Catalytic: N -pentane conversion on H-ZSM-5 at high pressure

Article abstract of DOI:10.1039/c5nj02733k

The effect of temperature (633-723 K), pressure (10-60 bar) and weight hourly space velocity (WHSV) (400-1500 g_C5 g_cat^-1 h^-1) on the conversion of n-pentane on H-[Al]ZSM-5 type catalysts has been investigated. Catalyst properties were tested using a packed-bed laboratory microreactor and reaction products were analyzed via online gas chromatography. 5-25% pentane conversion was observed at a pressure of 40 bar and temperatures in the range of 633-723 K. Reactant consumption rate approached saturation kinetics at pressures above 30 bar (～14% conversion, 673 K). At 40 bar and 673 K, increasing WHSV (400-1500 g_C5 g_cat^-1 h^-1) resulted in a reduction in pentane conversion (26-10%). In all cases, propane and butane were the major products, followed by heavier C₆₊ compounds and other lighter products (C₁-C₄ paraffins and olefins). Propane carbon selectivity increased from 24% at 633 K to 34% at 723 K, while butane carbon selectivity (～40%) was nearly constant. An inverse relationship between the production of C₆₊ and light products was observed with changes in reaction conditions. The carbon selectivity to C₆₊ compounds increased from 20% at 10 bar to 27% at 60 bar and decreased from 28% at 633 K to 18% at 723 K. At all reaction conditions, the observed product distribution can be explained as the result of fast bimolecular reactions, including hydride transfer and alkylation.

Full text of DOI:10.1039/c5nj02733k

NJC
View Article Online
View Journal
PAPER
Catalytic n-pentane conversion on H-ZSM-5 at
high pressure†
Cite this:DOI: 10.1039/c5nj02733k
Edward P. Schreiner, Shewangizaw Teketel and Raul F. Lobo*
The effect of temperature (633–723 K), pressure (10–60 bar) and weight hourly space velocity (WHSV)
h
ꢀ1) on the conversion of n-pentane on H-[Al]ZSM-5 type catalysts has been
ꢀ1
(400–1500 gC5 gcat
investigated. Catalyst properties were tested using a packed-bed laboratory microreactor and reac-
tion products were analyzed via online gas chromatography. 5–25% pentane conversion was
observed at a pressure of 40 bar and temperatures in the range of 633–723 K. Reactant consumption
rate approached saturation kinetics at pressures above 30 bar (B14% conversion, 673 K). At 40 bar
h
ꢀ1) resulted in a reduction in pentane conversion
ꢀ1
and 673 K, increasing WHSV (400–1500 gC5 gcat
(26–10%). In all cases, propane and butane were the major products, followed by heavier C6+
compounds and other lighter products (C1–C4 paraffins and olefins). Propane carbon selectivity
increased from 24% at 633 K to 34% at 723 K, while butane carbon selectivity (B40%) was nearly
constant. An inverse relationship between the production of C6+ and light products was observed
with changes in reaction conditions. The carbon selectivity to C6+ compounds increased from 20% at
10 bar to 27% at 60 bar and decreased from 28% at 633 K to 18% at 723 K. At all reaction conditions,
the observed product distribution can be explained as the result of fast bimolecular reactions, including
hydride transfer and alkylation.
