efficient

Efficient hydrogen supply through catalytic dehydrogenation
of methylcyclohexane over Pt/metal oxide catalysts
Anshu A. Shukla a
, Priti V. Gosavi a
, Jayshri V. Pande a
, Vanama P. Kumar b
,
Komandur V.R. Chary b
, Rajesh B. Biniwale a,
*
a
Environmental Materials Unit, National Environmental Engineering Research Institute (NEERI), Council of Scientific and Industrial Research,
Nehru Marg, Nagpur 440020, India
b
Indian Institute of Chemical Technology (IICT), Council of Scientific and Industrial Research, Hyderabad 500 607, India
a r t i c l e i n f o
Article history:
Received 14 October 2009
Received in revised form
1 February 2010
Accepted 2 February 2010
Available online 19 March 2010
Keywords:
Hydrogen delivery
Dehydrogenation
Pt over metal oxide
Perovskite
Methylcyclohexane
Pulse spray reactor
a b s t r a c t
This paper describes the results of experiments on dehydrogenation of methylcyclohexane
over Pt supported on metal oxides (Pt/MO) and Pt supported on perovskite (Pt/Per) catalysts.
The reaction is being considered as a means for delivery of hydrogen to fueling stations in
the form of more easily transportable methylcyclohexane. Among Pt/MO catalysts, the best
activity as determined by the hydrogen evolution rate was observed over Pt/La2O3 catalyst
at 21.1 mmol/gmet/min. Perovskite-supported catalysts exhibited relatively higher activity
and selectivity, with Pt/La0.7Y0.3NiO3 giving the best performance. This Pt/Per catalyst had
an activity of ca 45 mmol/gmet/min with nearly 100% selectivity towards dehydrogenation.
The catalysts were characterized using XRD, CO-chemisorption and SEM-EDXA techniques.
The present study reports catalysts that minimize the use of Pt and explores tailoring the
properties of the perovskite structure.
ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Developing hydrogen storage media having relatively high
capacity on weight and volume basis is one of the major
challenges as the hydrogen economy is facing today for its
real launch. The various materials being pursued for
hydrogen storage include metal hydrides, alanates, boranes,
carbon nano-tubes and chemical hydrides. Organic liquid
hydrides such as cyclohexane, methylcylohexane and dec-
alin have relatively high hydrogen content, 6–8% on weight
basis and ca. 60–62 kg/m3
on volume basis [1–4]. Due to
high boiling points, liquid organic hydrides provide poten-
tial media for transport of hydrogen using simple transport
equipment such as Lorries [1,5–10]. Additionally, the
advantages of using the cycloalkanes as a hydrogen carrier
include the supply of hydrogen without carbon-monoxide
and the recyclable aromatic products [1–3,5–7,11–15].
Accordingly, catalytic dehydrogenation of cycloalkanes has
been reported in several studies as an option for delivery of
hydrogen [1–3,16].
Pt based catalysts are the most widely reported catalysts
for dehydrogenation of cycloalkanes [1–3,13]. However, from
economic point of view there is a specific interest to minimize
the use of Pt [1–3,17]. We have earlier reported Ni/C as efficient
catalysts for dehydrogenation of cyclohexane and discussed
synergistic effect of addition of a small amount of Pt to Ni–Pt/C
* Corresponding author. Tel.: þ91 712 2249885x410, þ91 9822745768 (mobile); fax: þ91 712 2249900.
E-mail address: rb_biniwale@neeri.res.in (R.B. Biniwale).
Available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/he
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 5 ( 2 0 1 0 ) 4 0 2 0 – 4 0 2 6
0360-3199/$ – see front matter ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.ijhydene.2010.02.014

catalysts [2]. It has been reported in the literature that addition
of metal oxide results in promoting activity of Pt catalysts [13].
Metal oxides promote the activity and selectivity of Pt cata-
lysts through strong metal–support interaction [17].
