Single-step catalytic liquid-phase hydroconversion of DCPD into high energy density fuel exo-THDCPD

Article abstract of DOI:10.1039/c2gc16264d

Hydroconversion of dicyclopentadiene (DCPD) into high energy density jet propellant JP-10 has been successfully achieved with a greener single-step route over supported gold catalyst. The physicochemical properties of the catalysts were studied with XRD, SEM, TEM, N₂-adsorption, NH₃-TPD. The influence of reaction conditions like temperature, pressure, time etc. were studied in detail. The studies reveal that pressure and temperature play crucial roles in the reaction. Moderate acid sites in the catalysts are chiefly involved in isomerization and gold catalyzes hydrogenation of the intermediates. Analysis of the product stream at different intervals indicates a dissociation-recombination mechanism for the reaction. Reusability of the catalyst was tested by conducting five runs with the same catalyst. Even after the fifth run, the catalyst retains relatively high conversion and selectivity to exo-tetrahydrodicyclopentadiene (exo-THDCPD).

Full text of DOI:10.1039/c2gc16264d

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PAPER
Single-step catalytic liquid-phase hydroconversion of DCPD into high energy
density fuel exo-THDCPD†
M. G. Sibi, Bhawan Singh, R. Kumar, C. Pendem and A. K. Sinha*
Received 11th October 2011, Accepted 18th January 2012
DOI: 10.1039/c2gc16264d
Hydroconversion of dicyclopentadiene (DCPD) into high energy density jet propellant JP-10 has been
successfully achieved with a greener single-step route over supported gold catalyst. The physicochemical
properties of the catalysts were studied with XRD, SEM, TEM, N2-adsorption, NH3-TPD. The influence
of reaction conditions like temperature, pressure, time etc. were studied in detail. The studies reveal that
pressure and temperature play crucial roles in the reaction. Moderate acid sites in the catalysts are chiefly
involved in isomerization and gold catalyzes hydrogenation of the intermediates. Analysis of the product
stream at different intervals indicates a dissociation–recombination mechanism for the reaction.
Reusability of the catalyst was tested by conducting five runs with the same catalyst. Even after the fifth
run, the catalyst retains relatively high conversion and selectivity to exo-tetrahydrodicyclopentadiene
(exo-THDCPD).
Due to the easy availability and low cost of raw materials, jet
propellant JP-10 has high importance in the next generation of
1. Introduction
Cyclopentadiene and its derivative dicyclopentadiene (DCPD)
with highly active norborane and cyclopentadiene units are the
byproducts of pyrolysis of petroleum feedstocks.1–3 It has two
isomers, endo-dicyclopentadiene and exo-dicyclopentadiene.
Most of the chemical and physical properties of these isomers
are similar.4 Since space is limited in most aircraft, the amount
of energy contained in a fuel is very important. Due to the
strained cyclic structure the hydride of exo-DCPD, i.e. exo-tetra-
hydrodicyclopentadiene (exo-THDCPD), has a high energy
density.5,6 Due to the high volumetric energy content (39.6 MJ
L−1), flash point (55 °C) and low freezing point (−79 °C), it is
widely used as the main component of JP-10 fuel. JP-10 fuel
contains 98.5% exo-THDCPD and the remainder is endo-
THDCPD, and it provides much more propulsion energy than
conventional distilled fuels.7–9 When high energy density fuels
are used, it requires a smaller fuel tank, leaving more space for
electronics and other components of the aircraft.10 Low freezing
point, low viscosity, suitable flash point, high density and long
term storage stability makes exo-THDCPD a suitable JP-10
fuel.11,12 exo-THDCPD is also additionally used in other fuel
mixtures like JP-9, RF-1, RJ-5, etc.13 Moreover the chemical
and physical properties of exo and endo isomers are similar, so
the low percentage of endo-THDCPD does not affect the fuel
properties adversely. But endo-THDCPD has a much higher
freezing point (80 °C) than its exo isomer so it cannot be used
directly in JP-10 fuel and needs to be isomerized.
