Abstract: The platinum-rhodium-palladium triad has an honorable role and an entire era in industrial catalysis due to their non-alternative use in the production of catalysts for neutralizing exhaust gases of internal combustion engines. The role of these metals is no less significant for other areas of heterogeneous catalysis, as well as in the field of homogeneous catalysis. In the preparation of heterogeneous catalysts, starting metal compounds (precursor compounds) play an important role, from which they are applied to the carrier material. The overwhelming number of academic works and many industrial methods of preparing catalysts use chlorocomplexes or chlorides of these metals as precursor. On the other hand, chloride ions are often a catalytic poison and have a corrosive effect on the carrier material [3,4]. Other compounds of platinum group metals (PGM) can not only perform the function of a precursor, but also significantly surpass chlorocomplexes in terms of the activity of the formed catalysts, their stability and ease of preparation. The optimal precursor compound can be selected for each specific process and depending on the carrier material. Nitrate systems - nitric acid solutions of rhodium and platinum (solutions of rhodium and platinum nitrate), palladium nitrate - are the most widely used of such alternatives to halides of precursors on an industrial scale. Despite the great practical relevance, the systematic study of nitrate complexes formed and existing in nitric acid solutions of the platinum-rhodium-palladium triad has not been given significant attention by researchers. The same can be said in general about solutions of these metals in mineral oxoacids and complexes of PGM with oxoanions in general. This work presents the results of a comprehensive study on the oxyanionic complexes of MPG, which are derivatives of aqua-and aqua-hydroxo complexes obtained by replacing water molecules with corresponding anions - residues of inorganic acids such as nitric, sulfuric and carbonic. The work begins with a detailed examination of the methods used to prepare the corresponding solutions, and provides insight into the speciation of PGM in these solutions. As a result of the PGM speciation analysis, methods were developed to isolate individual oxyanion complexes into solid crystalline phases. The potential of PGM's oxyanions as effective precursors is illustrated through examples of the preparation of catalytic materials with promising activity in processes such as photocatalytic hydrogen production, CO oxidation and selective decomposition of hydrazine.

Cite: Vasilchenko D.
Oxoanionic complexes of platinum group metals: solution speciation, isolation and utilization for catalysts preparation
CATALYSIS: from science to industry 30 сент. - 3 окт. 2024