F.P. Cuperus

Catalytic membrane in reduction of aqueous nitrates: operational principles and catalytic performance

Abstract The catalytic membrane with palladium–copper active component supported over the macroporous ceramic membrane, and a series of γ-Al2O3 supported Pd–Cu catalysts were prepared and investigated. In reduction of nitrate ions by hydrogen in water at ambient temperature, pronounced internal diffusion limitations of the reaction rate were observed for Pd–Cu/Al2O3 catalysts. The catalytic membrane with Pd–Cu active component deposited over the macroporous ceramic membrane support was employed to minimize the diffusion limitations. Multifold increase in the observed catalytic activity was registered for the catalytic membrane operated with the forced flow of the reaction solution through the membrane, as compared to the value achieved at the same conditions, but in the absence of the forced flow (i.e. when the membrane porous space was accessible to the reactants due to diffusion only). These improvements are attributed to the intensification of the intraporous mass transfer attainable with the reactants forced flow in the membrane pores. The concept of catalytic membrane reactors explored in this study offers a new means to improve catalytic performance in the processes where internal diffusion limitations must be minimized and the use of finely dispersed catalysts is not desired.

A new integrated membrane process for producing clarified apple juice and apple juice aroma concentrate

An integrated membrane process for producing apple juice and apple juice aroma concentrates is proposed. The process involves the following operations: an integrated membrane reactor to clarify the raw juice; reverse osmosis (RO) to preconcentrate the juice up to 25°Brix; pervaporation (PV) to recover and concentrate aroma compounds, and a final evaporation step to concentrate apple juice up to 72°Brix. These operations were tested in laboratory and pilot plant units. Promising results were obtained with the membrane operations involved. In order to have an economic process assessment, the pilot plant units were assembled into an integrated unit and operated with raw apple juice. The products were more clear and brilliant than apple juice produced by conventional methods. The integrated membrane process also seemed to be more advantageous on the basis of economics than the conventional one.

Catalytic membrane in denitrification of water: a means to facilitate intraporous diffusion of reactants

The series of mono- and bi-metallic catalysts with Pd and/or Cu supported over γ-Al 2O 3 was investigated with respect to reduction of nitrate and nitrite ions in water by hydrogen. Pronounced limitations of catalytic performance due to intraporous diffusion of the reactants were observed in the reaction. Catalytic membrane containing the Pd-Cu active component supported over macroporous ceramic membrane-support was prepared, investigated and applied to facilitate the intraporous mass transfer. Forced flow of the reacting solution through the membrane was revealed to increase the effective catalytic activity. The approach explored in this study offers a cost-efficient alternative to the conventional concept of catalytic water denitrification process in a slurry reactor, presuming fixed-bed type operation with macroporous catalytic membranes at high level of catalytic activity

Enzymatic peroxycarboxylic acid formation in a hollow-fibre membrane reactor: kinetics and mass transfer

Abstract Peroxycarboxylic acids were produced enzymatically in a hollow-fibre membrane reactor, using R. javanicus and C. antarctica lipase as the biocatalysts. The peroxycarboxylic acids are commercially used to synthesize epoxides from unsaturated olefins. Here, oleic acid was converted to 9,10-epoxy stearic acid. A mass-transfer model, similar to heterogeneous catalysis was applied to the enzymatic reaction in a membrane reactor. The model enables the evaluation of the most important factors limiting the conversion rate in the reactor and the effect of the membrane material on mass transfer. It was found that the conversion is diffusion limited at a high concentration of the organic substrate. To illustrate the versatility of the model, it was applied to two situations performed under completely different circumstances.

Lipases Used for the Production of Peroxycarboxylic Acids

Stabilization of Upases by immobilization on different polymer materials has been shown. The Upases were used for triglyceride hydrolysis and the synthesis of the chemically very reactive peroxycarboxylic acids. Using in-situ produced peracids, epoxides were formed from oleic acid. Inactivation of the enzymes is probably due the substrate hydrogen peroxide.