advanced aircraft. Currently it is synthesized by the hydrogen-
ation of dicyclopentadiene over palladium on alumina/carbon
catalyst, or nickel on alumina catalyst,14–17 and followed by the
isomerization of hydrogenated product, endo-THDCPD, over
strong acid catalysts.18–21 Hydrogenation is very important
because the presence of unsaturated compounds leads to coke
deposition on acidic sites and causes catalyst deactivation and it
also affects the smoke point of the fuel. Generally hydrogenation
proceeds at relatively milder conditions and presents both con-
version and selectivity issues, and significant increase in temp-
erature can be observed due to the exothermicity of the reaction.
Complete hydrogenation of DCPD requires a high temperature
which unfortunately leads to a decreased yield due to cracking of
DCPD. Earlier studies revealed that strong acids like sulfuric
acid or aluminium chloride can be very effectively used as cata-
lysts for isomerization of endo-THDCPD to exo-THDCPD. But
strong acidity of these catalysts causes many problems like low
exo selectivity, formation of deposits, environmental problems
like corrosion and, most importantly, a high amount of sodium
hydroxide aqueous solution is used for the separation of pro-
ducts.22 Another disadvantage of using these catalysts is poor
recyclability. Xing et al. reported a greener synthetic route for
the production of exo-THDCPD from endo-THDCPD over
acidic zeolites.23 But due to the high deactivation rate of the cat-
alysts, it is not an attractive route. Dzhemilev et al. reported Pd
(acac)2 as a good catalyst with 99.5% of exo-THDCPD, but its
high cost limits its use at industrial scale.24 Sun and Li recently
reported a vapour phase isomerization of endo-THDCPD to exo
isomer over zeolite catalysts.25 But the use of a high amount of
carrier gas with a low amount of endo-THDCPD and the high
deactivation rate of catalysts were not suitable for industrial
CSIR-Indian Institute of Petroleum, Dehradun – 248005, India. E-mail:
asinha@iip.res.in; Fax: +91-135-266-203; Tel: +91-1352525842
†Electronic supplementary information (ESI) available. See DOI:
10.1039/c2gc16264d
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microscopy (SEM), and temperature programmed reduction
(TPR) etc. X-Ray diffraction patterns were obtained using Cu
Kα radiation (40 kV and 40 mA, Advanced Bruker D8 diffracto-
meter). The SEM images were realized by field emission scan-
ning electron microscope, FEI Quanta 200 F, using a tungsten
filament doped with lanthanum hexaboride (LaB6) as an X-ray
source, fitted with an ETD detector with high vacuum mode
using secondary electrons and an acceleration tension of 10 or
30 kV. Catalysts were analyzed by spreading them on a carbon
tape. Energy-dispersive X-ray spectroscopy (EDX) was used in
connection with SEM for elemental analysis. The elemental
mapping was conducted with the same spectrometer. The TEM
images and SAED patterns were taken on a Hitachi H7100 elec-
tron microscope operated at 75 kV. The porous properties of
metal-loaded catalysts were examined by N2 adsorption–
desorption isotherms at 77 K (BelsorbMax, BEL, Japan) and the
related data (surface area, SBET; pore volume, VT; pore diameter)
were calculated. The amount and strength of the acid sites were
measured by ammonia adsorption–desorption technique using a
chemical adsorption instrument, Micrometrics 2900, with a
thermal conductivity detector. About 0.20 g sample was satu-
rated with NH3 at 120 °C, then flushed with helium to remove
the physically adsorbed NH3, finally the desorption of NH3 was
carried out at a heating rate of 10 °C min−1 in helium flow.
Scheme 1 Existing reaction pathway of synthesis of exo-THDCPD
from endo-DCPD.
application. Therefore even today aluminium chloride is used as
a catalyst for isomerization of endo-THDCPD. The existing
route for the production of exo-THDCPD is shown in Scheme 1.