Mixed metal oxides such as perovskites, having definite
chemical structure, could be good candidates for supporting
Pt. The ABO3 type perovskite oxides are being used in various
applications due to its tailoring properties. The substitution at
A or B site with various elements creates valences and
vacancies, which are responsible for activity in different
applications [13]. For example, ferromagnetic nature of Ni
enhances magnetic moment at surface of its bulk which helps
to reduce magnetic ordering of Ni. This helps in dehydroge-
nation reaction mechanism [18]. It is reported by Pernifguez
et al. [17] that when a perovskite LaNiO3 is used in reducing
atmosphere the Ni migrate from LaNiO3 and forms Ni metallic
particles resulting in Ni/La2O3 phase. Re-oxidation results into
recuperation of the LaNiO3 Qiao and Bi [20] also reported using
XPS analysis of LaNiO3 and Pt/LaNiO3 that Ni exists in two
oxidation states Ni3þ
and Ni2þ
. They have further investigated
the effect of presence of Pt on reducibility of Ni in perovskite
and concluded that the Pt do not interfere with reducibility of
Ni. The presence of Ni along with Pt on the surface of catalyst
promotes formation of more active sites for dehydrogenation.
The presence of small amount of Pt inside the perovskite
structure or as co-catalyst, promotes the activity of
perovskite.
In this work, platinum promoted metal oxides were
studied as catalysts for dehydrogenation of methylcyclohex-
ane. The aim of this study is to find better support for plat-
inum in terms of improved catalytic activity and selectivity of
the catalyst. Selected metal oxides from transition, lantha-
nides, and metalloids series were used to support Pt. With
a view to improve activity, we have used perovskite with La at
A-site and Ni at B-site as support for Pt. Further, the perovskite
was modified by partial substitution of Y to La at A-site.
2. Materials and methods
2.1. Synthesis and characterization
Commercial metal-oxides namely La2O3, ZrO2, TiO2, CeO2,
Fe2O3, Al2O3 and MnO2 were used as supports for Pt catalyst.
Platinum was loaded by wet impregnation method using PtCl4
solution.
Perovskites, LaNiO3 and La0.7Y0.3NiO3 were synthesized
using co-precipitation method. In synthesis of LaNiO3,
lanthanum nitrate hexa hydrate solution (HIMEDIA, India)
was added to nickel nitrate solution (MERCK, India) in stoi-
chiometric ratio. The mixed nitrate solution was precipitated
in 50% ammonia solution. Resultant solution was stirred for
1 h and complete precipitation of nitrate solution was ensured
by adding excess of ammonia. Precipitate was allowed to
stand for 24 h, filtered and dried in oven at 110
C for 6 h. The
resultant hydroxide precursor was calcined at 800
C for 12 h
following a specific heating cycle. Similarly, La0.7Y0.3NiO3 was
synthesized using respective nitrates in required stoichio-
metric proportion. Further, Pt/Per catalysts were prepared by
wet impregnation method.
The catalysts were characterized using powder X-ray
diffraction (XRD, make RIGAKU, Miniflex II X-RAY Diffrac-
tometer), scanning electron microscopy-electron diffraction
X-ray analysis (SEM/EDXA, make JEOL 2300) and CO-
chemisorption techniques.
2.2. Experimental methods
The details of experimental setup are depicted in Fig. 1. The
experiments for catalytic dehydrogenation of methyl-
cyclohexane were carried out using a spray-pulsed reactor.
Atomized spray of reactant was fed to the reactor in pulsed
injection mode using a fine nozzle fitted at the top of the
reactor. A frequency generator was used to control the pulse
injection frequency and pulse width. The pre-treatment of
catalyst surface was performed using nitrogen flow at 300
C
with flow rate of 100 mL/min. The catalyst activation was
performed in the flow of hydrogen with the flow rate of
75 mL/min at 400
C following a defined heating cycle. All the
reactions were performed at atmospheric pressure under
nitrogen flow. In each experiment about 0.3 g of catalyst was
used. Pulse injection frequency and pulse width was kept
constant as 0.33 Hz (pulse injection of methylcyclohexane at
every 3 s) and 10 ms respectively. The temperature of the
surface of the catalyst was maintained at 350
C by a PID
temperature controller. The product from the reaction was
separated using a condenser to condense toluene and
unreacted methylcyclohexane. The gaseous products from
reactor were continuously monitored by using a TCD-GC
(SHIMADZU, with porapak-Q column, 3 m).
