Novel Cu and Cu2In/aluminosilicate type catalysts for the reduction of biomass-derived volatile fatty acids to alcohols

Article abstract of DOI:10.2478/s11532-012-0121-3

This work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products. Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous aluminosilicate were obtained by dehydrating and H²-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In₂O ₃ additive. In the catalysts modified by In₂O₃ additive formation of copper-indium alloy phase (Cu₂In intermetallic compound) was detected resulting in a different selectivity than the one recorded for the Cu/SiAl.

Full text of DOI:10.2478/s11532-012-0121-3

Cent. Eur. J. Chem. • 10(6) • 2012 • 1954-1962
DOI: 10.2478/s11532-012-0121-3
Central European Journal of Chemistry
Novel Cu and Cu2In/aluminosilicate type
catalysts for the reduction of biomass-derived
volatile fatty acids to alcohols
Research Article
Szabolcs Harnos1*, György Onyestyák1, Róbert Barthos1,
Magdalena Štolcová2, Alexander Kaszonyi2, József Valyon1
1Institute of Materials and Environmental Chemistry,
Research Centre for Natural Sciences, Hungarian Academy of Science,
Budapest H-1025, Hungary
2Department of Organic Technology, Slovak University of Technology,
Bratislava SK-81237, Slovak Republic
Received 2 March 2012; Accepted 13 August 2012
Abstract:
This work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products.
Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass
degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high
hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous
aluminosilicate were obtained by dehydrating and H2-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the
highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate
could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In2O3 additive. In the catalysts modified by
In2O3 additive formation of copper-indium alloy phase (Cu2In intermetallic compound) was detected resulting in a different selectivity
than the one recorded for the Cu/SiAl.
Keywords: Acetic acid reduction • Cu-zeolites • In2O3 doping • Ethanol • Ethyl acetate
© Versita Sp. z o.o.
1. Introduction
transportation fuel. The low-boiling fraction (up to 150°C)
of the distillate of bio-oil, obtained from lignocellulose
The technologies used to produce chemicals and fuels pyrolysis, contains lower carboxylic acids and aldehydes
on various biomass platforms involve combination of in relatively high concentration. Fuel alcohol can be
mechanical, chemical, bio- and thermochemical, and obtained by selective reduction of these components.
separation operations [1-3]. Except for the sugar-to- Instead of the less advantageous thermochemical
alcohol route, all biomass conversion processes generate routes, a novel and favorable microbiological destruction
carboxylic acids as intermediates. Acknowledging the /MixAlco/ process is elaborated [4]. In principle, the
need of transportation and other industrial sectors biogas process is suggested to be stopped after the rapid
for chemicals, there is a high commercial interest in anaerobic acidogenic digestion stage, which would be
the selective catalytic hydroconversion of bioacids to followed by the slow methanogenesis step, to produce
alcohols, ethers, and esters. The deep reduction of short the VFAs [5,6]. The selective hydrogenation of the fatty
chain carboxylic acids and other oxygenates provides acids to alcohols in a continuous flow system, working
gaseous paraffinic hydrocarbons. Because of the need in vapor phase under mild conditions, seems to be the
for liquid fuel the selective reduction of these components problem to be solved.
to alcohols is the most favored.
From the early 1930s up to now triglycerides were
The alcohols obtained from the volatile fatty used mainly to produce fatty alcohols [7]. The technology
acids (VFAs) can be used as chemicals as well as of fatty alcohols production involves hydrogenation of
* E-mail: harnos.szabolcs@ttk.mta.hu
1954

Sz. Harnos et al.
triglycerides over toxic chromium-containing catalysts. Table 1. Composition of the zeolites.
