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High-pressure thermal decomposition of tetrahydrotricyclopentadiene (THTCPD) and binary high-density hydrocarbon fuels of JP-10/THTCPD in tubular flowing reactor Xueke Jia, Baoman Guo, Baitang Jin, Xiangwen Zhang, Kai Jing, and Guozhu Liu Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b01128 • Publication Date (Web): 06 Jul 2017 Downloaded from http://pubs.acs.org on July 19, 2017

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High-pressure thermal decomposition of tetrahydrotricyclopentadiene (THTCPD) and binary high-density hydrocarbon fuels of JP-10/THTCPD in tubular flowing reactor Xueke Jiaa†, Baoman Guoa†, Baitang Jina, Xiangwen Zhanga,b, Kai Jinga, Guozhu Liua,b* (a. Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; b. Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin 300072, China) [†]These authors contributed equally to this work and should be considered as co-first authors. *Telephone/Fax: +86-22-85356099. E-mail: [email protected].

ABSTRACT: High-pressure thermal decomposition of tetrahydrotricyclopentadiene (THTCPD) and binary high-density hydrocarbon fuels of JP-10/THTCPD were investigated at 500-660 oC and 4.0 MPa in an electrically heated tubular reactor. The decomposition of THTCPD under high temperature, high pressure and low residence time were conducted to analyze their effects on the products. The experimental results of JP-10/THTCPD pyrolysis show that the THTCPD pyrolysis is greatly easier than the thermal cracking of JP-10, and the addition of JP-10 can significantly promote the THTCPD pyrolysis which is evidenced by the fact that THTCPD conversion increases up to 80% at 660 oC when blended with 50% JP-10. It may be ascribed to possible reason about the pathway and mechanism of JP-10/THTCPD pyrolysis is that the free radicals generated by the decomposition of THTCPD are help to promote the decomposition of JP-10 via H-abstraction reactions. Correspondingly, a large number of new free radicals generated from the JP-10 pyrolysis could also react with JP-10

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and THTCPD, which is helpful to promote the decomposition of THTCPD via H-abstraction reaction. Besides, the contribution of THTCPD to JP-10 could also explained by the chemical equilibrium point of view since JP-10 is one of the products of THTCPD. Meanwhile, the thermal isomerization pathways of THTCPD are also slightly changed in presence of JP-10. Our experiments could provide necessary information for the potential applications of THTCPD fuels in the advanced aircrafts. KEYWORDS:

Thermal

decomposition;

High-density

hydrocarbon

fuels;

JP-10/THTCPD; High pressure;


2

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1. INTRODUCTION Tetrahydrotricyclopentadiene (THTCPD) was a promising high-energy-density hydrocarbon fuel for the next generation aircrafts due to its high density (1.03 g/cm3) and high volumetric heat (43.3 MJ/L)

1-11

. However, its relative high viscosity

(ca.35.3 mPa·s at 20 oC) would lead to poor atomization and resist its ignition and combustion, which may limit its applications12, 13. To overcome this drawback, JP-10, a high density fuel having a similar structure to THTCPD but having a low viscosity (ca.3.56 mPa·s at 20 oC), was proposed to be blended with THTCPD to form a series of new binary high-density hydrocarbon fuels. For instance, a binary fuel of 30% JP-10 and 70% THTCPD still has a high density (1.0049 g/cm3 at 20 oC) above 1.0 g/cm3 but its viscosity (ca.14.1 mPa·s at 20 oC) drops by 50% which is good enough for the atomization. The binary fuel of JP-10/THTCPD was also suitable for the coolant for the thermal management of advanced aircrafts, which removes the waste heat from the engines, or other high-temperature components through the sensible and endothermic pyrolysis reactions. When the pyrolysis happens, the small molecules (hydrogen, ethylene, etc.) generated in the pyrolysis reactions may further help the atomization, ignition and combustion of fuel. 14-16 Previously, there was much work done on the JP-10 pyrolysis in both batch and flowing reactor under different pressure (from 25 torr to 5 MPa) in the literatures,17-22 but only a few papers reporting the thermal decomposition of THTCPD. Du et al. studied the decomposition of THTCPD at high temperatures from 700 oC to 880 oC under 0.1 MPa using a pyrolysis-gas chromatography/mass spectrometry, and reported the major products, the possible reaction mechanism, as well as the global reaction kinetics.23 Our group also studied the decomposition of THTCPD in the batch reactor at the temperature range of 385-425 oC under 4 MPa.24 We found different THTCPD isomers, and make a discussion about the kinetics, products distribution and possible reaction mechanism. However, there has been little work on the thermal decomposition of THTCPD under high temperature, high pressure and low residence time in the flowing system. The reaction conditions is in accordance 3


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with the working conditions of the advanced active cooling technology (3.5-7 MPa).25-27 In our previous work, it has been found that adding JP-10 into THTCPD has an obvious reduction on its viscosity, which can significantly improve its performance in engine. In order to comprehensively evaluate its performance in engine, we need to investigate the pyrolysis of the binary fuel of JP-10/THTCPD. However, a few studies have been reported on the thermal decomposition of the binary fuel of JP-10/THTCPD. Recently, some works on the pyrolysis of other binary Hydrocarbons were reported. Li et al.28 studied the thermal decomposition of JP-10/iso-octane mixtures in a stainless-steel tubular reactor at the temperature range of 883-963 K, and found that the addition of iso-octane can promote the decomposition of JP-10, which could be illustrated by the intermolecular H-abstraction reactions between the alkyl radicals and the H atoms of JP-10. Jiang et al.29 investigated the thermal decompositions of a serials of normal- and iso-dodecane mixtures with different iso/normal ratios in a tubular reactor at the temperature range of 550–680 oC under 4.0 MPa, and found that iso-dodecane has a promotion effect on the pyrolysis of the mixtures at an iso/normal ratio of 3/1. They believe that the decomposition conversion of the mixtures was closely related to the iso/normal ratio and the temperature. Yu and Eser30 studied the thermal cracking of several binary mixtures of jet fuel model compounds in a sealed tube reactors under supercritical condition, including n-dodecane/n-decane,

n-dodecane/n-tetradecane,

n-dodecane/

n-butylbenzene,

n-dodecane/n-butylcyclohexane, and n-butylbenzene/n-butylcyclohexane. Their data showed that n-tetradecane and n-butylcyclohexane could accelerate the cracking of n-dodecane while n-decane and n-butylbenzene may inhibit the cracking of n-dodecane. Zhou et al.31 studied the thermal cracking of cyclohexane and benzene binary mixtures under supercritical pressure, the result of which showed that the pyrolysis of benzene could be enhanced by adding cyclohexane, while the thermal decomposition of cyclohexane was reduced under the influence of benzene. From these studies, some possible blending effect of binary fuels (promotion or inhibition 4