3. Results and discussion
3.1. Characterization of catalyst
All the catalysts were characterized using XRD method. The
commercial metal oxides (La2O3, Al2O3, CeO2, MnO2, TiO2,
Fe2O3 and ZrO2) were found to be crystalline in nature. The
XRD patterns for 1 wt% Pt/LaNiO3, LaNiO3, 1 wt% Pt/La0.7Y0.3-
NiO3 and La0.7Y0.3NiO3 catalysts are depicted in Fig. 2. Presence
of platinum in case of 1 wt% Pt/LaNiO3 and 1 wt% Pt/
La0.7Y0.3NiO3 was confirmed by XRD peak corresponding to Pt
(JCPDS card no. 87-0640). The elemental composition of the
catalyst was confirmed by SEM/EDXA analysis (Figs. 3 and 4).
In addition to XRD, EDXA data also confirms the presence of Pt
on supports. The elemental compositions of 1 wt% Pt/LaNiO3
and 1 wt% Pt/La0.7Y0.3NiO3 are reported in Table 1.
3.2. Dehydrogenation of methylcyclohexane over
different Pt/MO catalysts
The rates of hydrogen evolution observed during dehydroge-
nation of methylcyclohexane over various Pt/MO type cata-
lysts are depicted in Fig. 5. Although, Pt loading was equal i.e.
3 wt% on each metal oxide support namely, La2O3, Al2O3,
CeO2, MnO2, TiO2, Fe2O3 and ZrO2 the catalysts exhibited
different catalytic activity in terms of hydrogen evolution
rates. This may be because of difference in their surface area
and platinum dispersion over the supports. The supports used
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 5 ( 2 0 1 0 ) 4 0 2 0 – 4 0 2 6 4021

for Pt can be ranked according to hydrogen evolution rate
(at 90 min) observed for each Pt/MO catalysts as follows;
La2O3 TiO2 Al2O3 MnO2 Fe2O3 ZrO2 CeO2
At 90 min from the start of the reaction, the rate of hydrogen
evolution during dehydrogenation of methylcyclohexane over
3 wt% Pt/La2O3 catalyst was 21.1 mmol/gmet/min. The reaction
over two catalysts 3 wt% Pt/TiO2 and 3 wt% Pt/Al2O3 exhibited
nearly the same hydrogen evolution rates of 9.7 and 7.6 mmol/
gmet/min respectively at 90 min. However, the trend for
hydrogen evolution rates in case of 3 wt% Pt/La2O3 and 3 wt%
Pt/Al2O3 catalysts was similar. The catalytic activity as
20 40 60 80
2θ
Intensity(a.u)
(d)
(c)
(b)
(a)
Fig. 2 – XRD patterns for various catalysts (a) 1 wt%
Pt/LaNiO3, (b) LaNiO3, (c) 1 wt% Pt/La0.7Y0.3NiO3 and
(d) La0.7Y0.3NiO3.
Fig. 3 – SEM and EDXA pattern of catalyst 1 wt% Pt/LaNiO3
(a) Scanning Electron Micrographs for 1 wt% Pt/LaNiO3
catalysts and (b) EDXA pattern for 1 wt% Pt/LaNiO3
catalysts.
0-200 cc/min
12MPa
N2
C7H14
Nozzle
MFC
Condenser
GC
(TCD)
Reactant
Spray
Catalyst TC 1
Fig. 1 – Schematic of experimental setup with spray-pulsed reactor.

determined by hydrogen evolution rates using 3 wt% Pt/MnO2,
3 wt% Pt/Fe2O3, 3 wt% Pt/ZrO2 and 3 wt% Pt/CeO2 catalysts was
observed as 3.7, 3.97, 1.5 and 0.89 mmol/gmet/min respectively
at 90 min. During ﬁrst 5 min from the start of the reaction
hydrogen evolution rates using 3 wt% Pt/La2O3 and 3 wt% Pt/
TiO2 catalysts were similar. While the hydrogen evolution rate
over 3 wt% Pt/Al2O3 was relatively low.
Accordingly, among the various Pt/MO catalysts used in
this study, 3 wt% Pt/La2O3 was found to be most active for
dehydrogenation of methylcyclohexane. Therefore, La2O3
may be the best support for Pt under the conditions used in
this study.
