R. Liu et al. / Journal of Catalysis 269 (2010) 191–200
199
Table 4
2
Results of hydrogenation of citral with various TiO -supported Pd and/or Au catalysts in n-hexane.
Entry
Catalysts
Time (h)
Conv. (%)
Selectivity (%)
DCAL
TOFb (hꢀ1
)
CAL
IOL
Othersa
1
2
3
4
5
6
7
8
Au(0)/TiO
2
6
6
6
2
2
3
3
6
1
34
4
15
19
6
19
7
6
66
58
67
70
77
53
78
79
0
0
15
6
1
9
8
7
6
2
Pd(2)/TiO
Pd(0)/TiO
Pd(2)/TiO
Pd(0)/TiO
2
2
2
2
22
28
85
36
66
47
37
23
12
10
8
20
8
488
621
430
182
151
108
821
+ Au (0)/TiO
+ Au (0)/TiO
2
2
Pd(2)/Au (0)/TiO
Pd(0)/Au (0)/TiO
2
2
Pd(0)/TiO
2
+ TiO
2
9
3
Reaction conditions: citral 2 mmol, H
2
4 MPa, n-hexane 5 cm , 80 °C, catalyst weight 20 mg for single component samples (entries 1–3, 6 and 7), 20 mg + 20 mg for the multi-
component samples (entries 4, 5 and 8).
a
Same as in Table 3.
Same as in Table 2.
b
catalysts may be larger in scCO
might be in the rate of hydrogen transfer over the surface of a cat-
alyst particle and from a catalyst particle to another in scCO med-
ium. Detailed kinetic analysis should be needed for further
discussion. The reactions were enhanced as the availability of
hydrogen in the vicinity of the adsorbed reactants on the surface
2
than in hexane. Another difference
Acknowledgments
2
The authors gratefully acknowledge the financial support from
the One Hundred Talent Program and KJCX2. YW. H16 from CAS,
the NSFC 20573104. This work was also supported by the CAS-JSPS
International Joint Project GJHZ05.
2
of the catalysts in the scCO solvent increased. As known, a hydro-
gen-rich environment increased the risk of over-hydrogenation in
the successive reaction. But as reported in our previous work,
the selectivity of the corresponding unsaturated alcohols was
improved because the C@O bond was activated through the
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2
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