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effect) can be observed. Therefore, it is necessary to get more insights into the thermal decomposition of THTCPD and the effect of the addition of JP-10, which could provide necessary information for the potential applications of those new high-density hydrocarbon fuels in the advanced aircrafts. In this paper, thermal decompositions of THTCPD and the binary fuels of JP-10/THTCPD with volume ratio of 3/7 and 1/1 were studied in a flowing tubular reactor under high pressure. The thermal decomposition of THTCPD was firstly performed at different flow rate, and the difference in the products in the batch and flowing reactor was discussed. And then thermal decompositions of JP-10/THTCPD mixtures with different ratio were conducted to get the possible effect of the JP-10 addition on the THTCPD pyrolysis by comparing products with that of THTCPD. The heat sink and detailed pyrolysis behaviors (conversion, product distributions) were studied and analyzed to get more insights into the effect of adding JP-10 on the pyrolysis process. This study contributes to the development of those new high-density hydrocarbon fuels in advanced aircrafts for the potential applications.

2. EXPERIMENTAL SECTION 2.1 Materials Both THTCPD and JP-10 were self-prepared according to the references which are similar with those in the previous study.24 The structures of THTCPD and their isomers were shown in Figure S1 of the Supporting Information. THTCPD was mixed with JP-10 with a volume ratio of 3/7 and 1/1. It is worth noting that the addition of a small amount of JP-10 is mainly used to reduce the viscosity of the binary fuel of JP-10/THTCPD and not significantly change its density. And the objective of this study is to investigate the decomposition of THTCPD and the effect of JP-10 on the thermal decompositions of THTCPD, therefore the proportion of JP-10 in the binary fuels of JP-10/THTCPD cannot exceed 1/1. The densities of obtained fuels (1.0049 and 0.9859 g/cm3 at 20 oC, see Table 1) are slightly lower than that of THDCPD, but their viscosities significantly drop by 50% and 76%. The 5


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properties of those fuels are listed in Table 1. Table 1 should be placed here. 2.2 Thermal decompositions of THTCPD and JP-10/THTCPD Thermal decompositions of both THTCPD and JP-10/THTCPD were conducted using an electrically heated tubular reactor. More details on the heating method could be found in our previous papers by Jiang et al.16, 29, 32 The tube reactor (100 cm long and 3 mm inner diameter) made of nickel-base super alloy was used with inert coating to prevent the possible catalytic reaction of wall. For a typical run, the fuel was pumped into the reactor with a P500 high-pressure liquid chromatography (HPLC) pump at the set flowing rate through a filter to remove any sediment. Before each run, the tubes were flushed with nitrogen for 10 times to exhaust the air in the reactor. The reaction system was heated using the direct current provided by a dc stabilized power supply with two copper bars. The fuel temperature was measured by K-type thermocouples which is directly inserted ca. 1 cm above the liquid with an error less than 5 K. The wall temperature was also measured by K-type thermocouples welded at 10 cm intervals along outside of the tube. The pressure was maintained at 4.0 MPa using a back-pressure valve. A differential pressure gauge was used to measure and timely track the reactor pressure drop, which was also an indicative of coke formation in tube reactor. After the pyrolysis, the high temperature fluid was quenched to 30 °C by a two-stage water-cooled heat exchanger, which was intend to avoid the impact of secondary reaction. The gaseous products were analyzed online, and the liquid products were collected. 2.2 Analysis method The gaseous products were analyzed online using an Agilent 3000A gas chromatography (GC) equipped with molecular sieve column (10 m× 12 µm), Plot U column (10 m ×30 µm) and alumina column (10 m ×8 µm). The gaseous products were analyzed both quantitatively and qualitatively with standard gas samples. The liquid products were analyzed qualitatively using an Agilent 6890A-5975 gas chromatography/mass spectrometry (GC/MS) with the HP-5MS capillary column (30 6


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m × 0.25 mm × 0.25 µm), programmed at 40 oC for 10 min, and then from 40 oC to 200 oC at a rate of 4 °C/min. And the liquid products were analyzed quantitatively using an Agilent 7890A gas chromatography with the PONA capillary column (50 m × 0.20 mm × 0.50 µm) and a FID. The conversion of THTCPD was defined as follows: 16, 33-38

 m × ∑ t 1= 44 min w  l t 1= 39 min li  x = 1× 100% t 0 = 44 min  m0 × ∑  w t 0 = 39 min 0 i   Overall conversion of JP-10/THTCPD was defined as follows:

 m × [( t1=44min w ) +( t1=23.40min wlJ )  ∑t1=39min li ∑t1=25.10min  ×100% l x = 1t 1= 44min   m × [(∑t1=39min w0 i ) + w0 J ] 0   Where ml and m0 were the mass of liquid phase and feed fuel during the same time, respectively. wli and w0i were the THTCPD mass fraction of liquid phase and feed fuel, respectively. wlJ and w0J were the JP-10 mass fraction of liquid phase and feed fuel, respectively. In this study, the molar yield of j, Yj, and the selectivity of j, Sj, were still defined as the same as before.24 The mass yield of j, Yj was defined as the mass ratio of product i to the initial feed as follows

Yj =

ml × wj m0

Where ml and m0 were the mass of liquid product j and feed fuel. wj was the mass fraction of product j in the liquid products.

3. RESULTS AND DISCUSSIONS 3.1 Thermal decomposition of THTCPD 3.1.1 Conversion and Gas Yield Thermal decomposition of THTCPD was carried out under 4 MPa (under supercritical condition) at the flow rate of 30, 45 and 60 g/min to analyze the effect of 7


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residence time on the pyrolysis of THTCPD. The conversion and gas yield were plotted with the fuel outlet temperature in Figure 1. Clearly, the THTCPD conversions increase with the fuel temperatures at all the flow rates as a result of increasing decomposition rate (see Fig 1a), which is also observed for the thermal decomposition reaction of the other hydrocarbons. It should be noted that the initial decomposition temperature of THTCPD always falls in the range of 500 °C to 600 °C, implying that the thermal cracking of THTCPD is more sensitive to temperature change under such pressure and residence time. With the increase of flow rate from 30 to 60 g/min, the initial decomposition temperature (Tid, defined as the temperature at conversion reaching 5%) of THTCPD shifts from 550 oC to 580 oC, and then to 590 o