The trends of activity observed for different catalysts can
be explained based on active particle diameter of Pt and ability
of support to keep Pt in reduced state. The active particle
diameter of Pt supported on various metal oxides was
estimated by CO-chemisorption method. Table 2 lists the
hydrogen evolution rates and particle diameters of Pt for
various Pt/MO catalysts. The active particle diameters of Pt in
case of 3 wt% Pt/La2O3 and 3 wt% Pt/MnO2 were estimated as
9.8 and 9.2 nm respectively. The activity of 3 wt% Pt/MnO2
catalyst in terms of hydrogen evolution rate was less than the
former. This indicates that in addition to the active particle
diameter of Pt, metal–support interaction has an effect on
catalytic activity. In the case of catalysts namely 3 wt% Pt/
Fe2O3, 3 wt% Pt/CeO2 and 3 wt% Pt/ZrO2 the lower catalytic
activity may be due to weak metal–support interaction
wherein Pt may be in higher oxidation state [12]. When elec-
tronic conﬁguration of La (5d1
6s2
) is considered, in La2O3, one
electron from 5d1
orbital is available for reducing Pt. This leads
to more active sites on the catalyst surface. Moreover, the
dehydrogenation reaction is a reversible reaction wherein it is
important to desorb hydrogen and limit the reverse rate of
reaction. Reduced state of Pt may favor hydrogen spillover
phenomena over catalyst surface. The role of the support for
metal catalysts has been explained in the literature for
hydrogen spillover with migration of hydrogen atom over
supports such as carbon and metal oxides. A hydrogen spill-
over phenomenon in metal oxides is well studied with mate-
rials such as MoO3 and WO3 [19]. According to a report, in
metal oxides hydrogen spillover is favorable because of the
thermodynamic and small energy barrier [18]. This can be
attributed to easy migration of H atoms from catalyst to
support and subsequent proton diffusion in the bulk. In case
of carbon based materials energy barrier is low however,
Fig. 4 – SEM and EDXA pattern of catalyst 1 wt% Pt/
La0.7Y0.3NiO3 (a) Scanning Electron Micrographs 1 wt%
Pt/La0.7Y0.3NiO3 and (b) EDXA pattern for 1 wt% Pt/
La0.7Y0.3NiO3.
Table 1 – Elemental analysis of catalysts using SEM-EDXA.
Composition Mass% Atomic%
Catalyst La Ni O Pt Y La Ni O Pt Y
1 wt% Pt/LaNiO3 84.6 7.47 7.24 0.64 – 51.16 10.62 37.95 0.27 –
1 wt% Pt/La0.7Y0.3NiO3 72.3 6.16 8.83 1.33 11.3 39.73 8.0 42.03 0.52 9.72
0
5
10
15
20
30 60 90
Time (min)
Hydrogenevolution(mmol/gmet/min)
(a)
(f)
(g)
(e)
(d)
(c)
(b)
Fig. 5 – Hydrogen evolution rates over various catalysts at
350 8C. (a) 3 wt% Pt/La2O3, (b) 3 wt% Pt/TiO2, (c) 3 wt% Pt/
Al2O3, (d) 3 wt% Pt/MnO2, (e) 3 wt% Pt/Fe2O3, (f) 3 wt% Pt/
ZrO2 and (g) 3 wt% Pt/CeO2.

proton diffusion would be energetically difﬁcult if H atoms get
chemisorbed. The role of metal oxide support and hydrogen
spillover effect is also evident form improved kinetic rate
constant for Pt/La2O3 as compared to Pt/AC. The reported
value for kinetic rate constant for dehydrogenation of meth-
ylcyclohexane over Pt/AC [6] is 1.16 per min (k ¼ 6.5 mmol/
min, volume of reactant 0.7 mL) at 300
C using alternate wet-
dry conditions. The Pt/La2O3 catalyst in the present study has
exhibited better rate constant of 6.3 per min indicating better
hydrogen spillover and strong role of support.
The active particle diameters of Pt in case of 3 wt% Pt/Al2O3
and 3 wt% Pt/TiO2 catalysts were estimated as 4.81 nm and
2.07 nm respectively. The active particle diameter of Pt in
3 wt% Pt/Al2O3 was larger but the catalyst exhibited lower
activity with relatively low hydrogen evolution rates. As
reported for TiO2, when it interacts with noble metals such as
Rh and Pt, It has tendency to reduce Ti4þ
to Ti3þ
[1,5,12,13]. Ti3þ
ions are ﬁxed in surface of lattices of anatase titania.
