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Methylcyclopentadiene dimer and trimer based fuels are synthesized from 5-methyl furfural for the first time with yields as high as 74.4%. They exhibit both high density and high thermal stability that are better than those of widely used fossil based jet fuels such as JP-10 and JP-7, and represent types of high-performance fuels. This work also provides a potential and scale-up feasible route for synthesizing high-performance jet fuels from biomass. [ABSTRACT FROM AUTHOR]

Thermal oxidation stability is an important parameter for jet fuel practical application. In this work, in order to evaluate the influence of deoxygenation on fuel stability, samples of typical fuels (JP-10 and RP-3) were subjected to deoxygenation by nitrogen purge and then subjected to accelerated thermal oxidation (180°C, 200°C, and 220°C). The parameters of hydroperoxide number, total acid number, size distribution of insoluble oxidation products, and concentration of remaining antioxidant (butylated hydroxytoluene, MIT) were monitored and analyzed. The results show that deoxygenation and thermal oxidation have very little influence on the fuel physical properties (density, net heating value, and kinematic viscosity). However, deoxygenation significantly reduces hydroperoxide number, total acid number, and remaining BHT concentration in the fuel after accelerated oxidation. Moreover, the deoxygenation treatment also inhibits the formation of soluble macromolecular oxidatively reactive species (SMORS) and insoluble oxidation products such as gums and deposits. [ABSTRACT FROM AUTHOR]

Renewable high-density spiro-fuels are synthesized from lignocellulose-derived cyclic ketones for the first time, which show higher density, higher neat heat of combustion and lower freezing point compared with other biofuels synthesized from the same feedstock, and thus represent a new type of renewable high-density fuel attractive for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dynamics and mechanism of JP-10 thermal oxidative deposition were investigated. • Both the peak deposit thickness and deposits volume of JP-10 increase with temperature. • The apparent deposition activation energy of JP-10 is approximately 71.2 kJ/mol. • The thermal oxidative deposition of JP-10 occurs via a series of radical reactions. High-energy–density (HED) fuels (like JP-10) have drawn more and more attention for volume-limited aerospace vehicles to extend the flight range and/or increase the payload. However, their thermal oxidation and deposition performance are still ambiguous. In this work, the dynamics and mechanism of JP-10 thermal oxidative deposition were investigated by the jet fuel thermal oxidation stability tester (JFTOT), ellipsometric tube rater (ETR) and comprehensive two-dimensional gas chromatography coupled with mass spectrometry and flame ionization detector (GC × GC–MS/FID). The results reveal that both the peak deposit thickness and total deposits volume of JP-10 increase with increasing temperature with the apparent deposition activation energy of approximately 71.2 kJ/mol. The deposits on the tube surface have globular structure, and they undergo particle formation, growth, adherence, agglomeration and size reduction during thermal stress. The fine characterizations of liquid products after JFTOT test confirm that the thermal oxidative deposition of JP-10 occurs via a series of radical reactions, such as oxidative decomposition and radical addition, which will be significantly accelerated at higher temperature. Importantly, the stability of alkoxy radical seems to be a significant factor affecting the thermal oxidation stability of HED fuels. This work may shed light on the possible deposition mechanism of HED fuels and will guide the rational design of HED fuels with high thermal oxidation stability. [ABSTRACT FROM AUTHOR]

• Methyl-substituted decalin was synthesized by one-step alkylation reaction. • The synthesized fuel possesses high density and well cryogenic properties. • The pseudo reaction kinetics of alkylation reactions are investigated in detail. • A mechanism of decalin methylation reaction with solvent and catalyst was proposed. Alkyl decalins are promising jet fuel components with high density and well cryogenic properties, but are difficult to obtain. Here we bring up a facile approach to synthesize methyl-substituted decalins including methyl decalin, dimethyl decalin and trimethyl decalin via catalytic alkylation reaction. The reaction conditions are optimized to obtain the high decalin conversion of 83.1 %. Based on a series of experiments, it is indicated that the intermediate complex formed by tetramethylsilane, aluminum chloride and dichloroethane is the key to accelerate the reaction rate, and the reaction mechanism is proposed. Moreover, a pseudo-first-order irreversible reaction dynamics is studied, and the reaction kinetics parameters and reaction rate equati andons are obtained. After vacuum distillation, the fuel product shows high density (0.872 g/cm3) and high volumetric neat heat of combustion (36.9 MJ/L), much higher than those of RP-3 fuel. This work provides a facile method to synthesize high-performance jet fuel. [ABSTRACT FROM AUTHOR]

