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Design and Synthesis of Supported Metal Oxide Catalysts on Activated Carbon for Removal of VOCs from Air

Zabihi, Mohammad | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46820 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Shaygan Salek, Jalaloddin; Khorasheh, Farhad
  7. Abstract:
  8. Emission of aromatic and aliphatic compounds to atmosphere is a major environmental concern for many urban societies. Catalytic oxidation of volatile organic compounds (VOCs) is an efficient and low operating cost technology for reduction of air pollution.
    First, dispersed copper oxide nano-catalysts supported on almond shell-based activated carbon were prepared for catalytic oxidation of toluene in air. The Response Surface Methodology (RSM) was used to express the catalyst removal efficiency in terms of catalyst metal loading and calcination temperature. Calcination temperature had a significant effect on the catalyst activity only at high metal loadings (upper 8% wt.). Two different catalyst preparation methods were employed to investigate the negative effect of impregnation technique on the deposition-precipitation method. Well-dispersed nano catalysts with higher efficiency towards oxidation of toluene were prepared by the heterogeneous deposition-precipitation (HDP) as compared with the combined impregnation and deposition-precipitation (IMP-DP) method. XRD results show two types of crystallite (large and small) were formed on the support as a consequence of using the combined catalyst preparation method. However, the XRD profiles for catalyst prepared by HDP method (HDPCu8/AC500) show almost uniform peaks with similar intensity due to CuO crystallites. The results of Scherrer equation indicated that the minimum size of crystallites formed on activated carbon were about 10 nm for HDP catalysts. FESEM and TEM images indicating that catalyst particles with misshapen (feather shape) morphology were formed by the IMP-DP method while copper oxide active sites with a “sphere” shape and smaller were formed by the HDP method. Reaction data indicated that among the transition metals, cobalt was the most active for complete oxidation of cyclohexane. Obtained results from characterization and reaction tests for supported cobalt oxide were similar to supported copper oxide catalyst in the study of different preparation methods. Toluene and cyclohexane conversion at 250oC and inlet concentration of 5000 ppmv was 94% and 79% over HDP catalyst, respectively. The Eley-Rideal rate expression was found to be appropriate to describe the kinetics of toluene and cyclohexane oxidation over the range of experimental conditions employed in this study. Copper and cobalt oxides supported on almond shell derived activated carbon (AC) with different loadings were synthesized for catalytic oxidation of gaseous mixtures of toluene and cyclohexane in air in a tubular flow reactor. The best performance was obtained 94% and 90% for total oxidation of toluene and cyclohexane in mixture, respectively, over the Cu2-Co6(mixed)/AC sample (250oC and 1000 ppmv) that indicated negligible deterrence effect of toluene on cyclohexane oxidation.. The catalysts and the support were characterized by Boehm test, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP), and thermogravimetric analysis (TGA). The high stability of dispersed nano bimetallic copper-cobalt oxide catalysts were prepared by HDP method for total oxidation of toluene and cyclohexane in mixture
  9. Keywords:
  10. Toluene ; Cyclohexane ; Catalytic Oxidation ; Activated Carbon ; Copper Oxide ; Cobalt Oxide ; Heterogeneous Deposition-Precipitation Method

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