III International Conference

PHASE ANALYSIS OF MULTIELEMENT CATALYSTS AND OTHERSUBSTANCES AND MATERIALS BY STOICHIOGRAPHIC METHODSPP-II-67Malakhov V.V., Vlasov A.A., Boldireva N.N., Dovlitova L.S.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: malakhov@catalysis.nsk.suThe elaboration of theory and application of the stoichiographic method of differentialdissolution (DD) is presented. The method is able to determine both stoichiometry andamounts of crystalline/amorphous phases with constant or variable composition when theyexist in multielement and heterogeneous mixtures. The main feature of DD is to be referencefreetechnique when analysis of unknown phase composition samples is carried out withoutresorting to standard reference phases.Factors such as selectivity and efficiency determining the separative ability of the DDprocesses are analyzed when dissolution of mixtures is realized under a flow dynamic regimedirectly in stoichiograph. The following factors are taken in account: the volume and linearrates of the solvent flow, the concentration variation of active components in the flow, thedissolution rate of the phases and washing out of the solutions formed from reactor. Newapproaches to collection and determination microphases appearing in inorganic multielementheterophase solids as by-products or as special additions are discussed.DD analysis is performed by means of special apparatus, stoichiograph, using ACP AESas a detector-analyzer. The technique shows high selectivity and sensitivity and performsrather simply and quickly single operations and analysis as a whole.Some fresh examples of phase analysis of various materials and preparative separation ofphase mixtures are given which were very important for understanding of the phase formationprocesses of various composite catalysts and other materials of complex nature.A great variety of multielement systems with crystalline and amorphous phases ofconstant or variable composition have already been analyzed by this technique. For eachsystem the optimal dissolution procedure was determined, for which composition andconcentration of active components in the differential solvent as well as their variation withtemperature and in time were found. To realize the dynamic regime of DD, thestoichiographic titration was most commonly used that provided the required selectivity andefficiency of the dissolution processes for each the system. For many systems the use of DD287