(293e) Microfibrous Supported Catalysts/Sorbents: Novel Heterogeneous Contacting Systems with Enhanced Reaction Rates

VOC (Volatile Organic Compounds) break-through tests on PICA activated carbon were used to demonstrate and understand the anomalous heterogeneous contacting efficiency exhibited by a novel micro-structured material: Microfibrous Entrapped Catalysts/Sorbents. These innovative heterogeneous contacting systems prepared in wet lay process have extremely uniform structures with high and variable voidages. They consist of 100-300 micrometer size catalyst/sorbent particles entrapped in micron-diameter fibers. Experimental results of break-through tests on packed beds of various particle sizes (150-800 micrometer) with varying dilutions and microfibrous supported carbon of varying void fractions will be presented. Mathematical models developed using Freundlich isotherm and linear driving force approximations for intra particle transport resistances are in good agreement with the experimental data. The typical flow conditions used in these materials correspond to extremely low particle Reynolds numbers (Re < 1).Computational fluid dynamics (CFD) have been used to investigate the effect of various characteristics of MSCS (voidage, particle and fiber diameter, etc.) on mass transfer rates in the bed. In accordance with the CFD findings and literature survey, in low Re regime the negative effect of the axial dispersion and intra-bed and wall channeling on the overall reaction rates was clearly pronounced in packed beds. The small diameter particles used in microfibrous media reduced transport resistances; the uniformity and the high voidages inherently present in these materials lead to substantial reduction in channeling and axial dispersion compared to packed beds of similar particle sizes. These unique properties of this material were found to produce significantly sharper breakthrough curves and hence better utilization of the adsorbent. Also high voidages and flexibility of MSCS to pleat resulted in remarkably reduced pressure drops.