Direct synthesis of a high-density aviation fuel using a polycarbonate

Article abstract of DOI:10.1039/d0gc03426f

High-density cyclic hydrocarbons were first synthesized with high carbon yields by a one-pot transfer hydrodeoxygenation of a polycarbonate (PC) using isopropanol as the solvent and hydrogen donor at the same time. RANEY nickel was found to be an effective catalyst for the conversion of the PC in isopropanol. Over it, the pure PC pellet was completely converted to a mixture of C₆-C₁₅oxygenates, aromatics and cycloalkanes after the reaction was carried out at 463 K for 1 h. The catalytic performance of RANEY Ni was further improved after the introduction of solid acids as co-catalysts. Among the investigated solid acids, ultrastable Y (USY), a commercial acidic zeolite, demonstrated the best promotion effect, which can be explained by its larger pore size and suitable acidity. Under the optimized conditions, an ～75% carbon yield of C₆-C₁₅cyclic hydrocarbons was achieved from the one-pot transfer hydrodeoxygenation of a chopped DVD disk under the co-catalysis of RANEY Ni and USY. According to our measurement, the C₆-C₁₅cyclic hydrocarbon mixture as obtained has a high density (0.94 g mL^?1), good volumetric net heat of combustion (NHOC) (41.5 MJ L^?1) and low freezing point (202 K-188 K). In real applications, it can be used as a potential substitute for currently used high-density aviation fuels.

Full text of DOI:10.1039/d0gc03426f

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Direct synthesis of a high-density aviation fuel
using a polycarbonate†
Cite this: Green Chem., 2021, 23, 912
a,b
a,c
a
c
a,d
Lulin Wang, Fengan Han, Guangyi Li, Min Zheng, Aiqin Wang,
a
a,e
a
a,d
Xiaodong Wang,
Tao Zhang, Yu Cong* and Ning Li
*
High-density cyclic hydrocarbons were first synthesized with high carbon yields by a one-pot transfer
hydrodeoxygenation of a polycarbonate (PC) using isopropanol as the solvent and hydrogen donor at the
same time. RANEY® nickel was found to be an effective catalyst for the conversion of the PC in isopro-
6
panol. Over it, the pure PC pellet was completely converted to a mixture of C –C15 oxygenates, aromatics
and cycloalkanes after the reaction was carried out at 463 K for 1 h. The catalytic performance of
RANEY® Ni was further improved after the introduction of solid acids as co-catalysts. Among the investi-
gated solid acids, ultrastable Y (USY), a commercial acidic zeolite, demonstrated the best promotion
effect, which can be explained by its larger pore size and suitable acidity. Under the optimized conditions,
an ∼75% carbon yield of C
ygenation of a chopped DVD disk under the co-catalysis of RANEY® Ni and USY. According to our
–C15 cyclic hydrocarbon mixture as obtained has a high density (0.94 g mL−1), good
measurement, the C
6
–C15 cyclic hydrocarbons was achieved from the one-pot transfer hydrodeox-
Received 12th October 2020,
Accepted 15th December 2020
6
DOI: 10.1039/d0gc03426f
volumetric net heat of combustion (NHOC) (41.5 MJ L−1) and low freezing point (202 K–188 K). In real
rsc.li/greenchem
applications, it can be used as a potential substitute for currently used high-density aviation fuels.
During the past years, a series of methods (including pyrol-
Introduction
4
5
3,6
7
8
ysis, hydrolysis, alcoholysis,
glycolysis and aminolysis )
Due to the increasing social concerns about energy and have been applied for PC waste recycling. Transfer hydrodeoxy-
environmental problems, the recycling of waste plastic as a genation is a technology that has been widely used for the pro-
9
10,11
feedstock to produce fuels and chemicals has drawn tremen- duction of fuels and chemicals.