A temperature of 400
C maintained during pre-treatment of
catalysts was favorable for anatase form of titania [15]. Thus,
the hydrogen evolution rate was found to be relatively better
with 3 wt% Pt/TiO2 than 3 wt% Pt/Al2O3.
Accordingly, choice of support, due to difference in metal–
support interaction, has effect on dehydrogenation of meth-
ylcyclohexane. Fig. 5 amply depicts the stability of catalyst up
to 90 min; leading to the conclusion that 3 wt% Pt/La2O3 has
relatively better stability compared to other Pt/MO catalysts in
this study.
The kinetics of reaction can be well explained by differ-
ential equation, in terms of rate law as follows:
ln

À
dCA
dt

¼ klnCn
A
where, CA is the concentration of hydrogen (mmol/min), k is
rate constant (per min). The reaction of dehydrogenation of
methylcyclohexane is of zero order with rate constants as 6.3
per min for 1 wt% Pt/La2O3. Thus, reactions are not concen-
tration dependant.
3.3. Selectivity towards hydrogen formation
The mechanism of dehydrogenation of methylcyclohexane
may be similar to reported mechanism for dehydrogenation of
cyclohexane. This involves the adsorption of methyl-
cyclohexane, with either simultaneous or rapid subsequent
dissociation of hydrogen atoms. The aromatic structure
formed is bonded through pi–electron interaction with metal
d-orbitals. The adsorbed hydrogen atoms then form mole-
cules and desorbs from the surface [9]. Toluene if not desorbed
Table 2 – Hydrogen evolution rate of all catalysts and their particle size.
Sr No. Catalysts Particle size (nm) Metallic surface area
as estimated by
CO-chemisorption
(m2
/g)
Hydrogen Evolution
rate at 350
C at
90 min in
(mmol/gmet/min)
1 3 wt% Pt/La2O3 9.81 0.85 21.11
2 3 wt% Pt/TiO2 2.07 4.04 9.7
3 3 wt% Pt/Al2O3 4.84 1.74 7.6
4 3 wt% Pt/Fe2O3 3.36 2.49 3.97
5 3 wt% Pt/MnO2 9.23 0.90 3.7
6 3 wt% Pt/ZrO2 2.87 2.91 1.5
7 3 wt% Pt/CeO2 2.67 3.13 0.8
8 1 wt% Pt/La2O3 9.94a
– 24.08
9 1 wt% Pt/LaNiO3 5.15a
– 17.79
10 1 wt% Pt/La0.7Y0.3NiO3 2.53a
– 45.76
a The particle size have been calculated using Scherer’s formula from XRD pattern.
Table 3 – Catalytic activity of various catalysts for
dehydrogenation of methylcyclohexane at 350 8C at
150 min.
Sr
No.
Catalysts H2 evolution
(mmol/gmet/min)
Methane formation
(mmol/min)
1. 1 wt% Pt/
La2O3
12.47 0.0009
2. 1 wt% Pt/
LaNiO3
30.30 0.0020
3. 1 wt% Pt/
La0.7Y0.3NiO3
45.26 BDLa
a BDL ¼ Beyond detectable limit by gas chromatograph.
0.00
0.01
0.01
0.02
0.02
0.03
0.03
0.04
0.04
0.05
A B C D
Catalysts
Products(mmol/min)
CH4
C7H8
C6H6
Fig. 6 – Rate of various products at 90 min over different
catalysts (A) 1 wt% Pt/La2O3, (B) 1 wt% Pt/LaNiO3, (C)
La0.7Y0.3NiO3, (D) 1 wt% Pt/La0.7Y0.3NiO3. Rate of hydrogen
production is not shown.

quickly then undergoes further dissociation. Although the
various metal oxides as discussed above are good supports for
Pt to design dehydrogenation catalysts, selectivity towards
hydrogen formation is an important issue. Along with
hydrogen, methane was observed in the product gas during
reaction over a few catalysts, indicating hydrogenolysis
reaction. It is reported that on well dispersed Pt catalysts
dehydrogenation reaction prevails whereas relatively higher
grain size leads to hydrogenolysis reaction. Methane forma-
tion was observed for catalysts, 3 wt% Pt/Al2O3, 3 wt% Pt/
MnO2, 3 wt% Pt/Fe2O3 and 3 wt% Pt/La2O3. No methane
formation was observed over 3 wt% Pt/TiO2, 3 wt% Pt/ZrO2 and
3 wt% Pt/CeO2 catalysts. It is evident that the La2O3 exhibits
higher activity and stability; however, it has relatively low
selectivity towards dehydrogenation reaction. In this study
when metal surface areas for various catalysts were compared
no direct correlation was found with catalytic activity. This
indicates that metal support interaction has major effect on
catalytic activity. When considering same support (same
metal oxide) higher dispersion may result into better activity.
