Permeable composite membrane as a catalytically active contactor for hydrogenation reactions

Article abstract of DOI:10.1016/j.cattod.2012.03.018

The efficiency of using of the permeable composite membrane (PCM) is demonstrated in the 3-phase reaction of liquid substrate with gaseous hydrogen on solid catalyst (PCM acts as a catalytically active contactor) - hydrogenation of fatty acid triglyceride. PCM provides a good combination of the opposite requirements of mild internal diffusion restrictions, low hydraulic resistance, high thermal conductivity, well-developed gas-liquid interface and high catalyst loading in the reactor volume, and thus assures the control of the course of the catalytic reaction.

Full text of DOI:10.1016/j.cattod.2012.03.018

Catalysis Today 193 (2012) 107–110
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Catalysis Today
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Permeable composite membrane as a catalytically active contactor for
hydrogenation reactions
T.P. Minyukovaa,b,∗, N.V. Shtertsera,b, A.A. Khassina,b, T.M. Yurievaa
a Boreskov Institute of Catalysis, 5 pr. Ak. Lavrentieva, Novosibirsk 630090, Russia
b Novosibirsk State University, 2 ul. Pirogova, Novosibirsk 630090, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
The efficiency of using of the permeable composite membrane (PCM) is demonstrated in the 3-phase
reaction of liquid substrate with gaseous hydrogen on solid catalyst (PCM acts as a catalytically active
contactor)—hydrogenation of fatty acid triglyceride. PCM provides a good combination of the opposite
requirements of mild internal diffusion restrictions, low hydraulic resistance, high thermal conductivity,
well-developed gas–liquid interface and high catalyst loading in the reactor volume, and thus assures
the control of the course of the catalytic reaction.
Received 14 September 2011
Received in revised form 28 February 2012
Accepted 2 March 2012
Available online 13 April 2012
Keywords:
Permeable composite membrane (PCM)
Fatty acids triglycerides hydrogenation
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
operation can hardly be enabled for strongly exothermic reactions.
Rather low content of the catalytically active component in the unit
A three-phase exothermal catalytic process (e.g. hydrogenation)
is hindered by mass-transfer restrictions at the gas–liquid inter-
face as well as by internal diffusion in the flooded pores of the
catalyst grain. Hot spots in the dry zones of the catalyst at the prox-
imity of the gas–liquid boundary may cause poor selectivity and
even lead to the process runaway. At that, hydraulic resistance of
the partially wetted catalyst bed may become severely inhomoge-
neous, while the process productivity and selectivity decrease in
the stagnation zones. Therefore, the requirements of intense inter-
nal diffusion, well developed gas–liquid interface, low and uniform
hydraulic resistance, high thermal conductivity, and high catalyst
loading must be simultaneously fulfilled.
This is a sophisticated task. Slurry reactors, including slurry bub-
ble column reactors (SBCR) and slurry stirred tank reactor (SSTR),
are often used. However, the slurry reactors need catalyst separa-
tion, which is not easy. Also, SBCR reactors are characterized by
a very low catalyst loading below 15 wt.%, since higher concentra-
tion of the particulate matter causes coalescence of gas bubbles and
critically decreases gas–liquid interface. The pore-through-flow
membrane reactors, used in some hydrogenation reactions [1,2]
allow to exclude the mass transfer limitations. In reviews [3,4] it is
concluded that the potential of the reactors in flow-through mode
both for gas and liquid phase reactions is high, but the isothermal
of the reactor volume and limited stability are another disadvan-
tages of the pore-through-flow membrane reactors.
Stable operation of the process at the gas–liquid interface may
be achieved by using contactor membranes, as it was earlier pro-
posed for hydration of propene [5], aqueous nitrate reduction [6],
multiphase ␣-methylstyrene hydrogenation [7].
As suggested in [8–12] plug-through permeable composite
membranes (PCM) for Fischer–Tropsch synthesis meet all the
requirements of the process. They have high heat conductivity
(isothermal regime of the catalyst bed), high mechanical strength
and high active component loading in the unit volume. Surely, like
other plug-through contactors they possess high permeability for
the gaseous and liquid reactants, the homogeneity of the catalyt-
ically active substance distribution in the body of PCM, arranged
porous structure, providing mass transfer and diffusion control
in the course of reaction. For Fischer–Tropsch synthesis such an
approach allowed to achieve high productivity of reactor and high
selectivity of the process together with flat temperature profile
across the membrane and reasonable pressure drop.
Same type of PCMs was successfully applied in the 2-phase
reaction of two gaseous reactants on solid catalyst, where PCM
acts as controller of an internal diffusion and heat transfer in
a structured catalyst bed—preferable CO methanation in CO2
containing hydrogen-rich gas [13,14]. For inlet gas composition
CO:CO2:H2:H2O = 1:21:60:18 the PCM based on NiCr oxide catalyst
provides the fine purification down to residual CO concentration of
10–30 ppm in the wide range of GHSV from 6000 to 17,000 h−1 and
ensures the selectivity above 0.5 at atmospheric pressure and in
∗
Corresponding author at: Boreskov Institute of Catalysis, 5 pr. Ak. Lavrentieva,
Novosibirsk 630090, Russia. Tel.: +7 383 330 91 09; fax: +7 383 330 80 56.
E-mail address: min@catalysis.ru (T.P. Minyukova).
0920-5861/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cattod.2012.03.018

