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The reaction we are presenting here requires the use of
pentanol, readily obtainable from biomass, but allows one to
obtain up to 72% yield in PV.
Table 2 Conversion of GVL to pentyl valerate and pentyl 4-penthoxypentanoate
Conv. (%) Sel PV (%) Selpentyl 4-penthoxypentanoate (%)
Moreover, the catalyst concept is quite new, involving a low
activity hydrogenation catalyst and a weakly acidic amorphous
material. Therefore, this reaction appears to be a valuable option
for process intensification in the multistep pathway from cellulose
to new generation biofuels.
8
8
% Cu–SiZr Ba 93
59
72
77
81
83
21
16
18
17
14
% Cu–SiZr B 92
’
’
’
’
’
’
91
92
90
Run conditions: 250 uC, 10 bar H
1
2
, 700 rpm, 20 h, GVL–catalyst =
a
0 : 1 wt., GVL–PA = 1 : 10 mol. GVL–PA = 1 : 5 mol.
Acknowledgements
Pasquale Illiano is kindly acknowledged for performing and
analyzing the NMR results. The authors thank the Italian
MIUR and Regione Lombardia for financial support through
the Projects ‘‘Ital-NanoNet’’ (prot. no. RBPR05JH2P) and
The formation of pentenoic or valeric acids can not be
excluded. However, under these conditions they would be readily
esterified as shown by a separate test (Scheme 2).
To increase the selectivity to PV we lowered the GVL–PA ratio to
: 5 mol. In this way, the chance of forming pentyl-ethers is
‘‘VeLiCa’’ (no. 14840/RCC) respectively.
1
strongly reduced.
References
Analysis of the recycle tests for the reaction with ethanol (Table
3
S1, ESI ) had shown that the selectivity to EV gradually increased
1
(a) A. J. Ragauskas, C. K. Williams, B. H. Davison, G. Britovsek,
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cycle, while keeping very good conversions, thus allowing the
2
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21
21
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2
similar increase in selectivity with time on stream was observed in
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29
Pt–Pd supported on amorphous silica alumina.
3
It should be underlined that this reaction has never been
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2
5
31
2
bar H ). In these reactions the selectivity to pentyl-valerate never
exceeded 1%.
As already mentioned, the one pot transformation of GVL to PV
has been carried out only by direct hydrogenation of GVL to
pentanoic acid and esterification with n-pentyl alcohol formed in
situ through over-reduction of the acid.
7
8
Conversions comparable with those obtained in the present
9
(a) R. Fischer and U. Vagi (BASF), US Pat., 4, 740, 613, 1998; (b) J.
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2
uC (95%) or 300 uC (100%) or 1% Pt–TiO
4 h time on stream. However, the selectivity to PV never
2
at 300 uC (96%) after 10–
32
10 J.-P. Lange, R. Price, P. M. Ayoub, J. Louis, L. Petrus, L. Clarke
1
and H. Gosselink, Angew. Chem., Int. Ed., 2010, 49, 4479.
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1
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1
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2
1
2
1
ChemSusChem, 2009, 2, 535; (b) R. Psaro, M. N. Ravasio and
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Scheme 2 Esterification of valeric acid into pentylvalerate over Cu–SiZr B.
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RSC Adv., 2013, 3, 1302–1306 | 1305