C, due to the reducing residence times. For instance, a low flow rate means a longer

residence time, which would lead to the relatively high conversion and a low Tid, while an opposite result was got for a high flow rate. The similar trends were also observed for the gas yield (see Fig 1b) which is generally taken as the index of decomposition degree for hydrocarbon fuels. These are consistent with the results of previous studies.24, 29, 32 Figure 1 should be placed here. 3.1.2 Gaseous Products The distribution of gaseous products at different temperatures is listed in Table 2. The gaseous products of the thermal decomposition of THTCPD were hydrogen, methane, ethylene, ethane, propene, propane, C4 alkanes, C4 alkenes and C5 alkanes. And among them, hydrogen, methane, ethylene, ethane, and propene are major products, and ethylene is the most abundant products. From Table 2, the selectivities of the alkenes are always higher than those of the alkanes, which is obviously different with our previous results that methane and ethane were the abundant products under low temperature (385-425 oC) and long residence time in the batch reactor experiments. This may be explained that the high temperatures (550 oC-660 oC) might be favorable for the β-scission, rather than the intermolecular abstraction reactions 39, and the secondary reactions of the generated alkenes were prevented in 8


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the short residence time 16. Likewise, the selectivity of hydrogen was 0.20 at 620 oC and increased to 0.42 at 660 oC, which indirectly indicate that the β-scission reaction is more likely to be occurred under the high temperatures (550 oC-660 oC). Similar results were also observed in other studies.29, 32 In addition, the selectivities of the alkanes (methane, propane, and ethane) always increase with the THTCPD conversion, while for the alkenes (such as ethylene, propene, etc.) their selectivities firstly increase and then drop slightly with the THTCPD conversion. This may be because the fact that at high conversion, the alkene are consumed by secondary reaction. Figure 2 descripts the change in the ratio of alkene/alkane in the gaseous products at different conversion. It can be seen that the ratio of alkene/alkane in the gaseous products was larger than 1. As well known, the formation of alkene in gaseous products was favorable for the endothermic process, while the formation of alkane was usually taken as the exothermic one. Therefore, the higher the ratio of alkene/alkane in gaseous products may be better for the endothermic capacity of the fuel 21, 40. In addition, the ratio of alkene/alkane decreases with conversion, due to the consumption of alkene in secondary reactions with reaction proceeding. Table 2 should be placed here. Figure 2 should be placed here. 3.1.3 Liquid Products Figure 3 describes the chromatograms of liquid products from the thermal decomposition of THTCPD with different conversions. The analysis of the liquid products indicates that the C5 components mainly included 1,3-cyclopentadiene, cyclopentene and cyclopentane, and the major C10 components were JP-10, dicyclopentadiene

and

3a,4,5,6,7,7a-hexahydro-4,7-methanoindene.

It can

be

observed that both C5 and C10 species were the major products at the weight ratio of 1:2 at the primary stage of decomposition (around the 500 oC), implying that the initial pathway was the intramolecular carbon-carbon bond breakage of THTCPD. Figure 3 should be placed here. 9


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With the increasing temperature or conversion, the yields of both C5 and C10 species increase as described in detail in Figure 4, but yield of C10 become lower than that of C5 after 600 °C. Figure 5 further presents the molar yields of typical C5 and C10 products. The yield of the C5 products (see Fig 5a, 5b, 5c) had a similar tendency that increased with temperature, but JP-10 (see Fig 5d) increased first and then decreased. The possible explanations for this phenomenon may be that the decomposition of primary C10 products into C5 or the other species may occur at 600 o

C, which is consistent well with the result obtained in Figure 4. Figure 5 also shows

that

the

yield

of

other

C10

products

(dicyclopentadiene

and

3a,4,5,6,7,7a-hexahydro-4,7-methanoin) increased with high temperature, implying different formation and consumption pathway with JP-10. It should be noted that in our previous batch experiments cyclopentane and JP-10 was observed as the major products of C5 and C10，but the yields of 1,3-cyclopentadiene and cyclopentene were relatively low, and that dicyclopentadiene did not appear at all.24 The possible reason for this difference was that the secondary reactions alkenes were prevented due to the short residence time, but the long residence time is beneficial for the formation of alkane due to the reactions.16, 40 Figure 4 should be placed here. Figure 5 should be placed here. The selectivities of main liquid products were analyzed, as shown in Figure 6. It shows that cyclo-C5 components (see Figure 6a, b, c) exhibited the similar trends that they increased first and then decreased, but JP-10 (see Figure 6d) and 3a,4,5,6,7,7a-hexahydro-4,7-methanoindene (see Figure 6e) decreased all along, which showed the opposite trends to those in the low temperaures.24 For the decreasing selectivities of C10, it was likely that at high temperatures C10 radical decomposed through β-scission to generate small molecules such as C5, rather than through intermolecular hydrogen abstraction reactions to form JP-10. This also can explain why selectivity of JP-10 was much less and selectivities of C5 were higher in this study. And the decline tendency of C5 implies that C5 are not only products in the 10


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THTCPD pyrolysis process but also reactants of the secondary reactions due to the long residence time. The possible reasons for this may be explained from two aspects. The first reasonable explanation might be that C5 (1, 3-cyclopentadiene, cyclopentene and cyclopentane) decomposed into small molecules through the ring-opening pathway, such as methane, ethane, ethylene, etc. The second possible explanation is that some C5 radicals converted to C6-C9 (benzene, toluene, etc.) and C11+ through bimolecular (hydrogen abstraction, methane and ethane etc.) reactions41-43, which could be further examined by the analysis of the C6-C9 products. Figure 6 should be placed here. Despite of C5 and C10 species, C6-C9 (benzene, toluene, etc.) and C11+ (1-ethynyladamantane, 2-methylnaphthalene) products were also observed and the conversion of ca. 5%, as shown in Figure 3. As the aromatics were prominent instead of cycloalkanes, the mass yield and selectivities of aromatics were plotted in Figure 7. The overall mass yield of aromatics (see Fig 7a) increased with high temperature and low flow rate, which was caused by the increasing conversion. Additionally, the yield of benzene is the highest, followed by toluene, and then ethylbenzene, styrene, 1,2,3,4-tetrahydronaphthalene and 2-methylnaphthalene were present at a temperature of 600 oC and a conversion of about 30%, which was described in detail in Fig 7b. It illustrates that the polycyclic aromatic hydrocarbon increased with temperature and conversion. The increasing trends were also observed for the selectivity of benzene (see Fig 7c), which corresponds exactly to the decline trend for that of C5 in Figure 6. The appearance of those products and their tendency to increase with conversion implies that the secondary reaction of C5 products or olefins may occur to form the aromatics or C11+ products as the long residence time. Of course, the partial gaseous products may be another secondary products of THTCPD or C10 products as reported previously. In the previous study of thermal decomposition of THTCPD in low temperature and long residence time, the main C6, C7 and C8 component were methylcyclopentane, ethylcyclopentane and cis-octahydropentalene, while the aromatics were relatively 11


