Potential Adsorbent for Light Hydrocarbon Separation:  Role of SBA-15 Framework Porosity

Abstract

Samples of mesoporous silica SBA-15 with and without controlled framework microporosity were prepared under microwave hydrothermal conditions. These samples were evaluated for their ability to separate ethane and ethylene by obtaining their equilibrium adsorption isotherms using volumetric adsorption at 303 and 323 K, respectively. The data obtained were analyzed using the Langmuir−Freundlich adsorption isotherm model. Although the mesoporous silica samples showed a higher adsorption capacity for ethylene, it was found to decrease upon reduction in the adsorbent's framework microporosity. Likewise, the isosteric heats of adsorption estimated by the Clausius−Clapeyron equation are higher for ethylene as compared to those for ethane and were also found to depend on framework microporosity. The sample with higher microporosity displayed strong affinity for ethylene and is comparable with those reported for π-complexation-based systems. This affinity was observed to weaken on the sample with lower microporosity and absent altogether on the micropore-free SBA-15 sample. Furthermore, the affinity of the micropore-free SBA-15 framework for ethylene and ethane was observed to be similar to and comparable with those obtained on MCM-41 type mesoporous silica. The thus-obtained trend has revealed the importance of framework microporosity in designing a SBA-15-based adsorbent for ethane/ethylene separation.

Bimodal micro‐mesoporous aluminosilicates for heavy oil cracking: Porosity tuning and catalytic properties

“…Generation of microporosity in ordinary SBA-15 materials has been suggested to be from the partial occlusion of hydrophilic poly ethylene oxide (PEO) chains into silica walls. 33,34 The synthesis parameters, 35 including silica/template ratio, 19 crystallization time and temperature level, 19 pH value of mixture, 36 presence of inorganic salt, 37 and length of the EO n bolck, 38 etc., would affect the microporosity of the resulting SBA-15 due to their influence on the hydrophilicity of PEO chains. However, the present results are quite different from those in literatures: the microporosity in the BMASs increases only with the increasing aging temperature of the preformed zeolite nanoclusters when the other synthesis parameters such as crystallization temperature and surfactant amount are kept constant.…”

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

“…As discussed in Section 3.3.3, addition of salts cause dehydration of ethylene oxide units from hydrated PEO from the side of the PPO core. This leads to an increase in the core radius [101,172], and the increase of the hydrophobic part of the micelles induces the formation of micelles and the sphere-to-rod transition which enhances the order of the material and a slight increase in the pore size. If instead a salt with salting-in properties is used, e.g.…”

“…The control of these walls and the microporosity within them are essential for optimizing the material, e.g. walls with low microporosity have higher thermal stability than high porosity walls [176] and adsorption selectivity of hydrocarbons is affected by the microporosity [171,172].…”

A Hexagonally Ordered Nanoporous Silica-Based Fiber Coating for SPME of Polycyclic Aromatic Hydrocarbons from Water Followed by GC–MS

“…SBA-15 materials have complementary micropores in the silica walls connecting the primary onedimensional mesopore channels to form a well-defined 2D hexagonal array. These SBA-type materials with bimodal pore distribution have been approved a high affinity for various volatile organic compounds (VOCs) due to their complementary nanopores [40][41][42][43]. It is expected that the incorporation of organic groups into the framework of the mesoporous materials will modify their adsorptive properties by improving their affinity to organic compounds [44].…”