1146
S. FINDIK AND G. GÜNDÜZ
The quoted studies, in general, describe the invention of a in a three-necked 250-mL flask. The necks housed a sampling
new catalyst for the production of camphene from α-pinene, syringe, a condenser open to the atmosphere, and a ther-
but knowledge of the effects of several parameters, such as mometer to measure the temperature of the reaction mixture.
temperature and catalyst amount and of the reaction kinetics The flask was heated with a thermostated heating mantle
is lacking, and it was the aim of the present work to improve (Electrothermal Engineering Ltd., Essex, United Kingdom)
this knowledge.
and was stirred magnetically.
For a typical run, a known amount of catalyst and wood
turpentine, containing α-pinene, was charged to the reactor
and equilibrated to the reaction temperature. Throughout the
MATERIALS AND METHODS
Catalyst preparation. Halloysite, clay, titanium dioxide, and run, the temperature was maintained constant within about
natural zeolite (clinoptilolite) were employed for preparation ±1°C. The mixture was stirred vigorously to slurry the cata-
of the catalysts to be used in selectivity studies. Halloysite lyst uniformly throughout the liquid. The condenser’s cool-
catalyst was prepared by the method of Kirkpatrick (3). A ing water was started. Representative samples were with-
˙
quantity of halloysite, composed of 27% Al O , 57% SiO
2
drawn periodically with a syringe (Birgi, Istanbul, Turkey),
2
3
and 16% H O (by weight), was reduced into the powder form and the catalyst was immediately separated from the liquid
2
and was contacted with a weak solution of acetic acid (14.3% phase by centrifuging. The sample of liquid phase was ana-
by wt) under continuous stirring for 1 h (Halloysite 1) or 2 d lyzed by a Hewlett-Packard gas chromatograph (Palo Alto,
(
Halloysite 2).
For preparation of the activated carbon catalyst, the HP-FFFAP. From the composition of wood turpentine before
method given by Davis and McBride (8) was employed. each run, the percentage yield of camphene, Y, was calculated
CA) with flame-ionization detector on a capillary column of
The clay catalysts were activated by the treatment of clay (Equation 1):
with HCl solution (9,11,12,15). Activated clay 1 was obtained
Weight of camphene obtained
from the margarine department of Taris Oil Company in
Izmir, Turkey. Activated clay 2 and activated clay 3 were ob-
tained by activating clay from Madak Company (Balıkesir,
Turkey) and green clay from the Ankara region, respectively,
by the dry method. Titanium-based catalysts were prepared
Y(%) =
×100
[1]
Weight of α-pinene in the original material
RESULTS AND DISCUSSION
by treatment of a mixture of titanium dioxide and silica gel in Selectivity studies. Wood turpentine (100 g) (Orta s¸ , Edremit,
the mole ratio of 1:1 with an HCl solution of 9% or by the Turkey), containing 85 wt% α-pinene, was used as the α-
treatment of 1 mole titanium dioxide by acetic acid after heat- pinene source in all runs given below. The results of the se-
ing in 25% aqueous solution of NaOH (16).
lectivity screening test are given in Table 1. The following
The zeolite tuffs, rich in clinoptilolite and obtained from was noted from the selectivity studies: (i) During the prepara-
Bigadic (Balikesir/Turkey), also were used as catalyst and ac- tion of the halloysite catalysts, increasing the treatment time
tivated as follows: A quantity of clinoptilolite was contacted with acetic acid from 1 h to 2 d did not make any significant
with distilled water for 2 h and then dried at 105°C. It was re- difference in the yield of camphene. (ii) Activated carbon was
duced into powder form by grinding and then activated at inactive in the production of camphene. (iii) It was difficult
3
00°C for 24 h. The composition of the catalyst was 74.86% to control the temperature during the runs with activated clay.
SiO , 0.42% Fe O , 0.70% MgO, 0.50% Na O, 2.71% K O, When the amount of catalyst was decreased from 2.5 to 1.0 g,
2
2
3
2
2
9
.04% H O, 2.42% CaO, and 9.35% Al O .
the reaction temperature could be maintained within the de-
2
2 3
Experimental setup. A schematic diagram of the experi- sired range. Activated clay 3 was more active than the others.
mental setup is given in Figure 1. The experiments were done (iv) Titanium catalysts treated with NaOH were not active.
Catalysts prepared by contact with HCl were rather selective
in the production of camphene. (v) Natural zeolite catalyst in
the form of clinoptilolite was the most selective catalyst when
compared with the others used in the study at the level of
2
.5 g. Although activated clay 3 seems to be the most selec-
tive in terms of the amount of catalyst used in the test, we se-
lected clinoptilolite as the most selective catalyst because of
the existence of zeolite tuffs reserves rich in clinoptilolite in
Bigadic (Balikesir/Turkey). Also, acid clay-catalyzed isomer-
ization reactions of α-pinene are rather uncontrollable and
often lead to severe explosions.
The effect of temperature. Figure 2 shows the effect of
temperature on camphene yield at a catalyst level of 2.5 g and
a reaction time of 2 h between 130–150°C. Below 130°C, the
yield of camphene was almost zero. Above 130°C, a sharp in-
FIG. 1. Experimental setup.
JAOCS, Vol. 74, no. 9 (1997)