Such chromium-promoted copper catalysts permit the
Sample
Si/Al
Al
Na
Cu
selective addition of hydrogen to carbon-oxygen bonds
but are relatively inactive in the hydrogenolysis of the
carbon-carbon bonds. However, because the use of
chromium raises environmental concerns, the current
research is focused on developing chromium-free
catalysts [8]. Since esters can be reduced with hydrogen
more easily than the carboxylic acids [9], the difficulty
of the selective fatty acid reduction was circumvented
by including an esterification step. Nevertheless, the
patent literature describes numerous catalysts for acetic
acid (AA) hydrogenation comprising of one or more
Group VIII noble metals dispersed on Group III or IV
metal oxides. Rachmady and Vannice have recently
shown related results in a series of papers describing
catalysts carrying platinum on TiO2, SiO2, Al2O3 and
Fe2O3 supports [10-14].
Recently, copper exchanged zeolites were reduced
by hydrogen and used as catalysts for hydrogenation of
octanoic acid, a model reactant. It was shown by X-ray
powder diffraction (XRD) that amorphous silica-alumina
supporting finely dispersed copper nanoparticles were
formed from Cu-forms of low Si/Al-ratio synthetic zeolites
(A, X, P). The In2O3 additive was shown to increase the
activity and selectivity of the supported copper catalyst
in the reduction of long chain fatty acids to alcohols [15].
The study presented hereby refers to the application
of similar catalyst systems for the selective reduction of
the VFAs to alcohols. Acetic acid (AA) has been used
as a model reactant in most of the experiments and
compared with the conversion of the long chain octanoic
acid (OA) to present more detailed studies of the nature
of the mono- and bi-metallic catalysts.
mmol g-1
NaP
0.95
7.31
6.58
5.80
3.12
6.86
6.11
6.02
3.01
6.77
6.05
6.08
3.06
0.12
0.50
1.18
0.87
-
-
NaA
1.21
NaX
1.48
-
NaY
2.57
-
14CuP
16CuA
15CuX
7CuY
-
-
-
-
2.20
2.52
2.39
1.10
using a fresh solution. The solid was separated again,
washed three times with distilled water and dried at
room temperature. The Cu2+ content of three (A, X, P)
catalysts was 14-16 wt.% and 7 wt.% Cu2+ for zeolite
Y which had lower Al or cation content and higher
Si/Al ratio (2.6). The Si/Al ratio was very low (approx. 1)
in Cu-A, -X and -P zeolites reflecting similar chemical
composition. Zeolite A (small pore) and faujasites
(zeolite X or Y, large pore) have different frameworks
but consist of the same building units (linked truncated
octahedra, β-cages). CuP is a small pore zeolite, but with
a quite different gismondite skeleton containing different
building units. The main chemical characteristics of
zeolites are summarized in Table 1.
Cu(II) acetate was impregnated on an industrial
amorphous silica-alumina (SiAl), having a Si to Al ratio
of 6.6, to obtain 20Cu/SiAl catalyst with 20 wt.% Cu
content. After drying, this impregnated sample was air
calcined at 550°C for 3 h to decompose the acetate to
copper oxide.
Composite catalysts were prepared by adding
indium(III) oxide (99.99% purity, from Aldrich) to the
CuZ samples and grinding the mixture in an agate
mortar. For comparison, an applied Adkins catalyst
was a commercial product obtained from Süd-Chemie
AG (consisting of 72 wt.% CuCr2O4 and 28 wt.%
CuO).
2. Experimental procedure
2.1. Catalysts
For the designation of the prepared catalysts the
symbol of the element copper (Cu) is used, followed
by the name of the zeolite (A, X, Y, P), such as CuX.
Specific samples are distinguished by including the
metal content, expressed in weight percent, in the
sample designation, such as 14CuP. The various
indium-containing CuZ samples are specified by the
amount of the admixed In2O3, in weight percent, followed
by the designation of the CuZ, such as 15In2O3/14CuP,
which means a sample obtained by admixing as much
indium(III) oxide to zeolite 14CuP, which amounts to
15 wt.% of the Cu-zeolite. The atomic ratio of Cu/In is
approx. 2 in this case.
