by David Genders

Salt splitting is a relatively new technology dependent on the availability of modern membranes. Its development has usually been driven by one of two major factors, both environmentally based. The first is the desire to produce caustic soda without the co-production of chlorine, and the second is the increased cost of disposing of heavily laden salt solutions.

Caustic is in Demand

Caustic soda is produced in the USA at a rate of 14 million tons per year, almost entirely by the electrolysis of brine. In this process chlorine is produced at the anode and caustic soda at the cathode in stoichiometric quantities. There is a growing awareness of the need for new processes for the manufacture of high purity sodium hydroxide that do not lead to co-production of chlorine. This requirement exists because the chlorine and sodium hydroxide markets are rarely in balance.

Despite the high demand for chlorine in the last two years, it is still expected that environmental pressures on chlorine will lead to an increased demand for caustic over the coming decade. Predictions are for a long-term trend in which the demand for sodium hydroxide will outstrip that for chlorine.

Several present markets for chlorine are expected to experience significant downturns due to environmental pressures or concerns about health hazards; these include pulp and paper bleaching, fluorocarbons, water treatment and chlorinated hydrocarbons. At the same time, the demand for sodium hydroxide is predicted to continue to grow.

Another trend is towards modular plants that allow the manufacture of chemicals on various scales including generation on a relatively small scale at the site of use.

Watts new salt splitting

by Derek Pletcher

Hydrogen peroxide is probably a unique chemical, ideally suited to the present age where environmental considerations are always to the fore.

Why unique?

Firstly, it is capable of very diverse chemistry. Hydrogen peroxide may act as either an oxidizing agent or a reducing agent. As an oxidizing agent, its application ranges from highly selective oxidation chemistries applicable to the manufacture of many organic com-pounds, through the bleaching of pulp, to the total oxidation of large organic compounds to carbon dioxide. Its reactivity as an oxidizing agent is determined largely by the ratio of the concentrations of H2O2 to substrate and the reaction conditions, particularly the choice of catalyst and factors such as UV irradiation.

Secondly, it is a strong oxidizing agent that may be formed by cathodic reduction under mild and varied conditions, opening up the possibility of producing the same product at both anode and cathode. Thirdly, the feedstock for electrogenerated hydrogen peroxide may be air (an unusually cheap and available feedstock!) while its reactions lead only to oxygen and/or water.

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by Murat E. Niyazymbetov

Over the past 25-30 years the use of electrochemistry as a synthetic tool in organic chemistry has increased remarkably. According to Pletcher and Walsh more than 100 electroorganic synthetic processes have been piloted at levels ranging from a few tons up to 105 tons. Such examples include reductive dimerization of acrylonitrile, hydrogenation of heterocycles, pinacolization, reduction of nitro aromatics, the Kolbe reaction, Simons fluorination, methoxylation, epoxidation of olefins, oxidation of aromatic hydrocarbons etc.

In this brief report we would like to review the use of electrochemical methods as a tool in lab scale synthesis, solving R&D objectives for a multi-step targeted synthesis, or one-step synthesis of intermediates or starting materials. There are many excellent reviews and monographs and publications we refer readers to some of them. These cover a broad spectrum of applications of electrochemical methods in organic synthesis including their use in the pharmaceutical industry. 3h,k Herein, we review some recent advances in using electrochemical methods in fine organic synthesis.

Moreover we will demonstrate that electrochemical methods are a tool that should become widely accepted in this area.

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by Norman L. Weinberg

The pharmaceutical industry, with annual worldwide sales of more than $200 billion, has for many years provided a wealth of opportunities for organic electrosynthesis of high value added intermediates. Many of these are now commercial. The most exciting R&D is occurring in electrosynthesis of chiral drug intermediates. These are enantiomerically pure single isomers of a mixture of possible diastereomers.

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by Derek Pletcher

The need to protect the environment from further contamination by transition and heavy metal ions is well established and universally reinforced by legislation which sets limits on the levels in effluents which may be discharged into sewers and local waters. All chemical plants, factories and other facilities employing solutions of such metals should therefore be treating their wastewater before discharge. Electrochemical methods compete with a number of other technologies including evaporation, precipitation, ion exchange and solvent extraction to offer solutions to the needs of the many industries involved.

Electrochemical methods, however, are uniquely capable of recovering pure metal for recycle. Although electrochemical technology for metal ion removal has been available for some time [1-3], it continues to develop to meet the challenges of lower consent levels and more complex effluent compositions. Moreover, the technology now on the market is based on diverse electrochemical concepts.

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