Chemical Engineering December 2011 - 42

Feature Report
Engineering Practice
Solubility of Water in Benzenes
As a Function of Temperature
The solubility of water in hydrocarbons is important
for several reasons, including product quality.
A new correlation is compared to experimental data
Carl L. Yaws, Preetam Rane
and Vishal Nigam
Lamar University
T
he solubility of water in hydrocarbons
contained in crude oil is
very important. This importance
will increase in the future in view
of processing, safety, hazard and environmental
considerations focusing on
product quality and equipment sustainability.
The following brief discussion
illustrates the importance.
Any processing involving the lowering
of temperature to values in the
range of the freezing point of water
may result in formation of solids
(freezing of water or hydrate formation).
Such solid formation will affect
both fluid flow in piping and operational
characteristics of equipment.
60,000
Equation (1) Data
50,000
40,000
1,000
30,000
100
20,000
10
10,000
Equation (2)
250
300
350
400
Temperature, K
FIGURE 1. The solubility of water in benzene plotted as a
function of temperature. The curve - generated from Equation
(1) - agrees well with experimental data
42 CHEMICAL ENGINEERING WWW.CHE.COM DECEMBER 2011
450
500
1
200 250 300 350 400 450 500 550 600
Boiling point, K
FIGURE 2. The solubility of water in benzenes as a function
of the compounds' boiling points is plotted here. The curves -
generated from the estimation equation at three different temperatures
- agree with experimental data
Data-benzenes-298
Data-benzenes-363
Equation (2)
Equation (2) Data-benzenes-478
10,000
For catalytic reactions, any water in
the hydrocarbon may be a poison to
the catalyst that promotes the hydrocarbon
reaction. For reactions in general,
any water in the reaction species
may result in the formation of undesirable
byproducts issuing from the
hydrocarbon reaction. The presence
of water in the product may be detrimental
to quality. If sufficient water
is in the product, it may prove to be
unuseable.
Results are presented here for solubility
of water in benzenes as a function
of temperature. A new correlation
for water solubility is also presented
that provides reliable solubility values
down to very low concentrations
(parts per million range). The correlation
is based on the boiling point temperature
of the benzenes. Correlation
100,000
values and experimental data are in
favorable agreement. The results are
useable in engineering applications
involving processing, safety, hazard,
environmental and " green " issues.
Correlation for water solubility
The correlation for water solubility as
a function of temperature is based on
the following equation:
(1)
Where:
S = solubility in water, parts per million
by weight, ppm (wt.)
T = temperature, K
A, B, and C = regression coefficients
The correlation applies to a temperature
range of about 298 to 478K. The
coefficients (A, B, and C) for the correlation
were determined from regression
of the available data. In preparing
the correlation, a literature search
was conducted to identify data source
publications [1-25]. The publications
were screened and copies of appropriate
data were made. These data were
Solubility of water, ppm (wt.)
Solubility of water, ppm (wt.)
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Chemical Engineering December 2011

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