Received (in Montpellier, France)
6th October 2015,
Accepted 11th January 2016
DOI: 10.1039/c5nj02733k
www.rsc.org/njc
driven by the thermal energy removed from the aircraft5,6 and a
target endothermic reaction is the cracking of hydrocarbons on
1. Introduction
This investigation is motivated by the need to develop more solid catalysts. For several decades, zeolites have been used as
efficient cooling technologies for the practical use of new catalysts for cracking of crude oil,7,8 but there are only a few
hypersonic engines. The flight of aircraft and missiles at hyper- reports of zeolite-based high-pressure cracking for endothermic
sonic speeds (greater than Mach 5) is hindered by overheating of fuel applications.9–12 To maximize endothermicity, the selective
the engine and electronic components caused by the high rate cracking of alkanes to produce an alkene and a smaller alkane is
of fuel combustion and air friction.1 Aircraft are currently the preferred reaction. It is also desired to further crack the
cooled by passive and active methods: when passive cooling alkene and alkane to produce hydrogen, ethene, and methane,
is used, cold air from the atmosphere is passed through the as these have better mixing and combustion characteristics than
engine, whereas when active cooling is used, onboard jet fuel is larger molecules.13
used as a heat sink.2 In such cases, the maximum amount of
Zeolite catalyzed cracking of alkanes proceeds via two major
heat that can be removed is determined by the heat capacity, mechanisms: monomolecular and bimolecular.14 Monomolecular
thermal stability, and initial temperature of the fuel. Chemical (i.e. protolytic) cracking reactions typically occur at low pres-
additives (e.g. 1,2,3,4-tetrahydroquinoline and tetralin) and sures and high temperatures.15–21 In this mechanism, a proton
special fuels (e.g. exo-tetrahydrodicyclopentadiene) with greater from the zeolite acid site is transferred to the adsorbed alkane
heat capacity and thermal stability have been designed for this to form a pentacoordinated alkanium ion that immediately
purpose, but future hypersonic vehicles will exceed the cooling undergoes protolytic cracking to form a neutral paraffin or
capacity of these special fuels.3,4
molecular hydrogen and a surface alkoxide. The surface
Cooling capacity can be improved by utilizing so-called alkoxide can desorb to produce an olefin and reform the zeolite
endothermic fuels, which undergo endothermic chemical reactions acid site.22–26 This sequence leads to a predictable, but approxi-
mate, product distribution. For example, the protolytic cracking
of butane can only yield three product pairs: hydrogen and
butene, methane and propene, or ethane and ethene. Surface
Center for Catalytic Science and Technology, Department of Chemical and
Biomolecular Engineering, University of Delaware, Newark, DE, 19716, USA.
alkoxides can also undergo further cracking through b-scission
E-mail: lobo@udel.edu; Fax: +1 302-831-1048; Tel: +1 302-831-1261
† Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nj02733k reactions.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016
New J. Chem.

View Article Online
Paper
NJC
Alkoxides may also participate in bimolecular reactions, 2. Experimental section
such as hydride transfer, oligomerization, and alkylation.8 In
bimolecular reactions, a molecule in the gas phase reacts with a
chemisorbed olefin on the surface of the zeolite. The simplest
way to detect bimolecular reactions is to observe molecules that
cannot be formed from monomolecular cracking; for example,
the production of pentane from hexane. Methane and pentene
can be produced from protolytic cracking of hexane. Pentene
then can be converted to pentane through hydride transfer.
Pentane can also be formed by cracking larger molecules that
formed through oligomerization.
2.1 Materials
NH4-[Al]ZSM-5 (CBV3024E) was purchased from Zeolyst Inter-
national and the material was used without further treatment
for the catalytic investigations. n-Pentane (Fisher, 99.7% purity)
was used as the feed for the catalytic tests. The following gases
were used for calcination and gas chromatograph operation: air
(Keen, Grade 0.1), Nitrogen (Keen, Grade 5.0), Hydrogen (Keen,
Grade 5.0), and Helium (Keen, Grade 5.0).
2.2 Characterization
There have been a few investigations of the supercritical
cracking of hydrocarbons on zeolites. Dardas et al. investigated
the effects of supercritical pressures on the conversion and
selectivity of n-heptane cracking on Y-type zeolites. The super-
critical pressures increased the conversion and paraffin yield
and decreased the amount of deactivation observed when compared
to subcritical pressures.9 Xian et al. studied supercritical cracking
of n-dodecane on wall-coated H-[Al]ZSM-5 catalysts and reported
that nanocrystalline catalyst particles produced higher conversions
and higher selectivity to ethylene and propylene than microcrystal
size particles.10 Kim et al. found that high pressure conversion
of methylcyclohexane on H-[Al]ZSM-5 yielded higher heats of
reactions as compared to H-[Al]Beta and H-[Al]Y.27 Luo et al.
have investigated the cracking of n-hexane on various zeolites.