Compared with the con-
1
dous attention. Polycarbonates (PCs) are a type of hard plastic ventional hydrodeoxygenation that uses hydrogen as the reac-
which have been widely used in construction, electric, automo- tant, transfer hydrodeoxygenation is relatively safe and easier
tive, commodity and medical industries. The annual global to handle. To the best of our knowledge, there is no report
2
12
polycarbonate productivity was estimated to be ∼6 million about the application of transfer hydrodeoxygenation in the
3
tons. Furthermore, the demand for PCs is continuously treatment of PC waste.
increasing in recent years. This will lead to plenty of PC waste
High-density cyclic hydrocarbons are the major com-
in the near future. To fulfil the need for sustainable develop- ponents of nontoxic propellants (such as RP-1, RJ-4 and JP-10),
1
3,14
ment, it is necessary to develop some environmentally friendly which are widely utilized for rockets and missiles.
Due to
and highly efficient technologies for the recycling of PCs. their relatively high volumetric heat values, the aerocrafts that
use cyclic hydrocarbons as fuels can fly further or carry more
than those powered by conventional aviation fuels. This
a
CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian
Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road,
Dalian 116023, China. E-mail: lining@dicp.ac.cn, ycong@dicp.ac.cn
characteristic can help rockets save more space (or weight) for
electronic equipment, astronauts and other components.
Moreover, this characteristic can also be used to decrease the
volume or radar reflection area and make missiles more agile
and difficult to be detected by the opposing side. Currently,
RP-1 fuel and its analogues are obtained from the refinement
of petroleum in few special oil fields. RJ-4 and JP-10 fuels are
produced with cyclopentadiene or methyl-cyclopentadiene,
which are obtained in very low yields from fossil energies (for
example, cyclopentadiene is produced from coal tar in a yield
of 10–20 g per ton or by steam cracking of naphtha in a yield
b
University of Chinese Academy of Sciences, 19 A Yuquan Road, Shijingshan District,
Beijing 100049, China
c
Department of Chemical Physics, School of Chemistry and Materials Science,
University of Science and Technology of China, Hefei 230026, China
d
Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian
1
e
16023, China
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese
Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
d0gc03426f
912 | Green Chem., 2021, 23, 912–919
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1
5
of 14 kg per ton). The yield of methyl-cyclopentadiene is
The acid amounts and acid strengths of the solid acids were
1
6
even lower . As a result, these fuels are more expensive than characterized by NH -chemisorption and NH -TPD, respect-
3
3
pure PCs. To fulfil the need for real applications, the explora- ively. Before each test, 0.1 g sample was placed in a quartz
tion of a new route for the synthesis of high-density aviation reactor, pre-treated under a He flow at 773 K for 0.5 h and
fuels with abundant resources is highly expected. In this work, cooled down under a He flow to 373 K. After the stabilization
a mixture of jet fuel range C –C15 cycloalkanes and aromatics of the baseline, pulses of NH (1 mL) were dosed in the reactor
6 3
was first synthesized by the RANEY® Ni and USY co-catalysed until saturation. The number of acid sites on the catalyst was
one-pot transfer hydrodeoxygenation of PCs using isopropanol calculated using the adsorptions of NH3 during the test.
3
as the hydrogen donor and solvent at the same time. This Subsequently, the desorption of NH was conducted under a
−
1
work offers another potential way for the reuse of PC waste.
He flow from 373 K to 1073 K at a heating rate of 10 K min .
The desorbed NH3 molecules were detected using an
OminiStar mass spectrometry (MS) system equipped with the
software Quadstar.
Experimental
Materials and methods
Activity tests
Transfer hydrodeoxygenation of PCs. The transfer hydro-
deoxygenation of pure PC pellets was carried out in a 100 mL
stainless steel batch reactor (Parr 4848) under an argon atmo-
sphere. For each test, 2 g of pure PC pellets and 45 mL of
alcohol were used. After purging the reactor three times with
argon, the mixture was stirred at 443 K–523 K for 1 h.
