Examination of Activity of Three-Way Catalysts Toward CO and Hydrocarbon Emission Reduction from Tehran Gasoline Taxis

Nasibi, Arman | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53075 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Hamzehlouyan, Tayebeh; Hosseini, Vahid
  7. Abstract:
  8. Air pollution is one of the main environmental problems in Iran's metropolises, especially in the city of Tehran. Taxis have a significant contribution to pollution due to the long distances they travel during the day. Due to the fact that the operation of automotive three-way catalysts is a function of their operating conditions, and considering the different fuel composition in Iran and the specific conditions of engine performance, exhaust gas composition can be different from similar cases abroad. A commercial three-way catalyst was tested to evaluate its performance under conditions relevant to the exhaust gas of Tehran's taxis fleet. In this study, CO and C3H6 were considered as the main air pollutants emitted from taxis. The reason for this choice is their significant contribution in Tehran air pollutants. First, BET, XRF, EDS and ICP tests were performed to identify the main parameters and elements of the catalyst, and Pd and Rh were identified as the active elements of the catalyst and Al2O3 and ZrO2 as the main washcoat compounds. In the next step, a series of experiments were performed for kinetic analysis, and the activation energy of 99.75 kJ/mol was obtained for CO oxidation in the temperature range of 127 to 173° C. Also, the reaction orders for CO and oxygen were 1.52 and 0.47, respectively. These numbers indicate the effect of CO inhibition and the positive effect of increasing oxygen concentration. . In propylene oxidation, the activation energy was 92 kJ / mol (temperature range 174 to 199), Propylene reaction order was 1.53 and oxygen reaction order was 1.28, indicating inhibition effect of C3H6. Next, oxidation tests were performed to evaluate the performance of the catalyst. First, the individual oxidation of each CO and C3H6 species was studied in the absence of other pollutants. Simultaneous oxidation of CO and C3H6 were tested and the effect of oxygen concentration was investigated in the presence of both pollutants. It was found that operating under lean conditions, i.e. oxygen concentration higher than stoichiometric concentration, improves the efficiency of the catalyst. Also, the effect of water vapor presence was investigated and it was found that the presence of 5% water vapor reduces the lightoff temperature by about 15 percent. In the last part of the research, the simultaneous effect of temperature, C3H6 concentration and CO concentration was investigated using Surface Response Method (RSM) by applying Design Expert software. The RSM model showed that only temperature and CO concentration affect the oxidation performance. According to these results, increasing the temperature and decreasing the CO concentration improves the conversion of CO and propylene
  9. Keywords:
  10. Kinetics Study ; Catalytic Activity ; Exhaust Gases ; Gas Purification ; Three-Way Catalyst ; Air Particulate Matter

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