808 Bull. Korean Chem. Soc. 2010, Vol. 31, No. 4 Seyed Ali Hosseini et al. DOI 10.5012/bkcs.2010.31.04.808 Gas Phase Oxidation of Toluene and Ethyl Acetate over Proton and Cobalt Exchanged ZSM-5 Nano Catalysts- Experimental Study and ANN Modeling Seyed Ali Hosseini, Aligholi Niaei, * Dariush Salari, and Azadeh Jodaei Department of Applied Chemistry, Faculty of Chemistry, University of Tariz, Tabriz, Iran. * E-mail: niaei@yahoo.com Received June 25, 2009, Accepted January 15, 2010 Activities of nanostructure HZSM-5 and Co-ZSM-5 catalysts (with different Co-loading) for catalytic conversion of ethyl acetate and toluene were studied. The catalysts were prepared by wet impregnation method and were charac- terized by XRD, BET, SEM, TEM and ICP-AES techniques. Catalytic studies were carried out inside a U-shaped fixed bed reactor under atmospheric pressure and different temperatures. Toluene showed lower reactivity than ethyl acetate for conversion on Co-ZSM-5 catalysts. The effect of Co loading on conversion was prominent at temperatures below 400 o C and 450 o C for ethyl acetate and toluene respectively. In a binary mixture of organic compounds, toluene and ethyl acetate showed an inhibition and promotional behaviors respectively, in which the conversion of toluene was decreased at temperatures above 350 o C. Inhibition effect of water vapor was negligible at temperatures above 400 o C. An artificial neural networks model was developed to predict the conversion efficiency of ethyl acetate on Co-ZSM-5 catalysts based on experimental data. Predicted results showed a good agreement with experimental results. ANN model- ing predicted the order of studied variable effects on ethyl acetate conversion, which was as follows: reaction tem- perature (50%) > ethyl acetate inlet concentration (25.085%) > content of Co loading (24.915%). Key Words: Catalytic oxidation, Cobalt exchanged ZSM-5, Volatile organic compounds, ANN modeling Introduction Increasing environmental awareness promotes the stricter regulation of industrial action. Volatile organic compounds are considered as one of the main air pollutants. Catalytic combus- tion for controlling volatile organic compounds (VOCs) emissi- ons is a competitive method to solve the environmental pro- blems. In this process, high elimination efficiency can be achiev- ed at relatively low temperature, which resulted in considerable environmental and economic benefits in comparison to the case of the thermal incineration. 1,2 In recent years, supported transition metal oxides were ex- tensively used in controlling VOCs emissions, and special atten- tion has been paid to these systems as a substitute for noble metal containing catalysts. 3 On other hand, the materials with high thermal stability, resistance to humidity, high specific sur- face area and ability to stabilize the metal particles in the por- ous structure are desired to use as catalyst supports. 4 The cataly- tic conversion of ethyl acetate and toluene which are commonly used as solvent in chemical processing and industries have been investigated on catalyst supported alumina and zirconia. 5-7 Nano catalysts because of having high specific surface show high catalytic performance. Metal oxide catalysts play an essen- tial role in the production of petrochemicals, as well as in energy applications and for environmental protection. Zeolites have been claimed as promising supports to stabilize transition metals with great potential as oxidation catalysts. 8 The availability of zeolites with several porous structures, different composition and hydrophobicity degree, as well as the possibility to control the acidic properties and location of exchanged cations and high specific surface area (nanostructure) have contributed to in- crease the advantages of zeolites relative to other traditional sup- port materials. 9 Some authors have explored the possibility of using transition metal exchanged or impregnated zeolite catalyst for deep oxidation. These results suggest that intrinsic properties of the zeolites, such as their acidity and high specific surface area play a determinant role in the catalyst performance, being ob- served cases in which the main effect of the metal is the modifi- cation of the acidity. 10-11 ZSM-5 is a type of common zeolites, which has been exhibited excellent catalytic activities. 12-17 VOCs are usually emitted in mixture to nature; however, there are few articles about their treatment under this form. The dif- ferent studies agree on the fact that VOC catalytic oxidation in mixture differs from its simple oxidation. 18-21 Modeling of chemical processes is an appropriate tool and easy method for investigating of reaction and predicting of variable effect on process. Artificial neural networks (ANNs) are now commonly used in many areas of chemistry and they represent a set of methods that may be useful in solving such problems. 22 One of the characteristics of modeling based on artificial neural networks is that it does not require the mathe- matical description of the phenomena involved in the process, and might therefore prove usefulness in simulating and up-scal- ing catalytic oxidation systems. In this work, catalytic oxidation of ethyl acetate and toluene (common VOCs with different natures) are studied over Na- ZSM-5, HZSM-5, Co-ZSM-5 catalysts. Properties of the catal- ysts are characterized by XRD, EDX, BET, XPS, SEM, TEM and ICP-AES techniques. The influences of parameters such as inlet concentration of organic compounds, reaction temperature, amount of cobalt loading, presence of water vapor as co-feed in inlet feed and effect of mixing of VOCs on the oxidation effi- ciency are studied. Furthermore, the catalytic oxidation of ethyl acetate on Co-ZSM-5 catalysts is modeled by artificial neural network, and the predicted (calculated) results are compared with experimental results and performance of ANN is also evaluated.