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Solar‐driven conversion of renewable biomass resources into high‐density hydrocarbon fuels can effectively realize biomass valorization and renewable energy conversion. In this work, an efficient self‐sensitized [2 + 2] photocycloaddition process is explored to develop highly strained fuel with high yield using norbornene and biomass‐derived cyclohexenone as feedstocks. The enhancement mechanism is revealed by phosphorescent measurement and theoretical calculation, and a reasonable reaction path for self‐sensitized [2 + 2] co‐cycloaddition is proposed. When using methanol as solvent, the apparent activation energy of co‐cycloaddition is 21.37 W/mol, which is lower than that of self‐cycloaddition (31.57 W/mol). Importantly, the jet‐fuel‐range highly strained fuel has high density (0.986 g/cm3) and high volumetric net heat of combustion (41.14 MJ/L), which are 5.34% and 4.39% higher than those of JP‐10, respectively. This work proposes a green and effective pathway for the preparation of high‐performance hydrocarbon fuel with polycyclic‐asymmetric structure. [ABSTRACT FROM AUTHOR]

Cyclopropane derivates are appealing to synthesis of high‐energy‐density fuels because of the high strained energy of the three‐numbered ring. The catalytic cyclopropanation of olefin with diazomethane is very effective to construct the carbocycle. The majority of the catalysts employed are nonrecyclable homogeneous compounds. Herein, we report cyclopropanation of polycyclic olefins catalyzed by heterogeneous Pd/C. The optimal cyclopropanation conditions were explored utilizing dicyclopentadiene as model substrate and a series of polycyclic olefins were cyclopropanated with high yield. Additionally, the catalyst has good recyclability and stability, as shown by characterizations as well as the fact that no inactivation happens after cyclopropanation. The synthesized cyclopropane derivates exhibit good fuel characteristics like high density (1.006–1.087 g/cm3), high volumetric net heat of combustion (42.58–46.45 kJ/cm3), good low‐temperature and combustion performance. This work shows industrial potential for cyclopropanation of polycyclic olefins with diazomethane. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PtSn/D β catalyst was prepared for high dehydrogenation performance. • Monocyclic cyclohexane without branched chains has the best dehydrogenation property and the highest heat sink. • The branched chain, ring number and five-membered ring have negative effects on dehydrogenation reaction. • Polycyclic alkanes with low H/C ratio and high M have both high density, high volumetric net heat of combustion and high heat sink. Polycyclic alkanes are not only the important components of high-density fuels, but also can be used to cool the overheating parts of hypersonic vehicle through catalytic endothermic dehydrogenation reaction. However, the dehydrogenation performances of cycloalkanes with different molecule structures vary widely. Herein, we investigated the effects of cycloalkane structures, including the length of branched chains, the number of branched chains, the number of rings, and the shape of rings, on the dehydrogenation performance. The results show that cyclohexane (CH) exhibits the best dehydrogenation performance (600 °C, 3 MPa) with >99% conversion, >99% benzene selectivity, and highest total heat sink of 4.47 MJ/kg. The branched chains, ring number and five-membered rings all have negative effects on dehydrogenation. Among them, the number of rings has the minimum negative impact. Moreover, we correlated the density, volumetric net heat of combustion (NHOC) and heat sink with the molecular structure of the cyclic alkanes and found that the polycyclic alkanes with low H/C ratio and high M have both high density, high volumetric NHOC and high heat sink. This work can provide guidance for development and design of advanced fuels for endothermic dehydrogenation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new HED endothermic fuel, HS-1,3-DMA, was synthesized by alkylation catalyzed by AlCl 3. • HS-1,3-DMA shows high density of 0.89 g·cm−3 and high combustion energy of 42.4 MJ·kg−1. • HS-1,3-DMA shows high heat sink of 1.93 MJ·kg−1 at 575 °C, 11.6% and 9.7% higher than JP-10 and 1,3-DMA. • The thermal cracking of HS-1,3-DMA leads to lower coke deposition. High-density endothermic fuels have drawn much attention for aerospace vehicles due to their advantage in high density and heat sink. Herein, a new high-density endothermic fuel, hexyl-substituted 1,3-dimethyl adamantane (HS-1,3-DMA), was synthesized by alkylation of 1,3-DMA with hexene catalyzed by AlCl 3. The alkylation reaction conditions (catalyst and its amount, 1,3-DMA/hexene ratio and reaction temperature) were optimized, and the 1,3-DMA conversion of 46.0% with HS-1,3-DMA selectivity of 67.9% can be obtained. Importantly, HS-1,3-DMA shows high density of 0.89 g·cm−3, high combustion energy of 42.4 MJ·kg−1 and high heat sink of 1.93 MJ·kg−1 at 575 °C (4 MPa), which is 11.6% and 9.7% higher than those of JP-10 and 1,3-DMA. Moreover, the thermal cracking of HS-1,3-DMA leads to lower coke deposition, whose amount is ca. 50.0% of JP-10 and 1,3-DMA. Notably, HS-1,3-DMA has a higher density and heat sink at low temperatures than that of EHF-80, respectively, while at high temperatures, heat sink of HS-1,3-DMA is also similar to that of EHF-80. This work provides a promising route to produce high-density endothermic fuel for practical application. [ABSTRACT FROM AUTHOR]

