Tailoring micropore dimensions in pillared clays for enhanced gas adsorption |
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| Affiliation: | 1. Department of Chemical Engineering, State University of New York, Buffalo, NY 14260, USA;2. Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA;1. Grupo de Investigación en Procesos Reactivos Intensificados con Separación y Materiales Avanzados - PRISMA, Colombia;2. Departamento de Ingeniería Química, Facultad de Ingeniería y Arquitectura, Universidad Nacional de Colombia, Sede Manizales, Campus La Nubia, km 9 vía al Aeropuerto la Nubia, Apartado Aéreo 127, Manizales, Colombia;3. Departamento de Física y Química, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Campus La Nubia, km 9 vía al Aeropuerto la Nubia, Apartado Aéreo 127, Manizales, Caldas, Colombia;4. GIPAB: Grupo de Investigación en Procesos Ambientales, Departamento de Ingeniería de Procesos, Universidad EAFIT, Cr 49 # 7 Sur 50, Medellín, Colombia;5. Lyles School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA;6. Division of Environmental & Ecological Engineering, Purdue University, West Lafayette, IN 47907, USA;1. Environmental Science Department, Faculty of Science, Port-Said University, Port-Said, Egypt;2. Chemistry Department, Faculty of Science, Menofia University, Shebin El-Kom, Menofia, Egypt;3. Water Quality Audit Department, Al-Menofia Water and Wastewater Company, Menofia, Egypt;4. Department of Polymers and Pigments, National Research Centre, Dokki, Cairo, Egypt;1. School of Environmental Engineering, Henan University of Technology, Zhengzhou, Henan 450001, China;2. Zhengzhou Sewage Purification Co. LTD, Zhengzhou, Henan 450051, China;1. School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, GA 30332, USA;2. Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA;1. Haskin Shellfish Research Laboratory, Rutgers University, USA;2. Center for Coastal Physical Oceanography, Old Dominion University, USA;3. National Marine Fisheries Service, Northeast Fisheries Science Center, USA;4. Virginia Institute of Marine Sciences, The College of William and Mary, USA;5. Gulf Coast Research Laboratory, The University of Southern Mississippi, USA;6. Departmento de Oceanografía, Universidad de Concepción, Chile |
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| Abstract: | A systematic investigation has been undertaken for tailoring the micropore structure of the pillared clay. Besides the type of metal oxide (e.g. Al2O3 vs. ZrO2) being used as the pillars, the important factors for determining the micropore structure are OH/Al ratio (for Al2O3-pillared clay), calcination temperature and the starting clay. The effect of the cation exchange capacity (CEC) of the clay on the microporous structure (and consequently the adsorption properties) is reported for the first time. Two clays with widely different CECs are used: Arizona montmorillonite (CEC = 1.40 mequiv./g) and Wyoming montmorillonite (CEC = 0.76 mequiv./g). The interlayer spacings of the pillared clays from these different clays are essentially the same, since the interlayer spacing is controlled by the sizes of the oligomers that intercalate between the clay layers. However, the pillar density in the pillared clay is substantially higher with a high CEC in the starting clay, and is shown to be approximately proportional to the CEC. Consequently, the interpillar spacing is substantially lower resulting from the higher CEC. The CH4 adsorption on the pillared clay is nearly doubled by the smaller interpillar spacing, due to the back-to-back overlapping potential in the micropores. The N2 adsorption was not significantly influenced because of its low polarizability (hence low inductive potential). Increasing the calcination temperature of the Al2O3-pillared clay from 400°C to 600°C can decrease the interlayer spacing, but only by 1 (from 8.7 to 7.7 ). The CH4/N2 adsorption ratio of 2.35 is reached on the Al2O3-pillared Arizona clay that is calcined at 600°C. Finally, the surface and pore volume are influenced by the OH/Al ratio (or pH) during pillaring, since this ratio determines the size and charge of the oligomers. A peak surface area is reached at OH/Al = 2.2. |
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