Study On Catalytic Wet Oxidation Of Refinery Spent Caustic Wastewater

Refinery spent caustic is a kind of spent alkali liquor produced in refinery industry of petroleum. The content of toxic organic compound such as phenol and organic is very high in the petrochemical spent caustic wastewater which results in the poor biodergradation, and poor performance of conventional treatment process and exerts a serious pollution on the environment. For solving the technical problems of refinery spent caustic of Changling branche of China Petrochemical Corp. This paper investigated the technology, the catalyst properties of treating refinery spent caustic wastewater in wet oxidation, and explored wastewater treatment mechanism of the reaction of wet oxidation catalyst.The study of Wet oxidation of refinery spent caustic wastewater was found: oxygen partial pressure was positively correlated with the effect of the treatment. When oxygen partial pressure increased to 2.0 MPa which is 1.18 times of the theory value, 71.43% COD removal efficiency can be acquired. At the same time, we founded, when the amount of oxygen which is not lower than 0.59 times of the theoretical strength, the problem of coking can be fundamentally resolved. 83.3% total COD removal rate was obtained by the combination process of acidification-wet oxidation for disposal refinery spent caustic wastewater; while 94.4% total COD removal rate was got by the assembled process of acidification-wet oxidation for treating refinery spent caustic wastewater. The effects of wet air oxidation was obviously improved, when homogeneous metal catalysts was Added.In this paper, MnO_x/γ-Al₂O₃, MnO_x-CeO_x/γ-Al₂O₃ and manganese oxides were studied for suitable refinery spent caustic wet oxidation. The results indicated that MnO_x/γ-Al₂O₃ showed high activity and stability in the system, the adding of Ce further improve its performance. Catalyst characterization results: it can been seen that the reaction of catalyst surface has more organic functional; and reaction catalyst phase of the changes reaction catalyst structure exists MnCO₃ and Al₄₅O₄₅(OH)₄₅Cl.This paper study the base of Mn catalyst for treating the refinery spent caustic wastewater, The removal efficiency of COD was 91.33% with the dose of catalyst 2.0 g/L at reaction temperature of 220℃and oxygen partial pressure of 2.0 MPa. More than 85.0% of COD removal rate can maintain to 10%MnO_x/γ-Al₂O₃ catalyst reused three times, and its catalytic activity was increased 1.87% by regeneration; The results indicated that the reusable catalyst can restored a high activity. and reached good stability.The mechanism of catalytic wet oxidation reaction was explored, high oxygen partial pressure can effectively raise the rate of reaction in theoretics, while loading and manganese catalyst too high or excessive dosage will inhibit oxidation reactions and produce negative catalyst, and adding CeO2 can enhance the activity and stability of MnOx/γ-Al₂O₃ catalyst.