• Strained quadricyclane is used as additive of JP-10. • Quadricyclane increases the density of JP-10. • 1% quadricyclane reduces the ignition delay time of JP-10 by 40%. • 1% quadricyclane increase the combustion efficiency of JP-10 by 5%. With the development of supersonic aerospace propulsion, the demand for high-density fuels with excellent ignition and combustion performance has become imperative. This work will explore the influence of strained quadricyclane (QC) on ignition and combustion properties of high-density fuel JP-10 utilizing shock tube, hot-plate ignitions, and oxygen bomb combustion. Shock tube test shows that 1% QC/JP-10 blended fuel gives a 40% decrease of ignition delay time and a 17% decrease of apparent ignition activation energy compared with pure JP-10, respectively. Hot-plate ignition test shows that adding 1% QC in JP-10 can decrease the ignition delay time by 20% and reduce the lowest ignition temperature by 20 °C. Oxygen bomb calorimetric test shows that 1% QC/JP-10 blended fuel gives the highest heat of combustion and the highest combustion efficiency in air excessive ratio range of 1.2–2. The most significant effect of 1% QC addition is attributed to the easy flammability and low activation energy of QC. This work also suggests QC as a good additive to enhance the combustion performance of high-density fuels. [ABSTRACT FROM AUTHOR]

A one‐pot Mannich–Diels–Alder reaction was developed for synthesis of high‐performance jet‐fuel‐range spirocycloalkane with an overall yield of 71.6% from biomass and petroleum derived cyclopentanone, formaldehyde, and cyclopentadiene. HZSM‐5 zeolite with Si/Al molar ratio of 130 exhibits much higher catalytic activity, along with good recycling ability. Over it, a high selectivity (81.6%) and yield (80.9%) of target adduct is achieved with almost complete conversion of cyclopentanone, attributed to the synergy effect of appropriate ratio of Lewis to Brønsted acid sites and mass transfer effect of porous zeolite. More importantly, after hydrodeoxygenation, the resultant spirocycloalkane has much higher density and volumetric neat heat of combustion (0.952 g·ml−1, 40.18 MJ L−1) than the wildly used JP‐10 fuel (0.936 g ml−1, 39.41 MJ L−1). This work provides a promising route to produce high‐performance jet‐fuel‐range hydrocarbons through co‐conversion of biomass and petroleum derivatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Functionalized energetic-microcapsules (nB@M−CS) are fabricated via microfluidics. • nB@M−CS have high size uniformity, low catalyst loading and homogenous dispersion. • nBs in the energetic-microcapsules can be released and ignited by micro-explosion. • Low catalyst loading and homogenous dispersion improve the interfacial catalysis. • Combustion can be enhanced by coupling the micro-explosion and interfacial catalysis. Energetic metal and metalloid nano-powders are highly promising as high-energy fuel or energetic additive of propellants. Specifically, boron has extremely high gravimetric and volumetric calorific values. However, the difficulty of ignition, slow combustion and uncomplete energy release limit its application. Herein, we developed an effective strategy to fabricate the functionalized energetic-microcapsules (nB@M−CS) with uniform size (with coefficient of variance lower than 3%) using droplet microfluidic technology, in which the boron nanoparticles (nBs) are uniformly encapsulated in chitosan (CS), with organometallic catalyst (M = Mo, Fe and Co) homogeneously dispersed inside. During combustion, nB@M−CS can overcome the agglomeration of nBs by generating micro-explosion to release and ignite the inner nBs, and the low loading (<2 wt%) and high dispersion of metal catalyst can shorten the mass transfer distance and enhance the contact area between nBs and M catalyst. These can significantly reduce the thermal oxidation temperature and accelerate the combustion rate. Specifically, nB@Mo-CS shows much lower initial oxidation temperature (393 °C) than the previously reported B particles, and exhibits the combustion heat and maximum pressurization rate increased by 114.3% and 7.3 times, respectively, compared with nBs. This work shows the great potential for designing and synthesizing functionalized propellant using microfluidic technology. [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]

