Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-II-7mechanistic and kinetic studies of such reactions. We have demonstrated for the first time [2]that parahydrogen-induced polarization (PHIP) can be observed in heterogeneoushydrogenations as well, with the use of transition metal complexes immobilized on suitablesolid supports. Furthermore, we have shown [3] that PHIP can be observed with supportedmetal catalysts (e.g., Pt/Al 2 O 3 , Pd/Al 2 O 3 ) as well. These demonstrations can be employed todevelop new advanced MRI-based approaches to study operating heterogeneous catalyticreactors [4], to visualize active regions of the catalyst bed, and to address in detail the reactionmechanism.To address the fundamental principles that govern the interplay of mass transport andnon-linear chemical reactions, we have studied the effect of liquid flow (advection) andconvection on the propagation of reaction fronts in a number of homogeneous autocatalyticreactions including non-oscillatory autocatalytic processes. In particular, convective motionof a fluid induced by the propagating concentration front was visualized and the quantitativespatially-resolved maps of convection flow velocities were detected for oxidation ofthiosulfate with chlorite carried out in a glass tube. Advection of reaction fronts in a porousmedium was studied for the same reaction carried out in a packed bed of glass beads. It wasdemonstrated for the first time [5] that under appropriate experimental conditions, stationarywavefronts can be observed for a wide range of velocities of the reactive medium flowingthrough the bead pack. These results are rationalized in terms of the reaction-diffusionadvectionmodel and imply the «wide gap» limit behavior and the effective quenching of theaxial diffusion of an autocatalyst by advection in a porous medium.AcknowledgmentsThis work was partially supported by RFBR (grants 07-03-12147, 08-03-00661), RAS(grants 5.2.3, 5.1.1), and SB RAS (integration grant 11). IVK thanks Russian Science SupportFoundation for financial support. AAL acknowledges the Council on Grants of the Presidentof Russian Federation (MK-5135.2007.3).References1. Igor V. Koptyug and Anna A. Lysova, in Stapf, S., Han, S.-I (Eds.), NMR Imaging in ChemicalEngineering. Wiley-VCH, 2005, p. 570.2. I.V. Koptyug, K.V. Kovtunov, S.R. Burt, M.S. Anwar, C. Hilty, S. Han, A. Pines, R.Z. Sagdeev, J. Amer.Chem. Soc., 2007, 129, 5580.3. K.V. Kovtunov, I.E. Beck, V.I. Bukhtiyarov, I.V. Koptyug, Angew. Chem. Int. Ed., 2008, 47, 1492.4. L.-S. Bouchard, S.R. Burt, M.S. Anwar, K.V. Kovtunov, I.V. Koptyug, A. Pines, Science, 2008, 319, 442.5. I.V. Koptyug, V.V. Zhivonitko, R.Z. Sagdeev, J. Phys. Chem. B, 2008, 112, 1170.88