Catalytic crackingof hydrocarbon fuels is an effective way tocool aircraft materials under hypersonic flight. Pseudohomogeneouscatalysis is an alternative to overcome the problems of traditionalcatalyst coatings. Herein, we employed the Brust–Schiffrinmethod to synthesize Pt and Pd nanoparticles (NPs) using oleylamineas the protecting ligand. The particle size can be controlled by tuningthe ratio of protecting ligand, and uniform NPs can be obtained atan oleylamine/NP molar ratio of 2, with Pt and Pd NPs of 1–3and 2–5 nm, respectively. IR and TG characterizations confirmedthat the amine group of oleylamine is chelated on the metal surfacewhereas the hydrophobic carbon chain is exposed in the hydrocarbonfuel. As a result, the NPs are highly dispersible in jet fuel JP-10without any precipitation after standing 12 months, providing thepossibility of pseudohomogeneous catalysis. Suspensions containingPt and Pd NPs (50 ppm) exhibited markedly enhanced cracking performance,with cracking conversions, gas yields, and heat sinks at 680 °Cthat were, respectively, 4.5, 4.4, and 1.3 and 3.1, 3.6, and 1.2 timesof pure JP-10. In particular, Pt NPs can reduce the onset temperatureof the cracking reaction from 650 to 600 °C. This work demonstratesthe potential of fuel-dispersible NPs in hypersonic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The jet-fuel precursor is obtained by alkylation reaction using acidic zeolites. • HUSY-150 exhibited excellent catalytic performance and stability. • The solvent-free liquid-phase alkylation was carried out at a large space velocity. • The feedstocks are lignocellulose-derived phenolics and cyclopentanol. It is significant to efficiently and feasibly produce high-performance jet fuel from renewable biomass. We reported here that lignin-derived phenolics can be alkylated by cellulose-derived cyclopentanol in a continuous-flow fixed-bed reactor packed with HUSY zeolite without the use of solvents. Under nitrogen pressure, the liquid-phase reaction was achieved. Among the investigated zeolites with different structures and SiO 2 /Al 2 O 3 , HUSY-150 exhibited excellent catalytic performance and stability. By adjusting reaction conditions, almost complete conversion of cyclopentanol was achieved, as well as high phenol conversion (∼70 %), and high polycyclic product selectivity (>95 %) over HUSY-150. Afterwards, we extended the range of feedstock from phenol to other phenolics (guaiacol, 2,6-dimethoxyphenol, and lignin oil surrogates), and even at a high LHSV (liquid hourly space velocity) of 36 mL/(g cat ·h), HUSY-150 maintained robust catalytic activity. This study demonstrates a feasible and effective method for producing high-performance jet fuel blends using lignocellulose-derived compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fuel blending was synthesized by hydro-isomerization of cyclohexylphenol from biomass. • Isomerization is enhanced through inhibiting the quick hydrogenation of intermediates using catalyst mixture of HZSM-5 and Pd/C. • The fuel blending here has an improved low-temperature property and keeps the density unchanged. • (Cyclopentylmethyl)cyclohexane has amazing fuel properties as jet fuel. Fuel blending generally exhibits better low-temperature flow properties (i.e. low viscosity, low freezing point) than pure component fuel. Here, a fuel bending containing bicyclohexane and (cyclopentylmethyl)cyclohexane was synthesized directly by hydroisomerization of cyclohexylphenol to reduce the freezing point. The selectivity of (cyclopentylmethyl)cyclohexane formed by isomerization is enhanced through inhibiting the quick hydrogenation of intermediates using mixing acid catalyst and metal catalyst. Zeolite with strong Brønsted acid site and big surface area, such as HZSM-5 is better for the isomerization. Catalyzed by mixture of Pd/C and HZSM-5, the obtained fuel blending improves the freezing point from 2.6 °C to−22 °C compared with pure bicyclohexane, meanwhile keep the high density of 0.880 g/mL unchanged. The improved low-temperature property is contributed to the formation of (cyclopentylmethyl)cyclohexane. Moreover, the pathways of isomerization and its competition with hydrodeoxygenation are also investigated. [ABSTRACT FROM AUTHOR]

