ADSORPTION ISOTHERM CORRELATION FOR OCTANE ADSORPTION ON ACTIVATED CARBON

Adsorption is defined as the concentration of gas molecules near the surface of a solid
material. The adsorbed gas is called adsorbate and the solid where adsorption takes
place is known as the adsorbent Adsorbent means having capacity or tendency to adsorb
or causes to accumulate on a surface. The four most widely used adsorbents in
decreasing order of commercial usage are activated carbon, molecular-sieve zeolites,
silica gel and activated alumina.
Hydrocarbon refers to any ofaclass oforganic chemical compounds composed only of
the elements carbon and hydrogen such as methane, phenol and butadiene. The carbon
atoms join together to form the framework ofthe compound; the hydrogen atoms attach
to them in many different configurations.
Adsorption isotherm is the relationship between the partial pressure ofan adsorbate gas
and the surface coverage of the adsorbent at constant temperature. Not all the
correlations can best fit all the data which covers wide range of the temperature and
pressure found in most process situations
The objectives ofthis project are to search for possible software to be used to regress or
correlate adsorption isotherms for data at a wide range of temperature and pressure..
Based on the analysis, comparison study on different types of adsorption isotherms is
conducted. The comparison is also done for different type of regression method from
Statistical Analysing System (SAS) and MATLAB programming.
The scope covers the study of a few selected adsorption isotherms, which are Modified
Antoine's Equation, Langmuir, Sips (Langmuir-Freundlich), Toth, Dubinin-
Radushkevich and Dubinin-Atakhov isotherms. The data used to determine the best
adsorption isotherm is Octane Adsorption on Activated Carbon (M. Shariff, A., 1995).
From the data onOctane, the pressure (kPa) and q (mol/kg) is given, thus deriving from
this, the unknown variable properties can be achieved. Microsoft Excel has been
identified as the software that will be used to correlate the adsorption Isotherm for
Octane Adsorption on Activated Carbon.
From the results obtained, the best fit of adsorption isotherm data is determined by
calculating the variance, where the lowest value of residual obtained shows the best fit..
Verification of the method used is done by comparing the result with published
literature .The comparison studywill be done between the result obtainedfrom SAS and
MATLAB programming using the same adsorption data, to identify the best software
for regression ofAdsorption Isotherms.
It can be concluded that, for nonlinear regression, the best approach is Microsoft Excel,
since it can provide better fit for the adsorption isotherm of hydrocarbon adsorption.
This method is capable for fitting adsorption data which covers wide range of
temperature and pressure. Sips equation is the best correlation for the representation of
octane adsorption on activated carbon as it gives the smallest value ofvariance.