Supercritical Methane Adsorption Research Articles

Adsorption Properties of Templated Mesoporous Carbon (CMK-1) for Nitrogen and Supercritical MethaneExperiment and GCMC Simulation

Nitrogen adsorption isotherms at 77 K and high pressure adsorption of supercritical methane at 303 K were measured on mesoporous carbon (CMK-1) prepared from the templating of MCM-48. These experimental isotherms were simulated with grand canonical Monte Carlo (GCMC) simulation using the rod-aligned slitlike pore (RSP) model. This RSP model gives good agreement with the experimental nitrogen adsorption isotherm in the low-pressure region, while it describes well the observed methane isotherm. The isothermal compressibility of the adsorbed methane at 303 K was calculated from the experimental and simulated isotherms. The isothermal compressibility of the adsorbed methane shows the intermediate state between the supercritical and liquid phase. This indicates that the adsorbed layer of supercritical methane is highly compressed by the strong interaction potential from the pore walls.

Experimental and Modeling Study of the Adsorption of Supercritical Methane on a High Surface Activated Carbon

The adsorption of methane on an activated carbon of high surface was measured in the range of 233−333 K and 0−10 MPa. The isotherms showed a considerably different feature than that measured on low surface carbon. A maximum appeared on isotherms at relatively low temperatures. All the experimental isotherms were well modeled by the Langmuir−Freundlich equation. The difference between the measured and the so-called absolute adsorption was properly accounted for in modeling. An assumption of monolayer adsorbate adsorbed was included in the model. The layer volume evaluated was consistent with the pore volume of adsorbent reported by CO2 adsorption. The intermolecular distance in the adsorbed phase was evaluated from a model parameter. This intermolecular distance was compared with that in the free sate, which revealed a basic picture of the physical state of the adsorbed phase at above-critical temperatures.

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0–10 MPa and 233–333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of ±2%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsor-bate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.

Comparative study of mean-field theory and Monte Carlo simulation of supercritical methane adsorption in zeolites

A comparison of mean-field theory and Monte Carlo simulations, supplemented by molecular modelling, of adsorption of methane in the zeolite silicalite at supercritical conditions is presented. It is found that for the `hot' supercritical temperature regime, adsorption isotherms predicted by mean-field theory are virtually indistinguishable from those of Monte Carlo simulations thereby providing a straightforward route for the prediction of supercritical adsorption isotherms for this system.

Macroscopic Evidence of Enhanced Formation of Methane Nanohydrates in Hydrophobic Nanospaces

The methane adsorption of water-preadsorbed carbons of different micropore widths w at 303 K was measured. Although the amount of adsorption of supercritical methane on microporous carbon at 303 K was less than 9.4 mg g-1 at 101 kPa, the presence of the preadsorbed water enhanced noticeably the methane adsorption at 303 K even under subatmospheric pressure. The adsorption increment of methane reached a maximum at 1−2 h after introduction of methane and decreased gradually to a steady value after 20−50 h. The adsorption increment of methane depended on the fractional filling φw of micropores by the preadsorbed water. The maximum increment of 110 mg g-1 for w = 1.1 nm at a methane pressure of 2.6 kPa was obtained at φw = 0.34, corresponding to the estimated adsorption amount at 21 MPa of methane (130 mg g-1). The methane-adsorption increment increased linearly with φw until φw = 0.35, indicating the formation of the stable methane−water clathrate of which the composition of methane to water is 1:2. Thus, the nano-order hydrates of methane should be formed in the micropore. The plausible model of the nanohydrate was proposed on the basis of the experimental results and simulation of methane adsorption.