catalyst. The autoclave was pressurised with H2 and placed in the oil bath,
preheated to the reaction temperature (140–180 uC). The resulting pressure
indicated that the acetone remained liquid under such conditions. After
reaction completion, the reactor was cooled to 0 uC, depressurised in a gas
bag and opened. The catalyst was separated by centrifugation. Products
were identified by GC-MS and quantified by GC equipped with flame
ionisation detector. A 30 m 6 0.25 mm BP5 capillary column was used to
analyse gas products (collected in the gas bag) and a 30 m 6 0.25 mm HP-
INNOWAX capillary column was used for liquid samples.
activity and gave less MIBK and DIBK and an increased amount
of MO and C9+ compared to the first run (Table 2). This shows
that the recovered catalyst partly lost its acidity and hydrogenation
activity which may be regenerated by aerobic treatment at 350 uC,
as described elsewhere.12
In conclusion, Pd/CsPW is an efficient bifunctional catalyst for
the one-step synthesis of MIBK from acetone, both in the gas and
liquid phase. The continuous gas-phase process and the batch
liquid-phase process yield MIBK together with DIBK with a total
selectivity of 91% and 98%, respectively. The gas-phase synthesis
occurs effectively at a remarkably low temperature (80–100 uC), no
catalyst deactivation is observed for at least 25 h on stream. In the
liquid-phase reaction, the catalyst performs well at a very low H2
pressure of 5 bar and can be reused. The selectivity of the
polyoxometalate-based multifunctional catalyst can be dramati-
cally changed by varying the metal function (e.g. by substituting Pt
for Pd), which may find application in other cascade reactions.
Work on catalyst characterisation and further process optimisation
is in progress.
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Thanks are due to Mr R. L. Al-Otaibi and Mr F. Al-Wadaani
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Notes and references
{ CsPW and Pd/CsPW were prepared as described elsewhere.12,13 Cu and
Pt catalysts were prepared by impregnating CsPW with Cu(acac)2 in
toluene and H2PtCl6 in water followed by reduction by H2 at 250 uC for 2 h.
The catalyst powders had ¡180 mm particle size, 2.26–2.31 g cm23 density
and SBET = 110–130 m2 g21
.
{ The gas-phase reaction was performed under atmospheric pressure in a
Pyrex glass fixed-bed microreactor (9 mm internal diameter, 0.20 g catalyst
bed, 10 ml min21 H2 flow rate, 0.36 s contact time, [acetone]/[H2] = 1 :
2.3 mol/mol, 2 h time on stream) with on-line GC analysis (30 m 6
0.25 mm HP-INNOWAX capillary column, flame ionisation detector). All
gas lines were made of stainless steel. The downstream lines and sampling
valves were heated at 150 uC to prevent product condensation. Prior to
reaction, the catalysts were pre-treated with hydrogen at 250 uC for 1 h.
§ The liquid-phase synthesis of MIBK was carried out in a 45 ml Parr 4714
stainless steel autoclave equipped with a magnetic stirrer. The reaction
mixture contained 2.0 g of acetone, 0.30 g decane (GC standard) and 0.20 g
784 | Chem. Commun., 2006, 782–784
This journal is ß The Royal Society of Chemistry 2006