H-[Al]ZSM-5 exhibited a higher pressure dependency on rates
and higher activation energies than H-[Al]USY, H-[Al]Mordenite,
and H-[Al]Beta, but had better selectivity towards olefins and
lower susceptibility to deactivation.11,12 In addition, the cracking of
hexane on ZSM-5 exhibited monomolecular-like reaction kinetics
under all pressures, but at high pressures on USY, mordenite, and
zeolite beta, bimolecular reactions were the dominant reaction
channels. Finally, Wang et al. found that heavily branched iso-
dodecane (mainly 2,2,4,6,6-pentamethylheptane) could affect
conversion of n-dodecane on H-[Al]ZSM-5 by acting as an inert
dilutent (positive) or by resisting diffusion (negative).28
Solid state 29Si MAS NMR (99.83 MHz, 10 kHz rotational speed,
2048 scans, and 30 s relaxation delay) and 27Al MAS NMR
(130.29 MHz, 10 kHz rotational speed, and 512 scans) spectra
of hydrated NH4-[Al]ZSM-5 were recorded with a Bruker AVIII500
NMR spectrometer. Surface area and micropore volumes (calculated
using the t-plot method) were determined through N2 adsorption
isotherms measured using a Micromeritics ASAP 2020 instrument.
The samples were pretreated at a temperature of 623 K and a
reduced pressure of 0.5 Torr for 6 h to remove any adsorbed
species. Powder X-ray diffraction patterns (PXRD) were measured
using a Phillips X’Pert X-ray diffractometer with a CuKa source
(l = 1.542 Å). Diffraction patterns were obtained using a step size
of 0.021 2Y with 2 s counting time at each step. Diffraction
patterns were measured between 51 and 501 2Y. SEM images
were taken with a JSM-7400F scanning electron microscope with
an accelerating voltage of 3.00 kV. Zeolite chemical compositions
were determined through inductively coupled plasma mass
spectrometry (ICP-MS) from Galbraith Laboratories, Inc.
2.3 Reactor system
Fig. 1 depicts the configuration of the experimental setup used
for high-pressure experiments. The reactant, n-pentane, was
contained in a pressurized tank (1 L); this limited amount
constrained the time on stream to under 9 h. Pentane was fed
In this report, the effects of temperature, pressure and weight
hourly space velocity (WHSV) on the conversion of n-pentane on
H-[Al]ZSM-5 were investigated to determine the potential of this
reaction/catalyst system for endothermic cooling. The solid acid
zeolite H-[Al]ZSM-5 was chosen as the catalyst because it is thermally
stable, readily available, and known to increase the yield of light
olefins in industrial fluidized catalytic cracking units.29 Pentane was
selected because it is the simplest liquid hydrocarbon at STP and
has a high cooling potential (pentane cracking to ethane and
propylene has a heat of reaction of 1.15 MJ kgꢀ1). In addition,
n-pentane cannot form neutral aromatic species by cyclization
and dehydrogenation without molecular weight growth.30 It was
found that under all reaction conditions investigated, bimolecular
reactions were the dominant reaction channels for the high-
pressure conversion of pentane on H-[Al]ZSM-5. Smaller alkanes
(C3, C4) with higher H/C ratios than pentane were produced,
while larger species (C6+) with lower H/C ratios than pentane
were necessarily produced to close the hydrogen and carbon
balance. This group of products has lower endothermic potential
than direct monomolecular cracking of the alkane.
Fig. 1 Process flow diagram of the experimental setup used for high
pressure experiments.
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016

View Article Online
NJC
Paper
into the system using a high-pressure liquid chromatography
(HPLC) pump (Chromtech, Series I). The system pressure was
controlled by a backpressure regulator (Swagelok, KPB series).