From the economical point of view, single-step processes are
cost effective. Herein, we report the greener catalytic single-step
liquid-phase synthesis of exo-THDCPD from DCPD over gold
supported on silica–alumina. There is no published literature for
the direct single-step synthesis of exo-THDCPD from DCPD by
either homogeneous or heterogeneous routes. To the best of our
knowledge, this is the first attempt for environmentally friendly
cost-effective preparation of high energy density jet propellant
JP-10.
2. Experimental
2.1. Materials
DCPD with a purity of 99% was purchased from Acros; analyti-
cal grade toluene, methanol and n-hexane were obtained from
SD-Fine Chemicals, India. Reference endo-THDCPD was
synthesized with the reported procedure14–17 from DCPD, then
distilled and purified followed by confirmation of the physio-
chemical properties of the material with various analytical tools.
The commercial exo isomer was used as a reference. Aurochloric
acid was purchased from Merck. The support material mesopor-
ous SiO2–Al2O3 was obtained from Sasol with a silica/alumina
ratio of 3 : 7 and used after calcination at 300 °C for five hours.
2.4. Hydrogenation and isomerization reaction
Gold and palladium deposited with different wt% loadings on
mesoporous silica–alumina were used as the catalysts for the
reaction. We studied the effects of temperature and pressure in
the range from 50–140 °C and 10–40 bar respectively.
Reusability of the catalysts were checked with repeated reactions
on the same catalyst without any further activation against calci-
nation, coke removal etc. Only multiple washing with solvent
was used to clean the catalyst, followed by drying at 120 °C
overnight.
2.2. Synthesis of catalyst
Hydrogenation and isomerization reactions were conducted in
batch mode, in a 500 ml stainless steel autoclave (Autoclave
engineers) at various temperature and pressure. The reactor was
equipped with a magnetically driven stirrer, a dip tube, and an
internal water cooling system. The temperature was controlled by
programmable PID controller. Reactant, catalyst and solvent
were placed inside the reactor and sealed, then the system was
purged with hydrogen three times to remove air. The whole
system was pressurized to 3 bar, and heating was started with
200 rpm stirring speed. When the system achieved the desired
temperature it was pressurized to the required pressure. The
hydrogen pressure, temperature and stirring were constant
throughout the reaction. Aliquots were withdrawn at equal inter-
vals through the special sampling port attached within the
reactor. The tiny catalyst particles were separated by filtration
and the product was analyzed by Varian CP 3800 gas chromato-
graph with VF-5ht-Ultimetal 30 × 0.25 (0.10) column. At the
end of the reaction the reactor was allowed to cool down to room
temperature and the catalysts were separated by filtration. The
products were selectively distilled and were used for testing of
various specific propellant properties. Density of the product is
analyzed with DMA 4500 M Anton Parr density meter.
Synthesis of the supported gold catalyst was carried out by the
modified method of Sinha et al.26 by deposition precipitation
method (DP) and it was reduced with sodium borohydride. In a
typical synthesis 1.5 wt% of gold precursor is stirred with
100 ml double-distilled water at 70 °C for one hour. Then the pH
of the solution is maintained by adding NaOH solution. After
reaching pH 7.5, 2 ml freshly prepared 0.1 molar sodium boro-
hydride was added dropwise to reduce the gold. The colour of
the solution is quickly changed from orange to wine red which
indicates complete reduction to gold nanoparticles. The whole of
the solution was stirred vigorously with the appropriate amount
of support for two hours. After completion of reaction the pre-
cipitate was filtered and washed with distilled water until chlor-
ide-free and then dried over night at 100 °C. The catalyst was
calcined at 300 °C for 8 hours at a rate of 1 °C per minute before
use for catalytic evaluations.