3.4. Improving selectivity towards dehydrogenation
reaction
In order to improve the selectivity and stability of Pt/La2O3 we
have used two different approaches namely, reducing the Pt
loading from 3 wt% to 1 wt% over La2O3 and use of LaNiO3
perovskite instead of La2O3 as a support. Reducing Pt loading
may improve the dispersion of Pt on support and therefore
may exhibit better selectivity towards dehydrogenation reac-
tion. In another approach the addition of second active metal
to oxides or using perovskite was expected to have synergistic
effect on activity. Further, partial substitution of La by Y in
LaNiO3 perovskites has been explored for designing active and
selective catalysts for dehydrogenation.
The methylcyclohexane was dehydrogenated over 1 wt%
Pt/La2O3. The feed rate of the reactant was kept constant as
3.38 mmol/min with pulse injection frequency of 0.33 Hz and
pulse width of 10 ms. The experiments were carried out for
a period of 150 min to observe stability of the catalyst.The
temperature of the catalyst surface was kept constant at
350
C. As listed in Table 3, the hydrogen evolution rate over
1 wt% Pt/La2O3 was 12.47 mmol/gmet/min at 150 min. In terms
of hydrogen evolution rate at 90 min (Table 2), the perfor-
mance of 1 wt% Pt/La2O3 is relatively better than 3 wt% Pt/
La2O3. The catalyst was modified using LaNiO3 perovskite as
support for Pt, to increase the efficiency and stability of the
catalyst. Hydrogen evolution rate over 1 wt% Pt/LaNiO3 was
observed as 30.3 mmol/gmet/min at 150 min, however,
formation of methane was also observed with 1 wt% Pt/LaNiO3
as listed in Table 3. Yttrium was used for the partial substi-
tution of La in LaNiO3. Hydrogen evolution rate of about
45.3 mmol/gmet/min at 150 min was observed using 1 wt% Pt/
La0.7Y0.3NiO3 with no methane formation.
From the above discussions, it can be observed that there
is a role of support in catalytic activity and using a mixed
metal oxide can be an option for supporting Pt. Perovskite
type mixed metal oxides having a definite structure and
excellent tailoring possibilities have been reported for many
catalytic reactions. While selecting perovskites composition,
we selected La at A-site and Ni at B-site in ABO3 structure,
since Ni is reported as a good reforming catalyst. In fact, as
reported for perovskite, B-site is catalytically active site. In
order to compare the catalytic activity of only perovskite with
Pt/Per catalysts the dehydrogenation of methylcyclohexane
was carried out over catalyst LaNiO3 and 1 wt% Pt/LaNiO3.
Only LaNiO3 catalysts did not exhibit activity for dehydroge-
nation. As reported by Pernifguez et al. [17], using XPS anal-
ysis of LaNiO3 and reduced LaNiO3, the reduced sample shows
a profile characteristics of a La2O3 phase indicated by
a doublet at 833.2 eV (3d5/2) and 850.0 eV (3d3/2). This report
suggests that the Ni migrate from LaNiO3 and forms Ni
metallic particles resulting in Ni/La2O3 phase. Re-oxidation
results into recuperation of the LaNiO3. Accordingly, Ni
migrates on the surface from the perovskite. Qiao and Bi [20]
also reported using XPS analysis of LaNiO3 and Pt/LaNiO3 that
Ni exists in two oxidation states Ni3þ
and Ni2þ
. They have
further investigated the effect of presence of Pt on reducibility
of Ni in perovskite and concluded that the Pt do not interfere
with reducibility of Ni. Similar effect is expected in our cata-
lysts wherein Ni migrates on the surface and provides more
active sites by co-existence of Pt and Ni under the reducing
conditions [19]. From above results, it can be observed that
there is a role of support in this reaction either for dispersion
of Pt or as a co-catalyst. In the case of perovskite, it is widely
reported that activity of B-site element can be improved with
partial substitution at A-site to create defects in the structure.
