1H and 13C-DEPT PFG NMR Studies of Diffusion in Catalysts
Advancing the chemical engineering fundamentals
Catalysis (T2-13P)
Keywords: diffusion, porous media, DEPT, PFG, NMR
D. Weber, L. F. Gladden
Department of Chemical Engineering, University of Cambridge, CB23RA Cambridge,United Kingdom
E.H. Stitt,
Johnson Matthey Catalysts, P.O. Box 1, Billingham, TS23 1LB Cleveland, United Kingdom
Quantifying molecular diffusion within porous catalysts is central to advancing our ability to design heterogeneous catalysts and catalytic processes. In particular, measurement of diffusion processes is relevant to furthering our understanding of the performance of catalysts used in trickle-bed reactor processes. In these systems, there is a need to characterise liquid transport phenomena and hence identify potential mass transport limitations, which lead to loss of catalyst effectiveness. Nuclear Magnetic Resonance (NMR) techniques have proved to be an invaluable tool characterising transport in porous media; measurements of molecular diffusion, dispersion and flow are possible. The study of diffusion phenomena with Pulsed Field Gradient (PFG) NMR techniques evolved in the 1960s and is nowadays part of the standard NMR toolbox. This project addresses two new implementations of PFG NMR, which will open up significant, new opportunities in studying catalytic systems in situ. First, the study of molecular diffusion within porous catalysts over a range of observation times is employed to discriminate between diffusion on the internal surface of the catalyst and in the bulk of the pore space. Second, measurement of diffusion coefficients using natural abundance 13C PFG NMR is discussed. This development opens up opportunities for measuring chemically-specific diffusion coefficients within catalysts.
Presented Wednesday 19, 13:30 to 15:00, in session Catalysis (T2-13P).