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T.P. Minyukova et al. / Catalysis Today 193 (2012) 107–110
Table 1
Characteristics of catalytically active components.
Catalyst
Cu loading
(at.%)
Activation
temp. (◦C)
Phase
composition
Me0 particle
size
after activation
CuZn(O)
CuCr(O)
8a
33
350
350
Cu0/a.m.ZnO
3–5 nm
5–10 nm
Cu0/H+-spinel
a
(Cu + Zn) = 100 at.%.
the temperature range of 195–215 ◦C. PCM was 18 mm in diameter
and 13 mm in height.
In the present study it is demonstrated that possessing these
properties provides the efficiency of using of the PCMs in
the 3-phase reaction of liquid substrate with gaseous hydro-
gen on the solid catalyst (PCM acts as a catalytically active
contactor)—hydrogenation of fatty (stearic) acid triglyceride.
2. Experimental
Fig. 1. Permeable composite membrane (PCM-cylinder) for triglyceride of stearic
acid hydrogenation. The height is 12 mm, outer diameter – 18 mm.
Transformation of triglyceride of stearic acid was carried out
over the PCM contactor membranes based on Cu-containing
catalytically active substances and over immersed granulated
Cu-containing catalyst. The procedure of PCM preparation was
described earlier in [9]. The PCM is prepared from a three-
component mixture of (1) a catalytically active substance, (2)
reinforcing metal with high heat conductivity and (3) pore-
producing agent.
A mixture of C18–17-alkanes, alkenes, alcohols and acids as well
as some C18–C3 and C18–C18 esters is found downstream in the
condenser. After cooling, the hydrocarbon mixture in reactor is
enriched in high-boiling products. Volatile products of hydrogena-
tion evaporate and condense downstream.
The analysis of the products was performed by the specially
developed accumulative NMR method. NMR spectra of dissolved
in CDCl3 or CCl4 probes of the reaction products were recorded at
Bruker Avance 400 at 400.13 MHz (1H) and 100.61 MHz (13C).
(1) We used appropriate mixed hydroxocarbonates as a catalyt-
ically active substance precursor. The size of granules was
0.15–0.25 mm, the catalytically active component loading was
1.5 g. The characteristics of used catalytically active compo-
nents are presented in Table 1.
(2) Dendritic copper was used as a reinforcing component for
PCMs, since it is rather inert with respect to hydrogen, water
vapors and other reactants and also it has a reasonable Tam-
mann temperature (of about 410 ◦C).
(3) Copper hydroxocarbonate (malachite) was used as pore pro-
ducing agent.
Finely mixed three component mixture is pressed in a form of a
hollow cylinder of 18 mm in an outer diameter and 12 mm in a
height, sintered and reduced in flowing hydrogen. So, the obtained
a permeable membrane that provides a gas flow permeating via
a set of the partially wetted transport pores. The direction of gas
flow is radial, from the center to the outer surface. Reverse flow
from the outer surface to the center is also possible. Fig. 1 shows
the appearance of the PCM.
By optimizing the composition and conditions of the PCM mem-
brane preparation, we managed achieving high permeability of ca.
300 mDarcy (causing low pressure drop), high catalyst loading of ca.
1 g/cm3 (the same as for fixed bed reactor), high heat conductivity of
1–4 W/(m K) (causing isothermic regime of reactor), small effective
size of catalyst grain of 0.15–0.25 mm (mild diffusion constrains)
and well developed pore structure (causing enhanced gas–liquid
interface) [9].
We used a specially designed reactor for PCM testing; the
scheme of this reactor is shown in Fig. 2. The direction of hydro-
gen is from the center to the outer surface. The PCM is immersed
in the liquid triglyceride. Rather intensive hydrogen flow prevents
the filling the transport pores with liquid. This type of reactor and
regime of its operation is suitable only for the reagents having sim-
ilar physical properties. The initial stearic acid triglyceride volume
was 21 ml, hydrogen flow – 7 l/h, reaction temperature – 340 ◦C,
pressure – 2 MPa. Reaction time was 3 h.
Fig. 2. Scheme of PCM reactor for triglyceride of stearic acid hydrogenation.

