奈米孔洞之層狀複合材料於高溫CO2捕捉與抗劣化技術開發

Abstract

在本研究中，主要利用添加了第二種金屬元素進入沸石咪唑骨架中，形成混合金屬沸石咪唑骨架孔洞粉體(zeolitic imidazolate framework, ZIF)及層狀薄膜應用於CO2捕獲及H2/CO2之氣體分離。首先第一部分先合成出ZIF-M- (M=Zn or Ca)奈米粉體及分析其相關特性與CO2物理及化學吸附的協同作用。本研究利用調控溶液中鹼液之比例，接著以XRD和FTIR驗證其特徵結構及鍵結，再利用氮氣等溫吸脫附測量其比表面積、孔體積及孔洞大小，最後搭配SEM觀察表面形貌和微結構。由硝酸鋅和硝酸鈷並加入鹼液三乙胺(TEA)於室溫合成出混合金屬沸石咪唑骨架奈米孔洞粉體(ZIF-Zn-)，隨著三乙胺莫耳濃度的增加，比表面積顯著的提高，並且從表面形貌可以觀察晶體顆粒隨之減小，達到晶體顆粒約為100nm左右之粉體，接著以不同比例的Ca含量進行置換以合成出具有奈米孔洞之ZIF-Ca奈米粉體，進而探討這些奈米粉體在不同熱處理溫度下之結構的穩定性以及CO2捕捉與抗劣化效果的分析。第二部分為利用微波水熱法進行二次生長合成出Co添加於ZIF-Zn混合金屬沸石咪唑薄膜(ZIF-Zn-Co)，合成之二次生長水溶液利用UV-Vis鑑定鈷離子配位為四配位，並且調控配位鍵與鹼液濃度搭配XRD和SEM觀察薄膜生長最優化條件，最後以GPA測試混合金屬沸石咪唑骨架層狀薄膜氣體分離特性。藉由鋅金屬及鈷金屬引入沸石咪唑骨架結構中，其鈷金屬對於二氧化碳氣體具有較強作用力，故其在氣體分離試驗中呈現較低的二氧化碳穿透能力，增加了氫氣/二氧化碳分離率。因此可以進一步用來評估其對於氫氣/二氧化碳分離的效果，以同時提升CO2捕捉的技術。

In this study, we proposed that the impregnation of two metal ions in the node of structure of zeolitic imidazolate framework (ZIF), formation of mixed metal ZIF-Zn- and ZIF-Ca- are applied to CO2 capture and H2/CO2 gas separation, respectively. In the first part, we tried to synthesize high specific surface area porous nanoparticles to investigate the CO2 capture capacity and structure stability. The ZIF structures characterization by XRD and FTIR. The surface area was determined by N2 adsorption-desorption isotherms and SEM was used to observe the surface morphology and microstructure. The ZIF-Zn- containing both zinc ions and cobalt ions are synthesized at room temperature under triethylamine (TEA) base aqueous conditions. With increasing mole concentration of triethylamine, the surface area increased significantly, and the particles size obviously decreased. The nanoparticles (100nm) can be uniformly and densely coated on the substrate support for subsequent film growth. Followed by different ratios of Ca2+ content was replaced with synthesized ZIF-Ca- nano-powders with nanopores. The structure stability of these nano-powders with different calcination temperatures and CO2 capture will be discussed. In the second stage, the hybrid mixed metal ZIF-Zn-Co membrane will be synthesized on the nanoparticle-seeded substrate by microwave hydrothermal method. We used the UV-Vis to identify cobalt ion in the tetrahedral coordination and changed the mole ratio of the ligand and base to optimize the membrane structure and morphology by XRD and SEM. Finally, the gas separation property of hybrid mixed metal ZIF-Zn-Co membrane was determined by GPA. Using introduced zinc ion and cobalt ion into the zeolitic imidazolate framework structure where cobalt has a strong interaction for the carbon dioxide. Therefore, the gas separation test displays lower permeation for carbon dioxide but higher hydrogen/ carbon dioxide separation factor. The permeation of ZIF-Zn-Co membrane was also examined at different temperatures and demonstrated the stable gas separation factor.