Oxidation of sulfurous acid

The electrolytic processes for commercial production of hydrogen peroxide are based on (/) the oxidation of sulfuric acid or sulfates to peroxydisulfuric acid [13445-49-3] (peroxydisulfates) with the formation of hydrogen and (2) the double hydrolysis of the peroxydisulfuric acid (peroxydisulfates) to Caro s acid and then hydrogen peroxide. To avoid electrolysis of water, smooth platinum electrodes are used because of the high oxygen overvoltage. The overall reaction is... 

Peracidox A process for removing sulfur dioxide from the tail gases from sulfuric acid plants by absorption in peroxomonosulfuric acid (Caro s acid). The peroxomonosulfuric acid is generated on-site by the electrolytic oxidation of sulfuric acid. Developed by Lurgi and Sud-Chemie and first operated in 1972. 

Pyrolusite, in oxidation of sulfurous acid to dithionate ion, 2 168 Pyrophosphates, determination of, in mixtures of phosphates, 3 93 Pyrophosphoric acid, 3 96, 97 Pyrosulfites, alkali metal, 2 162 Pyrosulfuryl chloride, 3 124, 126... 

Industrially, H202 was first produced by the anodic oxidation of sulfuric acid or bisulfates to persulfate, followed by hydrolysis and distillation [93]. The original process dates back to 1853 and was dominant for decades in spite of its high power consumption [1], In 1882, Traube obtained H202 by a cathodic reduction of dissolved 02 [2,94]. This is noteworthy because a strong oxidant with ° = 1.78 V at pH 0 was not expected to be formed at the cathode. The electrogeneration process can be written as follows ... 

Romero, A. Hernandez, G. Suarez, M. F. Pho-tocatalytic Oxidation of Sulfurous Acid, J. Chem. Educ. 2005, 82, 1234-1236. 

Another anodic polymerization process which has been the subject of much study, partly because of its industrial importance, is the oxidation of sulfuric acid to persulfuric acid. The eflSciency of this process has been found to run almost parallel with the proportion of HS07 ions present in solutions of different concentration. This fact has been regarded as supporting the view that the first stage in the anodic process is the discharge of IlSOr ions, thus... 

Schroeter LC. Oxidation of sulfurous acid salts in pharmaceutical systems. / Pharm Set 1963 52 888-892. 

Electrochemical oxidation of sulfuric acid or ammonium sulfate... 

The results in Table 7.6 confirm that the catalytic activity of carbon blacks in the oxidation of sulfurous acid is inferior to that of activated carbons. Carbon blacks that had been extracted with hot xylene to remove adsorbed organic molecules and subsequently heat-treated under Ar at 873 K were catalytically inactive. However, weak catalytic activity was observed after heat treatment of these carbon blacks at 1473 K, with the notable exception of an acetylene black that is free of nitrogen. Catalytic activity was also observed with the as-delivered carbon blacks after heat treatment at 973 to 1073 K. 

The results confirm earlier reports [98,99]. The reaction rate is dependent on the concentration of oxalic acid. It has a maximum at c = 2 mmol/L. A nearly constant reaction rate is established when the pH of the solntion is set to pH 2.3 by addition of sulfuric acid. Warburg (cited in ref. 57) fonnd the oxidation rate to be proportional to the square root of oxygen pressnre this was confirmed in ref. 94. The catalytic activity of activated carbons followed the same order as in the oxidation of sulfurous acid [94], and it increased after heat treatment at 973 to 1073 K or NH3 treatment [39]. Carbon blacks were inactive. Also in this case, KNO3 had an inhibiting effect, even at a concentration of 1 mEq/L, and more at higher concentrations. Na2S04 had no effect on the oxidation rate. 

The catalyzed oxidation of sulfurous acid, oxalic acid, or SO2 is inhibited by chemisorbed oxygen or chlorine, two electronegative elements (see Sections 7.3.1 section 7.3.3). The inhibition correlated well with the amount of chemisorbed chlorine on Anthralur or NH3-treated Anthralur [98], and the deactivation could be reversed by heat treatment under N2 or H2 at 1173 K [96] or with NH3... 

Schroeter, L. C. (1963) Kinetics of air oxidation of sulfurous acid salts. Journal of Pharmaceutical Science 52, 559-563... 

Dithionates may be prepared by the electrolytic or chemical oxidation of sulfurous acid and sulfites. Chemical oxidation is accomplished by the action of chlorine, iodine, hydrogen peroxide, or oxygen in an acid medium by the action of chromates or permanganates in neutral solution - ... 

Mitchell, J. S., Pitman, G. A., and Nichols, P. F. 1933. Inhibiting effect of certain substances upon oxidation of sulfurous acid. Ind. Eng. Chem., Anal. Ed. 6, 416-416. 

Two explanations have been put forward to account for this pH effect. Skye (1968) believes that acidification of the substratum finally makes it impossible for certain epiphytic communities (e.g., Xanthorion) to exist, so that pH per se operates to exclude sensitive lichens from all habitats except those strongly buffered at a high pH. The alternative idea (first put forward by food chemists trying to inhibit bacteria and mold in fruit juices) is that pH acts indirectly by affecting the ionization and rate of oxidation of sulfurous acid. 

Pure sulfuric acid is not encountered naturally on Earth, due to its great affinity for water. Apart from that, sulfuric acid is a constituent of acid rain, which is formed by atmospheric oxidation of sulfur dioxide in the presence of water - i.e., oxidation of sulfurous acid. Sulfur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burned. 

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