One-pot transfer hydrodeoxygenation. The one-pot transfer
hydrodeoxygenation of pure PC pellets (or the chopped DVD
disk) was carried out in a 100 mL stainless steel batch reactor
In this work, pure poly[2,2-bis(4-hydroxyphenyl)propane car-
bonate] (PC) pellets (product number: 1609T-11, 2 mm length
×
2 mm diameter) from Luxi Chemical Group Co., Ltd were
used to simulate the PC waste. According to the analysis using
a Waters 1525 & Agilent PL-GPC220 gel permeation chromato-
graphy (GPC) system and an X-5 micro melting point apparatus
(Beijing Tech Instrument Co. Ltd), the average molecular
weight and melting point of the pure PC pellets were found to
be 36 226 and 456 K–461 K, respectively. Based on thermo-
gravimetric-differential scanning calorimetry (TG-DSC) (see
Fig. S1 in the ESI†), the decomposition temperature of the PC
was found to be 718 K. To check the possibility of real appli-
cation, we also used a chopped DVD disk (a representative of
real PC waste) as the substrate for the activity test. Before the
test, the DVD disk was cut into 2 mm × 2 mm pieces with scis-
sors. RANEY® Ni, RANEY® Fe, RANEY® Co and RANEY® Cu
were bought from Dalian Tongyong Chemical Co., Ltd.
Methanol, isopropanol, cyclohexanol, phenol and ethylben-
zene were purchased from Damao Chemical Reagent Factory.
(
Parr 4848) under an argon atmosphere. For each test, 2 g of
pure PC pellets (or the chopped DVD disk) and 45 mL of iso-
propanol were used. After purging the reactor three times with
argon, the mixture was stirred at 463 K for 1 h, and then
quenched to room temperature with cold water. Subsequently,
0.2 g of solid acid was added into the reaction system. After
purging the reactor three times with argon, the reaction was
carried out at 463 K for another 1–5 h.
Based on our observation, the operating pressures for the
transfer hydrodeoxygenation (or one-pot transfer hydrodeoxy-
genation) were around 3 MPa under the investigated con-
ditions. After the activity tests, the reactor was quenched to
room temperature with cold water. The products were analyzed
using an Agilent 7890A Gas Chromatography (GC) system,
which was equipped with an HP-5 capillary column (30 m ×
2
-Butanol, ethanol and Al O were purchased from Sinopharm
2 3
Chemical Reagent Co., Ltd. Diphenyl carbonate and
n-dodecane (used as the internal standard in this work) were
obtained from Aladdin Chemical Reagent Co., Ltd. The
H-ZSM-5 and USY zeolites were purchased from Nankai
University. According to the information from the supplier, the
SiO /Al O molar ratios of the H-ZSM-5 and USY zeolites were
0.32 mm × 0.32 μm) and a flame ionization detector (FID) and
an Agilent 7890B-5977A gas chromatography-mass spec-
trometry (GC-MS) system which was equipped with an HP-5
capillary column. To minimize the vaporization of C cyclic
6
2
2 3
2
5 and 11, respectively.
hydrocarbons, the products were analysed within 1 h after they
were taken out from the batch reactor.
Characterization
The specific BET surface areas and pore sizes of the solid acids
The PC conversions and the carbon yields of oxygenates
used as co-catalysts in the one-pot transfer hydrodeoxygena- and cyclic hydrocarbons from the transfer hydrodeoxygenation
tion were determined by N -physisorption at 77 K using a (or one-pot transfer hydrodeoxygenation) were calculated
2
Micromeritics ASAP 2010 apparatus.
according to the following equations:
Conversion of PC ð% Þ ¼ ðinitial weight of pure PC pelletsðor chopped DVD diskÞ ꢀ the weight of residual PC pellets ðor residual
chopped DVD diskÞÞ=ðinitial weight of pure PC pellets ðor chopped DVD diskÞÞ ꢁ 100%:
Carbonyield of oxygenates or cyclic hydrocarbons ð%Þ ¼ ðmole of carbon atoms in the oxygenates or cyclic hydrocarbons generated
during the activity testÞ=ðtheoretical mole of carbon atoms in the PC ðor chopped DVD diskÞ used in the activity testÞ ꢁ 100%:
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Isopropanol and acetone have low boiling points (355.5 K catalyst. These products were generated from the alcoholysis of
and 329.4 K). After their removal of from the one-pot transfer PC. In the presence of the RANEY® Ni catalyst, a series of C6–
hydrodeoxygenation product of the chopped DVD disk by
C15 oxygenates (including cycloalcohols, diols and phenols)
vacuum distillation, a mixture of C –C15 cyclic hydrocarbons and cyclic hydrocarbons (including cycloalkanes and aro-
6
was obtained. The boiling point distribution of the cyclic matics) were obtained as the main products. The reaction
hydrocarbon mixture was analyzed by simulated distillation pathways for the generation of different products were pro-
using the ASTM D2887 method. The viscosity, density, freezing posed as shown in Scheme 1. According to Table S2 in the
point and net heat of combustion (NHOC) of the C –C cyclic ESI,† the C –C cyclic hydrocarbons obtained in this work
6
15
6
15
hydrocarbon mixture were measured using a rotational rhe- have high densities. In real applications, the cyclic hydro-
ometer (Physica MCR 301), a DMA 4500 M digital densi- carbon mixture as obtained can be potentially used as a high-
tometer, a NETZSCH DSC 200F3 and a TP638 calorimeter density aviation fuel. Meanwhile, we also analyzed the gas
(
ASTM D240-02), respectively.
