CL-131106
Received: November 27, 2013 | Accepted: December 13, 2013 | Web Released: December 21, 2013
Catalytic Dehydration of 1,2-Propanediol into Propanal over Ag-Modified SilicaAlumina
Daolai Sun, Ryosuke Narita, Fumiya Sato, Yasuhiro Yamada, and Satoshi Sato*
Graduate School of Engineering, Chiba University, Yayoi, Inage-ku, Chiba 263-8522
(
E-mail: satoshi@faculty.chiba-u.jp)
Vapor-phase catalytic dehydration of 1,2-propanediol was
investigated over several solid acid catalysts, such as alumina,
silicaalumina, HY zeolite, and β-zeolite. These acids catalyzed
the dehydration of 1,2-propanediol to produce propanal
gradually deactivated with time on stream. In a similar way,
higher than 90 mol % of selectivity to propanal with a complete
conversion was also obtained over zeolite catalysts, such as
ZSM-23, at 300 °C, whereas all of the catalysts was deactivated
1
2
(Figure 1), while zeolites were particularly deactivated because
in an initial stage of the reaction.
of deposition of carbonaceous species. An amorphous silica
alumina was modified with metals such as Ag and Cu to
stabilize the catalytic activity under hydrogen flow conditions.
Ag-modified silicaalumina is a promising catalyst for the
production of propanal from 1,2-propanediol.
An important issue in catalytic conversion under flow
conditions is deterioration of acidic catalysts. The stability of
catalyst is highly necessary in an industrial process. In our
group, an effective operation on the stabilization of catalytic
1
3,14
activity of acidic catalysts was reported.
Vapor-phase
dehydration of tetrahydrofurfuryl alcohol (THFA) into 3,4-2H-
1
3
dihydropyran (DHP) can be catalyzed by acidic alumina: the
conversion of THFA over alumina is seriously deteriorated in
nitrogen at 300 °C irrespective of its high initial activity.
Alumina modified with Cu exhibits stable catalytic activity with
high selectivity to DHP under hydrogen flow conditions. Prior to
the reaction, CuO was reduced to metallic Cu, which works as
a product remover together with hydrogen to prevent coke
formation. In the vapor-phase dehydration of pinacolone to
2,3-dimethyl-1,3-butadiene over modified alumina catalysts at
425 °C, Co/Al2O3 was also found to stabilize the conversion of
pinacolone to produce 2,3-dimethyl-1,3-butadiene selectively
In order to reduce damage to the environment, renewable
biomass must be used as an alternative to fossil resources.
Glycerol has been a well-known renewable chemical resource,
and its practical application has increased considerably in the
last decade because of its inevitable formation as a by-product of
1
biodiesel production. Catalytic conversion of renewable bio-
mass into valuable chemicals is expected to reduce damage to
the environment. Glycerol can be selectively dehydrated to
produce hydroxyacetone over copper2 and silver metals, and
hydroxyacetone can be readily hydrogenated into 1,2-propane-
diol (PDO) in a hydrogen flow.5 On the other hand, over acidic
catalysts, glycerol is dehydrated to produce dominantly acro-
,3
4
,6
14
under hydrogen flow conditions. In this paper, we investigated
the catalytic behavior of commercial solid acids modified by
several metals in the dehydration of PDO. We also demonstrated
efficient stabilization of the catalytic activity of amorphous
silicaalumina by the modification of silver metal.
7
lein.
Silica-supported heteropolyacids such as silicotungstic acid
(
H4SiW12O40) show excellent catalytic activity for the dehy-
8
dration of glycerol to produce acrolein. Since the acidic
catalysts can preferentially remove a secondary OH group of
glycerol, it is expected that propanal can be formed from PDO
over acidic catalysts. Actually, a silica-supported phosphotungs-
tic acid (H PW O ) shows catalytic activity for the dehydra-
Four commercially available catalysts, alumina (AL),
amorphous silicaalumina (SA), HY, and β (BEA)-zeolites,
were used. All the metal catalysts supported on SA are prepared
by incipient wetness impregnation using a solution with a
prescribed amount of aquous metal nitrate solution. After
impregnation, samples were calcined at 500 °C. The name of
supported metal catalyst is abbreviated as follows: “SA”-“loaded
metal or metal oxide”-“metal loading [wt %].” The experimental
3
12 40
tion of PDO into propanal, together with the formation of the
9
corresponding dioxolanes. Unfortunately, only a few examples
have been presented for the production of propanal from
912
15
PDO.
We have found that silicotungstic acid (H4SiW12O40) is an
details are described in Supporting Information.
Procedures for the catalytic reaction are briefly explained as
follows: the catalytic reaction was performed in a fixed-bed
down-flow glass reactor at 300 °C and ambient pressure. After
the catalyst bed had been preheated in either H2 or N2 flow at
300 °C for 1 h, PDO was fed into the reactor at a feed rate of
11
active catalyst for the formation of propanal from PDO. In
particular, silica-supported silicotungstic acid showed the high-
est catalytic activity in the formation of propanal. At low
conversions, however, the produced propanal reacted with
another PDO to produce cyclic acetal (2-ethyl-4-methyl-1,3-
dioxolane, DOXL). Such acetal formation reduced the selectiv-
ity to propanal. Although the propanal selectivity higher than
3
¹1
3.9 cm h . The reaction effluent collected every hour was
analyzed on a gas chromatograph connected to a hydrogen flame
ionization detector (FID-GC, Shimadzu GC-8A) using a 30-m
capillary column of TC-WAX (GL Science).
93 mol % was attained at PDO conversion of 100% at 200 °C
under optimum reaction conditions, the catalytic conversion was
Table 1 shows the reaction results over AL, SA, HY, and
BEA catalysts, and the changes in conversion and selectivity
over the catalysts with time on stream are shown in Figure S1.
1
5
OH
-H O
2
Propanal was the main product and the main by-products were
DOXL, 2,5-dimethyl-1,4-dioxane (DMDO), and acetol. Other
by-products such as 2-propen-1-ol, propionic acid, and 2-ethyl-
2-butenal were also detected. AL showed stable conversion of
O
OH
Figure 1. Dehydration of 1,2-propanediol to propanal.
© 2014 The Chemical Society of Japan