In-fact this is generally achieved by partial substitution
at A-site or B-site with metal having different valences such
as 2þ
or 4þ
. Nevertheless, partial substitution at A-site with
different metal loading leads to higher catalytic activity. We
have used La0.7Y0.3NiO3 catalyst that exhibited a comparable
activity with 1 wt% Pt/La2O3 and 1 wt% Pt/LaNiO3. Also
selectivity was observed to be enhanced as there was no
formation of by products like CH4 and C6H6 with La0.7Y0.3NiO3
(Fig. 6). In order to examine effect of co-existing Pt and
perovskite, we have used 1 wt% Pt with La0.7Y0.3NiO3. The
catalyst exhibited highest activity as compared to other
catalysts in this study.
It is evident that the use of perovskite La0.7Y0.3NiO3 in place
of La2O3 as support for Pt resulted in the improved catalytic
activity. This may be attributed to possible migration of Ni
from perovskite and then exhibiting behavior of Ni–Pt bime-
tallic catalyst as explained in above discussions. When Y is
substituted at La site of the perovskite it provides low energy
sites due to difference in electronic configurations of La and Y.
The lower energy sites of outer most orbital of 4d1
of Y
provides more access for Pt loading. This is evident from the
SEM-EDXA data in Table 1, wherein higher loading of Pt was
observed in case of Pt/La0.7Y0.3NiO3 as compared to Pt/LaNiO3.
With improved loading of Pt, the activity of the catalysts Pt/
La0.7Y0.3NiO3 was relatively higher.
In the case of the catalysts, wherein, Pt is supported on
La2O3, and LaNiO3 side reaction of hydrogenolysis of methyl-
cyclohexane was observed in addition to dehydrogenation
with formation of methane. It is important to avoid side
reaction to maintain the quality of hydrogen to be supplied to
fuel cell applications. Thus, 1 wt% Pt/La0.7Y0.3NiO3 which
found to be highly selective towards the dehydrogenation may
be the most promising catalyst.

The catalytic activity for dehydrogenation of methyl-
cyclohexane is reported in the literature for different reaction
conditions. Dehydrogenation using a fixed bed reactor over
0.1 wt% K þ 0.6 wt% Pt/Al2O3 is reported with hydrogen
evolution rate as 744 mmol/Lcat/min (equivalent to 132 mmol/
gmet/min) [21]. However, the reaction was carried out with co-
feed of H2 to keep the catalyst under reduced conditions. In
the present study without co-feed of hydrogen the activity over
1 wt% Pt/La0.7Y0.3NiO3 is ca 45 mmol/gmet/min with nearly 100%
selectivity. Under the conditions, the catalyst is a potential
candidate for the dehydrogenation of methylcyclohexane.
The rate constants were estimated as 8.3 per min for both
1 wt% Pt/LaNiO3 and 1 wt% Pt/La0.7Y0.3NiO3 catalysts. The
similar values of rate constants for 1 wt% Pt/LaNiO3 and 1 wt%
Pt/La0.7Y0.3NiO3 explain that partial substitution of La by Y has
no effect on the kinetics. Nevertheless, substitution has
significant impact on selectivity of hydrogen evolution. Rela-
tively higher rate constant for 1 wt% Pt/LaNiO3 and 1 wt% Pt/
La0.7Y0.3NiO3 catalysts as compared to Pt/La2O3 may be
attributed to contribution of Ni as active sites supporting
better hydrogen spillover phenomena.
4. Conclusions
The dehydrogenation of methylcyclohexane was successfully
carried out over Pt supported on metal oxides and Pt sup-
ported on perovskites. It was demonstrated that the selec-
tivity towards the dehydrogenation reaction can be achieved
by proper design of perovskite composition by substitution at
La-site. The loading of Pt on supports in this study was ca
1 wt%, which is promising to minimize the use of Pt in catalyst
compositions. With a cost-effective, active and selective
dehydrogenation catalyst available, the dehydrogenation of
methylcyclohaxane could be a potential option for hydrogen
transportation in future.
Acknowledgments
Financial support received from Ministry of New and Renew-
able Energy, New Delhi is acknowledged.
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