Journal of Molecular Catalysis A: Chemical 227 (2005) 217–222
Epoxidation of styrene by anhydrous hydrogen peroxide over boehmite
and alumina catalysts with continuous removal of the reaction water
V.R. Choudhary
a,∗
, N.S. Patil
a,b
, N.K. Chaudhari
a
, S.K. Bhargava
b
a
Chemical Engineering Division, National Chemical Laboratory, Pune 411008, India
b
Department of Applied Chemistry, Royal Melbourne Institute of Technology, Melbourne, 3000 Vic., Australia
Received 29 July 2004; received in revised form 4 October 2004; accepted 7 October 2004
Available online 8 December 2004
Abstract
Boehmite and alumina (obtained from the boehmite by its calcination at different temperatures 300–900
◦
C) are active and stable catalysts
for the selective epoxidation of styrene by anhydrous H
2
O
2
to styrene oxide with continuous removal of the reaction water. Influence of the
catalyst (boehemite) calcination temperature, H
2
O
2
/styrene ratio and catalyst loading on the styrene conversion and selectivity for styrene
oxide, phenyl acetaldehyde, benzaldehyde and benzoic acid in the epoxidation has been investigated. In the presence of water, the catalyst
shows very poor activity and selectivity in the epoxidation. The catalyst also catalyses H
2
O
2
decomposition and hence has optimum loading
for obtaining high-styrene conversion in the epoxidation.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Epoxidation of styrene; Styrene oxide; Boehmite; Alumina; Anhydrous hydrogen peroxide
1. Introduction
Epoxidation of styrene is commercially important reac-
tion for the production styrene oxide, an important organic
intermediate. Earlier studies reported for the epoxidation of
styrene were based on the use of TS-1 [1–4], Ti–SiO
2
[1,5,6],
Ti–MCM-41 [4], and TBS-2 and TS-1 [7] catalysts, using
different oxidising agents, such as TBHP [5], aqueous H
2
O
2
[1,2,6,7], and urea–H
2
O
2
adduct [3]. For all the above cata-
lysts, the use of aqueous H
2
O
2
resulted in a very poor selectiv-
ity for styrene oxide. High-styrene oxide selectivity (≥80%)
could be obtained using urea–H
2
O
2
adduct [3] and TBHP [5]
as the oxidising agents but only at a low-styrene conversion
(18 and 10%, respectively). It is, therefore, of great practical
interest to find a much better catalyst for the epoxidation of
styrene.
∗
Corresponding author. Tel.: +91 20 25890765;
fax: +91 20 25893041/3355.
E-mail addresses: vrc@ems.ncl.res.in, vrc@che.ncl.res.in
(V.R. Choudhary).
Recently, Mandelli et al. [8] have observed a good activity
and selectivity for -alumina in the epoxidation of limonene,
cyclohexene and 1-octene by anhydrous H
2
O
2
. However,
they observed catalyst deactivation due to accumulation of
the reaction water; after a certain reaction period (5 h), the
catalyst was deactivated. In the present paper, we report the
use of boehmite and alumina (obtained from the boehmite by
its calcination at different temperatures), which are not only
cheaper but also more active/selective catalysts, for the epox-
idation of styrene by an anhydrous H
2
O
2
with a continuous
removal of the reaction water. Because of the reaction water
removal, there was little or no deactivation of the catalyst
during the epoxidation.
2. Experimental
Boehmite was a commercial material and, before its use,
it was heated in a muffle furnace at 100 or 200
◦
C for 2 h.
Alumina catalysts were obtained by calcining the boehmite
in a muffle furnace at different temperatures (300, 400, 500,
1381-1169/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2004.10.025