Graduation Year

2005

Document Type

Thesis

Degree

M.S.Ch.E.

Degree Granting Department

Chemical Engineering

Major Professor

Aydin K. Sunol, Ph.D.

Committee Member

Sermin G. Sunol, Ph.D.

Committee Member

Carl J. Biver, Ph.D.

Keywords

cloud point, phase, supercritical, surfactant, template

Abstract

In the sol gel production of high surface area catalyst, the template, a surfactant, is

the key component of the process. A template too soluble in the supercritical dryingextraction

process can yield a catalyst with a lower surface area. A template completely

insoluble in the supercritical drying-extraction process can lead to a longer calcinations

step and lower catalyst surface area. Template recovery also enhances the economic

feasibility of plant scale production of high surface area catalyst. For these reasons

knowing surfactant solubility in supercritical media is important.

The solubility of surfactants tert-octylphenoxypolyethoxyethanol (commercially

available and hereafter referred to as Triton X-114) and alkyloxypolyethyleneoxyethanol

(commercially available and hereafter referred to as Tergitol 15-S-9) in supercritical

carbon dioxide and ethanol entrainer have been determined at five-degree increments

from 35

oC to 50oC. The solubility of the surfactants was determined by charging a

variable volume cloud point system with the entrainer-surfactant mixture followed by

liquid carbon dioxide. With the resulting stirred homogeneous mixture heated to

temperature, cloud point pressures were observed as the phase analyzer cell was

pressurized by adjusting the variable volume. An average of five values for cloud point

pressure is reported here. The mixture behaviors were modeled using the Improved

Rackett equation and the Peng-Robinson-Stryjek-Vera (PRSV) equation of state with

Wong-Sandler (WS) mixing rules.

For the Carbon Dioxide (CO

2) (1) – Ethanol/Triton X-114 (2) mixtures studied,

compositions ranged from 93.2 mol% CO

2 to 97.7 mol% CO2. The solubility of Triton

X-114 ranged from 0.02 mol% to 0.05 mol% at temperatures ranging from 35

oC to 50oC.

Cloud point pressures observed for this system range from 95 bar to 143 bar.

For the CO

2 (1) – Ethanol/Tergitol 15-S-9 (2) mixtures studied, compositions

ranged from 92.3 mol% CO

2 to 94.4 mol % CO2. The solubility of Tergitol 15-S-9

ranged from 0.02 mol% to 0.03mol% at temperatures ranging from 35

oC to 50oC. Cloud

point pressures observed for this system range from 89 to 154 bar.

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