Modified platinum/zeolite for removing air pollutants

다국어 초록 (Multilingual Abstract)

A novel platinum (Pt)/zeolite catalyst platform was designed to remove three major air pollutants. The catalyst targets formaldehyde (HCHO) and toluene in indoor and outdoor air, as well as nitrogen oxides (NOx) produced in semiconductor manufacturing processes under high-oxygen conditions (20% O2).
In the context of volatile organic compound (VOC) removal, Pt/zeolite utilization was initiated through a treatment process involving sodium hydroxide, which induced the formation of a mesoporous structure within the 2–50 nm range. After acid treatment, Pt precursors were impregnated to achieve uniformly dispersed Pt particles with an average size of 1–3 nm. Among the synthesized catalysts, the ZSM-5-based catalyst achieved over 80% formaldehyde conversion under high space velocity conditions. Meanwhile, the Beta-based Pt catalyst, optimized for Pt loading and space velocity, demonstrated a toluene removal rate approaching 100% at 140oC.
Selective catalytic reduction with hydrogen (H2-SCR) experiments conducted under high-oxygen conditions (20% O2) revealed that relatively large Pt particles, formed by high-temperature sintering, limited the Pt-zeolite interface area. This suppressed premature desorption of nitrogen oxide, consequently improving its conversion efficiency.
Furthermore, introducing an appropriate amount of palladium (Pd) into the Pt precursor significantly increased the nitrogen oxide conversion rate within the 85–100oC range. Adding an amorphous tungsten (W) layer during synthesis also enhanced SCR efficiency.
In summary, the following conclusions can be drawn: (1) The size of mesopores and Pt particles significantly affects VOC oxidation efficiency and (2) high-temperature sintering and the addition of Pd or W enhance H2–SCR performance.

국문 초록 (Abstract)

실내•외 공기에서 발생하는 HCHO와 toluene, 그리고 반도체 FAB‑RTO 공정에서 배출되는 고농도 산소( 20 % O2) 조건하의 NOx 등 세 가지 주요 대기오염 물질을 동시에 저감하기 위해 Pt/제올라이트 촉매를 합성하였다. VOC 제거용 Pt/Zeolite는 먼저 NaOH 처리를 통해 2–50 nm 범위의 메조 기공 구조를 형성하고, 이후 산 처리 후 Pt 전구체를 함침함으로써 평균 입경 1–3 nm의 균일하게 분산된 Pt 입자를 확보하였다. 이와 같이 합성된 촉매 중 ZSM‑5 기반 촉매는 상온, 고유속 조건에서 80 % 이상의 HCHO 전환율을 달성했으며, Pt 함량과 공간 속도를 최적화한 Beta 기반 Pt 촉매는 140 °C에서 100 %의 톨루엔 제거율을 나타냈다.
고농도 산소( 20 % O2) 환경에서 수행한 H2‑SCR 실험에서는 고온 소성에 의해 형성된 비교적 큰 Pt 입자가 Pt‑제올라이트 계면 면적을 제한함으로써 NO의 조기 탈착을 억제하고, 이에 따라 NO 전환 효율이 향상됨을 in situ FT‑IR 분석으로 확인하였다. 또한 Pt 전구체에 적정량의 Pd를 도입하면 85–100 °C 구간에서 NO 전환율이 추가로 증가했으며, 무정형 W 층을 추가하여 합성한 경우에도 저온에서 SCR 효율이 증가하였다.
종합적으로 (1) 메조기공과 Pt 입자 크기 제어가 VOC 산화 효율을 크게 향상시키고, (2) 고온 소성 및 Pd 혹은 W첨가가 H2‑SCR 성능을 강화함을 확인하였다.

목차 (Table of Contents)

• Chapter 1. Introduction and Background 1
• 1.1 "Share air" system for air purification 1
• 1.2 The nitrogen oxide in semiconductor fabrication(FAB) 7
• 1.2.1 FAB Processes that generate nitrogen oxide 7
• 1.2.2 Methods for Removing nitrogen oxide generated in FAB 10
• 1.2.3 Regenerativethermaloxidation process 12
• 1.3 Zeolite as a support 18
• 1.3.1 History and Applications of Zeolite 18
• 1.3.2 Advantages of Zeolite as a Support 20
• 1.4 Aim of the dissertation 24
• Chapter 2. Modified Platinum/Zeolite for removing volatile organic compounds 26
• 2.1 Introduction 26
• 2.1.1 Formaldehyde 26
• 2.1.2 Toluene 31
• 2.1.3 modified zeolite acid and base treatment 35
• 2.2 Experimental 38
• 2.2.1 Catalyst preparation 38
• 2.2.1.1 Zeolite preparation 38
• 2.2.1.2 Create mesopores 38
• 2.2.1.3 Acid treatment 39
• 2.2.1.4 Platinum impregnation 39
• 2.2.2 Catalyst Characterization 40
• 2.2.3 Catalyst performance evaluation 41
• 2.2.3.1 formaldehyde oxidation 41
• 2.2.3.2 toluene oxidation 43
• 2.3 Results and Discussion 44
• 2.3.1 Formaldehyde catalytic oxidation 44
• 2.3.2 Toluene catalytic oxidation 56
• 2.4 Conclusions 68
• Chapter 3. Platinum/Zeolite under FAB exhaust gas conditions for removing nitrogen oxide 70
• 3.1 Introduction 70
• 3.1.1 Selective catalytic reduction(SCR) of nitrogen oxides with hydrogen (H2-SCR) 70
• 3.1.2 Novel metal/zeolite catalyst for H2-SCR 72
• 3.2 Experimental 75
• 3.2.1 Catalyst preparation 75
• 3.2.2 Catalyst Characterization 76
• 3.2.3 Catalyst performance evaluation 79
• 3.3 Results and Discussion 80
• 3.3.1 Catalytic performance of novel metal/ZSM5 80
• 3.3.2 Promoter addition for SCR performance enhancement 98
• 3.3.2.1 Pt-Pd/ZSM5 98
• 3.3.2.2 Pt-WS2/ZSM5 103
• 3.4 Conclusions 118
• Reference 120
• 논문요약 140