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low, which was a considerable difference from the results observed from Figure 7b in this study. The comparison between the two conditions was made, as shown in Figure 8. It can be seen that the yield of aromatics was much less at low temperature (see Fig 8b), while that of aromatics at high temperature increased approximately linearly with conversion (see Fig 8a). All these indicated that the formation of cycloalkanes may be the first step during the cracking processes at low temperatures, which may be because that the formation of cycloalkanes is an exothermic process. As the temperature rising, the aromatics can be obtained from cycloalkanes via H-abstraction which is an endothermic process and is liable to happen at high temperatures. Meanwhile, this can explain why yield of hydrogen in this study was high. Figure 7 should be placed here. Figure 8 should be placed here. 3.1.4 Heat sink of THTCPD Heat sink is the ratio of heat absorbed to the mass of the fuel, which is an important evaluation index for high-density hydrocarbon fuels. In general, the heat sink of the fuel can be divided into physical heat sink and chemical heat sink. Physical heat sink refers to the heat absorbed by the fuel during the temperature rise or phase change, which is linearly related to the temperature. Chemical heat sink is the heat absorbed by the endothermic reactions of hydrocarbon fuels at high temperature, which can reflect the overall trend of cracking reactions to a certain extent. The heat sink of THTCPD at different flow rates were calculated as shown in Figure 9. Obviously, it can be seen that before 450 oC, the heat sink is linearly related to the temperature, indicating that the heat sink is the physical heat sink before 450 oC, and the cracking of THTCPD almost did not occur. After 450 oC, THTCPD was pyrolyzed as the temperature increased, then the chemical heat sink began to function and increased significantly after 600 oC. Simultaneously, it was obvious that the chemical heat sink increases as the flow decreases. This might be because the low flow rate means a long residence time which would lead to the relatively high conversion, and finaly resulting in an increase in the heat absorbed by the pyrolysis of 12


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THTCPD. Figure 9 should be placed here.

3.2 Thermal decomposition of JP-10/THTCPD 3.2.1 Conversion and Gas Yield Thermal decomposition of JP-10/THTCPD was performed under 4 MPa with the flow rate of 60 g/min. Conversion of THTCPD in JP-10/THTCPD mixtures was shown in Figure 10. Obviously, conversion of THTCPD in 30% JP-10 /70% THTCPD were slightly higher than that of THTCPD after 620 oC, and conversion of the two fuels were almost near before that. And conversion of 50% JP-10 /50% THTCPD was much higher than that of THTCPD. Although the addition of JP-10 contributed to the decomposition of THTCPD at a certain extent, the effects of the two blends was complicated by further analyzing the overall conversion of the JP-10/THTCPD mixtures, as shown in Figure 11. It can be found that the conversion of THTCPD was much higher than that of JP-10 and the thermal decomposition of JP-10 occurred until 600 oC, which indicated that the THTCPD pyrolysis is greatly easier than the thermal cracking of JP-10. It can be explained by the molecular structure that the more rings in the compound structures, the greater the repulsion between the atoms and the ring tension, meanwhile, they will be more unstable and more prone to cracking under high temperature conditions. Another reasonable explanation has been reported from some studies that the C-C bond dissociation energy of JP-10 (322.17 kJ/mol to 418.4 kJ/mol)44 is higher than that of THTCPD (17.42 kJ/mol to 200.53 kJ/mol)

24

, which further confirms our

results. In addition, the initial conversion of the JP-10/THTCPD mixtures were almost the same due to the only reaction of THTCPD self-dissociation. However, the conversion 30% JP-10/70% THTCPD was near to THTCPD while 50% JP-10/50% THTCPD was even higher than THTCPD after 600 oC. For example, conversion of THTCPD was 9.3% at 620 oC, and overall conversion of 30% JP-10/70% THTCPD was 7.8% while that of 50% JP-10/50% THTCPD was 13.6%. This difference was 13


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more obvious with temperature. For instance, conversion of THTCPD was 33.7% at 660 oC, and overall conversion of 30% JP-10/70% THTCPD was 34.6% while that of 50% JP-10 /50% THTCPD was 44.0 %. These results are different from the results obtained from the simple mixing theory that the conversion of 30% JP-10/70% THTCPD and 50% JP-10/50% THTCPD should be between the conversion of THTCPD and JP-10. All of these demonstrated that the binary fuel of JP-10/THTCPD make a synergistic effect on their thermal decomposition, therefore the decomposition of THTCPD was promoted, as well as that of JP-10. And the degree of promotion effect is closely related to the amount of JP-10. The reason will be discussed later. Figure 10 should be placed here. Figure 11 should be placed here. 3.2.2 Gaseous Products Table 3 descripts the distribution of gaseous products of JP-10/THTCPD mixtures at different temperatures. It shows that the kinds of gaseous products in the thermal decomposition of JP-10/THTCPD mixtures were not significantly different from that of THTCPD. After the addition of JP-10, the yield of ethylene was the highest, and the yield of propylene, hydrogen, ethane and methane were relatively high. Besides, gaseous products yield of thermal decomposition of 30% JP-10/70% THTCPD were close to that of THTCPD, while gaseous products yield of 50% JP-10/50% THTCPD were much higher than that of THTCPD due to the promotion effect of the binary fuel, which was corresponds to their conversions. The ratio of alkene/alkane in the gaseous products of THTCPD, 30% JP-10/70% THTCPD, 50% JP-10/50% THTCPD were calculated as 1.29, 1.59, 1.98, respectively. This exhibited an increasing trend in proportion of alkene/alkane with the addition of JP-10, which is more obvious as JP-10 increases. Table 3 should be placed here. 3.2.3 Liquid Products The chromatograms of liquid products from the thermal decomposition of 50% 14


