Catalytic Wet Oxidation of Phenol:  Kinetics of Phenol Uptake

Abstract

Catalytic phenol oxidation in aqueous phase under intermediate temperature and pressure has been carried out in order to determine the kinetic model of phenol uptake rate. The catalyst employed here was a commercial one based on copper supplied by Engelhard (Cu-0203T). Operational variables have been studied in the following ranges: temperature from 127 to 180 degrees C, oxygen pressure from 3.2 to 16 bar, initial phenol concentration from 680 to 1200 ppm, and catalyst concentration from 0 to 1550 g/L of liquid phase. Because of the wide interval here employed for the catalyst concentration, two experimental setups have been used: a basket stirred tank reactor (BSTR) with the liquid phase in batch and an integral fixed-bed reactor (FBR) with co-current upflow of gas and liquid phases. An important influence of the reaction in the bulk liquid was obtained in both types of reactor. This fact has been taken into account in the kinetic model according to different approaches. The first approach was a breakup of the reaction rate in two kinetic expressions, considering the homogeneous and heterogeneous contribution separately; the second approach was empirical where the reaction rate is a potential function of the catalyst concentration. It was found that the extent of reaction in the bulk liquid is also influenced by the catalyst concentration and that the first approach is not able to adequately predict the experimental results. Finally a kinetic model, based on the second approach, was discriminated, with a power law for the catalyst concentration with an order about 0.4. This model fits quite well the experimental data obtained in both experimental setups, BSTR and FBR, throughout the wide range of variables studied.

Carbon materials and catalytic wet air oxidation of organic pollutants in wastewater

“…The mode preferred in industry is the TBR [196] allowing for a variety of flow regimes depending on the gas and liquid flow rates employed. The same situation holds for CWAO, however only a few of the available studies attempted to experimentally assess the impact of gasliquid hydrodynamics and mass transfer on reactor performance under CWAO conditions [28,29,56,191,197]. Non-idealities in TBR operation during CWAO were detected by various researchers.…”

“…A higher reaction temperature shifted the reaction system to the gas-limited region and fully wetted catalyst particles lead to additional resistance for gas-liquid oxygen mass transfer. Santos et al [56,191] conducted phenol oxidation runs in a fixed bed reactor at different catalyst concentrations mixing inert and catalytic particle of same size. The authors reported a critical catalyst concentration below which the apparent reaction rate was not longer proportional to the catalyst concentration because of a significant homogeneous contribution to the reaction.…”

“…The lack of stable catalysts has prevented CWAO from being widely employed as industrial wastewater treatment. The most prominent supported catalysts prone to metal leaching in the hot acidic reaction environment are Cu based metal oxides [52][53][54][55][56] and mixed metal oxides (CuO, ZnO, CoO) [57,58]. Expensive supported noble metal catalysts (Pt, Pd, Ru, Rh, Ir, Ag) appear much more stable, although leaching was occasionally observed, e.g.…”

Influence of pH on the wet oxidation of phenol with copper catalyst

“…Once steady state conditions for temperature and pressure were achieved, phenol was loaded to the reactor by injecting a 10 mL loop of a concentrated aqueous solution of this compound (the phenol concentration in the loop was calculated in order to reach 1000 mg/L of phenol in the total reactor volume). Detailed schemes of both experimental set-ups (FBR and BSTR) are available elsewhere [26]. In all the runs the oxygen flow rate (Q G ) (pure oxygen was used as gas phase), the temperature (T) and the oxygen pressure (P O 2 ) were set at 150 mL/min (STP), 140°C and 16 bar, respectively.…”

Superparamagnetic Fe3O4 nanoparticles as catalysts for the catalytic oxidation of phenolic and aniline compounds

“…These compounds are harmful to human health, and suspected to be carcinogens. Many techniques including physical adsorption [3][4][5][6][7][8], electrochemical oxidation [9][10][11], biodegradation [12][13][14], catalytic wet oxidation [15][16][17], and Fenton reagent oxidation [18][19][20] have been adopted for the removal of phenolic and aniline pollutants. Though practicable and effective these methods are, they also have some drawbacks, such as high cost, incomplete removal, more toxic byproducts than original pollutants.…”