Reduction of Nitrogen Oxide with Hydrocarbon by Using Zeolite Contained Metal Catalyst

• Main Authors: Chin-En Lin, 林志恩
• Other Authors: Min-Hsin Liu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/23261567141170725544

碩士 === 朝陽科技大學 === 環境工程與管理系碩士班 === 93 === Nitrogen oxide, produced during the combustion process, causes acid rain and greenhouse effect. Furthermore, nitrogen oxide and hydrocarbon compound will occur photochemical reaction and result the secondary pollution. Nitrogen oxide includes nitrogen monoxide and nitrogen dioxide, are harmful to human. Selective catalytic reduction (SCR) is the most common method to deal with nitrogen monoxide pollutant. Recently, hydrocarbon is usually being substituted for ammonia as the reducing agent in SCR reaction. In this research, different zeolites were added to the metal catalyst Pt/Rh and Pd/Rh, and it was expected to increase the catalyst activity. Moreover, different hydrocarbons were utilized as reducing agent in the reaction to discover the optimal catalyst. The catalyst activity and operating parameters were investigated, and kinetic models were correlated with the data to understand the reaction gas behaviors on the surface of catalyst. Base on the experiment data, metal catalyst (Pt/Rh or Pd/Rh) adding CeO2 reduced the conversion efficiency of nitrogen monoxide whether propylene or propane was used. In comparison of two metal catalysts, the conversion efficiency of Pt/Rh catalyst was better than that of Pd/Rh, regardless of CeO2 addition. From two kinds of reducing agents screening, the best catalyst was Pt/Rh combing with FER zeolite (KJ06-1) rather than CeO2. During the operation parameter experiment with the optimal catalyst, the space velocity of 12,000 hr-1 was found to result optimal conversion efficiency. When oxygen was absent in the SCR reaction, the conversion efficiency of nitrogen monoxide was about 80% with propane, and approached to 100% when propylene was used. It merely oxygen and nitrogen monoxide reaction just derived 35% conversion efficiency. According to the Power-rate Law and Arrhenius equation, using oxygen had the highest activation energy (45.9 kcal/mole); following using propane (32.5 kcal/mole) and using propylene had the lowest activation energy (20 kcal/mole). Base on Mars-Van Krevelen, Langmuir-Hinshelwood and Eley-Rideal kinetic models, it was found that the existence of oxygen competed with reducing agent and nitrogen monoxide for the superficial active site of catalyst. Under oxygen free situation, the reducing agent contended with nitrogen monoxide for the same active site. Consequently, controlling the equal entrance flow rate of reducing agent and nitrogen monoxide will create a better reaction result.