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Energy & Fuels

JP-10/50% THTCPD with different conversions were shown in Figure 12. The analysis of the GC/MS shows that the C5 components mainly included 1,3-cyclopentadiene, cyclopentene and cyclopentane, and the major C10 components were JP-10 ， dicyclopentadiene, 3a,4,5,6,7,7a-hexahydro-4,7-methanoindene and 3-cyclopentylcyclopentene, which are substantially the same as the liquid products of THTCPD. However, it should be noted that the weight ration of the major products (C5 and C10) was 1:1 at the primary stage of decomposition (around the 500 oC), which was different from that of THTCPD with a weight ratio of 1:2. This may be due to the fact that JP-10 in the binary fuels was not be cracked at the initial cracking stage, as illustrated by the experimental results in Figure 11. Figure 12 should be placed here. Figure 13 describes the main C5 and C10 products distribution of thermal decomposition of JP-10/THTCPD. Obviously, the yield of the C5 products (1,3-cyclopentadiene, cyclopentene and cyclopentane) had a similar tendency that their initial yields (before 600 oC, see Fig 13a, b, c) in thermal decomposition of JP-10/THTCPD were approximate, which were lower than that of THTCPD. As the temperature increases, the yields of 50% JP-10 /50% THTCPD and 30% JP-10/70% THTCPD exceed the yield of THTCPD at 600 oC and 640 oC, respectively. These can be explained that at the initial thermal decomposition of JP-10/THTCPD, JP-10 did not participate in cracking, as a result, the C5 of 50% JP-10 /50% THTCPD and 30% JP-10/70% THTCPD were lower than that of THTCPD. While, with the proceeding of the cracking, JP-10 in JP-10/THTCPD decomposed into C5, which results in a higher C5 in the decomposition of 50% JP-10 /50% THTCPD and 30% JP-10/70% THTCPD than that of THTCPD. On the other hand, from Figure 11 it can be seen that after 600 oC, overall conversion of 30% JP-10/70% THTCPD was close to that of THTCPD, while 50% JP-10 /50% THTCPD was higher than them, and these can explain the above results. Figure 13(d) shows the yield of 3a,4,5,6,7,7a-hexahydro-4,7-methanoindene in thermal decomposition of JP-10/THTCPD was lower than that in THTCPD, which 15


Energy & Fuels

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will

be

more

obvious

with

the

3a,4,5,6,7,7a-hexahydro-4,7-methanoindene

addition started

Page 16 of 45

of

JP-10.

to

The

increase

yield

rapidly

of and

dicyclopentadiene appeared and increased at 600 oC, as shown in Figure 13(e), suggesting that JP-10 did not begin to undergo thermal decomposition until 600 oC. Besides, as shown in Figure 13(f), the yield of 3-cyclopentylcyclopentene in thermal decomposition of pure THTCPD was higher than that of 30% JP-10/70% THTCPD and 50% JP-10 /50% THTCPD below 600 oC. Then the opposite situation occurred which resulted from the decomposition of JP-10 when the temperature reached 600 oC. It was also a valid evidence of our experimental guess. Figure 13 should be placed here. Cycloalkene and aromatics variations in thermal decomposition of JP-10/THTCPD were shown in Figure 14. It was found that there was no significant difference in the yield of aromatic and cycloalkene in different binary fuels, which demonstrated that adding JP-10 had no much effect on aromatics and cycloalkene yield. Figure 14 should be placed here.

3.2.4 Possible mechanism As we all know, THTCPD, with a polycyclic structure, is liable to be cracked than JP-10. It can be explained form the molecular structure theory that the more rings in the compound structures, the greater the repulsion between the atoms and the ring tension, meanwhile, they will be more unstable and more prone to cracking under high temperature conditions. Although JP-10 is harder to crack, the cracking performance of the binary fuel was significantly changed that both THTCPD and JP-10 decomposition were promoted. Although the specific reaction mechanism is unclear, but it can be concluded that the binary fuel of JP-10/THTCPD make a synergistic effect on their thermal decomposition, and the degree of promotion effect is closely related to the amount of JP-10 according to the analysis of THTCPD conversion and overall conversion in the binary fuel of JP-10/THTCPD. In combination with the major products distribution, we speculate on the possible 16


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Energy & Fuels

mechanism of thermal cracking of the binary fuel of JP-10/THTCPD. There is no significant difference in the decomposition rate of JP-10/THTCPD and that of THTCPD at the initial decomposition stage (before 600 oC) due to the only reaction of THTCPD self-dissociation. At the initial stage of the binary fuel pyrolysis, THTCPD is firstly cracked through the broking of C-C bond because that the C-C bond dissociation energy of JP-10 (322.17 kJ/mol to 418.4 kJ/mol)44 is higher than that of THTCPD (17.42 kJ/mol to 200.53 kJ/mol)24. However, as the reaction continues，the free radicals generated by THTCPD are more likely to react with JP-10 via H-abstraction reaction due to the high molar ratio of JP-10 (59.77% in 50% JP-10/50% THTCPD) in the binary fuels, which can significantly promote the JP-10 pyrolysis. Correspondingly, a large number of new free radicals generated from the JP-10 pyrolysis could also react with JP-10 and THTCPD, which is helpful to promote the decomposition of THTCPD via H-abstraction reaction. Besides, the contribution of THTCPD to JP-10 could also explained by the chemical equilibrium point of view since JP-10 is one of the products of THTCPD since JP-10 was one of the products of THTCPD. In conclusion, the blending of THTCPD and JP-10 has a synergistic effect on the cracking of fuels, but it is still necessary to do more studies to obtain more insights into thermal decomposition and kinetics of JP-10/THTCPD. 3.2.5 Isomerization of THTCPD Meanwhile, isomers of THTCPD were also investigated to obtain more insights into thermal decomposition and kinetics of JP-10/THTCPD and show different concentration variations in thermal decomposition of THTCPD and JP-10/THTCPD, as shown in Figure 15. It is not difficult to find that the isomers concentration in JP-10/THTCPD is lower by comparing the isomer concentration of THTCPD, which implying that the presence of JP-10 inhibits the isomerization between the THTCPD isomers. And it may be related to the enhancing effect of JP-10/THTCPD. Their thermal stability was in the order of I > II > IV > V > III ≥VI (Figure S1 of the Supporting Information). The results were in agreements with the previous results reported.24 17


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Page 18 of 45

Figure 15 should be placed here. 3.2.6 Heat sink of JP-10/THTCPD The heat sinks of JP-10/THTCPD with different ratios were also calculated to investigate the effect of JP-10 on the heat sink of THTCPD, as shown in Figure 16. It can be seen that before 450 oC, the physical heat sinks of THTCPD, 30% JP-10/70% THTCPD and 50% JP-10/50% THTCPD are sequentially increased when the conversion of the three fuels are less than 5%. This shows that adding JP-10 to THTCPD is conducive to increasing the physical heat sink of the fuel, which is due to the increase in the number of moles of the binary fuel with the addition of JP-10. After 450 oC, the chemical heat sinks of the three fuels increased significantly due to the pyrolysis of the binary fuels. Obviously, after 600 oC, the chemical heat sinks of JP-10/THTCPD increased more significantly with the addition of JP-10, which is attributed to the promotion of the binary fuels in the pyrolysis process. The heat sink of the binary fuels are higher than that of THTCPD, which also proves that the addition of JP-10 contributes to the THTCPD pyrolysis. Figure 16 should be placed here. 4. CONCLUSIONS Thermal decomposition of THTCPD was carried out in a tubular reactor under 4 MPa and 550-660 oC. Ethylene and propane were the most abundant gaseous products, and ratio of alkene/alkane was significantly higher than that observed in the batch reactor. Both cyclopentene and C10 products were the major primary liquid products, and both the yield of cycloalkene and aromatics increased with increasing conversion as a result of the secondary reactions of primary products. Thermal decomposition of THTCPD and JP-10 mixtures (JP-10/THTCPD) was conducted at high pressure (4 MPa) and temperatures (500-660 oC). The results showed that the decomposition rate of THTCPD were enhanced by 100% by adding 50% JP-10, and the overall conversion of 30% JP-10/70% THTCPD improves by 30% compared with THTCPD, which illustrated that the decomposition of THTCPD was promoted with the addition of JP-10. And in turn, the decomposition of THTCPD was 18