Copper-zeolites (CuZ), such as zeolite CuA, CuX,
CuY and CuP, were prepared from NaA (Baylith),
NaX or NaY (products of the late VEB CKB, Bitterfeld-
Wolfen, Germany) and NaP (Crosfield Zeocross)
powders, respectively. The Cu-forms were obtained by
conventional aqueous ion-exchange using Cu(II) acetate
(purity >99%, from Merck) solutions. A slurry of zeolite
and an aqueous Cu(II) acetate solution, having a liquid
to solid weight ratio of about 10, was stirred at room
temperature. The amount of Cu2+ in the slurry was about
equivalent with the ion-exchange capacity of the zeolite.
After 8 hours of stirring the solid and the solution were
separated and the exchange procedure was repeated
1955

Novel Cu and Cu2In/aluminosilicate type catalysts for the
reduction of biomass-derived volatile fatty acids to alcohols
2.3. Catalytic experiments
The catalytic hydrogenation of AA (96%, from Reanal)
and OA (octanoic acid, purity ≥98%, from Aldrich) was
carried out in a high pressure fixed bed flow-through
reactor at 21 bar total pressure in the temperature range
of 300-380°C. The inner diameter of the flow reactor
was 16 mm and the height of catalyst bed - 120 mm.
The prepared catalyst powders were pressed to pellets
without using a binder and applied as catalysts in a form
of crashed particles of 0.63-1.00 mm in size. All the
catalysts were activated in 230 mL min-1 pure hydrogen
flow in situ in the reactor at 450°C for 1 h prior to using
them in reactions. Thereafter the system was cooled
down to the desired reaction temperature at which the
appropriate feed begun. The reaction was allowed to
run one hour at each temperature to attain a steady
state. Before taking a sample, the effluent was collected
during the second hour, depressurized and cooled to
room temperature.
The product mixture, liquid at ambient conditions,
was analyzed using a gas chromatograph (Shimadzu
2010) equipped with a flame ionization detector and with
a HP-Plot/U capillary column for organic AA products or
with a CP-FFAP CB capillary column for OA products.
The quantities of water produced were calculated from
the oxygen balance. The gaseous reactor effluent was
analyzed for CO2, CO, CH4 and light hydrocarbons using
an on-line gas chromatograph (HP 5890) with a thermal
conductivity detector (TCD) on Carboxen 1006 PLOT
capillary column.
The results are represented as stacked area graphs.
Notice that the distance between two neighboring
curves represents the concentration of a given product
at a given temperature in weight percent.
Figure 1.
HT-XRD patterns of (α) 14CuP (a, b) and 15In2O3/14CuP
(A, B, C) samples treated in H2 flow at the indicated
temperature for half an hour. Similar figures are shown for
16CuA (β) and 15CuX (γ).
3. Results and discussion
2.2. Methods
3.1. Structural changes in the catalysts
X-ray patterns were recorded by Philips PW 1810/1870
diffractometer applying monochromatic Cu Kα radiation
at elevated temperatures in hydrogen flow using a high-
temperature XRD cell (HT-XRD). The mean crystallite
size of the copper particles was estimated by the Debye-
Scherrer equation.
The HT-XRD results suggest that in the catalysts,
activated at 450°C in H2 flow before the reaction
of carboxylic acid hydroconversion, all the copper
was present in finely dispersed metal nanoparticles
(Figs. 1α-1γ). The admixed In2O3 could be reduced at
higher temperature than the copper ions.
Nitrogen physisorption measurements were carried
out at -196°C using Quantochrome Autosorb 1C
instrument for determination of specific surface areas.
The Al, Na and Cu contents of the zeolites were
determined by Atomic Absorption Spectroscopy (AAS),
using Varian Spectra A20 spectrophotometer, after
digesting the zeolite powders in concentrated HF
solution.