The reactor consisted of the catalyst supported by quartz wool
inside a 316 SS tube (4.6 mm ID). Two thermocouples were
installed, one at the bottom and one at the top of the catalyst
bed, to monitor the temperature difference across the bed; the
thermocouples also helped maintain the position of the bed
within the reactor tube. A preheater (coiled 1/800 tube wrapped
with heating tape) and tubular furnace (Lindberg Blue M) were
used to control the reaction temperature. Gas transfer lines
were heated to 453 K using heating tape to avoid condensation
of products. The reactor effluent was analyzed using an online
gas chromatograph (GC) (Agilent 7890B) equipped with a flame
ionization detector (FID). Separation of chemical species within
the reactor effluent was performed in the GC with an Alumina
column (Agilent, 50 m ꢁ 530 mm ID). Helium was used as the
carrier gas and nitrogen was used as the makeup gas. The
following temperature program was used for product detection:
a 5 minute hold at 373 K, a ramp to 473 K at a rate of 20 K minꢀ1
,
and a final 30 min hold at 473 K.
Fig. 2 SEM image of CBV3024E (top), 29Si NMR (left), and 27Al NMR (right)
2.4 Catalytic tests
of the ZSM-5 catalyst.
The catalyst powder was pressed, gently crushed and sieved to
particle sizes between 250 and 425 mm (40–60 mesh). Each
experiment was performed using 50 mg of catalyst powder.
Prior to each experiment, the catalyst was calcined in situ at a
temperature of 823 K for 5 hours in zero air (Keen, 60 mL minꢀ1).
A variety of reaction conditions were investigated: pressure was
investigated up to 60 bar and reaction temperature was studied
in the range of 633–723 K. Most experiments were performed in
the supercritical regime of n-pentane (tc = 470 K and pc = 34 bar).31
The weight hourly space velocity (WHSV, defined as grams
of pentane fed pꢀer1 gram of catalyst per hour) ranged from
375–1500 gC5 gcat hꢀ1 and was controlled by changing the
The SEM image (Fig. 2) shows that the material was an aggregate
of particles smaller than 2 mm. Presence of only one signal at
55 ppm on the 27Al MAS NMR spectra of the hydrated samples
showed that nearly all aluminum atoms were in tetrahedral
coordination (Fig. 2). Only a small fraction (1%) was observed
near 0 ppm and was assigned to extra-framework octahedral
aluminum. The nominal Si/Al ratio of this commercial sample
determined by ICP (Si/Al = 15.7) was consistent with the
aluminum concentrations determined by other studies on
similar samples (Si/Al = 15–17).15,32 29Si MAS NMR spectra from
this sample indicated that the sample contained predominantly
Si(4Si) groups and 4.2% of Si(3Si, Al), resulting in an estimated
framework Si/Al of 23. The aluminum concentration is slightly
less than the amount observed by ICP, and confirms that only a
small fraction of the Al is located in extra-framework positions.
The micropore volume, obtained from N2 adsorption isotherms
pentane liquid flow rates in the range of 0.5–2.0 mL minꢀ1
.
Conversion of n-pentane was defined as 100% minus the
percentage of unreacted pentane (all isomers included) in
the product stream. Product carbon selectivity was defined as
the fraction of carbon in each product as compared to the total
amount of carbon in the effluent that was not pentane.
and analyzed using the t-plot method, was 0.11 cm3 ꢀ1. This
g
micropore volume is slightly smaller than observed for high
quality samples (usually B0.14 cm3 gꢀ1) and suggest that some
extra-framework species may be present in the zeolite pores or that
a non-porous phase (undetected by XRD) is present in the sample.
The observed BET surface area (380 m2 gꢀ1) and micropore volume
are in agreement with previous reports for the same material.32
3. Results
The conversion of n-pentane over zeolite H-[Al]ZSM-5 (Si/Al = 15)
was investigated considering the effect of temperature (633–723
K), pressure (10–60 bar), and weight hourly space velocity (WHSV)
(375–1500 gC5 gcat
ꢀ1
h
ꢀ1). The reaction kinetics were measured
using a packed-bed laboratory microreactor and reaction products
3.2 Catalytic conversion of n-pentane
were analyzed via online gas chromatography.
