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Gas-liquid Interface (gas-liquid + interface)
Selected AbstractsDeactivation of Formate Dehydrogenase (FDH) in Solution and at Gas-Liquid InterfacesBIOTECHNOLOGY PROGRESS, Issue 6 2005Andreas S. Bommarius Enzymes, increasingly important in the synthesis of fine chemicals and pharmaceutical intermediates, are often insufficiently stable under reacting conditions. We have investigated the stability, in homogeneous aqueous solution and at gas-liquid interfaces, of formate dehydrogenase (FDH), important for cofactor regeneration, from Candida boidinii and overexpressed in E. coli. When exposed to mechanical stress, residual activity, [E]t/[E]0, and residual protein were found to scale proportionally with gas-liquid surface area in the bubble column, verifying a surface-driven process, and with time and total throughput in a gear pump, but did not seem to be influenced much by shear in a Couette viscometer. All FDH variants are deactivated by chaotropes but not kosmotropes: the first-order deactivation constant kd correlates well with the Jones-Dole coefficient B but not well with the surface tension increment ,, of various concentrated ammonium salt solutions. This finding might provide guidance for focusing the search for quantitative theories of Hofmeister effects. [source] Increased gas solubility in nanoliquids: Improved performance in interfacial catalytic membrane contactorsAICHE JOURNAL, Issue 2 2009Marc Pera-Titus Abstract The kinetics of gas-liquid catalytic reactions can be strongly promoted when these are performed in interfacial catalytic membrane reactors instead of other three-phase reactors such as slurry stirrers or trickle beds. The well-defined gas-liquid-catalyst contact in this system avoiding diffusional limitations is usually argued as the main reason for such enhancement. In this work, using nitrobenzene hydrogenation as a model reaction, we propose that this increased catalytic performance might also be attributed, at least partially, to increased gas solubilities in mesoconfined solvents (or simply "nanoliquids") in interfacial contactors overcoming the values predicted by Henry's Law. To support this hypothesis, we provide experimental evidence of a dramatic increase of H2 solubility in confined ethanol using mesoporous ,-Al2O3 as confining solid. Gas-liquid solubilities can be enhanced up to five times over the corresponding bulk values for nanoliquid sizes lower than 15 nm as long as the gas-liquid interface is confined in a mesoporous array. In such a situation, the volume of the gas-liquid interface is no longer negligible compared to the total volume of the confined liquid, and the high surface excess concentrations of the gas adsorbed on the liquid surface make solubility grow up dramatically. According to these measurements, we discuss how nanoliquids might form in catalytic membrane contactors, which gas-liquid configuration in the reactor appears to be more appropriate, and how the structure of the mesoporous catalytic layer contributes to their increased gas solubilization performance. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Multiphase CFD Simulation of a Solid Bowl CentrifugeCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2009X. Romaní Fernández Abstract This study presents some results from the numerical simulation of the flow in an industrial solid bowl centrifuge used for particle separation in industrial fluid processing. The computational fluid dynamics (CFD) software Fluent was used to simulate this multiphase flow. Simplified two-dimensional and three-dimensional geometries were built and meshed from the real centrifuge geometry. The CFD results show a boundary layer of axially fast moving fluid at the gas-liquid interface. Below this layer there is a thin recirculation. The obtained tangential velocity values are lower than the ones for the rigid-body motion. Also, the trajectories of the solid particles are evaluated. [source] Deactivation of Formate Dehydrogenase (FDH) in Solution and at Gas-Liquid InterfacesBIOTECHNOLOGY PROGRESS, Issue 6 2005Andreas S. Bommarius Enzymes, increasingly important in the synthesis of fine chemicals and pharmaceutical intermediates, are often insufficiently stable under reacting conditions. We have investigated the stability, in homogeneous aqueous solution and at gas-liquid interfaces, of formate dehydrogenase (FDH), important for cofactor regeneration, from Candida boidinii and overexpressed in E. coli. When exposed to mechanical stress, residual activity, [E]t/[E]0, and residual protein were found to scale proportionally with gas-liquid surface area in the bubble column, verifying a surface-driven process, and with time and total throughput in a gear pump, but did not seem to be influenced much by shear in a Couette viscometer. All FDH variants are deactivated by chaotropes but not kosmotropes: the first-order deactivation constant kd correlates well with the Jones-Dole coefficient B but not well with the surface tension increment ,, of various concentrated ammonium salt solutions. This finding might provide guidance for focusing the search for quantitative theories of Hofmeister effects. [source] | ||||||||||