• Two spirocyclopropane high-energy–density fuels have been synthesized from cyclopentadiene. • Optimal cyclopropanation conditions were explored to obtain high yield. • The reaction process for cyclopropanation of CPD has been proposed. • Cyclopentadiene-based spirocyclopropane high-energy–density fuels exhibit high energy density, specific impulse and excellent low-temperature properties. High-energy–density fuels play a vital role in the development of the aviation industry because they can provide more propulsion energy than conventional liquid fuels. Constructing more five- or six-membered rings in fuel molecules is an efficient way to increase fuel density. However, as the number of rings increases, the hydrogen content of fuel molecules gradually decreases, resulting in a decrease in the mass calorific value, which limits the further improvement of the volumetric calorific value, meanwhile, the low-temperature characteristics of the fuel become worsen. Considering the high strain energy stored in cyclopropane moiety and the good cryogenic properties of spiro fuel, in this work, two spirocyclopropane high-energy–density fuels have been synthesized from cyclopentadiene by phase transfer catalytic cyclopropanation and palladium catalytic cyclopropanation, and the reaction conditions have been optimized. The synthesized fuels possess heat value and specific impulse higher than the widely used high-energy–density fuel JP-10. Additionally, their kinematic viscosity at low temperatures is only about one-third that of JP-10. The outstanding properties of the synthesized strained fuels suggest their good potential as high-energy–density fuels. [ABSTRACT FROM AUTHOR]

• Jet-fuel-ranged blending is synthesized with high molar yield of 83.9% in one-pot reaction using phenol and cyclopentanol. • The fuel blending has high density and good low-temperature property. • Feedstock is derived from lignocellulose. • Cyclopentylcyclohexane with high density 0.88 g/mL and low freezing point <−75 °C. Synthesizing high performance jet fuel from biomass provides potential way to convert low-cost biomass to valuable fuels and meets the requirements of sustainable development. Here, we report a one-pot synthesis of high density and low freezing point jet-fuel-ranged blending from bio-derived phenol and cyclopentanol, which is with high yield, simple and low-cost for scale-up. With the co-presence of acid catalyst like Hβ and metal catlayst like Pd/C, the alkylation first happens to produce bi-and tri-cyclic compounds under N 2 atomphere, then in H 2 atmosphere the remained reactant is partly hydrogenated and takes part in alkylation again to produce cyclic compounds, finally hydrodeoxygenation happens to convert all the compounds to cyclic hydrocarbons. A jet-fuel-blending containing bi- and tri-cyclic alkanes is obtained at high molar yield of 83.9% from the starting reactant, which shows high density of 0.89 g/mL, freezing point lower than −75 °C. Especially, the major component, i.e. cyclopentylcyclohexane shows much better low-temperature properties compared with reported hydrocarbons with similar molecular structure. This result provides a simple, low-cost way to synthesize high performance jet fuel from biomass. [ABSTRACT FROM AUTHOR]

Bicyclic and multi-cyclic hydrocarbons usually have high density over 0.87 g/cm 3 , which is very popular to synthesize from biomass-derived renewable chemicals, but their cryogenic properties need to be further improved for practical applications. In this work, we synthesized ethyl-substituted bicyclic high-performance hydrocarbons with improved cryogenic properties from the biomass-derived 4-ethylphenol and phenylmethaol. For the alkylation reaction between 4-ethylphenol with phenylmethanol, the reaction conditions were optimized, under which the conversion of phenylmethanol can achieve 100% with monoalkylated products (2-benzyl-4-ethylphenol and 3-benzyl-4-ethylphenol) selectivity of 71%. After hydrodeoxygenation catalyzed by a mixture catalyst of Pd/C and HZSM-5, the alkylation products were mainly converted to the ethyl-substituted dicyclohexylmethane. The obtained fuel shows a high density of 0.873 g/cm 3 (20 °C), gravimetric net heat of combustion of 42.7 MJ/kg, and the freezing point of −42 °C, which is promising to serve as a blend component for jet fuel application. [ABSTRACT FROM AUTHOR]

