Journal of Chemical & Engineering Data
Article
dehydration to 1-octene and 1-octene isomerization) are also
found and compared to estimated values from the standard
formation enthalpy of reactants and reaction products.
2.4. Procedure. Exploratory experiments in the temper-
ature range (413 to 453) K, starting from pure 1-octanol, show
that alcohol equilibrium conversion was higher than 96 %.
Since water is partially miscible in 1-octanol, and 1-(octyloxy)-
octane is practically immiscible in water, at such alcohol con-
versions some problems arose by the split of reaction medium into
two immiscible phases by the presence of water in large amounts.
First, taking online reliable liquid samples of each phase without
stopping the reaction is difficult. In addition, analysis of data is
complex with simultaneous chemical and phase equilibriums.
Therefore, mixtures of composition close to equilibrium were used
as raw material instead of pure alcohol. On the other hand, in the
determination of the equilibrium constant of the 2-methyl-1-
propene hydration to 2-methyl-2-propanol on ion-exchange resins,
2. EXPERIMENTAL SECTION
2.1. Materials. 1-Octanol, 1,4-dioxane, 1-octene, and 1-(octyloxy)-
octane were used without further purification. Supplier and
purity of these compounds are pointed out in Table 1.
Bidistilled water was obtained in our laboratory.
Table 1. Source, Purity, and Analysis Method of Used
Materials
mass fraction
substance
-octanol
source
purity
analysis method
18
Delion et al. used 1,4-dioxane and a number of solvents. It was
1
1
1
1
Acros Organics
Sigma Aldrich
Fluka
> 0.995
> 0.998
≥ 0.970
0.99
gas chromatography
gas chromatography
gas chromatography
gas chromatography
found that the values of the chemical equilibrium constant
determined from the composition at equilibrium were similar
regardless the solvent used within the limits of the experimental
error. As a consequence,1,4-dioxane was used as solvent to avoid
the liquid splitting into aqueous and organic phases, as it was found
,4-dioxane
-octene
-(octyloxy)octane Sigma Aldrich
15,16
suitable in previous works.
It is to be noted that the resin
The thermally stable ion-exchange resin Amberlyst 70 was
used as the catalyst to speed up reaching the chemical equilibrium.
Amberlyst 70 is a macroreticular PS-DVB ion-exchange resin with
low cross-linking degree. In its synthesis, hydrogen atoms in the
polymer backbone are substituted by chlorine, which confers it
catalyst does not undergo morphological changes by interaction
with 1,4-dioxane since it has been reported that this cyclical ether
15
does not swell the Amberlyst 70 beads. Finally, it was checked in
blank experiments that 1,4-dioxane did not undergo any chemical
15
reaction in the assayed temperature range.
thermal stability up to 473 K. The sulfonic groups (−SO H),
3
3
In each experiment, 70 cm of a mixture of 1,4-dioxane (mass
which are the active sites of the catalyst, are attached to benzene
rings of polymer through treatment with sulfuric acid. Its acid
fraction 0.7), 1-octanol, 1-octene, water, and 1-(octyloxy)octane,
with a composition presumably close to chemical equilibrium, was
prepared and loaded into the reactor. Amberlyst 70 in its
17
capacity, determined by the Fischer−Kunin method, was found
+
−1
to be 2.65 mol H kg dry resin.
.2. Experimental Setup. Experiments were carried out in
commercial distribution of bead sizes (d = 551 μm) was dried at
p
2
−3
3
83 K in an oven, first at 0.1 MPa for 1 h and then for 15 h at 10
3
a 100 cm nominal stainless steel autoclave operated in batch
mode at the temperature range (413 to 453) K. The
temperature was controlled to within ± 0.1 K by an electrical
MPa. Dry catalyst (4 g) was added into the reactor which was
pressurized at 2.5 MPa. After checking the absence of leakages, the
reaction system was heated up to the working temperature and
stirred at 300 rpm. Stirring speed was selected to avoid attrition of
the catalyst during the long-term equilibrium experiments. It was
considered that chemical equilibrium was reached when the
composition of the reaction medium remained constant, and in
addition, thermodynamic equilibrium constants reached a constant
value over time within the limits of the experimental error.
Experiments carried out at (413 and 453) K were repeated to
evaluate the reliability of data.
furnace. The pressure was set at 2.5 MPa by means of N to
2
maintain the liquid phase. The reactor outlet was connected
3
directly to a sampling valve, which injected 0.1 mm of liquid
into a GLC apparatus. The reaction was controlled by a PC
with a designed LabView software program. More detailed
10
information can be found elsewhere.
.3. Analysis. Chemical analyses were carried out by means
2
of a Hewlett-Packard GLC equipped with a thermal conductivity
detector (TCD). A HP Pona methyl siloxane (HP 190915-001)
capillary column (50 m length × 200 μm I.D. × 0.5 μm width of
stationary phase) was used to determine 1-octene, (2Z)-2-octene,
3
. RESULTS AND DISCUSSION
(2E)-2-octene, (3Z)-3-octene, (3E)-3-octene, 4-octene, 1-octanol,
3.1. Experimental Equilibrium Constants. To evaluate
1
-(octyloxy)octane, water, and 1,4-dioxane. The column was
the chemical equilibrium constant of the dehydration of 1-octanol
to 1-(octyloxy)octane, the composition of the reaction medium
has to be determined, which involves the chemical species
participating in the main reaction (water, 1-octanol, and 1-
(octyloxy)octane), and byproducts formed by secondary reactions.
1-Octene, (2Z)-2-octene, (2E)-2-octene, (3Z)-3-octene, (3E)-3-octene,
−1
temperature programmed with a 0.167 K·s initial ramp from
3
−1
(323 to 523) K and then held for 360 s. Helium (0.5 cm s ) was
the carrier gas. All of the species were identified by using a gas−
liquid chromatograph (GLC) equipped with MS (Agilent GC/MS
5973) and chemical database software.
Figure 1. Equilibrium reactions studied. (I) Intermolecular dehydration of 1-octanol to 1-(octyloxy)octane; (II) intramolecular dehydration of
-octanol; (III) isomerization of 1-octene to 2-octene.
1
7
42
dx.doi.org/10.1021/je301236k | J. Chem. Eng. Data 2013, 58, 741−748