E. Plattner

Oxydation Du MnSO4 en dioxyde de manganese dans H2SO4 30

The electrochem. oxidn. of Mn(II) in H2SO4 (30% wt.) has been studied using cyclic voltammetry. The mechanism was shown to be of the type ECE (Electrochem.-Chem.-Electrochem.). The deposition of MnO2 on the anode can be avoided by inhibiting the chem. reaction step, either by slowing it or by minimizing the mean residence time of Mn(III) ions near this electrode. [on SciFinder (R)]

The preparation and behaviour of Ti/Au/PbO2 anodes

Ti/Au/PbO2 electrodes have been prepared and their stability in H2SO4 (2–12 mol dm−3) has been studied. It has been found that incorporation of a gold layer between the Ti substrate and the PbO2 decreases the resistance of the electrode. The corrosion of an electrode polarized anodically increases with H2SO4 concentration especially above 8 mol dm−3 H2SO4.

Estimation of current bypass in a bipolar electrode stack from current-potential curves

A simple method is proposed for the estimation of the current bypass from experimental current-potential (i-U) curves measured for a “bipolar reactor” and with a one-element cell of similar geometry. The model is valid only in the region where a lineari-U relation is obtained.

The electrochemical production of cobaltic sulphate

The electrochemical preparation of cobaltic sulphate has been studied and we have found that the reaction is best effected in 40 wt% H2SO4 in the presence of silver ions as the catalyst, using PbO2 as the anode, with a low current density and a low conversion.

Electrochemical production of ceric sulphate in concentrated H2SO4

The electrochemical preparation of ceric sulphate has been studied in concentrated H2SO4(10 mol dm−3) and we have found that the current efficiency of the reaction increases considerably if a mixed catalyst is used (Ag2SO4 + MnSO4).

The oxidation of o-nitrotoluene to o-nitrobenzaldehyde with electrogenerated cobaltic sulphate

Indirect electrochemical oxidation ofo-nitrotoluene too-nitrobenzaldehyde by Co (III) has been studied. The highest aldehyde yield (∼ 80%) is obtained in dispersing a 70-fold excess ofo-nitrotoluene in a solution of CO2(SO4)3 in 60% H2SO4 at 12° C. The influence of acid concentration, excess of nitrotoluene and presence of catalyst are discussed and found to be compatible with a mechanism proposed by Bawn.

Reactions of organic compounds in aqueous hydrofluoric acid

Anthraquinone with HNO3 or N2O4 in 80-98% HF gave nitroanthraquinone. The presence of H2O enabled the reaction temp. of 30-40 Deg to be maintained without external pressure and made the sepn. of the 2 isomers easier. Me(CH2)7SH with NO2 and HF gave Me(CH2)7SO2F. The yield varied with the concn. of HF; no product was obtained with an HF concn. of <40%. [on SciFinder (R)]

Electrochemical perfluorination of organic acids. Contribution to the knowledge of the mechanism

Electrochemical perfluorination of octane-sulphofluoride (OSF) and octanoic-fluoride (OF) to the perfluoro compounds (POSF and POF) has been studied over a wide range of experimental conditions. Significant improvement of the reported yield of perfluoro-product has been achieved with electrolysis at high potential. The results are explained in terms of a model involving simultaneous adsorption of the reactant and of fluorine on a NiF2 surface.

Treatment Techniques for Waste Water from Chemical Industries

Besides inorganic materials (acids, bases and salts), industrial waste water also contains organic substances which have to be “mineralized”, i.e. oxidized to CO2, H2O, N2 (or NO3 −), Cl− and SO4 −, before the water can be discharged. The main methods for analyzing organic material in waste water are: TOC total organic carbon [mg C/l] COD chemical oxygen demand [mg O/l] BOD5 biological oxygen demand in five days [mg O/l]

Current efficiency losses in indirect electrochemical processing

In this process a carrier (Mn+) is electrochem. oxidized (or reduced) and then allowed to react with the org. compd. in a sep. vessel. When the reaction is complete a sepn. of product is made and the spent liquor is returned to the electrochem. cell where the carrier is regenerated. The loss of current efficiency (CE) using the Mn2+/Mn3+ system in 88% H2SO4 was due to the oxidn. of the org. compd. (mainly to CO2) carried over with the electrolyte back to the cell. The study was extended to 50% H2SO4 and a simple relation proposed which permits the calcn. of the loss in CE from the total org. C present in the recycled electrolyte. The oxidn. of PhMe and its derivs. to the corresponding benzaldehydes was carried out with electrogenerated Mn2(SO4)3 in H2SO4. [on SciFinder (R)]