Upon zeolite dehydration and reduction of charge
compensating Cu2+ cations, the zeolite P and A structure
collapsed at temperatures below 250°C (Fig. 1αa and
1βa). Regarding their structural instability towards
dehydration and H2-reduction the zeolites CuP, CuA, and
CuX seem to behave similarly, a low level of crystallinity
remained (XRD lines from the zeolites disappeared or
intensities dropped to a low level). However the degree
1956

Sz. Harnos et al.
of the destruction is significantly different and depends (ICDD number: 42-1475). It can be concluded that: if
on the original tectonic aluminosilicate skeleton. The the catalyst contains enough reduced metallic copper
reason is that the dehydration of the catalyst containing nanoparticles (some are not detectable because of
divalent copper cations, as well as the reduction of their small size), the total mass of indium reduced at
these ions with hydrogen, is paralleled by the formation lower temperature can form Cu-In alloy and thus In0
of structurally unstable acidic zeolite forms (H-zeolites). diffraction lines do not appear after cooling. The shape
The diffraction line, assigned to the metallic copper and intensity of the diffraction lines assigned to Cu2In
phase (Cu0), appeared only between 250 and 350°C. phase are different for zeolites X and A or P reflecting a
Thus, the metal nanoparticles were formed only when different structure of the precursor. For example, Cu2In
the zeolite structure had already collapsed or been phase is less detectable in the less permeable, more
deeply damaged.
compact (specific surface area of 8 m2 g-1) destructed
The destructed Cu-zeolite catalysts have specific CuA sample, where the detectable average copper
surface areas of 8 m2 g-1 for 16CuA, 18 m2 g-1 for particle size is the smallest one, 7 nm. The average
15CuX, and 30 m2 g-1 for 14CuP. These surface areas particle size of Cu2In nanoparticles practically seems
are low in comparison with the 221 m2 g-1 surface area to be equal to monometallic particles.
of the 20Cu/SiAl amorphous industrial aluminosilicate
3.2. Conversion of the carboxylic acids over
catalyst. There is no simple correlation between the
surface area and the hydroconversion activity because,
the base Cu-catalysts
in this relation, the size of copper nanoparticles has also
some relevance. The largest copper particles, having
an average diameter of 98 nm, are in the 20Cu/SiAl
catalyst. In this catalyst the specific surface area of the
support is the largest and that of the copper metal is the
smallest among all the studied catalysts. The average
copper particle size in 16CuA, in 15CuX, in 7CuY and
in 14CuP catalysts are 7 nm, 26 nm, 55 nm and 17 nm,
respectively. In the stable CuY and the unstable CuX,
where in the large pore faujasite framework copper
cations have more or less free access to the reducing
agent hydrogen and the formed copper atoms can
migrate to the surface of the zeolite crystals without a
barrier, the average copper particle sizes are larger.
In general, the modification by indium changes
the hydrogenation activity of the copper catalyst. An
appearance of an intemetallic compound seems to be
responsible for the significant change in the catalytic
behaviors the new active Cu2In alloy phase (Fig. 1).
XRD patterns of the composite catalyst samples show
that above 350°C In2O3 lines completely disappear,
indicating a total reduction, however upon cooling
to room temperature indium metal particles can not
be detected (not shown). This final state still differs
from the state when small copper particles were not
present at all. In0 diffraction lines can only be detected
after cooling to R.T., far below the melting point of
the support, which has no copper nanoparticles (not
shown).After reduction of the In2O3 phase, liquid indium
(its melting point being 156.4°C) is formed and spreads
over the solid surface. New lines at a bit lower Bragg
angles than the most intense line of copper at 43.3°
appear in the diffractograms which can be assigned to
some kind of Cu-In alloy [16], mainly to Cu2In phase.