2.3. Characterization of the catalyst
The physicochemical properties of the catalyst and support were
characterized by X-ray diffraction (XRD), scanning electron
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BJH method, and are shown in Fig. 3. From these results it is
clear that impregnation of gold and repeated reaction of the cata-
lyst has no change in the nature of the isotherm, i.e. support pore
structure is sustained with impregnation and high temperature
reactions. But Table 1 indicates a change in physical properties
like surface area, total pore volume, mean pore diameter. The
differences in surface area and total pore volume of the support
and catalysts indicate the presence of gold deposited inside the
pores. The differences between the used catalysts with fresh cata-
lyst indicate the presence of coke inside the catalyst. Since gold
is deposited inside and outside the pores, the pore structure and
size are very important. The presence of large pores in the
support material is suitable for the diffusion of reactant and
3. Results and discussion
3.1. Characterization of catalyst
Typical XRD patterns of the support material, catalyst and the
used catalyst are shown in Fig. 1. The used and fresh catalysts
show weak and broad [111] and [200] peaks due to Au particles.
The porous properties of the catalysts were studied by N2 adsorp-
tion–desorption isotherms at 77 K. The adsorption–desorption
isotherms and the pore size distribution curves are shown in
Fig. 2 and 3 respectively. The other physicochemical properties
of the catalysts are listed in Table 1. From these results it can be
seen that the support material and catalysts shows type IV iso-
therm with H1-type hysteresis loop at a p/p0 of 0.6–0.9 and large
mesopores with narrow pore size distribution. The pore size dis-
tributions were calculated from the adsorption isotherm, using
Fig. 1 Wide angle X-ray diffraction pattern of catalyst (a) Au/SiO2–
Al2O3, (b) used Au/SiO2–Al2O3.
Fig. 2 N2-adsorption desorption curve of support and catalyst (a)
SiO2–Al2O3, (b) Au/SiO2–Al2O3, (c) used Au/SiO2–Al2O3.
Fig. 3 Pore size distribution of catalyst and support (a) SiO2–Al2O3, (b) Au/SiO2–Al2O3, (c) used Au/SiO2–Al2O3.
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product because the size of the exo and endo THDCPD is high,
i.e., with a critical dimension of 0.67 nm × 0.60 nm and a
kinetic diameters σ 0.60 × 0.53 nm.17
Adsorption of NH3 was used to determine the acidity of the
catalysts. It provides the total acidity (Table 1) and strength of
the acid sites. Fig. 7 shows the NH3–TPD curves of the catalysts
calcined at 300 °C. Both strong and weak acid sites were present
in the support and fresh catalyst. But there is a decrease in both
strong and weak acid sites in the used catalyst, which may be
one of the reasons for the decrease in the catalyst activity, as dis-
cussed later.
The morphologies of the synthesized catalysts were examined
by scanning electron microscope. A representative SEM image
of the catalyst is shown in Fig. 4. Au dispersion on the support
was confirmed with the EDX analysis. The elemental mapping
of the catalyst reveals a homogeneous distribution of Au on the
silica–alumina support surface (Fig. 5). The dispersion and size
of gold on the support material were analyzed by TEM and are
shown in Fig. 6 (the corresponding SAED is shown in the
ESI†). From the figure it is clear that the <10 nm size particles
with average particle size of 3–6 nm are dispersed throughout
the support. The SAED patterns from the fine nanoparticles
exhibit diffuse rings.
Table 1 Physicochemical properties of catalysts
Surface Total pore Mean pore Surface
area
volume
diameter
(nm)
acidity NH3
S. No Catalysts
(m2 g−1) (cm3 g−1
)
(mmol g−1
)
1
2
3
SiO2–Al2O3
232
Au/SiO2–Al2O3a 203
Au/SiO2–Al2O3 197.3
0.827
0.723
0.470
14.19
14.19
9.5
0.65
0.79
0.57
a Catalysts after 5th reaction run.
Fig. 4 SEM image of the catalyst Au/SiO2–Al2O3.
Fig. 5 Elemental mapping of the catalyst (a) silica (b) alumina (c) gold.
Fig. 6 TEM images of the fresh (left) and used (right) catalysts.
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Fig. 7 NH3–TPD curves of (a) SiO2–Al2O3, (b) Au–SiO2–Al2O3, (c)
used Au/SiO2–Al2O3.
