Simulation of alkane adsorption in the aluminophosphate molecular sieve AlPO(sub 4)-5

Article Abstract:

A surprisingly complex behavior is predicted from grand canonical Monte Carlo simulations of adsorption isotherms of alkanes ranging from methane to pentane in the microporous aluminophosphate AlPO(sub 4)-5. A low density-high density transition resembling capillary condensation is found at low temperatures for methane and ethane. A high-density structural transition is noted at intermediate temperatures, wherein the adsorption increases stepwise. Such a transition is signaled by a small inflection point in the isotherms at room temperature. A similar high-density transition is found for propane, a transition that is not present for butane and pentane.

Alkanes, Aluminum compounds

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Diffusion of cyclohexane and alkylcyclohexanes in silicalite

Article Abstract:

A simultaneous thermal analyzer was used to examine the diffusion of cyclohexane and numerous alkylcyclohexanes in silicalite. The analyzer was able to measure the heats of sorption and diffusion coefficients while zero length chromatography was used to monitor the diffusivities of some of the adsorbates. The sequence of diffusion rates determined was trans-1,4-dimethylcyclohexane >> methylcyclohexane > cyclohexane > ethylcyclohexane, cis-1,4-dimethylcyclohexane. The quick diffusion of methylcyclohexane relative to cyclohexane is attributed to transition entropy.

Diffusion, Diffusion (Physics)

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Mechanical stability of mesoporous molecular sieve MCM-48 studied by adsorption of benzene, n-heptane, and cyclohexane

Article Abstract:

Research was conducted to examine the synthesis of the silica mesoporous material MCM-48 which was carried out in a 5 L autoclave. X-ray powder diffraction and 29Si MAS NMR were used to monitor the progress of the synthesis which was formed by an intermediate phase whose conversion ito the cubic phase was triggered by condensation of the silanol groups. Powder X-ray diffraction, nitrogen adsorption and subcritical organic vapor adsorption isotherms and breakthrough curves were employed to study the mechanical stability of MCM-48.

Gases, Benzene, Gas absorption, Gas adsorption, Cyclic compounds

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