This phase was determined using the ICDD database
The catalytic activity and selectivity of the prepared
catalyst are characterized by the product distribution as
function of temperature (see Figs. 2 and 3). Gaseous
products (mainly ethane and traces of CH4, CO and CO2)
were produced only over the industrial amorphous silica-
alumina, 20Cu/SiAl catalyst containing 20 wt% of copper
(Fig. 3c). Main products formed from AA over all In-free
Cu-catalysts were ethanol and ethyl acetate (Figs. 2a-
2c and 3b, 3c, and 3C). Almost no acetaldehyde, formed
as an intermediate, was detected for Cu catalysts,
although it was proven at various experiments, that the
acid was converted first to an aldehyde and then to an
alcohol. Depending on the reaction conditions fractions
of the reactant acid and the product alcohol formed
ethyl acetate according to the Fischer esterification
mechanism. The change in ethyl acetate concentration
indicates that its formation is dependent on both the
reactant (acid) and the product (alcohol) concentration
decreasing or increasing, respectively.
Whenconvertingalongercarbonchainfattyacid, e.g.
octanoic acid (OA), as a reactant over CuPcatalysts [15],
an alcohol and its monomolecular dehydrated derivative
(octenes in case of OA) are also found as products
(Fig. 3a). Neither ether nor ester has been detected as
a product of conversion of long chain carboxylic acids.
The effects of different alkyl-chain lengths of reactants
and of adsorption affinities determining the coverage of
the reactant or product compounds on the same active
surface result in significant differences in the catalytic
activity and the product distribution (compare Figs. 3a
and 3b).
With the exception of 16CuA and 7CuY, all other
catalysts (Figs. 2b, 3b and 3c) were significantly more
active than the commercial chromium-containing Adkins
catalyst (Fig. 3C) and show a different selectivity with
1957

Novel Cu and Cu2In/aluminosilicate type catalysts for the
reduction of biomass-derived volatile fatty acids to alcohols
Figure 2. Product distribution of 16CuA (a,A), 15CuX (b,B), 7CuY (c,C) catalysts and (A, B, C) their composites with 15 wt.% In2O3 in the
conversion of AA as function of reaction temperature at 21 bar in stacked area graphs. The partial pressures of AA and H2 were 2.1 and
18.9 bar. The WHSV of AA was 1 h-1 (calculated for the CuZ mass only). The temperature was increased in 20°C steps. Data represent
steady-state activities.
ethyl acetate being the main product. Such a direct the entire zeolite crystallites. However it seems to be a
reaction route to the valuable ester product can be disadvantageous catalyst for the reaction investigated
economically more attractive and environmentally similarly to other thermally stable Cu-zeolites and unlike
benign by replacing the conventional two-step process thermally unstable, destructed forms (Cu-A, -X and -P).
and eliminating the costly intermediate ethanol stage
3.3. Conversion of the carboxylic acid over the
[17]. The copper catalysts prepared from zeolites A, X
and P (Figs. 2a, 2b and 3b) have nearly the same Cu
In doped Cu-catalysts
content and very similar aluminosilicate composition, When fatty acids of longer chains, e. g. OA, were
but even so, show quite different activity and selectivity. reduced over the same catalysts, the addition of In2O3
The catalyst 14CuP, showing the highest activity among to the catalyst drastically increased the conversion
zeolites, is the most selective for ethanol formation at and the yield of octanol (Fig. 3a-A) [15]. While using
higher reaction temperature. The 7CuY catalyst is the AA as a reactant, the indium doping changed mainly
most divergent zeolite among those studied because of the selectivity, but not the conversion (Fig. 3b-B), with
solely stable structure under the pretreatment conditions. exception of 16CuA, where In2O3 admission (Fig. 2a-A)
It shows the lowest activity having the lowest Cu-content, also increased drastically the activity. The appearance of
but at the same time containing the highest Brönsted high concentration of acetaldehyde at lower conversions
acid site population in the non-damaged, intact faujasite became important and the ethyl acetate yield was
micropore structure. This catalyst embodies a crystalline significantly lower. The product distribution could be
microporous HY support well permeable for the reactant hardly influenced by increasing the amount of the In2O3
without any damage of the microporous framework and modifying agent from 5 to 36 wt.%. This was not the case
has the biggest copper particles on the outer surface of if the reactant was either OA [15] or AA over CuA. When
1958

Sz. Harnos et al.