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Energy & Fuels

also contributed to the JP-10 pyrolysis. The possible reason about the pathway and mechanism of JP-10/THTCPD pyrolysis is that the free radicals generated by the decomposition of THTCPD are help to promote the decomposition of JP-10 via H-abstraction reactions. Correspondingly, a large number of new free radicals generated from the JP-10 pyrolysis could also react with JP-10 and THTCPD, which is helpful to promote the decomposition of THTCPD via H-abstraction reaction. Besides, the contribution of THTCPD to JP-10 could also explained by the chemical equilibrium point of view since JP-10 is one of the products of THTCPD. The major decomposition products in presence of JP-10 were observed to be similar with those of THTCPD, but the ratio of alkene/alkane in gaseous products increased after adding JP-10. In addition, the presence of JP-10 also inhibits the isomerization between the THTCPD isomers, which may be the possible reason for the enhancing the decomposition of THTCPD. ASSOCIATED CONTENT Supporting Information The component distribution (wt%) of liquid residuals from thermal decomposition of THTCPD, 30% JP-10/70% THTCPD and 50% JP-10/50% THTCPD were shown in Table S1. The structures of THTCPD and their ismoers were shown in Figure S1. In addition, conversion of JP-10 in JP-10/THTCPD mixtures were listed in Figure S2. ACKNOWLEDGEMENT The authors sincerely acknowledge financial support of the National Natural Science Foundation of China (21522605). REFERENCE 1.

Xiong, Z., Development of Synthesized High-Density Hydrocarbon Fuels. Progress In Chemistry

2005, 17, (2), 359-367. 2.

Zou, J. J.; Zhang, X. W.; Wang, L.; Zhen-Tao, M. I., Synthesis Advance of High-Density

Hydrocarbon Fuels. Chemical Propellants & Polymeric Materials 2008, 06, (01), 26-30. 3.

Zou, J. J.; Guo, C.; Zhang, X. W.; Wang, L.; Mi, Z. T., High-density liquid hydrocarbon fuels for

aerospace propulsion: synthesis and application. Tuijin Jishu/journal of Propulsion Technology 2014,

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Tetrahydrotricyclopentadiene: Synthesis of High-Energy-Density Liquid Fuel. Energy & Fuels 2009, 23, (5), 2383-2388. 10. Ware, R. E.; Janoski, E. J.; Schneider, A., Isomerization of tetrahyd rotricyclopentadienes to missile fuel. In 2015. 11. Wang, W.; Cong, Y.; Chen, S.; Sun, C.; Wang, X.; Zhang, T., One-Pot Catalytic Transformation of Dicyclopentadiene to High Energy Density Fuel Exo-tetrahydrotricyclopentadiene. Topics in Catalysis 2015, 58, (4), 350-358. 12. Rizkalla, A. A.; Lefebvre, A. H., The Influence of Air and Liquid Properties on Airblast Atomization. Journal of Fluids Engineering 1974, 97, (3), 316. 13. Jasuja, A. K., Atomization of crude and residual fuel oils. Trans ASME J Eng Power. Journal of Engineering for Gas Turbines & Power 1979, 101, (2), 250. 14. Puri, P.; Ma, F.; Choi, J. Y.; Yang, V., Ignition characteristics of cracked JP-7 fuel. Combustion & Flame 2005, 142, (4), 454-457. 15. Xu, L.; Ouyang, L.; Zhuang, G.; Hua, L.; Zhen, H.; Lu, X., Experimental and Kinetic Study on Ignition Delay Times of Liquified Petroleum Gas/Dimethyl Ether Blends in a Shock Tube. Energy &

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of n-decane. Chemical Engineering Journal 2014, 243, (4), 127-136. 28. Li, G.; Zhang, C.; Wei, H.; Xie, H.; Guo, Y.; Fang, W., Investigations on the thermal decomposition of JP-10/iso-octane binary mixtures. Fuel 2016, 163, 148-156. 29. Jiang, R.; Liu, G.; He, X.; Yang, C.; Wang, L.; Zhang, X.; Mi, Z., Supercritical thermal decompositions of normal- and iso-dodecane in tubular reactor. Journal of Analytical & Applied Pyrolysis 2011, 92, (2), 292-306. 30. Yu, J.; Eser, S., Supercritical-phase thermal decomposition of binary mixtures of jet fuel model compounds. Fuel 2000, 79, (7), 759-768. 31. Zhou, H.; Gao, X.; Liu, P.; Zhu, Q.; Wang, J.; Li, X., An experimental and simulated investigation on pyrolysis of blended cyclohexane and benzene under supercritical pressure. Petroleum Chemistry 2017, 57, (1), 71-78. 32. Jiang, R.; Liu, G.; You, Z.; Luo, M.; Wang, X.; Wang, L.; Zhang, X., On the Critical Points of Thermally Cracked Hydrocarbon Fuels under High Pressure. Industrial & Engineering Chemistry Research 2011, 50, (15), 9456-9465. 33. Fortin, T. J.; Bruno, T. J., Assessment of the Thermophysical Properties of Thermally Stressed RP-1 and RP-2. Energy & Fuels 2013, 27, (5), 2506-2514. 34. And, P. C. A.; Bruno, T. J., Thermal Decomposition Kinetics of RP-1 Rocket Propellant. Industrial & Engineering Chemistry Research 2010, 44, (6), págs. 1670-1676. 35. Widegren, J. A.; Bruno, T. J., Thermal Decomposition Kinetics of the Aviation Turbine Fuel Jet A. Industrial & Engineering Chemistry Research 2008, 47, (13), 4342-4348. 36. Widegren, J. A.; Bruno, T. J., Thermal Decomposition Kinetics of Kerosene-Based Rocket Propellants. 1. Comparison of RP-1 and RP-2. Energy & Fuels 2013, 23, (11), 5517-5522. 37. Gough, R. V.; Widegren, J. A.; Bruno, T. J., Thermal Decomposition Kinetics of the Thermally Stable Jet Fuels JP-7, JP-TS and JP-900. Energy & Fuels 2014, 28, (5), 3036–3042. 38. Widegren, J. A.; Bruno, T. J., Thermal Stability of RP-2 as a Function of Composition: The Effect of Linear, Branched, and Cyclic Alkanes. Energy & Fuels 2013, 27, (9), 5138-5143. 39. Savage, P. E., Mechanisms and kinetics models for hydrocarbon pyrolysis. Journal of Analytical & Applied Pyrolysis 2000, 54, (1–2), 109-126. 40. Edwards, T.; Harrison, W.; Schobert, H.; Edwards, T.; Harrison, W.; Schobert, H. In Properties

