V-O-Cr-, but both bondings of -V-O-Cr- and. -V-O-V- are included in Y. In V-Cr-C, only V20s is thought te be active and the activity of this species is considered to be diluted with Cr20s which is inactive. The activity for oxidation can be put in the following order V-Cr-A- V-Cr-B- V-Cr-C (Fig.1). Furthermore, a catalyst obtained by washing V-Cr-A with NH3 in order to remove V20s and therefore thought to be mainly cemposed of structure Y, showed higher activity than the original catalyst V-Cr-A (Fig.3 and Table 2). Consequently, it is concluded that the structure Y is mainly. formed in the catalyst prepared from NHaVOs + Cr(NO3)3.9 H20 and, as V205, it has large contribution to the activity of the V-Cr catalysts.