The exploration to increase the fuel energy density is stimulated by the payload and cruising range concerns in aerospace industry. The high-density fuels are always rationally designed for the advanced volume-limited aircrafts to fulfill more complicated missions. Alkyl adamantanes gradually become a prospective class of high-energy-density fuels. Herein, in this work, we reported an approach to synthesize asymmetric cyclopentyl adamantane via AlCl 3 -catalyzed alkylation of adamantane and cyclopentene with an attractive combination of a high density of 0.990 g/mL as well as a low freezing point of −30 °C. The obtained 1-cyclopentyl-adamantane was well designed with the cyclic substituent (enhance the density) and asymmetric structure (lower the freezing temperature). Subsequently, the comprehensive fuel performance of cyclopentyl adamantane, i.e. , density, freezing point, low-temperature viscosity, heating value, and combustion properties were evaluated. It was shown that both density and combustion properties of cycloalkyl adamantane were superior to the typical high-density JP-10 fuel. In addition, the properties of binary fuel mixture (1-cyclopentyl-adamantane and JP-10) demonstrated that cyclopentyl adamantane could be used as a promising blendstock with conventional jet fuel to enhance the energy density and promote the combustion performance of the final fuel blends. [Display omitted] • Asymmetric cycloalkyl adamantane was synthesized via alkylation. • Cyclopentyl adamantane owned higher density than reported adamantanes and JP-10. • Relationships between molecular structure and properties were discovered. • Cyclopentyl adamantane was a novel hydrocarbon fuel for aerospace propulsion. [ABSTRACT FROM AUTHOR]

Upgrading lignocellulosic ketones to Jet fuel precursors by aldol condensation is the key step for the synthesis of high-grade bio-Jet fuels. State-of-art works are confined in pure feedstock used, catalysis sites leaching and coking. Therefore, we synthesized a strong solid acid HfTPA/MCM-41 and used it to catalyze aldol condensation of lignocellulosic ketone mixture to bio-jet fuel blending precursors, where 80 %Hf 1.5 TPA/MCM-41 shows better activity than 80 %HPW/MCM-41 and commercial zeolites with 66.8 % yield of products obtained. The good performance of the catalyst is ascribed to good acid properties, large surface area and especially new strong L acids and good stability based on anti-coking and water tolerance by Hf doping, which changes the electronic structure of the catalyst surface to efficiently activate C O bond of ketones to form a metal enolate intermediate and anchoring HPW from leaching. This work demonstrates an efficient way to synthesize high-performance acid catalyst applied in bio-jet fuel synthesis. [Display omitted] • A good-performance strong solid acid catalyst with new strong L acid and good stability was synthesized. • The good-performance of the catalyst is attributed to the Hf doping. • This catalyst was simply synthesized by combination of equivalent-volume impregnation and co-deposition. • High-performance bio-jet fuel blending precursors were synthesized using lignocellulosic derivatives ketones. [ABSTRACT FROM AUTHOR]

Branched decalins are promising jet fuel components with high density, high thermal stability and low freezing point, but its accessibility is limited by fossil resources. Here we report a novel H 2 SO 4 catalytic one-pot synthesis process using cyclic alcohols (cyclohexanol, cyclopentanol) and branched cycloalkanes (methylcyclohexane, methylcyclopentane) that can be derived from lignocellulose and/or refineries as feedstock. The reaction occurs in a consecutive way of dehydration, alkylation, rearrangement and hydrogen transfer to produce branched decalins. The dehydration/oligomerization of alcohols also produces branched cycloalkanes but the carbon yield and selectivity are very low, and the presence of branched cycloalkanes significantly improves the reaction. The reaction goes smoothly at room temperature and continuous feeding of alcohols can further increase the yield. Under optimized reaction conditions, the carbon yield and branched decalins selectivity vary in range of 61–87%, dependent on the reactants used. The branched decalins show good fuel properties like density as high as 0.88 g/mL and freezing point as low as −110 °C, and can be produced in large scale. [ABSTRACT FROM AUTHOR]