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and producibility of advanced jet fuels, Joint Propulsion Conference and Exhibit, 2006; 2006; pp 439-447. 41. Djokic, M. R.; Geem, K. M. V.; Cavallotti, C.; Frassoldati, A.; Ranzi, E.; Marin, G. B., An experimental and kinetic modeling study of cyclopentadiene pyrolysis: First growth of polycyclic aromatic hydrocarbons. Combustion & Flame 2014, 161, (11), 2739-2751. 42. Kim, D. H.; Mulholland, J. A.; Wang, D.; Violi, A., Pyrolytic Hydrocarbon Growth from Cyclopentadiene. Journal of Physical Chemistry A 2010, 114, (47), 12411. 43. Mebel, A. M.; Landera, A.; Kaiser, R. I., Formation Mechanisms of Naphthalene and Indene: From the Interstellar Medium to Combustion Flames. 2017, 121, (5), 901-926. 44. Hudzik, J. M.; Castillo, Á.; Bozzelli, J. W., Bond Energies and Thermochemical Properties of Ring-Opened Diradicals and Carbenes of exo-Tricyclo[5.2.1.0(2,6)]decane. Journal of Physical Chemistry A 2015, 119, (38), 9857-78.

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Table Captions Table 1 The composition and properties of the fuels used in this work. Table 2 The selectivity of gaseous products of thermal decomposition of THTCPD at different temperatures (60 g/min, 4 MPa). Table 3 The yield (mol %) of gaseous products of thermal decomposition of JP-10/THTCPD

24


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Energy & Fuels

Table 1 The composition and properties of the fuels used in this work Items

THTCPD

30% JP-10/

50% JP-10/

70%THTCPD

50%THTCPD

JP-10 added (volume, %)

0

30

50

JP-10 content (wt %)

1.6

31.1

49.0

1.0326

1.0049

0.9859

Viscosity (mPa·s, 20 C)

35.3

14.1

8.5

Flash point (oC)

116

71

63

3

o

Density (g/cm , 20 C) o

25


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Table 2 The selectivity of gaseous products of thermal decomposition of THTCPD at different temperatures (60 g/min, 4 MPa) Gaseous components

620 oC

640 oC

660 oC

Conversion %

9.28

21.10

33.73

H2

0.20

0.48

0.42

CH4

0.10

0.31

0.34

C2H4

0.26

0.67

0.58

C2H6

0.17

0.43

0.39

C3H8

0.026

0.077

0.079

C3H6

0.23

0.46

0.42

C4 alkanes

0.0032

0.010

0.011

C4 alkenes

0.039

0.054

0.068

C5 alkanes

0.0022

0.0066

0.0065

26


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Energy & Fuels

Table 3 The yield (mol %) of gaseous products of thermal decomposition of JP-10/THTCPD Gaseous

THTCPD

30% JP-10/70% THTCPD

50% JP-10/50% THTCPD

components

640 oC

640 oC

640oC

H2

10.06

8.07

16.60

CH4

6.53

5.47

10.09

C2H4

14.10

12.02

24.78

C2H6

9.02

7.02

12.71

C3H8

1.62

1.32

3.42

C3H6

9.63

9.50

26.29

C4 alkanes

0.21

0.18

0.29

C4 alkenes

1.13

0.92

1.97

C5 alkanes

0.14

0.10

0.32

27


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Figure Captions Figure 1 The thermal decomposition conversion (a) and gas yield (b) of THTCD at different feed flow rates. (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa) Figure 2 The ratio of alkene/alkane in the gaseous products from the thermal decomposition of THTCPD (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa) Figure 3 Typical chromatograms of liquid residuals with the flow rate of 60 g/min at different temperatures; 4 MPa: (a) (1) THTCPD feed fuel; (2) 500 oC; (3) 550 oC; (4) 600oC; (5) 620 oC; (6) 640 o C;(7) 660 oC); (b) A,1,3-cyclopentadiene; B, cyclopentene; C, cyclopentane; D, 1-methylcyclopentene; E, benzene; F, 1-ethylcyclopentene; G, toluene; H, ethylbenzene; I, styrene; (c) J, dicyclopentadiene; K, indane; L, indene;M,3a,4,5,6,7,7a-hexahydro-4,7-methanoindene;N,JP-10;O,3-cyclopentylcyclo pentene; P,2,3-dihydro-4-methyl-1H-indene;Q,3-methyl-1H-indene;R,1,2,3,4-tetrahydronaphth alene; S,naphthalene;T,1-ethynyladamantane;U, 2-methylnaphthalene) Figure 4 The liquid products distribution of the thermal decomposition of THTCPD with the rate of 60 g/min at different temperatures (■ C5, ● C6, ▲ C7, ▼ C8, ◄C9, ►C10; 4 MPa) Figure 5 The main C5 and C10 products distribution with the feed flow rate and temperature (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa) Figure 6 Selectivities of main liquid products from THTCPD decomposition with the feed flow rate and temperature (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa) Figure 7 The mass yield and selectivity of aromatics (4 MPa) (a) The mass yield of aromatics (■ 30 g/min, ● 45 g/min, ▲60 g/min); (b) Mass yield of each aromatic at 60 g/min (■ benzene, ● toluene,▲ ethylbenzene,▼ styrene, ◄indane, ►indene, ◆ 2,3-dihydro-4-methyl-1H-indene, 3-methyl-1H-indene, ★ 1,2,3,4-tetrahydronaphthalene, ★ naphthalene,● 2-methylnaphthalene, ■ 1-methylnaphthalene); (c) The selectivity of benzene; Figure 8 Selectivity comparison of aromatics between high (550-660 oC) and low temperatures (385-425 oC) (a) Selectivity of aromatics at high temperatures (550-660 oC) (■ 30 g/min, ● 45 g/min, ▲ 60 g/min; 4 MPa) (b) Selectivity of aromatics at low temperatures (■385 oC, ●400 oC, ▲415 oC, ▼ 28