Conversion of n-pentane on H-[Al]ZSM-5 at high pressures was
performed in a packed-bed reactor. Reactor effluent was analyzed
3.1 Catalyst characterization
The XRD patterns of the zeolite samples showed that the zeolite via an online GC with injections being taken approximately every
samples were highly crystalline and did not reveal the presence 40 min. As seen in Fig. 3, reactor conversion remained stable
of any amorphous material or other crystalline impurities. during the 6 h of time on stream at temperatures up to 673 K.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016
New J. Chem.

View Article Online
Paper
NJC
of the system from 10 bar up to a total pressure of 30 bar, which
is before the transition to the supercritical phase (34 bar),
caused an increase in conversion. Further increases in pressure
up to 60 bar did not increase the total conversion of pentane.
Pressure changes had little effect on carbon selectivity of the
major products: propane and butane. Conversely, increases in
pressure decreased selectivity to the light products and increased
selectivity to the C6+ fraction (Fig. 5).
Fig. 6 shows the conversion and carbon selectivity during
the n-pentane reaction at a temperature of 673 K and a pressure
ꢀ1
of 40 bar as a function of WHSV (375–1500 gC5 gcat
h
ꢀ1).
Conversion of pentane increased with decreasing WHSV, or in
other words, increased as the residence time increased. Selectivity
of the major products (propane and butane) and C6+ fraction did
not change appreciably with changes in WHSV, but carbon
selectivity of the light products increased with increasing WHSV.
Fig. 3 Conversion of n-pentane over 6.5 h time on stream during high
pressure conversion on H-[Al]ZSM-5. Rꢀe1action conditions: T = 633–723 K,
P = 40 bar, and WHSV = 1120 gC5 gcat hꢀ1
.
Deactivation was observed at temperatures above 673 K, with the
greatest amount at the highest reaction temperature of 723 K.
Conversion and selectivity data were calculated from the average of
the GC measurements over the 6.5 h time on stream.
4. Discussion
Fig. 4 shows the conversion of n-pentane and product
carbon selectivity at temperatures betweeꢀn1 633 K and 723 K
The formation of more than 50 different species upon the reaction
of n-pentane on H-[Al]ZSM-5, including many compounds heavier
than pentane, is clear evidence of secondary bimolecular reactions
controlling the product distribution at high pressure. In addition,
the ratios of C3/C2 and C4/C1 products were greater than 1 under
all conditions, which further indicates a role of bimolecular
reactions in the catalyst. If monomolecular cracking were
occurring, the average H/C ratio of the cracked products would
equal that of the feed (n-pentane H/C = 2.4), while the average
H/C of products lighter than pentane was between 2.5–2.6.
Since the observed C1–C5 species had an average H/C greater
than the feed, either the olefins produced from monomolecular
cracking were consumed in secondary reactions or the paraffins
were produced via a reaction other than n-pentane cracking.
The consumption of olefins lighter than pentane through
secondary bimolecular reactions is consistent with changes in
the carbon selectivity of the light olefins: ethene, propene, and
butene (Fig. 7). Carbon selectivity of the light olefins decreased with
increasing pressure, with the change being most clear at pressures
below B30 bar, where pentane is gas-like. Although pentane
(P = 40 bar and WHSV of 1120 gC5 gcat
h
ꢀ1). Conversion
increased rapidly with increasing temperature. The major
products of the reaction were propane and butane (B6 : 4 n : iso
isomeric ratio). At all experimental conditions investigated, the
selectivity to methane, ethane, ethene, propene and butenes
was low (o10%), hence these fractions were combined and
reported as ‘lights’. This fraction never exceeded 10% of the
overall carbon in the product stream. A typical carbon composition
of the lights was 1% methane, 5–10% ethane, 4–8% ethylene,
20–30% propylene, and 50–70% butenes. As temperature
increased, selectivity to propane increased, while selectivity to
butane remained nearly constant. On the other hand, selectivity
to higher molecular weight products (C6+) decreased with
increasing temperature. A small (o2%) increase in selectivity
to light products was observed with increasing temperature.
