Microkinetic study for the effects of promoters on the oxidative coupling of methane over Na2WO4/SiO2 catalysts
- 주제(키워드) oxidative coupling of methane , OCM , microkinetic , kinetic modeling , promoter
- 주제(DDC) 621.042
- 발행기관 아주대학교
- 지도교수 박명준
- 발행년도 2023
- 학위수여년월 2023. 8
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000032838
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
The microkinetic model for the oxidative coupling of methane over Na2WO4/SiO2 catalyst was established by theoretical analysis and investigations through a kinetic study. The mechanism was proposed based on the experimental data and literature. The methane is activated on the active oxygen site on the catalyst surface, and the produced methyl radical is converted to the products. Two reaction pathways are suggested in the mechanism: main product production and by-product production. The ab-initio calculation (DFT) and semi-empirical method (UBI-QEP) calculated adsorption and activation energies. The actual activation energy and rate constant for Na2WO4/SiO2 catalyst and various promoters were calculated based on the theoretical results. Results indicated that all the activation energies for reactions from the molecules (over 320 kJ/mol by UBI-QEP) are relatively higher than those from the radicals (under 200 kJ/mol by UBI-QEP). And the difference in magnitude of the rate constant for methyl radical coupling and activation energy of ethylene decomposition causes the difference in primary product yields.
more목차
Chapter 1 Introduction 1
1.1 Motivation of research 1
Chapter 2 Background theory 3
2.1 Density functional theory (DFT) 3
2.2 Transition state theory 5
2.3 The unity bond index-quadratic exponential potential (UBI-QEP) method 7
Chapter 3 Oxidative coupling of methane (OCM) 10
Chapter 4 Experiments 13
4.1 Experiments [69] 13
4.2 Experiment results 18
4.2.1 Base case 18
4.2.2 Promoter: Zn and Ni 18
4.2.3 Promoter: Co and Ce 18
4.2.4 Promoter: Cu and Cr 19
4.2.5 Comparison with Mn promoter 20
Chapter 5 Reaction mechanism 26
Chapter 6 UBI-QEP analysis 28
6.1 Catalyst structure 28
6.2 DFT Calculations 32
6.3 Activation energy calculation 32
6.4 UBI-QEP results 35
Chapter 7 Reaction kinetic model 36
7.1 Reaction kinetic model 36
7.2 Parameter estimation 38
7.3 Estimation results 40
7.4 Effects of operating conditions 42
7.5 Activation energy comparison 44
Chapter 8 Conclusion 51
Reference 52
Abstract in Korean (국문초록) 58
