Promotion Of Mass Transfer Research Articles

Chemically modified β-cyclodextrins in biphasic catalysis: a fruitful contribution of the host–guest chemistry to the transition-metal catalyzed reactions

Biphasic hydroformylation, Wacker oxidation and hydrocarboxylation of water insoluble olefins have been investigated in the presence of chemically modified β-cyclodextrins. In all cases, cyclodextrins appear more efficient than common mass transfer promoters to increase the activity and the selectivity of reactions. Most of the results are interpreted from the molecular recognition between the host cavity of modified cyclodextrins and substrate. The stability of the chemically modified cyclodextrins is also reported.

Influence of electrolyte flow on the electrodeposition of zinc-iron alloy.

An engineering interest to develop an electroplating cell which assures uniform alloy plated coastings at high current density has initiated this study. Due consideration should be given to a number of design factors, such as anode length, electrode separation gap, fluid injection and its control. Emphasis is focussed on the effect of oblique fluid impingement in terms of streamwise uniformity of alloy deposits along the cathodic strip.Zn-Fe alloy electroplating from sulphate bath was performed in a rectangular flow channel cell with interchangeable fluid injection angle under galvanostatic conditions. Streamwise variation of Fe content and crystal phase/structure of Zn-Fe alloy deposits revealed non-uniform distribution for wall jet flow system compared with that of parallel flow system, which would be an indication of difference in local mass-transfer rate along the cathode. In case of inclined fluid injection, Fe content in alloy film increased with increasing distance from the incident point, eventually coasting to a plateau corresponding to the value of parallel flow system, which may reflect the downstream transition of turbulent velocity profiles from wall jet flow to Poiseuille pipe flow.Codeposition of trace indicator ion during anomalous alloy deposition in a parallel plate rectangular cell was found to be a first-order rate process, which exceedingly showed promotion of mass transfer at the cathode presumably owing to simultaneous evolution of hydrogen gas. Such enhanced mass transfer implies a key role for the bubble stirring effect in the concentration boundary layer in the vicinity of cathode surface, which seems to give rise to dense and adhesive electrodeposits ensuring successful operation of alloy electrodeposition at high current densities.

Characteristics of Net-type Spacer as Mass Transfer Promoter in Electrodialysis

Characteristics of Net-type Spacer as Mass Transfer Promoter in Electrodialysis