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425 oC; 4 MPa) Figure 9 The heat sink of THTCPD (■30 g/min, ●45 g/min, ▲60 g/min, the dash line stands for the physical heat sink; 4 MPa) Figure 10 Conversion of THTCPD in JP-10/THTCPD mixtures (■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa) Figure 11 Overall conversion of JP-10/THTCPD mixtures (▼JP-10, ■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa) Figure 12 Typical chromatograms of liquid residuals for thermal decomposition of 50% JP-10/50% THTCPD at different temperatures (4 MPa) (a) (1) 450 oC; (2) 500 oC; (3) 550 oC; (4) 600oC; (5) 620 oC; (6) 640 oC; (7) 660 oC; (b) A, 1,3-cyclopentadiene; B, cyclopentene; C, cyclopentane; D, 1-methylcyclopentene; E, benzene; F, 1-ethylcyclopentene; G, toluene;H, 3-ethenylcyclopentene; I, cis-bicyclo [3.3.0]oct-2-ene; J, ethylbenzene; K, styrene; (c) L, dicyclopentadiene; M, indane; N, indene; O,3a,4,5,6,7,7a-hexahydro-4,7-methanoindene; P, JP-10; Q, 3-cyclopentylcyclopentene;R, endo-TCD; S, 1-cyclopentylcyclopentene; T, 2,3-dihydro-4-methyl-1H-indene; U,3-methyl-1H-indene; V, 1,2,3,4-tetrahydronaphthalene; W, naphthalene; X,2-methylnaphthalene) Figure 13 The main C5 and C10 products distribution of thermal decomposition of JP-10/THTCPD (■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa) Figure 14 The mass yield of cycloalkane (a) and aromatics (b) (■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa) Figure 15 Isomers molar concentrations relative to the feed (■ I, ● II, ▲ III, ▼ IV, ◄ V, ► VI; 4 MPa) Figure 16 The heat sink of JP-10/THTCPD (■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD)

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Figure 1 The thermal decomposition conversion (a) and gas yield (b) of THTCD at different feed flow rates. (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa)

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Figure 2 The ratio of alkene/alkane in the gaseous products from the thermal decomposition of THTCPD (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa)

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Figure 3 Typical chromatograms of liquid residuals with the flow rate of 60 g/min at different temperatures (4 MPa) (a) (1) THTCPD feed fuel; (2) 500 oC; (3) 550 oC; (4) 600oC; (5) 620 oC; (6) 640 o C;(7) 660 oC); (b) A,1,3-cyclopentadiene; B, cyclopentene; C, cyclopentane; D, 1-methylcyclopentene; E, benzene; F, 1-ethylcyclopentene; G, toluene; H, ethylbenzene; I, styrene; (c) J, dicyclopentadiene; K, indane; L, indene;M,3a,4,5,6,7,7a-hexahydro-4,7-methanoindene;N,JP-10;O,3-cyclopentylcyclo pentene; P,2,3-dihydro-4-methyl-1H-indene;Q,3-methyl-1H-indene;R,1,2,3,4-tetrahydronaphth alene; S,naphthalene;T,1-ethynyladamantane;U, 2-methylnaphthalene) 32


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Figure 4 The liquid products distribution of the thermal decomposition of THTCPD with the rate of 60 g/min at different temperatures (■ C5, ● C6, ▲ C7, ▼ C8, ◄C9, ►C10; 4 MPa)

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Figure 5 The main C5 and C10 products distribution with the feed flow rate and temperature (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa)

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Figure 6 Selectivities of main liquid products from THTCPD decomposition with the feed flow rate and temperature (■ 30 g/min, ● 45 g/min, ▲60 g/min; 4 MPa)

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Figure 7 The mass yield and selectivity of aromatics (4 MPa) (a) The mass yield of aromatics (■ 30 g/min, ● 45 g/min, ▲60 g/min); (b) Mass yield of each aromatic at 60 g/min (■ benzene, ● toluene,▲ ethylbenzene,▼ styrene, ◄indane, ►indene,◆2,3-dihydro-4-methyl-1H-indene, 3-methyl-1H-indene, ★1,2,3,4-tetrahydronaphthalene,★naphthalene,● 2-methylnaphthalene, ■ 1-methylnaphthalene); (c) The selectivity of benzene;

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Figure 8 Selectivity comparison of aromatics between high (550-660 oC) and low temperatures (385-425 oC) (a) Selectivity of aromatics at high temperatures (550-660 oC) (■ 30 g/min, ● 45 g/min, ▲ 60 g/min; 4 MPa) (b) Selectivity of aromatics at low temperatures (■385 oC, ●400 oC, ▲415 oC, ▼ 425 oC; 4 MPa)

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Figure 9 The heat sink of THTCPD (■30 g/min, ●45 g/min, ▲60 g/min, the dash line stands for the physical heat sink; 4 MPa)

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Figure 10 Conversion of THTCPD in JP-10/THTCPD mixtures (■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa)

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Figure 11 Overall conversion of JP-10/THTCPD mixtures (▼JP-10, ■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10 /50% THTCPD; 4 MPa)

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Figure 12 Typical chromatograms of liquid residuals for thermal decomposition of 50% JP-10/50% THTCPD at different temperatures (4 MPa) o

(a) (1) 450 C; (2) 500 oC; (3) 550 oC; (4) 600oC; (5) 620 oC; (6) 640 oC; (7) 660 oC; (b) A, 1,3-cyclopentadiene; B, cyclopentene; C, cyclopentane; D, 1-methylcyclopentene; E, benzene; F, 1-ethylcyclopentene; G, toluene;H, 3-ethenylcyclopentene; I, cis-bicyclo [3.3.0]oct-2-ene; J, ethylbenzene; K, styrene; (c) L, dicyclopentadiene; M, indane; N, indene; O,3a,4,5,6,7,7a-hexahydro-4,7-methanoindene; P, JP-10; Q, 3-cyclopentylcyclopentene;R, endo-TCD; S, 1-cyclopentylcyclopentene; T, 2,3-dihydro-4-methyl-1H-indene; U,3-methyl-1H-indene; V, 1,2,3,4-tetrahydronaphthalene; W, naphthalene; X,2-methylnaphthalene) 41


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Figure 13 The main C5 and C10 products distribution of thermal decomposition of JP-10/THTCPD (■ THTCPD, ●30% JP-10/70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa)

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Figure 14 The mass yield of cycloalkane (a) and aromatics (b) (■ THTCPD, ●30% JP-10 /70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa

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Figure 15 Isomers molar concentrations relative to the feed (■ I, ● II, ▲ III, ▼ IV, ◄ V, ► VI; 4 MPa)

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Figure 16 The heat sink of JP-10/THTCPD (■ THTCPD, ●30% JP-10 /70% THTCPD, ▲50% JP-10/50% THTCPD; 4 MPa)

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High-Pressure Thermal Decomposition of ... - ACS Publications

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