Fig. 8 Percentage of composition of intermediate and products: (■)
DCPD, (●) endo-THDCPD, (▲) exo-THDCPD, (▼) CPD, (◆) con-
version, (◄) selectivity, (►) yield (130 °C and 30 bar).
3.2. Hydrogenation and isomerization of DCPD to
exo-THDCPD (JP-10) over Au/SiO2–Al2O3 catalysts
Hydrogenation and isomerization of DCPD is a multiphase cata-
lytic reaction over gold catalysts. Literature reports that the syn-
thesis of JP-10 involves two steps: (1) hydrogenation of DCPD
in to endo-THDCPD on a hydrogenation catalyst and (2) isomer-
ization of endo product into exo-THDCPD over acidic
catalyst.18–21 This process is economically less favorable and
environmentally not friendly. Bifunctional catalysts with strong
acid sites and hydrogenating metal are promising systems to
overcome the drawbacks. In view of this, gold on silica–alumina
catalyst could be a suitable solution. The relative strength of
surface acidity and reducing ability of gold determine a new
reaction pathway with high selectivity to exo-THDCPD. Based
on our studies of changing various parameters with time, we
concluded that the suitable reaction time is 6 hours with a temp-
erature of 130 °C and a pressure of 30 bar (Fig. 8). It is clear
from Fig. 8 that DCPD has very quickly cracked into two cyclo-
pentadiene molecules within one hour and then slowly it con-
verts selectively into exo-THDCPD on gold catalyst. After the
reaction time the catalyst gives an exo selectivity of 93.54 with
5% endo-THDCPD. From the figure we can see that a steep
decrease of CPD and corresponding increase of exo-THDCPD
with a very slow increase of endo-THDCPD. Moreover, the
yield of exo-THDCPD continuously increased with the reaction
time and a yield of 94% is attained after six hours. These results
prove that the supported gold catalyst is highly efficient and
selective for the single step hydrogenation and isomerization of
DCPD. Distillation of the reaction mixture produces 99% pure
exo-THDCPD. The fuel properties like density and freezing
point of the purified product were analyzed and it matched with
those for pure exo-THDCPD.
Fig. 9 Effect of pressure on reaction stream at 130 °C: (■) selectivity,
(●) conversion.
forms faster (the kinetically controlled product) than exo-
THDCPD (the thermodynamic product). The conditions of the
reaction, such as temperature, time and pressure, control the
favored reaction pathway, either the kinetically controlled or the
thermodynamically controlled one. The influence of reaction par-
ameters like temperature, pressure and time were systematically
investigated to arrive at optimized conditions. The reaction
pressure has a very high impact on conversion and selectivity.
From Fig. 9 it can be seen that exo-THDCPD selectivity of the
reaction shows a sudden increase from 20 bar pressure to 30 bar
pressure. But conversion has not been much affected. Analysis
of the reaction products at different intervals reveals that reaction
pathway was directed by pressure. From Fig. 10 it is clear that at
lower pressures initially (1 hour) the formation of endo-
THDCPD was very high and presence of CPD is less. After
2 hours endo-THDCPD concentration decreased while CPD con-
centration increased. But a slight increase in endo-THDCPD is
3.3. Influence of reaction parameters
Conversion of DCPD (and its equilibrium monomer CPD)
follows competing pathways leading to different products and
the reaction conditions influence the selectivity. endo-THDCPD
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Fig. 10 Percentage of composition of intermediate and products: (■)
DCPD, (●) endo-THDCPD, (▲) exo-THDCPD, (▼) CPD, (◆) con-
version, (◄) selectivity, (►) yield (130 °C and 15 bar).
Fig. 12 Percentage of composition of intermediate and products: (■)
DCPD, (●) endo-THDCPD, (▲) exo-THDCPD, (▼) CPD, (◆) con-
version, (◄) selectivity, (►) yield (130 °C and 40 bar).
hydrogenation reaction most of the dicyclopentadiene molecules
would dissociate and would be hydrogenated at high pressure by
recombination and then isomerized to form exo-THDCPD. From
these results it can be concluded that pressure plays a crucial role
for the selective synthesis of exo-THDCPD from endo-DCPD on
the bifunctional Au/silica–alumina catalyst.
