In the quinhydrone method of gases purification from hydrogen sulfide as an oxidizer of chemosorbed hydrogen sulfide, a quinhydrone catalyst is used. It is obtained by oligomerization of benzoquinhydrone in an alkaline solution. The oxidation-reducing properties of the quinhydrone catalyst are very important for the process of gases purification from hydrogen sulfide.
Previous studies on the preparation of a quinhydrone catalyst are mainly related to the purification of ventilation (oxygen-containing) gases. In the process of purification of natural and technological (oxygen-free) gases, more concentrated absorbing solutions are used, which requires additional studies on the quinhydrone catalyst preparation.
Soda solution of quinhydrone (concentration of quinhydrone 25 g/dm3 and sodium carbonate 50 g/dm3) was investigated by cyclic voltammetry (CV), infrared (IR) and ultraviolet (UV) spectroscopy during exposure of 0, 1, 5, 30 and ~ 3000 days for air access. It has been shown that there is an oligomerization of quinhydrone in the process of solution exposure and a change in its oxidation-reducing properties.
The oxidation-reducing potential of carbonate solution of quinhydrone an increase from -200 to -150 mV and pH a decrease from 10.3 to 9.4 in the exposure time. During the process in the atmosphere of air, the oxidation of the reducing forms of the quinhydrone catalyst is gradually doing, which can be observed with a reduction and complete fade of oxidation currents on the CV curves, indicating the stabilization of the properties of the oligomer. However, this process not completely finishing in 5 days. With an increase in the concentration of quinhydrone in solution (within 5...25 g/dm3), it is necessary to provide a time of exposure 5...10 days for the complete disappearance of reducing forms of the catalyst. It has been established that oxide forms are present in a solution of a quinhydrone catalyst for more than 8 years, and this solution does not lose oxidizing properties in relation to chemisorbed hydrogen sulfide.
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