Elucidation of Thermal-Structural and Adsorption Properties of ZIF-8
- 주제(키워드) Zeolitic Imidazolate Framework (ZIF) , ZIF-8 , Thermal Activation , Thermal Stability , Structural Collapse or Damage
- 발행기관 고려대학교 대학원
- 지도교수 최정규
- 발행년도 2014
- 학위수여년월 2014. 8
- 학위구분 석사
- 학과 일반대학원 화공생명공학과
- 원문페이지 70 p
- 실제URI http://www.dcollection.net/handler/korea/000000052089
- 본문언어 영어
- 제출원본 000045808560
초록/요약
Several zeolitic imidazolate frameworks (ZIFs) that provide pore sizes appropriate for H2 separations have been manufactured in the form of membranes and the resulting membranes showed high H2 separation performance. Despite the promise of ZIFs for reliable membrane-based separations, to the best of our knowledge, a systematic study on their thermal stability has not been conducted yet, though thermal activation is inevitable for fully opening the pore space. In particular, we explored the thermal stability test of ZIF-8s, because among many ZIFs it has been intensively used in many applications; membranes, adsorptions, fillers in mixed matrix membranes, supports for catalysts via encapsulation and deposition, sensors, drug delivery etc. H2 separations for example in the pre-combustion process are often required at harsh conditions (high temperature, high pressure), understanding the thermal stability of ZIF-8 is crucial to realize the intrinsic properties of ZIF-8. In this study, we compared four types of ZIF-8 with varying sizes and shapes to see the effect of synthesis origins on their thermal stability up to 400 °C under air atmosphere. The ZIF-8 phase was converted completely into the zinc oxide phase at ~300 °C under air atmosphere, though TGA indicated that it was stable up to ~300-400 °C. However, in the inert argon environment, the phase of ZIF-8 was well preserved at the temperature higher than 500 °C. A longer exposure at 100-250 °C up to ~30 d suggested that ~200 °C was a maximum temperature to preserve the structure of ZIF-8 under air atmosphere and its original adsorption property. In addition, the N2 physisorption isotherms at 77 K of ZIF-8s heat-treated at 100-250 °C under air and vacuum indicate that ~50% of area was inaccessible due to the partial structural damage (possibly condensation) activation at 250 °C under air, while other conditions were proper for full activation. Finally, CO2 adsorption isotherms of appropriately activated ZIF-8s followed the Henry’s law and the corresponding heats of CO2 adsorption were estimated to be ~17.3-18.0 kJ•mol-1, in a good agreement with the literature values.
more목차
ABSTRACT Ⅰ
국 문 요 약 Ⅲ
CONTENTS Ⅴ
LIST OF FIGURES ⅤⅠ
LIST OF TABLE ⅩⅠ
1. INTRODUCTION 1
2. EXPERIMENTAL 5
2.1. Synthesis of ZIF-8 particles 5
2.2. Stability Tests of ZIF-8 Particles 8
2.3. Characterizations 8
3. Results and discussion 10
4. Conclusions 51
ACKOWLEDGE 53
REFERENCES 54