Clear changes in conversion and carbon selectivity were
observed as the pressure was increased at a temperature of
673 K and WHSV = 1120 gC5 gcatꢀ1 hꢀ1. Increasing the pressure
Fig. 4 Conversion of n-pentane (left) and selectivity to product groups (right) during high pressure conversion on H-[Al]ZSM-5. Reaction conditions:
T = 633–723 K, P = 40 bar, and WHSV = 1120 gC5 gcat hꢀ1
.
ꢀ1
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016

View Article Online
NJC
Paper
Fig. 5 Conversion of n-pentane (left) and selectivity ꢀto1 product groups (right) during high pressure conversion on H-[Al]ZSM-5. Reaction conditions:
T = 673 K, P = 10–60 bar, and WHSV = 1120 gC5 gcat hꢀ1
.
Fig. 6 Conversion of n-pentane (left) and selectivity to product groups (right) during high pressure conversion on H-[Al]ZSM-5. Reaction conditions:
T = 673 K, P = 40 bar, and WHSV = 375–1500 gC5 gcat hꢀ1
.
ꢀ1
conversion did not change above 30 bar, product selectivity high temperatures as seen in Fig. 4. As reaction temperature
continued to change with increasing pressure. Elevated pressures increases, cracking rates of the C6+ fraction become greater
promote oligomerization of olefins,33–35 a reaction also observed than oligomerization rates, leading to an increase in the production
here. Increasing pressure decreased light olefin production and of propane. Carbon selectivity of the light olefins also increased
increased formation of C6+ compounds. Although elevated with increasing WHSV. With less time to react, a greater percentage
pressures promote oligomerization, the larger compounds in of light olefins formed through monomolecular cracking of
the C6+ fraction eventually become more reactive and crack at pentane survived without undergoing further bimolecular reactions.
Fig. 7 Selectivity of products within the lights fraction at various temperatures (left), pressures (middle), and WHSV (right). Reaction conditions: T = 633–
723 K, P = 10–60 bar, and WHSV = 375–1500 gC5 gcat hꢀ1
.
ꢀ1
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016
New J. Chem.

View Article Online
Paper
NJC
Fig. 8 Simplified reaction network demonstrating the production of
propane and butane.
From the observed trends in carbon selectivity of the light olefins,
a simplified reaction network can be proposed to illustrate the
formation of the major products: propane and butane.
Fig. 8 displays a simplified reaction network consistent with
the observed formation of propane and butane. After protolytic
cracking of n-pentane, propene and ethane are formed and
the propene then can react with another pentane via hydride
transfer. This forms one of the major products, propane. The
pentene can crack via beta scission to form another molecule of
propene and ethene. Any ethene that is formed can dimerize to
form butene. The butene can react with another pentane via
hydride transfer yielding the second major product, butane.
Through oligomerization, compounds heavier than pentane can
form and subsequently crack to form lighter products or cyclize
and aromatize. In reality, a more complex reaction network of
monomolecular and bimolecular reactions exists, as evidenced
by the product distribution and trends in activation energy.
If monomolecular cracking were the dominant reaction channel,
as pressure increases, the apparent activation energy should
also increase and approach the intrinsic activation energy. This
trend occurs because saturation kinetics are reached at elevated
pressures, reducing the effect of adsorption enthalpy on the
apparent activation energy.11 As seen in Fig. 9, the apparent
activation energy based on consumption of n-pentane decreases
with increasing pressure, which is opposite of the expected
trend for monomolecular cracking. Furthermore, Luo et al.
reported the intrinsic activation energy of n-hexane cracking
on ZSM-5 to be 170 kJ molꢀ1, while Gounder et al. reported the
intrinsic activation energy of propane cracking on ZSM-5 to be
Fig. 9 Activation energies at 10 bar (square), 20 bar (circle), and 40 bar
(triangle). Reaction conditions: T = 633–673 K, P = 10–40 bar, and
ꢀ1
WHSV = 1120 gC5 gcat hꢀ1
.