Energetic particles have been used in solid propellant to increase the energy content, but for liquid fuel, the addition of such particles is still challenging because of severe particle precipitation. Here we demonstrate the possibility of adding surface-modified boron nanoparticles (NPs) in jet fuel JP-10. Trioctylphosphine oxide is very effective to stabilize NPs by inhibiting the contact and agglomeration. After 6 weeks, 12.7 wt% NPs are still dispersed in fuel, which increases the density and volumetric energy from 0.93 g/mL and 39.4 MJ/L to 0.98 g/mL and 43.4 MJ/L, respectively. The suspension flows freely like liquid fuel and has relatively low viscosity at low temperature. [ABSTRACT FROM AUTHOR]

• The effects of phenolic antioxidants on high-energy–density fuel thermal oxidation and deposition were investigated. • The addition of antioxidants can significantly inhibit fuel oxidation. • TBDP and TBMP show better performance in antioxidation than BHA, DTBP and BHT. • The addition of phenolic antioxidants cause more severe deposition. The addition of antioxidants is normally adopted to improve the thermal oxidation stability of jet fuel, but the detailed antioxidation mechanism is still ambiguous. Herein, the inhibition of exo -tetrahydrodicyclopentadiene (the main component of JP-10) toward thermal oxidation and deposition by phenolic antioxidants (2,6-di- tert -butyl-4-methyphenol (BHT), 6- tert -butyl-2,4-dimethyphenol (TBDP), 2,6-di- tert -butylphenol (DTBP), 2- tert -butyl-4-methoxyphenol (BHA) and 2- tert -butyl-4-methylphenol (TBMP)) was investigated to reveal antioxidation mechanism and screen the best antioxidant for high-energy–density fuel. The theoretical and experimental results show that the addition of all phenolic antioxidants can significantly inhibit fuel oxidation and prolong the shelf life. Importantly, TBDP and TBMP show better performance than other antioxidants since they can scavenge more radicals per antioxidant molecule. However, antioxidants form dimer products via the addition between phenoxyl radicals and alkyl radicals during short-term thermal stress, which has a higher tendency to produce deposits. Consequently, the addition of phenolic antioxidants causes more severe deposition when jet fuel serves as the coolant in aircrafts. This work would guide the rational design of antioxidant for practical application in high-energy–density fuel. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of high-performance bio-jet fuel by directly making fuel blending. • Making jet fuel blending using lignocellulosic derivatives as feedstock. • Develop an efficient catalyzing and energy-saving method of synthesis of jet fuel blending by co-conversion of biomass mixture. Bio-jet fuel synthesis is a promising way to upgrade the value of lignocellulose and contributes to the sustainable development. Presently the property of bio-jet fuel is weakened by single component produced using pure feedstock and water produced in the reaction leading to acid leaching. Therefore, we synthesized a hydrophobic acid resin (R-x) and used it to catalyze lignocellulose-derived mixture upgrading to high-performance bio-jet fuel blending, where R-x shows better activity than Amberlyst-15, Nafion-212 and Hβ with 75.4% of product yield obtained in co-conversion of lignocellulosic derivatives. The better activity of R-x is ascribed to the strong acid, big acid concentration, large surface area and especially super hydrophobicity resulting as R-x recycled steadily in consecutive 5 runs. After hydrodeoxygenation, jet fuel blending with high density and excellent freezing point better than JP-7 was obtained. This work demonstrates an efficient catalyzing method to synthesize high-performance jet fuel by co-conversion of lignocellulosic derivatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Water-tolerant SBA-16 confined phosphotungstic acid catalysts were synthesized. • This acid catalyst was efficient and stable for aldol condensation. • Jet-fuel was obtained by cross-condensation of lignocellulose-derived cyclic ketones. • The bio-jet fuel has density of 0.906 g/mL and freezing point lower than −50 °C. Synthesizing high-performance jet fuels from lignocellulose-derived ketones through aldol condensation is significant for expanding the sources of jet fuel and promoting high-value conversion of biomass. The main problem in aldol condensation is that water generated in such a reaction will decrease the activity of the acid catalyst. Herein, we developed a highly stable, efficient, and water-tolerant SBA-16 confined phosphotungstic acid (HPW) catalyst and applied it to controllably catalyze cross-condensation of cyclopentanone and cyclohexanone. The surface of SBA-16 was modified by alkylimidazole, which creates a relatively hydrophobic environment and anchor points for HPW, leading to resistance to HPW leaching and maintenance of a stable performance for the catalyst. After hydrodeoxygenation, a high-performance fuel blend with a density of approximately 0.905 g/mL and a freezing point lower than −50 °C was obtained. This study provides a general method for preparing highly efficient and stable catalysts for reactions affected by water. [ABSTRACT FROM AUTHOR]

