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S. Ogo et al. / Applied Catalysis A: General 402 (2011) 188–195
100
100
80
60
40
20
0
Sr-P
Ca-P
Ca-V
18.2
80
60
8.0
12.7
81.8
40
62.5
42.7
20
CA
2-B-1-O
BA
Substrate
0
30
40
50
60
70
80
90 100
Fig. 10. The hydrogen transfer reaction of crotonaldehyde, 2-buten-1-ol, and
butyraldehyde with 2-propanol over the Sr–P hydroxyapatite catalyst. Substrates:
Conversion (mol%)
CA = crotonaldehyde, 2-B-1-O = 2-buten-1-ol, BA = butyraldehyde. Products:
1-
Fig. 11. The hydrogen transfer reactions of 2-buten-1-ol with 2-propanol over the
Ca–P, Sr–P, and Ca–V hydroxyapatite catalysts. Reaction condition: catalyst 0.2–1.0 g,
reacion temperature 300 ◦C, time on stream 6.5 h, 2-buten-1-ol 0.1 mol%, 2-propanol
butanol,
C7-alcohols. Reaction condition: catalyst 1.0 g, reaction temperature
300 ◦C, time on stream 6.5 h, substrates 0.1 mol%, 2-propanol 12.6 mol% (Ar bal-
anced).
hyde, the aldol condensation of acetaldehyde into crotonaldehyde,
and the hydrogenations of crotonaldehyde, 2-buten-1-ol, and/or
butyraldehyde into 1-butanol, which was the same reaction mech-
anism as that described in Scheme 1 [11]. And, as shown in Fig. 10,
the 1-butanol selectivity from 2-buten-1-ol (62.5 C%) was lower
than that from butyraldehyde (81.8 C%), which suggested that 1-
butanol synthesis from butyraldehyde might be superior to that
from 2-buten-1-ol.
selectivity, which was almost the same as those of Sr–P hydroxya-
patite catalyst. The Ca–V hydroxyapatite catalyst exhibited higher
crotonaldehyde selectivity of 79.3 C% and lower aromatics selectiv-
ity of 4.4 C% than those of Sr–P hydroxyapatite catalyst.
Fig. 11 shows changes in the 1-butanol selectivities against the
2-buten-1-ol conversion over the Ca–P, Sr–P, and Ca–V hydroxyap-
atite catalysts. 1-Butanol was formed over the any hydroxyapatite
catalysts, but the 1-butanol selectivity depended on the component
ions. The Sr–P hydroxyapatite catalyst exhibited 70 mol% of the 1-
butanol selectivity at 95 mol% of the 2-buten-1-ol conversion. The
C7-alcohols, derived from the 2-buten-1-ol and 2-propanol, were
also observed about 3 mol% yield (not shown data) in the ends
of reactor, which indicated that the main side reaction might be
coking. The Ca–P hydroxyapatite catalyst exhibited 52 mol% of the
1-butanol selectivity and 8 mol% of the C7-alcohols selectivity at
95 mol% of the 2-buten-1-ol conversion. The Ca–V hydroxyapatite
catalyst exhibited 23 mol% of the 1-butanol selectivity and mol% of
the C7-alcohols selectivity at 95 mol% of the 2-buten-1-ol conver-
sion. These results indicated that the Sr–P hydroxyapatite catalyst
showed the high selectivity for the hydrogen transfer reaction of
2-buten-1-ol into 1-butanol and relatively inhibited the coking.
Based on above results, the effects of component ions of hydrox-
yapatite catalysts on the ethanol conversion were considered as
follows. The Sr–P hydroxyapatite catalyst showed high selectiv-
ity into crotonaldehyde in the aldol condensation of acetaldehyde
and relatively inhibited the coking in the hydrogen transfer reac-
tion of 2-buten-1-ol into 1-butanol. These were reasons why the
Sr–P hydroxyapatite catalyst exhibited the highest 1-butnaol selec-
tivity in the catalytic conversion of ethanol among the prepared
hydroxyapatite catalysts. The Ca–P hydroxyapatite catalyst showed
almost the same crotonaldehyde selectivity in the aldol condensa-
tion of acetaldehyde as those of the Sr–P hydroxyapatite catalyst,
but lower 1-butanol selectivity in the hydrogen transfer reaction of
2-buten-1-ol. Therefore, it was considered that the 1-butanol selec-
tivity of Ca–P hydroxyapatite catalyst in the catalytic conversion
of ethanol was lower than those of the Sr–P hydroxyapatite cat-
alyst. The Ca–V hydroxyapatite catalyst exhibited higher catalytic
activity and crotonaldehyde selectivity in the aldol condensation of
acetaldehyde than those of the Sr–P hydroxyapatite catalyst. How-
ever, the Ca–V hydroxyapatite catalyst showed higher selectivity
into ethylene in the conversion of ethanol. These were reasons why
the Ca–V hydroxyapatite catalyst exhibited lower 1-butanol selec-
tivity in the catalytic conversion of ethanol than that of the Sr–P
3.4. Effects of component ions of hydroxyapatite catalysts on
product selectivity
In order to clarify the effects of component ions of hydrox-
yapatites on the ethanol conversion, the aldol condensation of
reaction of 2-buten-1-ol with 2-propanol into 1-butanol were per-
formed over the Ca–P, Sr–P, and Ca–V hydroxyapatite catalysts at
300 ◦C.
Table 2 shows the product yields in the aldol condensations of
acetaldehyde over the Ca–P, Sr–P, and Ca–V hydroxyapatite cat-
alysts. The Ca–V hydroxyapatite catalyst showed higher catalytic
activity for the acetaldehyde conversion than those of the Sr–P
and Ca–P hydroxyapatite catalysts. Crotonaldehyde was the major
reaction product, and C6-aldehydes, C8-aldehydes and aromatics
were the minor products over any catalysts of Ca–P, Sr–P, and Ca–V
hydroxyapatite. The selectivities of crotonaldehyde, aromatics, C6-
aldehydes and C8-aldehydes over the Sr–P hydroxyapatite catalyst
were 62.7 C%, 23.6 C%, 4.4 C%, and 5.6 C%, respectively. The Ca–P
Table 2
The aldol condensations of acetaldehyde over the Ca–P, Sr–P, and Ca–V hydroxyap-
atite catalystsa.
Catalyst
Ca–P
42.7
Sr–P
32.8
Ca–Vb
33.5
Conversion (C%)
Selectivity (C%)
Hydrocarbons
Ethanol
1.7
1.1
0.7
0.8
0.0
0.6
Butyraldehyde
Crotonaldehyde
C6-aldehydes
C8-aldehydes
2-buten-1-ol
Aromatics
5.4
58.9
6.8
5.8
0.4
0.0
62.7
4.4
5.6
0.0
1.0
79.3
7.4
6.4
0.0
17.5
23.3
4.4
aCatalyst 1.0 g (b 0.6 g), reaction temperature 300 ◦C, time on stream 9 h, acetalde-
hyde 0.037 mol% (Ar balanced).