J. CHEM. RESEARCH (S), 1996 53
version. The advantages of fixed-bed reaction conditions are:
(i) there is no need to separate the solid catalyst from the
products and (ii) higher phenol selectivities are obtained.
These preliminary studies under unoptimised reaction condi-
tions suggest the feasibility of the use of solid catalysts to
replace environmentally hazardous mineral acids like sulfuric
acid catalysts in CHP cleavage.
Since under fixed-bed conditions the deactivation of the
catalyst with time-on-stream is an important parameter, the
effect of time-on-stream on activity and selectivity for the
decomposition of cumeme hydroperoxide into phenol and
acetone under fixed-bed conditions using H-Al-Beta catalyst
was studied (Fig. 1). The time-on-stream data show that over
10 h, while the conversion remained the same (at ca. 99%)
the phenol selectivity decreased slightly from ca. 95 to 90%.
The successful use of a zeolite catalyst is thus demonstrated
for the first time. Another advantage is that the zeolite can be
regenerated in situ, regaining the initial activity and selec-
tivity.
Fig. 1 Decomposition of cumene hydroperoxide into phenol
and acetone over zeolite Beta (Si/Al = 14): temperature = 60 °C,
LHSV, 2 hꢀ1; Conv = cumene hydroperoxide conversion, mol%;
Sel = phenol selectivity, mol%
Received, 24th July 1996; Accepted, 21st October 1996
Paper E/6/05186C
sion was slightly less (96%) and the phenol selectivity was ca.
85%. However, over ZSM-12,13 NCL-1,14 ZSM-22,13 EU-1,13
MCM-2215 and ZSM-4813 (entries 10–15), lower conversions
as well as selectivities were obtained. Medium-pore zeolites
with unidimensional channels, such as ZSM-22, ZSM-48 and
EU-1, exhibit lower conversions and selectivities due to diffu-
sional restrictions imposed by the channel system of these
zeolites on the reactant and products. However, large-pore
unidimensional zeolites, such as ZSM-12, NCL-1 and MCM-
22, show ca. 85–90% conversion and selectivity. Entries 16
and 17 show the conversions and selectivities of cumene
hydroperoxide over AlPO4-516 and SAPO-517 molecular
sieves. Unlike aluminosilicates with strong Bro¨nsted acidity,
aluminophosphates (neutral) and silicoaluminophosphates
(weak Bro¨nsted acidity) exhibit lower activity in the cumene
hydroperoxide decomposition, clearly suggesting the require-
ment of strong Bro¨nsted acid-sites for the decomposition of
cumene hydroperoxide into phenol and acetone.
The above results indicate that strong Bro¨nsted acid sites
are needed for this reaction. Since Beta, ZSM-5 and Morde-
nite possess stronger acid sites compared to zeolites like Y,
ZSM-22, ZSM-48, etc.,18,19 the conversion is complete using
the former. Furthermore, with the reaction being quite fast,
the quick diffusion of the reactants into the zeolite channels
and of the products from the zeolite channels (as is the case
of zeolite Beta with three-dimensional 12-membered-ring
large-pore channels) will reduce the formation of secondary
products such as quinones, a-methylstyrene, catechol, etc.
and also the small amount of acetophenone. Hence it may be
stated that a combination of strong Bro¨nsted acid sites and
large pore intersecting channels in a high silica zeolite cata-
lyst is suitable for this reaction.
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Entry 18 exhibits the results obtained using a fixed-bed,
down-flow reactor giving 95% phenol selectivity at 99% con-