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Evaluation of Zeolite-Based Catalysts for Selective Catalytic Reduction of Nox As Part of Diesel After-Treatment System

Asadimanesh, Hoda | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57233 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Hamzehlouyan, Tayebeh
  7. Abstract:
  8. Urban air pollution has emerged as a significant environmental concern in recent times. NOx is classified as a criterion pollutant. In 2021, the Tehran Air Quality Control Company reported that the ambient concentration of this pollutant in Tehran is around 50 ppb which exceeds both the initial and final target recently established by the World Health Organization (40 ppb and 10 ppb, respectively). Diesel vehicles are the primary contributor to NOx emissions in Tehran. To control NOx emissions from diesel engines, Selective Catalytic Reduction (SCR) systems are used according to Euro 4 and Euro 5 standards. Considering the novelty of this technology within the nation, it is critical to formulate catalysts and assess their performance under simulated operational conditions of the diesel fleet of the country. In this research, after investigating reported formulations for this catalyst, catalysts based on ZSM-5 and Y zeolites containing copper active phase were prepared, and their performance for NOx reduction was evaluated. Catalyst synthesis was performed using two methods: aqueous ion exchange and solid-state ion exchange. Four samples of ZSM-5-based catalysts containing 1.5%, 1.9%, and 2.5% copper were prepared, along with two samples of Cu-Y catalysts with 7.0% and 8.9% copper loading. ICP, BET, XRD, SEM, and EDS analyses were conducted to determine the characteristics of the prepared catalysts. Among the six synthesized samples, three of them were selected as preferred samples based on characterization results, and standard NH3-SCR reactor tests were performed to evaluate the performance of the fresh selected samples. The Cu-Y catalyst, which was loaded with 8.9% copper, demonstrated the most favorable low-temperature activity, as evidenced by its T50 value below 100°C and temperature range of 125°C to 480 °C. The LT activity of Cu-ZSM-5 loaded with 1.9% copper, which exhibited a T50 of 190°C and a temperature window of 230-550°C, subsequently surpassed that of Cu-ZSM-5 loaded with 2.5% copper, which demonstrated a T50 and a temperature window of of 210°C and 240-490°C, respectively
  9. Keywords:
  10. Selective Catalytic Reduction (SCR) ; Zeolite ; Nitrogen Dioxide ; Zeolite Catalyst HZSM-5 ; Copper Active Phase ; ZSM-5 Zeolite

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