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Situ Regeneration (situ + regeneration)
Selected AbstractsChiral alcohol production by NADH-dependent phenylacetaldehyde reductase coupled with in situ regeneration of NADHFEBS JOURNAL, Issue 9 2002Nobuya Itoh Phenylacetaldehyde reductase (PAR) produced by styrene-assimilating Corynebacterium strain ST-10 was used to synthesize chiral alcohols. This enzyme with a broad substrate range reduced various prochiral aromatic ketones and ,-ketoesters to yield optically active secondary alcohols with an enantiomeric purity of more than 98% enantiomeric excess (e.e.). The Escherichia coli recombinant cells which expressed the par gene could efficiently produce important pharmaceutical intermediates; (R)-2-chloro-1-(3-chlorophenyl)ethanol (28 mg·mL,1) from m -chlorophenacyl chloride, ethyl (R)-4-chloro-3-hydroxy butanoate) (28 mg·mL,1) from ethyl 4-chloro-3-oxobutanoate and (S)- N-tert -butoxycarbonyl(Boc)-3-pyrrolidinol from N -Boc-3-pyrrolidinone (51 mg·mL,1), with more than 86% yields. The high yields were due to the fact that PAR could concomitantly reproduce NADH in the presence of 3,7% (v/v) 2-propanol in the reaction mixture. This biocatalytic process provided one of the best asymmetric reductions ever reported. [source] The removal of iron and cobalt from aqueous solutions by ion exchange with Na-Y zeolite: batch, semi-batch and continuous operationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2002Jong Sung Kim Abstract The removal of single component and binary mixtures of divalent cobalt and iron from water by ion exchange with synthetic Y zeolite has been studied in batch, semi-batch and continuous modes of operation; the initial metal solution concentration did not exceed 2,mmol,dm,3. Binary Co/Na and Fe/Na ion exchange equilibrium isotherms (294,K) are presented wherein exchange site heterogeneity is evident in the case of the iron treatment. Under conditions of stoichiometric ion exchange, removal efficiencies for both cobalt and iron decrease with increasing metal concentration (0.2,2,mmol,dm,3) and the values were similar for both metals. Removal of cobalt under transient conditions was found to be temperature dependent. In the fixed bed operation, break-through behavior was sensitive to changes in both flow rate and inlet concentration. The break-through profiles for both metals under competitive and non-competitive conditions are presented; iron removal is lower in the presence of cobalt and vice versa. An in situ regeneration of the fully loaded zeolite by back exchange with sodium is considered and the exchange capacity of the regenerated zeolite is reported. The feasibility of employing cycles of heavy metal uptake/zeolite regeneration is addressed. © 2002 Society of Chemical Industry [source] Hydrosulphide oxidation pathways in oxic alkaline media containing iron/cerium oxide-hydroxideTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2008Catalin F. Petre Abstract The oxidation kinetics of hydrosulphide by iron/cerium oxide-hydroxide (FeCeOx) and dissolved oxygen (DO2) was studied at 0.1 MPa and 298 K in a batch slurry reactor. The oxidation of hydrosulphide by the FeCeOx/DO2 system proceeded via a combined heterogeneous,homogeneous pathway to yield zerovalent sulphur and thiosulphate. The role of dissolved oxygen was twofold: (i) it reoxidized the iron from Fe(II) to active Fe(III), (ii) it prompted the homogeneous oxidation of hydrosulphide to polysulphides and of polysulphides to thiosulphate. The Fe(III) in situ regeneration by DO2 showed that FeCeOx holds promise for a redox scrubbing process targeting the elimination of H2S from the Kraft mill effluents. La cinétique d'oxydation de l'hydrosulphure par l'oxyde-hydroxyde de fer/cérium (FeCeOx) et l'oxygène dissous (DO2) a été étudiée à 0.1 MPa et 298 K dans un réacteur agité liquide-solide. L'oxydation de l'hydrosulphure par le système FeCeOx/DO2 s'accomplit par une voie combinée hétérogène,homogène pour produire du soufre zérovalent et du thiosulphate. Le rôle de l'oxygène dissous est double: (i) il réoxyde le fer ferreux en fer ferrique; (ii) il promeut l'oxydation homogène de l'hydrosulphure en polysulphures et des polysulphures en thiosulphate. La régénération in situ du Fe(III) par DO2 indique que FeCeOx pourrait être un matériau intéressant visant l'élimination de H2S dans les émissions des industries papetières kraft. [source] Phosphite-driven, [Cp*Rh(bpy)(H2O)]2+ -catalyzed reduction of nicotinamide and flavin cofactors: characterization and application to promote chemoenzymatic reduction reactionsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2010Maria Mifsud Grau Abstract The organometallic compound [Cp*Rh(bpy)(H2O)]2+ is a versatile catalyst for the in situ regeneration of reduced nicotinamides and flavins by catalyzing the electron transfer between the cathode or formate to the oxidized cofactors and prosthetic groups. In the present contribution we demonstrate the feasibility of phosphite as an alternative source of reducing equivalents. Thus, [Cp*Rh(bpy)(H2O)]2+ combines the catalytic activities of hydrogenases, formate and phosphite dehydrogenases in one catalyst. The catalytic properties of this novel regeneration approach are investigated, demonstrating that the general catalytic properties of [Cp*Rh(bpy)(H2O)]2+ are preserved. The principal applicability to promote alcoholdehydrogenase-catalyzed reduction reactions is demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||