Luo et al. also investigated the product selectivity for the
cracking of n-hexane on ZSM-5.12 With increasing conversion
under isothermal conditions, an increase in selectivity to higher
molecular weight species was observed. For the conversion of
n-pentane on ZSM-5, increasing conversion under isothermal
conditions did not result in any significant change in selectivity
to higher molecular weight species. However, there were two
trends in product selectivity that were similar between the
conversion of pentane and hexane on ZSM-5. First, the major
products of hexane conversion were butanes and pentanes,
analogous to propane and butanes for pentane conversion.
Second, increasing pressure caused a decrease in selectivity to light
olefins for the conversion of both pentane and hexane on ZSM-5.
The decrease in activation energy with increasing pressure is
evidence of a shift from a higher activation energy reaction
channel to a lower activation energy reaction channel. While
the conversion of pentane and hexane on ZSM-5 have similar
trends in product selectivity with changing pressure, the differences
in apparent activation energy suggest the conversion occurs via
alternative reaction pathways.
204 kJ molꢀ1 11,15
Based on these observations, it is expected
.
that the activation energy above the saturation pressure of
5. Conclusions
n-pentane (430 bar) to be near those of propane and hexane.15
At 40 bar, the apparent activation energy for the consumption of The high selectivity (470%) to propane and butane, along
n-pentane was 86 kJ molꢀ1, which was much less than expected with the observed changes in the selectivity to lights and C6+
for monomolecular cracking, but consistent with the results compounds, indicate that bimolecular reactions, such as
obtained using other zeolite frameworks as solid acid catalysts. hydride transfer and alkylation, control product distribution.
Luo et al. recently investigated the high pressure cracking of While the product distribution from the high pressure conversion
n-hexane on H-USY, H-Beta, and H-Mordenite. In the work, of pentane resulted in an endothermic process, hydride transfer
the apparent activation energy for cracking on zeolite beta reactions led to the transformation of high energy olefins into
(63 kJ molꢀ1) and USY (55 kJ molꢀ1) did not change with lower energy paraffins and aromatics, resulting in a decrease
pressure, while the apparent activation energy on mordenite of the process endothermicity from a target of 1.1 MJ kgꢀ1 of
decreased from 77 kJ molꢀ1 at 1 bar to 66 kJ molꢀ1 at 137 bar.12 n-pentane converted to an estimated 0.6 MJ kgꢀ1. Hydride
The activation energies observed from the cracking of hexane transfer occurs readily on H-[Al]ZSM-5 and other zeolites, and
on USY, zeolite beta, and mordenite are consistent with those an alternative catalyst that suppresses these reactions should
for the cracking of n-pentane on ZSM-5, but differ from the improve selectivity to light olefins, which will increase cooling
cracking of n-hexane on ZSM-5.
capacity of the endothermic fuel.
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016

View Article Online
NJC
Paper
17 T. F. Narbeshuber, H. Vinek and J. A. Lercher, J. Catal., 1995,
157, 388–395.
18 A. Janda and A. T. Bell, J. Am. Chem. Soc., 2013, 135,
19193–19207.
19 A. Bhan, R. Gounder, J. Macht and E. Iglesia, J. Catal., 2008,
253, 221–224.
Acknowledgements
The authors would like to acknowledge the Air Force Office of
Scientific Research for funding (AFOSR 400487-13105-1200)
and also Dr Michael Berman as the technical monitor.
20 B. Xu, C. Sievers, S. B. Hong, R. Prins and J. A. van Bokho-
ven, J. Catal., 2006, 244, 163–168.
References
1 H. Lander and A. C. Nixon, J. Aircr., 1971, 8, 200–207.
2 D. G. Norton, R. J. Perry, J. Osaheni, P. Pastecki, P. Glaser
21 M. Derewinski and F. Fajula, Appl. Catal., A, 1994, 108,
53–61.
and A. B. Mhadeshwar, US Pat., US 2012/0305712 A1, 2012. 22 V. B. Kazansky, Catal. Today, 1999, 51, 419–434.