• The oxidation stability and deposition propensity of C10 hydrocarbon fuels were investigated. • The oxidation stability follows the order of n- decane > exo -THDCPD > trans- decalin > cis- decalin > tetralin. • The deposition propensity follows the order of trans- decalin > exo- THDCPD > n- decane > cis- decalin > tetralin. • The oxidation stability is highly associated with molecular-structure-dependent C–H bond dissociation enthalpy. • The deposition propensity is associated with the stability of oxidation intermediates. Thermal oxidation stability is a key issue for jet fuel when serving as a coolant in aircraft. However, the deposition propensity and mechanism of hydrocarbons with different molecule structures remain ambiguous. In this study, the oxidation stability and deposition propensity of C10 hydrocarbon fuels, i.e. , tetralin, cis- / trans- decalin, exo -tetrahydrodicyclopentadiene (exo- THDCPD), and n- decane, were determined. The oxidation stability of hydrocarbons follows the order of n- decane > exo- THDCPD > trans- decalin > cis- decalin > tetralin, which is highly associated with the molecular-structure-dependent C–H bond dissociation enthalpy. Differently, the deposition propensity follows the order of trans- decalin > exo- THDCPD > n- decane > cis- decalin > tetralin, which can be associated with the stability of oxidation intermediates, especially the hydroperoxides. The more stable the intermediates are, the fewer deposits will be produced. These results demonstrate the relationship between thermal oxidation stability and hydrocarbon molecular structure, which is helpful for a better understanding of jet fuel deposition mechanism. [ABSTRACT FROM AUTHOR]

In current aircraft designs, jet fuel serves a dual role as a coolant to satisfy the cooling requirements and as a propellant to provide propulsion power, especially in high-performance aircraft. Importantly, thermal oxidative stability is one of the key issues for jet fuels that serve as coolants since the formation of deposits during heat exchange will directly influence the operational safety of the aircraft. This review summarizes the research progress on the thermal oxidation and deposition of jet fuel during autoxidation, with particular emphasis on the research performed over the past few decades. The precise concept of thermal oxidative stability is first introduced. Then, the oxidation and deposition mechanisms of jet fuel and the corresponding reaction kinetics during thermal stress are comprehensively summarized. After that, different evaluation techniques (oxidation and deposition), as well as the factors influencing the thermal oxidative stability of jet fuel (chemical and physical factors), are presented in detail. Finally, the corresponding improvement methods for delaying fuel oxidation and mitigating deposition are proposed. This review will be beneficial for the design of jet fuel with high thermal oxidative stability and the further development of high-performance aircraft. [ABSTRACT FROM AUTHOR]

