Carbon monoxide oxidation by atmospheric oxygen on catalysts prepared by pyrolysis of transition metal β-diketonates on the synthetic foam ceramics

Abstract

The results of development of new catalytic systems for the carbon monoxide oxidation to dioxide are systematized. The catalysts were produced by gas-phase thermal decomposition of the transition metal acetylacetonates on the synthetic foam ceramics. The kinetic and activation parameters of the oxidation on the catalysts were studied and their relative activity was explored. The activity of catalysts at the oxidation with air oxygen were found to depend on the nature of the deposited metal and the carrier. A synergistic effect in the bimetallic copper catalysts was revealed.Carbon monoxide (CO) is a permanent component of the Earth's atmosphere, its natural cotent is 0.01-0.09 mg m -3 . By the total mass, CO is the leader among the polluting emissions [1].There are different approaches to the purification of gases: adsorption of polluting gas by a solid, absorption by a liquid, thermal decomposition, and the chemical catalytic methods. Among these, the chemical catalytic oxidation is the most promising, its application allows converting harmful impurities in the harmless or less harmful, and even in the useful substances [2].Among the catalysts for CO oxidation not based on a noble metal, the intermetallides Al 3 M (M = Gd, Y) [3], CdTe [4], high-temperature superconducting materials (HTSM) [5,6] and metal oxides of the perovskite [7] and spinel [8,9] structure have been investigated in sufficient detail. Among the supported catalysts not inferior in activity to the intermetallides and metal oxides a copper-cerium oxide catalysts containing 5 wt % Cu [10-13] should be noted; the high activity of the catalyst is due to the synergistic effect caused by the Cu-Ce interaction. Manufacturing of such supported catalysts is easier and consumes significantly less amount of active ingredients.Undoubted effectiveness in CO oxidation showed the catalysts containing noble metals. Therewith, some catalysts are more active than pure metals [14] due to the presence of a "size effect" of positive nature: the reaction rate increases with the decrease in the size of the supported metal particles. This phenomenon greatly reduces the cost of some catalysts containing noble metals. However, at the use of such metals for catalyst preparation the problem of recycling raises and the use of additional processes and equipment to extract the active ingredient. Therefore, the use of the noble metals in catalytic systems leads to increase in expenses and thus limits their application to solving environmental problems.Grainy, granular, and fibrous materials [9], and cellular metallic carriers with a high mechanical strength are used as catalysts [15]. A promising support for catalysts is the porous ceramics, which is advantageous due to the ability to form blocks.It has been noted that the activity of catalytic systems is affected not only by the sequence of depositing oxides on the support [13], but also by the method of the catalyst preparation. Currently an intensive research of new methods of catalyst preparation is performed.