Influence of operational parameters and kinetic modelling of catalytic wet air oxidation of phenol by Al/Zr pillared clay catalyst.

Document Type: Research Article

Authors

1 Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa

2 Advanced Materials Division, Mintek, Randburg, South Africa

3 1. Advanced Materials Division, Mintek, Private Bag X3015, Randburg 2125; RSA 2. Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa

Abstract

Single and mixed oxide Al/Zr-pillared clay (Al/Zr-PILC) catalysts were synthesized and tested for catalytic wet air oxidation (CWAO) of aqueous phenol solution under milder conditions, in a semi-batch reactor. The catalysts were synthesized from natural bentonite clay using ultrasonic treatment during the aging and intercalation steps and were characterized by means of high resolution scanning electron microscopy-energy dispersive angle X-ray spectrometry (HRSEM-EDX), powder X-ray diffraction (p-XRD), nitrogen adsorption/desorption, Fourier Transforms Infrared Spectroscopy (FTIR) and zeta potential. Successful pillaring of aluminium and zirconium oxides into the clay was confirmed by p-XRD with increased basal spacing (1.92 nm) and higher specific surface area (230 m2/g). The influence of stirrer speed (200-1000 rpm), catalyst dosage (1-3 g/L), initial pH (1-3), initial phenol concentration (500-1500 mg/L), effect of temperature (80-150 °C) and oxygen pressure (5-15 bar) was evaluated on phenol conversion and their reaction kinetics. At the optimum conditions of initial pH of 3, catalyst dosage of 2 g/L, initial phenol concentration of 1000 mg/L, reaction temperature of 100 °C and oxygen pressure of 10 bar , the complete removal of phenol was achieved by Al/Zr-PILC within 120 min. The CWAO process was well-described by first-order power rate law kinetics model. The apparent activation energy of the reaction calculated by Arrhenius equation was 21.306 kJ mol−1.

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