Adsorption and Diffusion Behavior of Ethane and Ethylene in Sol-Gel Derived Microporous Silica

Abstract

High surface area silica (500 m 2 /g) was synthesized by the sol-gel method from tetraethyl orthosilicate. The total porosity of the sample was 37% and most of the pores were well below 2 nm in size. The adsorption characteristics of ethylene and ethane in the silica were measured from 300-350 K by gravimetry, and Langmuir adsorption constants and enthalpies and entropies of adsorption were determined. Quasielastic neutron scattering was used to determine the translation and rotational diffusivities of both adsorbates from 200-270 K. Based on the adsorption and translational diffusion characteristics of ethylene and ethane, separation factors of 1.1-2 for olefin to paraffin are predicted.

Imidazolium-based ionic liquids with cyano groups for the selective absorption of ethane and ethylene

“…The search for alternative separation processes led to the investigation of ionic liquids as new separating agents for olefin/paraffin gas separation, serving as absorbents or alternatively as solvents for the chemical complexation of olefins with silver or copper salts [3,4], ion exchanging resins [2], adsorption on high surface-area SiO 2 [5], on alumina [6], on zeolites [7] and molecular sieves [8], or on metallic organic frameworks [9], and the use of several types of membranes [10]. The use of absorbent agents can be less energy demanding but it is often technologically more challenging as the absorbent needs to be efficiently separated and then recycled with reasonable purity.…”

Adsorption and Diffusion of Light Hydrocarbons in UiO-66(Zr): A Combination of Experimental and Modeling Tools

“…The use of QENS for the measurement of the alkane diffusion has also been extended to a study of sol−gel derived silica. 40 Binder et al 28 have illustrated the use of interference microscopy for the exploration of the intracrystalline diffusion of small hydrocarbons in DDR zeolites. Dai et al 41 performed pulsedfield gradient (PFG) NMR experiments to study the selfdiffusivities of ethane and ethylene in large-crystalline SAPO-34.…”

“…The main contribution emanates from Jobic, − Kaerger, − and co-workers who explored diffusion phenomena in diverse zeolites including MFI, silicalite, NaY, NaX, ZSM-5, and AlPO 4 -5. The use of QENS for the measurement of the alkane diffusion has also been extended to a study of sol–gel derived silica . Binder et al have illustrated the use of interference microscopy for the exploration of the intracrystalline diffusion of small hydrocarbons in DDR zeolites.…”

Effect of Unsaturation on the Absorption of Ethane and Ethylene in Imidazolium-Based Ionic Liquids

“…Alternative processes for separating gaseous olefins from paraffins include ion exchanging resins, adsorption on high-surface-area SiO 2 , on alumina, on zeolites and molecular sieves, or on metallic organic frameworks, and the use of several types of membranes. ,, Most of the alternatives proposed involve liquid or solid selective absorbents containing transition metals such as copper or silver, which are believed to form a complex with the unsaturated gas molecule. − ,, These alternatives have not been applied to an industrial scale due to several drawbacks linked to the synthesis, the efficacy, the reliability or the contamination of the different materials and also related to economical obstacles. ,, …”

“…Thus the high demand for an alternative energy-saving separation process. 1−4 Alternative processes for separating gaseous olefins from paraffins include ion exchanging resins, 5 adsorption on highsurface-area SiO 2 , 6 on alumina, 7 on zeolites 8 and molecular sieves, 9 or on metallic organic frameworks, 10 and the use of several types of membranes. 3,11,12 Most of the alternatives proposed involve liquid or solid selective absorbents containing transition metals such as copper or silver, which are believed to form a complex with the unsaturated gas molecule.…”