| 摘要: | 碳氫氣體如甲烷、乙烷、丙烷、乙烯、丙烯通常在化學工業上製造，這些氣體對於化工上的應用具有很大的貢獻。舉例來說:甲烷是天然氣中常見的成分;而乙烷跟丙烷是非常基本的原料，可以生成乙酸、橡膠和塑料;乙烯可以應用於果實的催熟或是做為聚乙稀的原料，並且丙烯可以生成聚丙烯。在傳統的工業氣體分離，通常是用低溫蒸餾的方法進行，主要是在低溫及高壓的環境下進行分離程序，這需要耗費大量的能量。最近許多研究發現金屬有機骨架（MOFs）是潛在的氣體儲存和分離材料，因為該材料具有高表面積、無毒、具有高效率的儲氣能力。而在許多的MOF中，UiO-66系列是有機框架的結構中較為新穎的一種材料，因為它們易於合成並且具有熱穩定性和化學穩定性。而其改質的衍生物也引起了許多的關注，改質的衍生物對於氣體的吸附跟儲存會造成一定的影響力，因此，UiO-66及其改性材料被認為是氣體儲存和分離的理想候選材料。
在本研究中，我們使用UiO-66和改性衍生物與功能化有機連接體，如-NO2、-NH2、-Br和-(CH3)2來模擬純氣體和混合碳氫氣體吸附和分離，如C2H6 / CH4、C3H8 / C2H6，C2H6 / C2H4和C3H8 / C3H6。而在吸附的MOF結構中，其數據來自於劍橋晶體數據中心(Cambrdige Crystallographic Data Centre)以及模擬方法使用具正則蒙地卡羅法(grand canonical Monte Carlo)計算碳氫氣體的吸附、選擇比、能量分布以及氣體在結構中的分布位置。透過這項研究我們發現改性後的UiO-66在低壓下表現出比未改性結構更高的選擇性，並且在高壓下UiO-66具有良好的選擇性和比較大的氣體儲存量。此研究的優勢在於使用的模擬手法，系統性的探討鋯金屬有機框架的衍生物對於碳氫氣體的吸附行為與機制。
;Light hydrocarbon gases such as methane, ethane, propane, ethylene, and propene are commonly used in industrial manufacturing and are important for the chemical industry. For example, methane is the most common component of natural gas, and ethane and propane are very basic raw materials that can be used to produce acetic acid, rubber, and plastics. Ethylene and propylene can be synthesize into polymers. Traditionally, gas separation is mainly done by cryogenic distillation, which should be operated at high pressure and low temperature, and requires massive amounts of energy. Recently, many research studies found that metal–organic frameworks (MOFs) are potential gas storage and separation materials because of their high surface area, nontoxic properties, and large gas storage capacity. UiO-66, a relatively new type of MOF, and its modified materials have attracted increased attention, because they can be easily synthesized and are thermally and chemically stable. Therefore, UiO-66 and its modified materials are considered ideal candidates for gas storage and separation.
In this work, we studied UiO-66 and modified derivatives with functionalized organic linkers, such as –NO2, –NH2, –Br and –(CH3)2 to simulate mixed light hydrocarbons adsorption and separation, such as C2H6/CH4, C3H8/C2H6, C2H6/C2H4, and C3H8/C3H6 pairs and respective pure composition adsorption. Cambridge Crystallographic Data Centre (CCDC) database was used to find initial experimentally determined MOF structures, while grand canonical Monte Carlo (GCMC) calculations were performed to obtain adsorption isotherm and adsorption site energy distribution data. A major finding of this work, is the different behavior of the materials at low and high pressures. Modified UiO-66 exhibits higher selectivity than the unmodified structure at low pressure, and at high pressure UiO-66 has good selectivity and large gas storage. This research provides discussion aimed at improving our understanding of gas adsorption behavior in zirconium-based MOFs and related functionalized forms. |