T.P. Minyukova et al. / Catalysis Today 193 (2012) 107–110
109
Fig. 3. Triglyceride of stearic acid hydrogenation main products distribution, obtained on granulated CuZn catalyst and PCMs, based on CuZn and CuCr oxide catalysts.
3. Results and discussion
The results of analysis of the products, obtained on the gran-
ulated CuZn oxide catalyst (1.5 g, as in PCM) and PCMs, based on
CuZn and CuCr oxide catalysts are presented in Fig. 3. The high
conversion of 92–99% was achieved in the experiments.
The set of the reaction products obtained on the granulated
catalyst and on the catalyst in the form of PCM is the same, prob-
ably owing to the same catalytically active component—copper.
The main products are C18 hydrocarbons, C18–C18 ester, C18 alco-
hol and C18 acid. The result obtained in the present study for the
granulated CuZn catalyst is in accordance with the literature data
[15]. Saturated and unsaturated C18 hydrocarbons are the main
Fig. 4. The scheme of triglyceride of stearic acid hydrogenation on the granulated
Cu–Zn oxide catalyst [15,16].
products of stearic acid triglyceride hydrogenation on granulated
CuZn oxide catalyst, small amounts of C18 – alcohol, C18–C18
–
ester and C18 – acid are observed. Hydrocarbons are also formed
on PCMs, while oxygen containing products are formed in signifi-
cant amounts. Comparing the product distribution for PCM based
on different active component it may be noted that the rate of the
ester formation is higher for CuZn-PCM than for CuCr-PCM.
It is known from the literature [15,16] that in traditional reactors
(tubular or multiple-shell reactor) under the action of hydro-
gen at increased pressure and temperature triglyceride of stearic
acid hydrogenation occurs on sprinkled or immersed Cu-catalysts
according to the scheme, presented in Fig. 4, and that the main
products are alcohol and hydrocarbons.
The obtained products composition makes it possible to assume,
that triglyceride of stearic acid hydrogenation on PCMs occurs via
another scheme (Fig. 5). The proposed scheme shows the way of
stearyl stearate formation. Stearyl stearate is an intermediate prod-
uct, which can be transformed into the alcohol and acid and then
can be hydrogenated according to the scheme in Fig. 5. It is well
known from the literature [1,17] that membrane reactor provides
the set of conditions for achieving the high selectivity to the inter-
mediate product of the consecutive reaction.
Fig. 5. Proposed scheme of triglyceride of stearic acid hydrogenation on PCMs.

110
T.P. Minyukova et al. / Catalysis Today 193 (2012) 107–110
So, the use of PCM for triglyceride of stearic acid hydrogenation
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