• The thermal oxidation and deposition behaviors of decalin were investigated. • The decomposition of hydroperoxides gives gas products and polar species. • Comparing with SMORS, the insoluble deposits contain more highly polar species. • The oxygen plays a determining role in forming the final insoluble deposits. • The molecule structures and formation process of insoluble deposits were proposed. Highly thermal-stable jet fuel plays an important role in the advanced supersonic aircrafts, but its oxidation to the insoluble deposits is a serious problem when serving as a coolant. However, there are few reports as to the deep insights of insoluble deposits formation. Here we apply the PetroOxy device to investigate the thermal oxidation and deposition behaviors of highly thermal-stable jet fuel, using decalin as the model jet fuel, in order to explore the formation mechanism of insoluble deposits. All oxidation products (gas, liquid and solid) of fuel at different oxidation stages were separated and carefully characterized. The initial oxidation of fuel produces hydroperoxides, which then decompose rapidly to produce gas products (H 2 , CO or CO 2) as well as large amounts of polar species (soluble oxidized products, e.g. , alcohols, ketones, and molecular growth products). Meanwhile, these polar monomer species condense to produce soluble macromolecular oxidatively reactive species (SMORS) and insoluble deposits. The SMORS amount increases during the overall oxidation process, but the amount of insoluble deposits increases only in the presence of oxygen. The characterizations of liquid chromatography/electrospray ionization mass spectrometry and solution-state 2D heteronuclear single quantum coherence NMR confirm that the concentration of highly polar macromolecular species in insoluble deposits is much higher than that in SMORS, which causes the precipitation of the insoluble deposits from the bulk fuel. We further propose the detailed formation process and chemical structures of the insoluble deposits during the autoxidation of highly thermal-stable jet fuel, which would be helpful for a better understanding of the deposition mechanism of jet fuel and the improvement of its thermal stability. [ABSTRACT FROM AUTHOR]

• Jet-fuel-ranged blending is synthesized in one-pot reaction. • Reduced graphene oxide can improve the carbon yield and properties of obtained fuel. • Feedstock are both derived from lignocellulose. • The fuel blending has high density, low freezing point and high thermal stability. Synthesis of jet fuel with high density, good low-temperature property and high thermal stability is significant to aerospace industry. Here, a great-performance jet fuel blending including bi- and tri-cyclic hydrocarbons (C10 ~ C16) is synthesized with high yield through reduced graphene oxide (rGO) assisted H 2 SO 4 catalytic one-pot reaction of cyclopentanol and methylcyclopentane. The reaction occurs through a consecutive way of dehydration, alkylation, rearrangement and hydrogen transfer. Carbon-based materials especially rGO are used as additive to increase the carbon yield by promoting the emulsification of reactants in sulfuric acid. Promoted emulsification improves the alkylation of cyclopentanol with methylcyclopentane and makes the hydrogen transfer easier, which highly increases the conversion of methylcyclopentane (54.9%), the carbon yield (83.2%) and the selectivity (97.3%) of products. Finally, a jet-fuel-ranged blending with overall yield of 71.8% is obtained by distillation, which shows high density of 0.90 g/mL, low freezing point of ＜-72 °C and a high oxidation onset temperature of 195.0 °C. This work provides a simple, efficient and low-cost way to synthesize high performance jet fuel from biomass. [ABSTRACT FROM AUTHOR]

• The impacts of hydrogenation degree on jet fuel oxidation were investigated. • The impacts of hydrogenation degree on jet fuel deposition were investigated. • The oxidation products of jet fuels were analyzed by GC × GC–MS. • The roles of heteroatomic species and aromatics in thermal oxidative stability were analyzed. Thermal oxidative stability is a key issue for jet fuel serving as a coolant of high-performance aircraft. This study investigated the effects of the hydrogenation degree on the oxidation and deposition of jet fuel (RP-3). Fuels with different hydrogenation degrees were achieved by a commercial catalyst, with the aromatic content reduced from 12.6 wt% to 0.4 wt%, resulting in a slight density decrease and a slight increase of the net heating value. Meanwhile, the total sulfur content of hydrogenated fuel was lowered to below 1 ppm, and the naturally occurring phenols were completely removed. The initial oxidation reactivity and deposition tendency of hydrogenated fuels were investigated by pressure differential scanning calorimetry and jet fuel thermal oxidation tester, respectively. For the initial oxidation, both the oxidation OT (onset temperature) and IP (induction period) of jet fuel decrease with increasing hydrogenation degree and show good linear correlations with the aromatic content. For thermal deposition, pristine RP-3 cannot pass the JFTOT test (355 °C for 5 h), while all hydrogenated RP-3- t can pass 355 °C JFTOT test, owing to the almost total removal of inherent heteroatomic species (sulfurs and phenols) by hydrogenation. This work confirms that deep hydrogenation is a promising approach to improve the thermal oxidative stability of jet fuel (fewer deposits) for the practical applications. [ABSTRACT FROM AUTHOR]