2
24
A. Alsalme et al. / Applied Catalysis A: General 390 (2010) 219–224
1
00
and supported heteropoly acid catalysts based on H PW12O40 in
3
a fixed-bed flow reactor to yield camphene as the main product
8
6
4
2
0
0
0
0
0
in a mixture with other monoterpenes such as limonene, ter-
pinolenes, terpinenes, -pinene, p-cymene, etc. The performance
of these catalysts, regarding the product selectivity and catalyst
resistance to deactivation, is profoundly dependent on the catalyst
acidity. Bulk H3PW12O40 and Cs2.5H0.5PW12O40 possessing very
strong Brønsted acid sites suffer from deactivation. Conversely,
the catalysts prepared by supporting H3PW12O40 on Nb2O5, ZrO2
Conversion
Camphene
Limonene
and TiO , although weaker acids, exhibit more stable as well as
2
more selective performance in this reaction. The catalyst compris-
ing H PW12O supported on TiO2 gives a camphene yield of 51%
0
5
10
15
3
40
◦
and a total camphene and limonene yield of 58% at 200 C after 15 h
on stream.
Time, h
1
00
Acknowledgements
8
6
4
2
0
0
0
0
0
Financial support from the EPSRC, UK (grant EP/F014686/1) and
the scholarship for A. Alsalme from King Saud University, Saudi
Arabia are gratefully acknowledged.
Conversion
Camphene
Limonene
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The acid-catalysed isomerisation of ␣-pinene is of industrial
1
value to produce camphene and limonene, important interme-
diates for organic synthesis. Here this reaction has been studied
at the gas–solid interface over a range of pre-characterised bulk