• Acid-catalyzed rearrangement to synthesize high-performance biomass-based alkyl-adamantanes is reported. • The rearrangement products have high density, low viscosity and high thermal oxidative stability. • The rearrangement products can improve the combustion performance of JP-10. Biomass-based aviation fuel is attractive for sustainable development. Herein, we report a facile route to synthesize alkyl-adamantanes (AAMs) via acid-catalyzed rearrangement of biomass polycyclic sesquiterpene derivatives (bio-PCS derivatives). The reaction conditions including catalysts, solvents, reaction temperature and reaction time were optimized. Notably, a total AAMs yield of 65.1% was achieved under the optimal conditions. The kinetics of rearrangement reaction was investigated, and the reaction rate constant (k) and apparent activation energy (E a) were calculated based on the experimental kinetic data. The rearrangement products possess high density of 0.90 g/cm3, high net heat of combustion of 42.6 MJ/kg, low viscosity (22.5 mm2/s at −20℃) and high thermal oxidative stability. The blending of rearrangement products with JP-10 can significantly shorten the ignition delay time (IDT) of JP-10. This work provides a method to synthesize high-performance biomass-based AAMs. [ABSTRACT FROM AUTHOR]

• HED fuel is synthesized by photoinduced [2 + 2] cycloaddition of norbornene. • The fuel shows high density of 1.024 g/mL and high volumetric NHOC of 42.98 MJ/L. • The photosensitized processes contain triplet energy transfer, cyclization and relaxation. • The pseudo reaction kinetics parameters and reaction rate equations are obtained. High-energy–density (HED) fuels have attracted extensive attention for volume-fixed aerospace vehicles because they can provide more propulsion energy to increase the payload and range of aerospace vehicles. Herein, we report a route for synthesis of HED fuel, pentacyclo[8.2.1.14,7.02,9.03,8]tetradecane (PCTD) with strained structure, by photoinduced intermolecular [2 + 2] cycloaddition of norbornene (NBE). The triplet quenching and phosphorescence quenching results indicate that NBE cycloaddition is conducted through the photosensitized processes containing triplet–triplet energy transfer, cyclization and relaxation. The reaction conditions are optimized to obtain the high photocatalytic activity, with the NBE conversion and PCTD selectivity reaching 78.7% and 94.4%, respectively. Moreover, a kinetic model is proposed with the reaction rate equation being correlated with the incident light flux, with the pseudo reaction kinetics parameters and reaction rate equations obtained. Importantly, PCTD shows high density of 1.024 g/mL and high volumetric net heat of combustion of 42.98 MJ/L, much higher than those of JP-10. In addition, blending with JP-10 or QC can significantly improve cryogenic properties of blended fuels, which is very promising for the practical application. [ABSTRACT FROM AUTHOR]

