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283086 Simple Prediction of Adsorption Henry Constants for Supercritical n Alkanes On 5A Zeolite

Simple Prediction of adsorption Henry Constants for Supercritical n alkanes on 5A zeolite

ABSTRACT

A simple model is proposed to calculate
Henry constants for supercritical n alkanes on 5A zeolite using mid isotherm
data. The Gaussian isotherm contains three model parameters, *q _{max}*

_{ }the saturation loading

_{, }

*s*

*the standard deviation and*

_{e}*P*

_{50}_{ }the log mean pressure for the entire isotherm. Since the slope of the Gaussian isotherm approaches zero as the pressure approaches zero, the equation

*dlnq/dlnp*= 1 is used instead for the derivation of the Henry constants. Using this equation, the dimensionless temperature-independent Henry constant may be derived as

where is
expressed as *K _{H}*P_{50}/q_{max}*.

*Z*is the

_{H}*Z*value for the Gaussian model at the point where

*dlnq/dlnp*= 1, and

*σ*is the standard deviation of the isotherm. For supercritical n alkanes on 5A zeolite,

_{e}*σ*is equal to

_{e}*ln 10*and

*Z*is equal to -1.92. Upon substitution

_{H}*K*becomes:

_{H}^{*}The temperature-independence of occurs
because the temperature dependence of *K _{H}* is cancelled by the
temperature dependence of

*P*the log mean pressure for the entire isotherm. It is important to note that

_{50}*P*is calculated at the middle of the isotherm. Therefore Henry's constants can be estimated for isotherm data far from the Henry's Law region. Using the equation, , the model is observed to satisfactorily predict the Henry's law data for all supercritical n alkane isotherms on 5A zeolite.

_{50}To completely predict Henry's constants for this system, a predictive model is incorporated based on a correlative approach for 63 isotherms for carbon numbers varying from 1 to 10. The calculated values from this approach are also in remarkable agreement with reported experimental values. A summary of the equations needed to predict the properties of supercritical isotherms of n alkanes on 5A zeolite is provided.

**KEYWORDS**: separations,** **Henry constants, 5A
zeolite, n alkanes, supercritical isotherms

**Extended Abstract:**File Not Uploaded

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