phase products from the transfer hydrodeoxygenation of PC.
Based on the GC chromatogram shown in Fig. S6 in the ESI,†
hydrogen, methane and carbon dioxide were detected.
Hydrogen was produced from the dehydrogenation of isopro-
panol, carbon dioxide was generated from the hydrolysis of
Results and discussion
First of all, a series of RANEY metals were found to be effective PC, while methane was generated from the hydrogenolysis of
catalysts for the degradation of pure PC pellets (denoted as PC the carbonate group in PC.
in the following text) in isopropanol. As we can see from Fig. 1,
isopropanol has low reactivity for the degradation of PC. Under effects of different alcohols on its catalytic performance for
the investigated conditions, low PC conversion (or C –C
the transfer hydrodeoxygenation of PC (see Fig. 2). Among
Taking RANEY® Ni as an example, we investigated the
6
15
oxygenate yield) was obtained. It is interesting that the the investigated alcohols, isopropanol exhibited the highest
presence of RANEY metal significantly promoted the degra- reactivity for the degradation of PC. The reactivities of
dation of PC. Over them, evidently higher PC conversions were different alcohols decreased in the order of isopropanol >
achieved under the same reaction conditions. For example, the 2-butanol > methanol > ethanol. From the analysis of pro-
PC was completely converted over the RANEY® Ni catalyst after ducts (see Fig. S7 in the ESI†), a strong dependence was
the reaction was carried out at 463 K for 1 h. Even over the noticed between the product distribution and the type of
RANEY® Co, RANEY® Cu and RANEY® Fe catalysts (which are alcohol used in the reaction. When the degradation was
less effective than RANEY® Ni under the investigated con- carried out in primary alcohols (such as methanol and
ditions), good results were achieved with further increment of ethanol), bisphenol A and carbonates from the alcoholysis of
the catalyst dosage (see Fig. 1, Table S1 and Fig. S2–S4 in the PC were obtained. In contrast, alcohols, diols and hydro-
ESI†).
carbons were obtained when the reaction was conducted in
Based on our analysis of liquid phase products (see Fig. S5 secondary alcohols (such as isopropanol and 2-butanol).
in the ESI†), bisphenol A and 4-(2-(4-hydroxyphenyl)propan-2- According to the literature on the transfer hydrogenation of
1
0
yl)phenyl isopropyl carbonate were obtained as the pro- phenol, this result can be explained by the adsorption
ducts when the reaction was carried out in the absence of a mode of the intermediate. When the reaction was carried out
in primary alcohols, the alkoxy groups generated by the clea-
vage of the O–H bond may block the metal surface and make
it inactive for the subsequent transfer hydrogenation (or
transfer hydrodeoxygenation). In contrast, the Ni catalyst was
unblocked in isopropanol (or 2-butanol) because the O–H
and α-C–H bonds were cleaved at the same time. This is the
reason why transfer hydrodeoxygenation can take place in
secondary alcohols. Therefore, we concentrated on the degra-
dation of PC over RANEY® Ni using isopropanol as a hydro-
gen donor in the following research.