High-energy-density (HED) fuels have drawn substantial attention for volume-limited aerospace vehicles because they can provide high propulsion energy. Herein, we report a route for synthesis of HED fuel pentacyclo[5.3.0.02,5.03,9.04,8]decane (PCD) with strained structure by photoinduced intramolecular [2 + 2] cycloaddition of dicyclopentadiene (DCPD). The reaction conditions, like photosensitizer, solvent, concentration, temperature and light intensity, were optimized for achieving the best photochemical performance, with the high DCPD conversion of 95.89% and high PCD selectivity of 62.08%. The triplet quenching and phosphorescence quenching results show that DCPD cycloaddition proceeds under the photosensitizer photoexcitation, triplet-triplet energy transfer, cyclization and relaxation. Moreover, a reaction kinetic model is established with the reaction rate constant being correlated with light intensity, with the pseudo reaction kinetics parameters and reaction rate equations obtained. As a caged fuel, PCD possesses both high density (1.066 g/cm3) and high volumetric neat heat of combustion (44.43 MJ/L), which is very promising to blend with current high density liquid fuels to obtain high-performance fuels for practical application. • PCD is synthesized by a one-step photoinduced intramolecular [2 + 2] cycloaddition. • The triplet sensitization mechanism was proposed. • A reaction kinetic model correlated with light intensity is established. • PCD exhibits both high density and high volumetric neat heat of combustion. • PCD is a promising high-energy additive for practical application. [ABSTRACT FROM AUTHOR]

• Jet-fuel-range fuel is synthesized by dimerization reaction using acidic zeolites. • Hβ-25 shows the best performance with high NBE conversion and dimers selectivity. • The obtained fuel has high density and high volumetric neat heat of combustion. • The dimers fuel shows lower ignition temperature and shorter delay time than JP-10. Given a volume-fixed oil-tank, the advanced fuels with high energy density will increase the payload and range of the aircraft. Herein, we synthesized the high-energy–density liquid fuel via catalytic dimerization of norbornene by the acidic zeolites. Importantly, we reveal the relationship between the structural properties (i.e. , B/L acid site ratio and porous structure) of acidic zeolites and the conversion and selectivity of dimerization, and demonstrate the mechanism and kinetics of isomerization-dimerization two-step process. Among the investigated catalysts, Hβ-25 exhibits the best activity with high norbornene conversion and acceptable dimers selectivity, which is attributed to the synergy effect of appropriate B/L acid site ratio and suitable pore size. After hydrogenation, the obtained fuel has high density (0.978 g/cm3) and high volumetric neat heat of combustion (41.49 MJ/L), which are much higher than those of widely used JP-10 fuel. This work provides a promising route to produce high-energy–density fuel for practical application. [ABSTRACT FROM AUTHOR]

• Three families of polycyclic hydrocarbons were proposed for high-energy-density fuels candidate. • The physicochemical and propulsion properties of polycyclic hydrocarbons were estimated. • The relationship between the propulsion performance and hydrocarbon structure characteristics was established. • The strained rings in molecules improves the density and specific impulse of polycyclic hydrocarbons. Polycyclic hydrocarbons have great potential as advanced high-energy-density (HED) fuels, and their physicochemical and propulsion properties are highly important for propulsion purposes. In this work, the fuel properties including density, melting point, boiling point, critical temperature/pressure, enthalpy of vaporization, enthalpy of fusion, enthalpy of combustion and specific impulse of three families of polycyclic hydrocarbons (a, cyclopropyl and methyl-substituted derivatives of tri-, tetra- and penta-cyclic hydrocarbons; b, [n]prismanes; and c, homocubanes) were evaluated by combining the group contribution and quantum chemical methods. The applied method properly predicts the physicochemical properties of polycyclic hydrocarbons, which are highly dependent on their molecule structures. For category (a), the hydrocarbons with low H/C ratio generally have higher density, volumetric specific impulse and volumetric combustion heat. Importantly, for all three families of polycyclic hydrocarbons, introducing additional strained rings (cyclopropyl ring or cyclobutyl ring) in molecules remarkably improves their density and specific impulse, which are highly appropriate for volume-limited aerospace vehicles to extend the flight range and increase the payload. The study on the relationship between the propulsion performance and structure characteristics of these hydrocarbons will give the general rule for the rational design of HED fuels. [ABSTRACT FROM AUTHOR]