Chemical Engineering Use of Catalyzed Sulfite Oxidation Kinetics for the Determination of Mass Transfer Characteristics of Gas-Liquid Contactors

The absorption of oxygen into sodium sulphite solution

Über ungesättigte Peroxyde. Zugleich ein Beitrag zur Kenntnis der Autoxydationsvorgänge

Publisher Summary Dispersion of gases in a liquid can be achieved by bubbling the gas through the liquid by using sparge pipes at the bottom of the contactor. Mixing impellers of the turbine type are frequently used to increase the rate of mass or heat-transfer over that obtained without the use of the mixer. Consequently, the contacting of gas and liquid in a mixing vessel equipped with a rotating impeller is generally used for the absorption of sparingly soluble gases. Some of the more common applications are in biochemical fermentation, hydrogenation, hydrocarbon oxidation and various other oxidation processes. Efficient contact is produced between the phases in agitated gas–liquid contactors and, therefore, this type of equipment can also be useful for those absorption and stripping operations for which conventional plate or packed towers may not be suited. This chapter refers to mechanically agitated gas–liquid dispersions. However, most of the theoretical and experimental conclusions also apply to any type of gas–liquid dispersion. The total surface area for diffusion is increased because the bubble diameter is smaller than for the free-bubbling case at the same gas flow rate; hence there is a resultant increase in the overall absorption rate. One approach to the analysis of gas–liquid dispersion has been to develop simplified theoretical models that provide an approximation to the real processes and mechanisms operating in the system. Typically, their application to the design problem requires knowledge of factors, such as bubble velocity relative to the agitated liquid and rate of surface renewal or film thickness as functions of mixing conditions.

Gas-Liquid Dispersions

Photoinitiated electron transfer reactions are among the earliest photochemical reactions documented in the chemical literature and (ground state) electron donor-acceptor interactions have been known for over one hundred years. Some aspects of plant photosynthesis were already known to Priestly in the eighteenth century. The photooxidation of oxalic acid by metal ions in aqueous solution was discovered by Seekamp (UVI) in 1805 and by Dobereiner (FeIII) in 1830. The electron donor-acceptor interactions between aromatic hydrocarbons and picric acid were noticed by Fritzsche in the 1850s; the quinhydrones are even older, having been described by both Wohler (1800–1882) and Laurent (1807–1853). One-electron reductions (e.g. of benzil by potassium) were carried out by Laurent in 1835, a one-electron oxidation (of chrysene by sulfuric acid) by Liebermann in 1871. The development of photoinitiated electron transfer from the observation of a few isolated and poorly understood examples to its current status as a highly sophisticated, interdisciplinary branch of science is delineated.

Hans L. J. Bäckström

Papers

The mechanism of inhibition in auto-oxidation reactions