Figure 3. Product distribution of 14CuP (a,A) converted OA, 14CuP (b,B), 20Cu/SiAl (c) and conventional Adkins catalysts (C) converted acetic
acid under conditions applied in Fig. 2. Fig. 3A and B show the effects of 15 wt.% In2O3 admission.
However the greatest change took place at low
loading, below 2 wt.%, suggesting that indium was
effective already at low concentration. Catalyst 7CuY
showed exceptional behavior compared with aluminium-
rich zeolites (A, X, P), because In-doping could hardly
influence its activity and product distribution (Fig. 2c-C).
Unlike ethanol, the octanol can be in part dehydrated
to olefins over CuP catalyst (Fig. 3a-A). The octyl
octanoate formation was not significant but important
octanal production could be observed. The octanol
from OA and the ethanol from AA appeared together
with the aldehydes at lower reaction temperature and
conversions. The In2O3 additive mitigated the octene
or ethyl acetate formation catalyzed by Brönsted acid
sites and brought about higher yields of aldehydes
from both carboxylic acids. Although a blocking effect
of indium doping on acid sites could be recognized, the
main effect should be a drastic quality change of the
active metal surface in the presence of metallic indium,
producing higher yields of the least reduced product,
aldehydes (e.g. see Figs. 3A and 3B) at lower reaction
temperature.
Figure 4. Comparison of 16CuA catalysts with various amounts of
In2O3 admission in the hydroconversion of AA at 340°C
and 21 bar. The partial pressures of AA and H2 were 2.1
and 18.9 bar. The WHSV of AA was 1.0 h-1.
comparing the 16CuA composite catalysts doped with
various amounts of In2O3, the hydroconversion of AA at
340°C showed (Fig. 4) continuous, but weak increase of
the overall activity and the ethanol yield between 2 and
15 wt.% In2O3.
1959

Novel Cu and Cu2In/aluminosilicate type catalysts for the
reduction of biomass-derived volatile fatty acids to alcohols
Themodificationbyindiumchangesthehydrogenation
activity of the copper catalyst that is reflected in the
appearance of less reduced compounds, aldehydes,
in a relatively higher concentration in the product
mixture (Figs. 2A-2B and 4A-4B). The acetaldehyde
yield increased at the expense of the ethyl acetate
yield. This selectivity change is more pronounced at
lower temperatures. It is an exciting observation that
the monometallic destructed zeolite catalysts, having
lower activity without indium doping (16CuA with AA or
14CuP with OA, cf.: Fig. 2a-A or Fig. 3a-A), show highly
increased hydroconversion activity following the In2O3
admission. In the systems giving a higher conversion
before In doping (15CuX or 14CuP with AA, cf.:
Fig. 2b-B or Fig. 3b-B) only the selectivity is changed.
3.4. Effects of reaction parameters
Fig. 5 shows the product yields and selectivities as a
function of the reaction temperature under higher weight
hourly space velocity (3 h-1 instead of 1 h-1) resulting in
lower conversions. The total conversion changed about
linearly with the temperature in the full temperature
range. The In2O3 additive did not show significant effect
on the total conversion under this condition however, it
decreased the yield of ethyl acetate and increased the
yield of acetaldehyde and ethanol. Ethyl acetate can be
formed from the reactant AA and the product ethanol
by Fischer esterification. The Cu2In alloy seemed to be
showing less activity than pure copper in the second
hydrogenation reaction step to ethanol, resulting in
higher acetaldehyde (an intermediate product) yields,
and be more active in ester hydrogenation (see in
Scheme 1, where all the reactions responsible for the
found products are summarized).