The influences of the reaction time and temperature on the
catalytic performance of RANEY® Ni were also studied. As we
can see from Fig. 3, the total carbon yield of cyclic hydro-
carbons over the RANEY® Ni catalyst firstly increased with the
reaction time and then stabilized after 1 h. Further increment
of the reaction time only led to the increase of the cycloalkane
carbon yield and the decrease of the aromatic carbon yield at
6
Fig. 1 Conversions of PC and the carbon yields of C –C15 oxygenates
and cyclic hydrocarbons over different RANEY metal catalysts. Reaction
conditions: 463 K, 1 h; 2 g of pure PC pellets, 0.4 g of catalyst and
the same time. This result indicates that at least one part of
cycloalkanes in the product may be generated by the transfer
hydrogenation of C –C aromatics.
45 mL of isopropanol were used in each test.
6
15
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Scheme 1 Reaction pathways for the generation of different products from the degradation of PC in isopropanol.
6
Fig. 2 Conversions of PC and the carbon yields of C –C15 oxygenates
Fig. 3 Conversions of PC and the carbon yields of C
6
–C15 oxygenates
and cyclic hydrocarbons over the RANEY® Ni catalyst. Reaction con-
ditions: 463 K, 1 h; 2 g of pure PC pellets, 0.4 g of RANEY® Ni catalyst
and 45 mL of alcohol were used in each test.
and cyclic hydrocarbons over the RANEY® Ni catalyst as a function of
the reaction time. Reaction conditions: 463 K; 2 g of pure PC pellets,
0
.4 g of RANEY® Ni and 45 mL of isopropanol were used in each test.
From Fig. 4a, it is noticed that a higher reaction tempera- dicyclic hydrocarbons. Therefore, we fixed the reaction temp-
ture is favorable for the conversion of PC into cyclic hydro- erature at 463 K in the following research.
carbons (especially cycloalkanes). This can be comprehended
To get an idea about how to improve the performance of
because the dehydrogenation of isopropanol is an endother- the catalyst, we explored the transfer hydrodeoxygenation (or
mic reaction. However, the beneficial effect resulting from transfer hydrogenation) of a series of model compounds over
raising the reaction temperature is limited. After we increased the RANEY® Ni catalyst. First, we studied the reaction of
the reaction temperature from 463 K to 523 K, the total carbon diphenyl carbonate, a good model compound which has a
yield of C –C cyclic hydrocarbons only increased from 31.0% chemical structure similar to PC. Under the standard reaction
6
15
to 44.7%. Furthermore, a too high reaction temperature also conditions as we used for pure PC pellets, cyclohexane and
led to hydrocracking, which can be indicated by the higher cyclohexanol were obtained as the products (see Fig. 5 and
molar ratio of C and C products to C products (see Fig. 4b Fig. S9 in the ESI†). From Scheme 2, we can see that cyclohexa-
6
9
15
and Fig. S8 in the ESI†). As we can see from Table S2 in the nol was generated from the transfer hydrogenation of phenol
ESI,† the monocyclic hydrocarbons generated by hydrocrack- (i.e. the alcoholysis product of diphenyl carbonate). As for the
ing at a high temperature have lower densities than those of generation of cyclohexane, there are two pathways: one is the
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Fig. 5 Carbon yields of different products from the transfer hydrodeox-
ygenation of model compounds over the RANEY® Ni catalyst. Reaction
conditions: 463 K, 1 h; 8 mmol of the model compound and 45 mL of
isopropanol were used in each test.
Scheme 2 Reaction pathways for the generation of cyclohexane and
cyclohexanol from the transfer hydrodeoxygenation of diphenyl
carbonate.
6
Fig. 4 Conversions of PC, the carbon yields of C –C15 oxygenates and
cyclic hydrocarbons over the RANEY® Ni catalyst (a) and the molar ratio
of C and C /C15 compounds in the transfer hydrodeoxygenation
6
9
product (b) as a function of the reaction temperature. Reaction con-
ditions: 1 h; 2 g of pure PC pellets, 0.4 g of RANEY® Ni and 45 mL of iso-
propanol were used in each test.
