VOC Catalyst Deactivation and Regeneration

As has already been reported throughout this chapter, an adequate catalyst for the destruction of chlorinated VOCs must show high oxidation activity at low 

In general, for the catalytic oxidation of Cl-VOCs there are several reasons for catalyst deactivation. These include  

The interaction between chlorine formed during the catalytic combustion of Cl-VOCs and metals present on the catalyst surface could lead to the formation 

In order to elucidate the deactivation pathway of commercial Cr-based catalysts, Padilla et alJ carried out a long-term test. After the catalyst had been used for dichloromethane oxidation for 50 hours, the authors noticed the formation of thin red deposits on the inner wall of the reactor exit along with some light-green or yellow condensates. Although the exact loss of the active phase from the catalyst was not measured, the presence of chromium in the condensates was confirmed. Consequently, the activity decrease was related to the loss of chromium, probably via the formation of Cr02Cl2 species due to the attack of chlorine. 

In agreement with this fact, Padilla et aV concluded that for low Cl-contents and/or high H/Cl ratios (as in the case of VC, with only one chlorine atom/molecule), chromium-based catalysts can be recommended due to their high activity, but for relatively high Cl-contents or low H/Cl ratios (as in the case of TCE, with three chlorine atoms/molecules) chromium is lost from the catalyst resulting in its deactivation. Thus, the overall amount of Cl and the H/Cl ratio in the flue gas are key factors in determining the loss of chromium and consequently the life of the catalyst. 

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