Molten Salt Catalysis

First publications on molten salt catalysis appeared more than 100 years ago and now processes with molten salt catalysts (molten metal halides and oxides and their mixtures: ZnCl2, AlCl3, CuCl2, V2O5, MoO3 etc.) are widely used in the industrial production of isoparaffins, chlorination of hydrocarbons, gasification of coal etc. It was also proved that the catalytic SO2 oxidation during the sulfuric acid production takes place in a film consisting of V2O5 in molten alkali pyrosulfates.
Molten salt catalysis is the usual type of homogeneous catalytic reaction. However molten salt catalysts have the peculiar properties which make them sometimes the only possibility to synthesize definite organic or inorganic compounds due to:
1. High working temperatures.
2. Absence of water.
3. High concentration of catalyst.
4. Wide acid-base range.
5. High thermal and electric conductivity.
Study on the mechanism of the catalytic SO2 oxidation was the main aim of BRITE/Euram II Project Contract no. BRE2.CT93.0447. In this investigation the V2O5 - M2S2O3 (M is alkali metal) melt was used as a model of the catalyst for the sulphuric acid production. It was shown that electrochemical techniques can be a powerful tool in the study of the mechanism of a catalytic reaction.