The effect of temperature on the reaction stream is shown in
Fig. 13. Conversion and selectivity of the reaction varies with
temperature. At lower temperature the formation of exo-
THDCPD was comparatively lower. But on increasing the temp-
erature the formation of exo-THDCPD increases with an increase
of cyclopentadiene concentration. This is an indication that at
higher temperature the dissociation of DCPD is high but at lower
temperature it is less.
Reaction time is another important parameter used in this
study. All the studies give the information that the minimum
time required for completion of the reaction was six hours. But
within an hour, conversion of DCPD reaches maximum but the
selectivity for exo-THDCPD is low. We carried out a number of
reactions at temperatures greater than 150 °C and noted a loss of
selectivity. It might be due to the formation of oligomers, i.e. the
oligomerization of DCPD with CPD. From all these results it
can be concluded that pressure plays a crucial role along with
temperature and time.
Fig. 11 Percentage of composition of intermediate and products: (■)
DCPD, (●) endo-THDCPD, (▲) exo-THDCPD, (▼) CPD, (◆) con-
version, (◄) selectivity, (►) yield (130 °C and 20 bar).
again noted after three hours of the reaction indicating reversible
conversion between CPD and endo-THDCPD. Here the highly
reactive norborane bond is first hydrogenated followed by the
hydrogenation of the second cyclopentyl ring, while the isomeri-
zation into exo-THDCPD is a much slower reaction and hence
less favored at these conditions. Increasing the reaction pressure
to 20 bar (Fig. 11), the formation of endo-THDCPD is sup-
pressed. But at 40 bar pressure (Fig. 12) the presence of CPD
was very high – this may be because at very high pressure CPD
is more stabilized and has lower adsorption on the catalyst and
hence is less reactive. Normally, at high pressure the rate of
hydrogenation is very high and dissociation of molecules is
much less. But due to the very slow heating rate of the reaction
(1 °C min−1, with 2–3 bar H2) before the initiation of the
3.4. Proposed reaction pathway and mechanism
The existing reaction pathway for the formation of exo-
THDCPD is shown in Scheme 1. The norborane ring with lower
bond strength and bond order is hydrogenated first and then the
cyclopentadiene bond will be hydrogenated on the metal cata-
lyst, followed by isomerization of the product with acid catalysts
wherein the endo-norbornyl fragments of THDCPD are isomer-
ized into exo configurations but the endo cyclopropyl fragments
remain unchanged.27 Here we discuss a reaction pathway
which is similar to the synthesis of dicyclopentadiene from
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cyclopentadiene.28 The most plausible reaction pathway is
shown in Scheme 2. The reaction is a dissociation–recombina-
tion, i.e. the dicyclopentadiene first dissociates into two cyclo-
pentadiene molecules on the acid sites and redimerizes into exo-
DCPD followed by rapid hydrogenation into thermodynamically
stable exo-THDCPD on the gold surface. The work of Xang
et al. on the isomerization of endo-DCPD to exo-DCPD also
shows that this type of rearrangement is possible.29 This assump-
tion is proved by withdrawing samples at regular intervals,
which reveals that within one hour nearly 97% of the DCPD is
converted into 88% of cyclopentadiene and 5% exo-THDCPD
(Fig. 7). After 6 hours reaction time nearly 99.5% of the CPD is
converted to exo-THDCPD. It is also noted that the presence of
endo-THDCPD is much less and slowly increases as the reaction
progresses. This is a clear indication that the reaction selectively
goes through our proposed pathway and not via the hydrogenated
intermediate pathway. GC analysis also showed the absence of
3,4-DHDCPD and 8,9-DHDCPD in the reaction stream, but
these intermediates are found in the reaction with palladium on
silica–alumina catalyst. Zou et al. selectively produced endo-
THDCPD through these intermediates and they have not
reported the presence of exo-THDCPD.17,30 To clarify the reac-
tion pathway we studied the reaction in the absence of hydrogen
and confirmed the formation of exo-DCPD. It may be also
pointed out that it is reported in the literature too that exo-DCPD
is formed when endo-DCPD is heated at elevated temperature
and pressure in the absence of hydrogen for a prolonged period.
