Quantitative Structure-activity Relationship Study On Non-catalytic And Catalytic Supercritical Water Oxidation Of 20 Organic Compounds

Supercritical water oxidation?SCWO?is an innovative and promising treatment technology,which can degrade organic matter rapidly and effectively,and has no secondary pollution.Due to the varieties of organic compounds and high treating cost,the quantitative structure-activity relationship has become an efficient and inexpensive research method,which can effectively predict the activity of new organic compounds.This paper investigated the TOC removal rate of 20 organic compounds by supercritical water oxidation?SCWO?.Then compared the effect of 20 different catalysts on the degradation of potassium hydrogen phthalate?KHP?.The TOC removal rate of the same 20 organic compounds by catalytic supercritical water oxidation?CSCWO? was also studied with the change of the temperature and residence time.The kinetic constants of SCWO(K_scwo) and CSCWO(K_cscwo) were calculated by using the first-order kinetic model.Combined the experimental results with quantum chemistry calculation results,it analyzed the correlation between K_scwo or K_cscwo and the molecular structure parameters respectively,and established the quantitative structure-activity Relationship?QSAR?models.The main results are as follows:?1?Supercritical water oxidation could effectively degrade organic compounds,and degradation rate has a prominent increase with temperature and retention time enhanced.When the retention time is 1.5 min,the temperature rises to 525?,the degradation rate of almost all organics could reach 90%.When the temperature is 425?,the supercritical water oxidation reaction could be completed quickly within 6 min,and the removal rate reaches 90%.The degradation kinetic constants(K_scwo)of 20 organic compounds are between 0.320 min^-1 and 2.068 min^-1.?2?Both the metal catalysts and heteropolyacid catalysts have a promoting effect to the degradation of KHP.The catalytic effect of different metal in the order is Cu²⁺?Fe³⁺?Mn²⁺?Zn²⁺?Ag⁺?Ni⁺?Zr⁺?Ce³⁺.The effect of different anion to the performance of the catalyst in order is NO^3-?Cl^-?SO₄^2-.Catalytic effect of different heteropolyacid catalyst in the order is PTA>STA>PMA.In comprehensive,the optimal catalyst is Cu?NO?₂,and the degradation rate of KHP was increased by 31.7% when the temperature of 425? and retention time of 1 min.?3?The addition of catalyst could increase the reaction rate,reduce the reaction temperature and shorten the reaction time.The average temperature at removal rate of 90%in CSCWO decreases by 61.9? compared to in SCWO.The average retention time at removal rate of 90%shortens by 2.9 min.The K_cscwoscwo of 20 organic compounds are between 0.855min^-1 and 2.731 min^-1.?4?q?H⁺?_max,Fukui?-?_min and Fukui?0?_min have high correlation with K_scwo,and q?H+?_max,? and Fukui?-?_min have high correlation with K_cscwo.It indicated that the degradation effect of organic compounds by SCWO or CSCWO is closely related to the reactive sites of the substance.?5?The optimal model of SCWO is M3_scwo:K_scwo=0.082+3.531q?H+?_max+2.368 E_LUMO-3.875 Fukui?-?_max,with R²=0.825,R² _adj=0.782,q²=0.571,Q²=0.577.The M3_SCWO contains“sites active”factor q?H+?_max and Fukui?-?_max,“bond energy”factor E_LUMO.The optimal model of CSCWO is M4_cscwo:K_cscwo=0.365+3.262 q?H+?_max+7.909 Fukui?-?_max+3.079 E_HOMO-0.195?,with R²=0.830,R² _adj=0.768,q²=0.630,Q²=0.987.The M4_CSCWOSCWO contains“affinity”factor?,“sites active”factor q?H+?_max and Fukui?-?_max,“bond energy”factor E_HOMO.Both the model M3_scwocwo and M4_cscwo have good stability and prediction ability,which could be used to predict the kinetic constants of new organic compounds in SCWO or CSCWO respectively.