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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

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Efficient hydrogen supply through catalytic dehydrogenationof 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, Indiab 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

* Corresponding author. Tel.: þ91 712 224988E-mail address: [email protected]

0360-3199/$ – see front matter ª 2010 Profesdoi:10.1016/j.ijhydene.2010.02.014

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 equipment such as Lorries [1,5–10]. Additionally, the

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

5x410, þ91 9822745768 (m(R.B. Biniwale).sor T. Nejat Veziroglu. Pu

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

obile); fax: þ91 712 2249900.

blished by Elsevier Ltd. All rights reserved.

mailto:[email protected]

http://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 4021

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 PtCl4solution.

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 overdifferent 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

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.


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 802θ

Inte

nsity

(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.

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.

0

5

10

15

20

30 60 90Time (min)

Hyd

roge

n ev

olut

ion

(mm

ol/g

met

/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.


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

Table 1 – Elemental analysis of catalysts using SEM-EDXA.

Composition Mass%

Catalyst La Ni O Pt

1 wt% Pt/LaNiO3 84.6 7.47 7.24 0.64

1 wt% Pt/La0.7Y0.3NiO3 72.3 6.16 8.83 1.33

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,

Atomic%

Y La Ni O Pt Y

– 51.16 10.62 37.95 0.27 –

11.3 39.73 8.0 42.03 0.52 9.72

Table 2 – Hydrogen evolution rate of all catalysts and their particle size.

Sr No. Catalysts Particle size (nm) Metallic surface areaas estimated by

CO-chemisorption(m2/g)

Hydrogen Evolutionrate 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.

0.03

0.04

0.04

0.05

l/min

)

CH4C7H8C6H6


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.

Table 3 – Catalytic activity of various catalysts fordehydrogenation of methylcyclohexane at 350 8C at150 min.

SrNo.

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.

The kinetics of reaction can be well explained by differ-

ential equation, in terms of rate law as follows:

ln

�� 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

0.00

0.01

0.01

0.02

0.02

0.03

A B C DCatalysts

Prod

ucts

(mm

o

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 dehydrogenationreaction

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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