A dissociation–recombination mechanism has been suggested to
explain this phenomenon.29
We also carried out a control experiment with cyclopentene
under the same reaction conditions and we could not observe
any partially hydrogenated intermediate, thus excluding the
interaction of cyclopentene in the reaction mechanism.
3.5. Reusability of the catalyst
The successful recovery and reuse of the catalysts is an essential
aspect of green chemistry. So, heterogeneous catalysts play a
crucial role to produce an environmentally friendly chemical
environment. In addition, multiple use and regeneration of the
catalysts gives economical advantages. Hence we studied the life
of the catalyst with multiple reaction runs. Reusability of the cat-
alyst was tested with the same catalyst without any regeneration.
Catalyst was repeatedly washed with toluene and dried overnight
at 120 °C and used as such. The results obtained after reuse are
given in Fig. 14. It clearly indicates that the selectivity to exo-
THDCPD continuously decreases (with increase in CPD yield)
Fig. 13 Effect of temperature on reaction stream at 30 bar: (■) endo-
THDCPD, (●) CPD, (▲) exo-THDCPD.
Fig. 14 Reusability of the catalyst upon selectivity and conversion:
(■) conversion, (●) selectivity, (▲) yield.
Scheme 2 Proposed single step reaction pathway of synthesis of exo-THDCPD from endo-DCPD.
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but the conversion of DCPD decreases only slightly with
repeated reactions. A detailed study of the used catalyst reveals
that the main reason for the loss in activity is coke formation.
From Table 1 we can see that there is a huge decrease in the pore
diameter and pore volume of the used catalyst which is due to
the deposition of coke in the pores of the support which not only
restricts the transportation of the reactant and products but also
blocks the active acid sites. NH3-TPD analysis shows a decrease
in the total acidity from fresh to used catalyst. ICP-AES analysis
confirmed negligible loss of gold from the catalyst. Most zeolite
catalysts lose their activity within hours4 due to coke deposition
but deactivation is much less in our catalyst and it shows com-
paratively higher activity and selectivity. The deactivation of the
catalyst with respect to the presence of coke was studied by
TGA analysis and the results obtained are shown in the ESI.† A
gradual increase in coke is observed after each cycle. TEM
analysis of the fresh and used catalyst did not show any observa-
ble increase in the Au particle size (Fig. 6). More detailed
studies on the activity of regenerated catalysts after coke removal
is being done.
Acknowledgements
The Director, IIP, is acknowledged for approving the work. BS
thanks UGC, India for a Senior Research Fellowship. The
authors thank Analytical Science Division Indian Institute of
Petroleum for analytical services.
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Gold supported on mesoporous silica–alumina was used to cata-
lyze the hydrogenation and isomerization of dicyclopentadiene
to high density jet propellent JP-10 (exo-THDCPD). The exper-
imental results show that the catalyst is highly active and selec-
tive for the synthesis of JP-10. The presence of gold selectively
produces exo-THDCPD on the moderately acidic support with
nearly complete conversion. The operational parameters like
temperature, pressure and time have considerable effect on the
performance of the reaction. Detailed study of the reaction by
varying various parameters confirmed that the suitable reaction
condition is a temperature of 130 °C and at 30 bar pressure with
a reaction time of six hours giving 99% conversion with highest
selectivity. Based on the proposed mechanism, the formation of
exo-THDCPD is a dissociation–recombination and this is
confirmed from the analysis of the reaction products. The mul-
tiple reuse of the catalyst gives the information that the catalyst
is reusable and comparatively tolerant to coke deposition.
It can be concluded that this catalyst could completely replace
the existing liquid acid and AlCl3 in the second step of synthesis
of JP-10 to make the process environmentally friendly. In
addition it may become more economical since the fuel is pro-
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promising for commercial production.
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