over RANEY® Ni, while the transfer hydrodeoxygenation (or C–O
cleavage) of phenol or cyclohexanol is difficult to occur over
RANEY® Ni under the investigated conditions. The increase of
hydrogenation of benzene from the hydrogenolysis of diphenyl the reaction temperature is beneficial for the dehydrogenation
carbonate (by the direct cleavage of the C–O bond between the of isopropanol and the hydrogenolysis of the C–O bond over
benzene ring and ester group) and the other is the transfer RANEY® Ni. As a result, a higher total carbon yield of hydro-
hydrodeoxygenation of phenol or cyclohexanol generated from carbons was obtained with the increment of the reaction temp-
the alcoholysis route. To check which pathway is correct, we erature. However, the increment of the reaction temperature
studied the reaction of phenol and cyclohexanol under the also promotes the hydrogenolysis of the C–C bond (or the pro-
standard conditions. It was noticed that the conversion of duction of monocyclic hydrocarbons) over the RANEY® Ni
phenol (or cyclohexanol) to cyclohexane was very difficult. Low catalyst. Moreover, the transfer hydrogenolysis and alcoholysis
yields of cyclohexane were obtained. When we used phenol of carbonate take place in parallel under the investigated con-
and ethylbenzene as the substrates, cyclohexanol and ethyl- ditions. The generation of cyclic hydrocarbons from the trans-
cyclohexane were identified as the major products, respectively. fer hydrodeoxygenation of phenols (or cycloalcohols) is
Therefore, we believe that the cyclohexane from the transfer difficult under the investigated conditions. That is the reason
hydrodeoxygenation of diphenyl carbonate was mainly gener- why the beneficial effect of the high reaction temperature is
ated by the direct cleavage of the C–O bond between the limited.
benzene ring and ester group.
As a solution to this problem, we developed a one-pot
Based on the mechanism research about the transfer hydro- process that contains two steps. In the first step, the PC was
deoxygenation of diphenyl carbonate, we can see that the degraded in isopropanol using RANEY® Ni as the catalyst.
transfer hydrogenation of the benzene ring group in aromatics After reacting at 463 K for 1 h, the reaction system was cooled
(or phenol) to cycloalkane (or cyclohexanol) is an easy reaction down to room temperature. Subsequently, a solid acid was
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Table 1 Specific surface areas (SBET), acid amounts and pore sizes of
the solid acids used in this work
a
b
S
BET
Acid amount
Solid acid (m g−1) (mmol g
2
−1
)
Pore size (nm)
Ref.
c
USY
H-ZSM-5
657
328
204
0.880
0.975
0.430
0.74 × 0.74
17
17
—
c
0.51 × 0.55 0.53 × 0.56
a
Al
2
O
3
8.9
a
b
Measured by N
2
-physisorption. Measured by NH
3
-chemisorption.
c
The values are reported in the literature.
According to the characterization results (see Fig. 7 and
Table 1), the excellent promotion effect of USY can be
explained by two reasons: (1) larger pore size. This is because
the Y zeolite (IZA structure, FAU type) is characterized by large,
essentially spherical, internal cavities (supercages) linked tetra-
hedrally through pore openings of about 0.8 nm and defined
by rings of twelve oxygen atoms. As we know, the mass transfer
is very important for the liquid phase reaction at low tempera-
ture. This is the reason why USY has a better promotion effect
than that of H-ZSM-5. (2) Suitable acidity. As we can see from
6
Fig. 6 Conversions of PC and the carbon yields of C –C15 oxygenates
and cyclic hydrocarbons under the co-catalysis of RANEY® Ni and
different solid acids. Reaction conditions: 463 K, 1 h; 2 g of pure PC
pellets, 0.2 g of solid acid, 0.4 g of RANEY® Ni and 45 mL of isopropanol
were used in each test.
introduced into the reaction system, and the reaction was con-
ducted at 463 K for another 1 h. Fig. 6 illustrates the PC con-
versions and the carbon yields of C –C15 cyclic hydrocarbons
6
from the one-pot process under the co-catalysis of RANEY® Ni
and some often-used solid acids. As we expected, the presence
6
of solid acid increased the total carbon yield of C –C15 hydro-
the NH -TPD profiles of different solid acids (see Fig. 7), USY
3
2 3
has a higher acid strength than that of Al O . It is well known
that a strong acid is more active than a weak acid for dehydra-
tion. Dehydration followed by hydrogenation is an important
18
pathway for hydrodeoxygenation. Due to these two reasons,
2 3
USY has a better promotion effect than that of Al O .
carbons from the transfer hydrodeoxygenation of PC. Among
the investigated solid acids, USY demonstrated the best pro-
motion effect. In the presence of USY, the products shifted
from oxygenates to cyclic hydrocarbons (see Fig. 7 and Fig. S10
and S11 in the ESI†).
