We have developed a noncontact method to probe the electrical conductivity and complex permittivity of single and polycrystalline samples in a flow-through reactor in the temperature range of 20-500 1C and in various gas atmospheres. The method is based on the microwave cavity perturbation technique and allows the simultaneous measurement of microwave conductivity, permittivity and of the catalytic performance of heterogeneous catalysts without any need for contacting the sample with electrodes. The sensitivity of the method towards changes in bulk properties was proven by the investigation of characteristic first-order phase transitions of the ionic conductor rubidium nitrate in the temperature range between 20 and 320 1C, and by studying the temperature dependence of the complex permittivity and conductivity of a niobium(V)-doped vanadium-phosphorous-oxide catalyst for the selective oxidation of n-butane to maleic anhydride. Simultaneously, the catalytic performance was probed by on line GC analysis of evolving product gases making the technique a real in situ method enabling the noninvasive investigation of electronic structure-function relationships.

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Don’t touch! Without electrode contacts, but contact-free with microwaves in a resonant cavity the electronic conductivity of a VPO powder catalyst could be measured under the reaction conditions of the selective oxidation of n-butane to maleic anhydride. As a result, a linear correlation between conductivity and formation rate of maleic anhydride was observed

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We report on a systematic study of the use of palladium nanoparticles immobilized on spherical polyelectrolyte brushes -Pd@SPB -for Heck-and Suzuki-type coupling reactions. The spherical polyelectrolyte brush particles serving as carriers for the palladium nanoparticles consist of a solid polystyrene core with a radius of 46 nm onto which long chains of cationic polyelectrolytes are grafted. The palladium nanoparticles have directly been generated within this brush layer and the stabilization of the nanoparticles is effected by the colloidal carriers, no further surface stabilization is necessary. We demonstrate that these composite particles present robust catalysts for the Heck-and Suzuki-type coupling reactions. This was shown by carrying out the Suzukiand Heck-type coupling reactions at relatively low temperatures (Suzuki reaction: 50 8C, Heck reaction: 70 8C). We demonstrate that the catalytic composite particles are not changed by these reaction conditions and retain their full activity for at least four runs. The yields obtained for both reactions are good to excellent. The mild operation conditions of the palladium nanoparticles are traced back to the absence of surface stabilization. Further mechanistic implications are discussed.