3 T. J. Bruno and J. A. Widegren, Energy Fuels, 2009, 23, 23 A. Corma, P. J. Miguel and A. V. Orchilles, J. Catal., 1994,
5523–5528.
4 H. S. Chung, G. S. H. Chen, R. a. Kremer, J. R. Boulton and 24 T. F. Narbeshuber, A. Brait, K. Seshan and J. A. Lercher,
G. W. Burdette, Energy Fuels, 1999, 13, 641–649. J. Catal., 1997, 136, 127–136.
5 N. Gascoin, G. Abraham and P. Gillard, J. Anal. Appl. 25 J. H. Yun and R. F. Lobo, J. Catal., 2014, 312, 263–270.
145, 171–180.
Pyrolysis, 2010, 89, 294–306.
6 J. Kim, D. H. Hyeon, S. H. Park, B. H. Chun, B. H. Jeong,
J. S. Han and S. H. Kim, Catal. Today, 2014, 232, 63–68.
26 J. H. Yun and R. F. Lobo, Catal. Sci. Technol., 2015, 5,
264–273.
27 J. Kim, S. H. Park, B. H. Chun, B. H. Jeong, J. S. Han and
S. H. Kim, Catal. Today, 2012, 185, 47–53.
¨
7 M. Stocker, Microporous Mesoporous Mater., 2005, 82,
257–292.
28 Y. Wang, X. Xian, X. Hou, X. Zhang, L. Wang and G. Liu,
J. Anal. Appl. Pyrolysis, 2014, 113, 133–136.
8 A. Corma, Chem. Rev., 1995, 95, 559–614.
9 Z. Dardas, M. G. Suer, Y. H. Ma and W. R. Moser, J. Catal., 29 A. Farshi and H. R. Abri, Pet. Sci. Technol., 2012, 30,
1996, 159, 204–211. 1285–1295.
10 X. Xian, G. Liu, X. Zhang, L. Wang and Z. Mi, Chem. Eng. 30 E. V. Anslyn and D. A. Dougherty, Modern Physical Organic
Sci., 2010, 65, 5588–5604.
Chemistry, University Science Books, 2006.
11 J. Luo and R. J. Gorte, Catal. Lett., 2013, 143, 313–316.
31 D. J. Rosenthal and A. S. Teja, AIChE J., 1989, 35, 1829–1834.
´
´
12 J. Luo, B. V. Bhaskar, Y. H. Yeh and R. J. Gorte, Appl. Catal., 32 J. C. Groen, J. A. Moulijn and J. Perez-Ramırez, Ind. Eng.
A, 2014, 478, 228–233. Chem. Res., 2007, 46, 4193–4201.
13 W. Ning, P. Yu and Z. Jin, Proc. Inst. Mech. Eng., Part G, 2012, 33 R. Quann, L. Green, S. A. Tabak and F. J. Krambeck, Ind.
227, 1780–1794. Eng. Chem. Res., 1988, 27, 565–570.
14 W. O. Haag and R. M. Dessau, Duality of Mechanism for Acid- 34 B. Chiche, E. Sauvage, F. Di Renzo, I. I. Ivanova and
Catalyzed Paraffin Cracking, Princeton, NJ, 1985. F. Fajula, J. Mol. Catal. A: Chem., 1998, 134, 145–157.
15 R. Gounder and E. Iglesia, J. Am. Chem. Soc., 2009, 131, 35 C. Bertrand-Drira, X. Cheng, T. Cacciaguerra, P. Trens,
1958–1971.
G. Melinte, O. Ersen, D. Minoux, A. Finiels, F. Fajula and
C. Gerardin, Microporous Mesoporous Mater., 2015, 213,
142–149.
16 S. M. Babitz, B. a. Williams, J. T. Miller, R. Q. Snurr,
W. O. Haag and H. Kung, Appl. Catal., A, 1999, 179, 71–86.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016
New J. Chem.