Title:
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A study of the electrochemical reduction of nitrobenzene and o-halonitrobenzenes in acidic media
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The electrochemical reduction of nitrobenzene and o-halonitrobenzenes has been studied in aqueous organic solvents containing sulphuric acid. The reaction products and their maximum rate of production depend upon the solvent, cathode metal, electrode potential, concentration of acid and the rate of stirring of the catholyte. From studies in a glass batch reactor it was possible to find conditions (i.e. using 1:1 1-propanol/water, a copper cathode, a 3M sulphuric acid and rapid stirring at low electrode potentials) where the yield of p-aminophenol was over 75% at a current density of 150 mA.cm 2. Conditions for the complete 6e reduction to the corresponding anilines were also defined. The highest yield was obtained with a mercury electrode, 0.114 HZSO4, slow stirring and a higher negative electrode potential. With nitrobenzene, o-fluorcnitrobenzene and the o-chlorocomuound, the anilines were formed in yields exceeding 75% and current densities above 100 mA.cm 2. With o-bromonitrobenzene the yield was lower because of competing cleavage of the C-Br bond. The reactions were also investigated in a prallel plate reactor with recycled electrolyte flow and conditions closer to those in an industrial electrochemical cell. The study revealed that p-aminophenol could be produced with a 76% material yield and 5.7 Kwh Kg 1 energy consumption, and anilines at 95% material yield and 10 Kwh Kg 1 energy consumption. The results compare very favourably with other attempts to produce these compounds.
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