ИСТИНА

1. By Method XRD, SEM, XPS received bismuth-based metal oxides: Bi-Cо, Bi-Со-К were characterized. Catalytic activity of these systems in diesel soot oxidation with oxygen was studied in microcatalytic reaction cell in pulsed mode at 300-520°С in a tight and loose contact with soot. 2. In a tight contact both systems demonstrate high catalytic activity in diesel soot oxidation at 400°C. Initial temperature of progressing soot oxidation corresponds to 320 - 340°C in both cases, while pure soot starts noticeably to oxidize only at 460-480°C. In this case the activity of the system Bi- Co- K is higher. In loose contact with soot the catalytic activity of the system Bi-Co-C is slightly decreasing but still remains high, while the system Bi-Co without potassium practically loses activity. 3. XPS was used to determine the chemical state of synthesized catalysts and soot/catalyst mixtures’ surfaces before and after oxidation. As a result, in the process of soot oxidation in presence of Bi- Co and Bi- Co -K was detected C1s state of the electron with binding energy 286.6eV and 288.8eV indicating the formation of soot on the chemical bond of C-O surface. According to [1], these lines can be linked to the presence on the soot surface of the carbonyl (286.6 eV) and the carboxyl ( 288.8 eV) functional groups. The K2p 3/2 binding energy is about 293.0eV, which is typical for K 1+. The Co2p 3/2 binding energy is about 780.1eV; this is similar for all samples and corresponds to Co3O4. The Bi4f 7/2 binding energy is about 158.8eV and this is typical for Bi 3+. 4. The concentration of oxygen bound with the soot surface varies depending on the treatment conditions. XPS data demonstrate that the lowest oxygen concentration is un-oxidized soot surface specific (the value of C/O = 60). During the oxidation of initial soot at 500°C the oxygen concentration on the soot surface increases (С/О = 40). In presence of Bi- Co and Bi- Co –K the soot surface is strongly saturated with oxygen. For sample Bi- Co -K the oxygen concentration is maximal (C/O = 3) and 5 times more than for the sample Bi-Co (C/O= 14). In such a manner the presence of catalysts (this more relates to potassium containing system) effectively increases the soot surface quantum capable to adsorb O2 with formation of surface oxygenbearing functional groups. Comparing XPS data with the results of the catalytic activity of systems in the soot oxidation makes note: the system Bi- Co -C demonstrating the highest catalytic activity in the soot oxidation also shows the maximum activity in the soot surface’ oxygen saturation (ratio C/О = 3); the carbon oxygen system Bi- Co is less able to saturate the soot surface with oxygen (C/О = 14) and is less catalytically active. In [2] the high catalytic activity of the transition-metal oxides in the soot oxidation with oxygen is explain by formation and decomposition of the surface oxygen-bearing functional groups (≡С-OH, ≡C-OOH, = C = O, and others) to CO and CO2 and the role of oxides is a strong saturation of the soot surface by these groups. Besides this behavior is explained by a redox mechanism due to the oxide’ own oxidizing action. Our results demonstrate that in presence of Bi-Co, Bi-Co-K system the soot oxidation is carried out via, probably, the formation and decomposition of surface groups, since the XPS data show that the K, Co, Bi oxidation degree in soot oxidation conditions is not changing. Potassium ion, according to [3], is prone to strong saturation of carbon with surface groups, in particular with OH – groups, at this formed is a phenolate complex ≡C (soot) - OK causing thus deformation of the C-C -bonds on the soot surface that further facilitates these bonds rupture under the influence of oxygen. It is also important that potassium ion introduces into the interlayer space of graphite structure with the formation of intercalates, and their subsequent transformation into graphite oxide. It appears that the combination of these factors results in high activity of a Bi-Co-K systems. References: [1] Boehm H.P., Carbon 40 (2002) 145. [2] Mul G., Neeft J.P.A., Kapteijn F. et al., Carbon 36 №9 (1998) 1269. [3] Mitlin S.M, Pushkin A.N., Rudenko A.P., Russ. J. Phys. Chem. 65. №2 (1991) 351.