A number of techniques harnessing radiant energy have demonstrated the potential for imaging methods to provide valuable insights into local phenomena occurring within a variety of engineering systems [1]. Of the techniques reported, magnetic resonance imaging (MRI) stands out as a technique capable of non-invasively probing opaque systems to obtain images which may be analysed to measure local structure, flow, molecular diffusion and chemical composition and provide valuable insights into the design of new and existing products and processes [2].

In this study a multinuclear MRI approach has been used to track the hydrogenation of 1-octene on a Pd/Al₂O₃ catalyst at near-ambient conditions in a 25 mm I.D. trickle-bed reactor. Using the ¹³C DEPT MRI pulse sequence [3] the evolution of concentration profiles during the hydrogenation of 1-octene has been followed with time-resolution of 15 min. These data provide local measurements of composition as the trickle-bed moves from an initial start-up composition through to a steady-state reaction profile. A partial least-squares model has been developed and applied to analyse the ¹³C DEPT MRI measurements to provide in situ measurements of intra-particle composition during the hydrogenation of 1-octene at a range of 1-octene:hydrogen molar-flow ratios in the range 2.0 – 13.5. The ¹³C DEPT MRI composition profiles obtained have been analysed to provide measurements of local reaction-rate, local selectivity, and local effectiveness factor. An estimate of the concentration-gradient existing between intra-particle and bulk-liquid during mass-transfer limited reaction is also obtained. A detailed analysis of local selectivity profiles within the bed reveals the effect of increasing hydrogen feed-flow rate on the initial rate of reaction and the distance hydrogen penetrates into the reactor before being fully consumed.

The combination of ¹³C DEPT MRI measurements of local composition, reaction-rate and selectivity with hydrodynamic and structural measurements obtained by ¹H MRI techniques [4, 5] offers the opportunity to obtain measurements which shed light on the interaction of hydrodynamics, reaction, and mass-transfer within multiphase reactors and provide a tool to optimise the performance of catalytic reactors.

References [1] J. Chaouki, F. Larachi, and M.P. Dudukovic, Ind. Eng. Chem. Res. 36 (1997) 4476-4503. [2] L.F. Gladden, M.D. Mantle, and A.J. Sederman, Advances in Catalysis, Vol 50, 1-75. [3] B.S. Akpa, M.D. Mantle, A.J. Sederman, and L.F. Gladden, Chem. Commun. (2005) 2741-2743. [4] L.F. Gladden, L.D. Anadon, M.H.M. Lim, A.J. Sederman, and E.H. Stitt, Ind. Eng. Chem. Res. 44 (2005) 6320-6331. [5] M.D. Mantle, A.J. Sederman, and L.F. Gladden, Chem. Eng. Sci. 56 (2001) 523-529.