Product distributions of 14CuP (a) and 15In O /14CuP (b)
Figure 5.
2
catalysts in the conversion of AA as function3of reaction
temperature at 21 bar. The partial pressures of AA and H2
were 2.1 and 18.9 bar. The WHSV of AA was 3 h-1.
The AA conversion to ethanol and ethyl acetate
increases roughly linearly with increasing hydrogen
partial pressure over 14CuP and 15In2O3/14CuP
composite catalysts (Fig. 6) similarly to the conversion
dependence of octanoic acid. It can be understood that
high H2 partial pressures do not favor the accumulation
of acetaldehyde, an intermediate on the consecutive
reaction pathway to alcohol, over the In doped sample.
The acetaldehyde yield is the highest at lowest hydrogen
partial pressures (at low conversions); it increases as the
hydrogenation activity is suppressed, for instance, by
an increased AA coverage (higher AA partial pressures)
(see in Fig. 7). The found dependence of activity on the
reactant partial pressures is in line with the Langmuir-
Hinshelwood type kinetics and mechanism.
As expected the ethyl acetate selectivity responded
also to the water content of the reactant mixture. As the
conversion of acetic acid on the base of the detected water (which is always present in the light biomass-
Scheme 1. Schematic diagram of reactions involved in the
products.
derived liquors) content of the feed was increased
1960

Sz. Harnos et al.
Figure 6. Product
distribution of 14CuP and 15In2O3/14CuP Figure 7. Product
distribution of 14CuP and 15In2O3/14CuP
catalysts in the conversion of AA/H2/He mixture as function
of AA partial pressure at 21 bar total pressure and 340°C.
The WHSV of AA was 1.0 h-1. Constant partial pressure of
H2 was 11 bar. The AA partial pressure was changed by
changing the AA/He ratio.
catalysts in the conversion of AA/H2/He mixture as function
of hydrogen partial pressure at 21 bar total pressure and
340°C. The WHSV of AA was 1.0 h-1. Constant partial
pressure of AA was 2.1 bar. Hydrogen partial pressure
was changed by changing the H2/He ratio.
(equal amount of water added to the acetic acid preparations have high activity and selectivity in the
reactant) at 340°C over 15In2O3/14CuP composite hydroconversion of biomass-derived carboxylic acids to
catalyst, the selectivity of the aldehyde (15 → 25%) and alcohols, aldehydes and esters. The catalytic properties
the alcohol (60 → 64%) increased at the expense of were shown to depend on the original zeolite structure.
the ethyl acetate selectivity (24 → 7%). Although the Hydrogenation activity and selectivity of the supported
esterification can be suppressed by addition of water, as Cu/aluminosilicate catalysts can be significantly modified
observed, bearing in mind the process economy other by In addition; the copper-indium alloy phase obtained
solutions are searched to increase the alcohol yield. It is has a moderated hydrogenation activity, permitting
a matter of course if the reduction of the catalyst acidity the accumulation of the acetaldehyde intermediate in
has positive effect.
the product mixture. The reaction parameters, which
Combining relatively simple pyrolytic (or biochemical) are favouring ethanol or ethyl acetate formation, are
and catalytic technologies, bioethanol and chemicals, diametrically opposite.
such as acetaldehyde and ethyl acetate, can be obtained
from biomass, e.g. lignocellulosic raw material.
Acknowledgements
4. Conclusions
The authors wish to express their appreciation to Mrs.
Ágnes Farkas Wellisch for her technical assistance.
Small copper particles can be generated on amorphous
aluminosilicate by dehydration/H2-reduction of low-
silica Cu-zeolites. The obtained Cu/aluminosilicate
Thanks is due to the Hungary-Slovakia Cross-border
Co-operation Programme (Project registration number:
HUSK/1101/1.2.1/0318) for supporting this research.
1961

Novel Cu and Cu2In/aluminosilicate type catalysts for the
reduction of biomass-derived volatile fatty acids to alcohols
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