The effect of the reaction time on the catalytic performance
of RANEY® Ni + USY was investigated as well (Fig. 8). With the
extension of the reaction time of the second step to 3 h, an
∼80% total carbon yield of cyclic hydrocarbons was achieved
under the co-catalysis of RANEY® Ni and USY.
To fulfil the need for real application, we also studied the
catalytic performance of the RANEY® Ni + USY catalyst for the
production of cyclic hydrocarbons with the chopped DVD disk
6
Fig. 8 Conversions of PC and the carbon yield of C –C15 oxides and
cyclic hydrocarbons as a function of the reaction time. Reaction con-
ditions: 463 K; 2 g of pure PC pellets, 0.2 g of USY, 0.4 g of RANEY® Ni
and 45 mL of isopropanol were used in each test.
3 2 3
Fig. 7 NH -TPD profiles of USY, H-ZSM-5 and Al O .
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Table 2 Properties of the currently used classic high-density aviation substitute for the currently used high-density aviation fuels.
fuels and the cyclic hydrocarbon mixture obtained in this work
This work offers a new option for the recycling of PC waste.
DVD disk
derived fuel
1
9
14
14
Property
RP-1
RJ-4
JP-10
Conflicts of interest
Density (g mL−
1
)
0.81
225
0.927
<233
—
39.0
36.2
0.936
194
3.2
42.1
39.4
0.939
202–188
18.5
44.2
41.5
b
Freezing point (K)
There are no conflicts to declare.
a
Viscosity (mPa s) (at 298 K) 2.4
−
1
NHOC (MJ kg
)
43.9
35.6
−
1
Volumetric NHOC (MJ L
)
a
b
Acknowledgements
Not available. The boiling point distribution and DSC profile of the
cyclic hydrocarbon mixture are shown in Fig. S12 and S13 in the ESI.†
This work was supported by the National Natural Science
Foundation of China (no. 21776273; 21721004; 21690082), the
DNL Cooperation Fund, CAS (DNL180301), DICP (Grant: DICP
I201944), the Strategic Priority Research Program of the
Chinese Academy of Sciences (XDB17020100, XDA 21060200),
and the National Key Projects for Fundamental Research and
Development of China (2016YFA0202801).
which can be considered as a representative of real PC waste.
As we expected, a high total carbon yield (75%) of C –C15
6
cyclic hydrocarbons was achieved under the optimized con-
ditions for pure PC pellets. Based on this result, it is estimated
6
that 3.68 tons of C –C15 cyclic hydrocarbons can be produced
if 6 million tons of PC waste was converted by this technology.
As we know, acetone and isopropanol have low boiling
points (329.4 K and 355.5 K). After their removal from the
product by vacuum distillation, we measured the properties of
the cyclic hydrocarbon mixture by a series of technologies.
From the results presented in Table 2, we can see that the
cyclic hydrocarbon mixture obtained from the one-pot transfer
hydrodeoxygenation of the chopped DVD disk has better pro-
perties than those of RP-1 and RJ-4. Its density, volumetric
heat value and freezing point are comparable to those of JP-10,
the most successfully used high-density aviation fuel. The only
disadvantage of the cyclic hydrocarbon mixture is its relatively
high viscosity. In real applications, this problem can be solved
by blending it with current bio-jet fuels (i.e. mixtures of
biomass derived low-freezing point synthetic paraffinic kero-
senes), which can make the process even greener. As we have
mentioned previously in the Introduction, JP-10 fuel has a
much higher price than that of pure PC (∼7000 USD per ton
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A high-density cyclic hydrocarbon aviation fuel was first syn-
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deoxygenation of PC. RANEY® Ni, a commercial metal catalyst,
was found to be effective for the degradation of PC. The pro-
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6
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