Asian Journal of Chemistry; Vol. 25, No. 8 (2013), 4441-4443
Esterification of tert-Butanol and Acetic Acid by
Silicotungestic Acid Catalyst Supported on Bentonite
*
JIAN-ZHONG JIN and NA-BO SUN
College of Biological and Environmental Engineering, Zhejiang Shuren University, Hangzhou, 310015, P.R. China
*Corresponding author: Fax: +86 571 88297098; Tel: +86 571 88297171; E-mail: hzjjz@sohu.com
(Received: 5 May 2012;
Accepted: 13 February 2013)
AJC-12984
A series of solid acid catalysts were synthesized by incipient wetness impregnation method by varying the wt % of silicotungstic acid on
bentonite. Silicotungestic acid supported on bentonite was used to catalytic synthesis of tert-butyl acetate with acetic acid and tert-butyl
alcohol. The main reaction parameters such as silicotungstic acid loading on bentonite, the amount of catalyst, molar ratio of reactants,
reaction temperature and reaction time have been investigated. The optimum conditions were determined as follows: silicotungstic acid
loading on bentonite 25 wt %, catalyst 0.7 g, mole ratio of tert-butanol to acetic acid 1:1.1, reaction temperature 110 ºC and reaction time
2 h. The esterification yield of tert-butyl acetate was about 87.2 %. The catalyst could be used repeatedly for many times without distinct
loss in activity.
Key Words: tert-Butyl acetate, Silicotungstic acid, Bentonite, Esterification.
ester, hence, it is necessary to investigate systematically the
effect of these reaction parameters. The optimum conditions
were determined as follows: silicotungestic acid loading on
bentonite 25 wt %, catalyst 0.7 g, mole ratio of tert-butanol to
acetic acid 1:1.1, reaction temperature 110 ºC and reaction
time 2 h. The esterification yield of tert-butyl acetate was about
87.2 %. The catalyst could be used repeatedly for many times
without distinct loss in activity.
INTRODUCTION
Esterification of alcohols, particularly normal alcohols,
by carboxylic acids using homogeneous acid catalysts(viz.
mineral acids) is well known1. However, it is extremely difficult
to prepare tert-butyl ester by the esterification of tert-butanol
using an acid catalyst. This is because of the high reactivity of
tert-butanol in the presence of an acid, causing a rapid
dehydration of the alcohol to iso-butylene, even at the room
temperature2. Hence, there is a need to develop an environ-
mentally benign method for the esterification of tert-butanol
using a highly acitive, selective and reusable solid catalyst
having a little or no acitivity for the dehydration of tert-
butanol.
EXPERIMENTAL
Bentonite was obtained from Zhejiang Sanding Group
Co. Ltd. and other reagents were of chemical grade and used
without further purification.
The catalysts were prepared by wet impregnation method.
A series of catalysts having different loading ranging from
10-30 wt % were synthesized by impregnating 5 g of bentonite
with an aqueous solution of silicotungestic acid (STA) (30
mL of conductivity water) under constant stirring 6 h followed
by heating till complete evaporation of water. It was dried in
an oven at 110 ºC for 4 h, then in miffle at 250 ºC for 5 h.
Esterification reaction: The esterification reaction was
carried out under batch reaction conditions using a 250 mL
flask fitted with a water divider, a stirrer and a thermometer.
The outlet of the water divider was connected to a reflux con-
denser. The temperature of the oilbath was fixed at the certain
reaction temperature until reaction time was reached.A typical
reaction mixture in the reactor contained acetic acid (0.165
At present, the esterification reaction could be catalyzed
by heterogeneous catalysts instead of homogeneous ones.
Some heterogeneous catalysts reported include ion exchange
resin, H-ZSM-5, zeolites-Y, niobic acid, sulfated oxides and
SBA-15 supported heteropolyacids (HPA)3-6. They have many
advantages, for example, they can be more easily separated
and have higher catalytic activity.
In this work the silicotungestic acid catalyst supported on
bentonite was employed in the synthesis of tert-butyl acetate.
The main reaction parameters are silicotungestic acid loading
on bentonite, the amounts of catalyst, molar ratio of reactants,
reaction temperature and reaction time. Accurate control of
these parameters is required in order to improve the yield of