Rearrangement of Tetrahydrotricyclopentadiene Using Acidic Ionic Liquid: Synthesis of Diamondoid Fuel

Abstract

As a work successive to AlCl 3 catalytic isomerization of tetrahydrotricyclopentadiene (THTCPD) [Wang, L.; Zhang, X.; Zou, J.-J.; Han, H.; Li, Y; Wang, L. Energy Fuels 2009, 23 (5), 2383À2388], the reaction using chloroaluminate ionic liquid (IL) was investigated. It is found that IL catalysis gives totally different product distribution. The endo-cycloproyl fragments of THTCPD that cannot be isomerized by AlCl 3 catalysis are transferred to exo conformation easily. Furthermore, the hydrocarbons are transferred to diamondoids, including methyl-1,2-tetramethyleneadamantane, methyl-diethyl-adamantane, and methyl-diamantane via skeletal rearrangement, with the first diamondoid as the primary and dominant product (selectivity > 80%). The IL shows much higher activity than superacid CF 3 SO 3 H, attributed to the synergetic effect of strong acidity and the novel solvent environment. Increasing the temperature, IL dosage, and AlCl 3 in IL can promote the rearrangement rate with a slight decrease in the selectivity of methyl-1,2-tetramethyleneadamantane. The presence of trace water in IL forms superacid and induces considerable cracking byproducts, and solvent typically used in rearrangement decreases the reaction rate. The diamondoid-based product shows a low freezing point and high hydrogen content and, thus, is superior as a high-energy-density fuel. This work may open a door for facile synthesis of diamondoid fuel. INTRODUCTIONThe rapid expansion of aeronautical and space technologies has been raising higher requirements for aerospace fuels, and a high volumetric energy content is specifically preferred for volumelimited aircrafts, such as missiles, rockets, and spacecrafts. 1À5 High-energy-density fuels provide much more propulsion energy than conventional distillated fuel and, thus, significantly increase the payload and flight range. They generally possess a compact cyclic structure to afford a high density and high energy content, such as tricyclic JP-10 (with a density of 0.94 g/mL and an energy content of 39.6 MJ/L) and pentacyclic RJ-5 (with a density of 1.08 g/mL and an energy content of 44.9 MJ/L). 1,5 Besides, the low-temperature performance of fuels, typically freezing point, is critical because they often encounter harsh environments, such as cold weather and high altitudes. JP-10 is the current standard missile fuel attributed to its low freezing point (À79°C), and RJ-5 is abolished because of its high freezing point (about 0°C).Diamondoids are hydrocarbons that have carbon framework superimposable on the diamond lattice, in which the adamantane cage is the basic unit. 6À8 Naturally occurring diamondoids are first discovered in some crude oil and natural gas condensates. Lower diamondoids, such as adamantane, diamantane, and triamantane, have been synthesized, but molecules containing more than four adamantane cages have not been prepared because of their complicated structure. 9À11 Owing to their compact structure, diamondoids has been regarded as a new kind of highenergy-density fuel, and the alkyl-su...

Oligomerization of endo-dicyclopentadiene using a mesoporous catalyst in a fixed-bed reactor

“…The products of endo-DCPD oligomerization contained various isomers of TCPD and tetraicyclopentadiene (TeCPD) [12,15]. The isomerization selectivity of TCPD Oligomerization of endo-dicyclopentadiene using… was calculated based on the conversion of endo-, exo-, endo-TCPD (endo-TCPD) to other isomers.…”

A Study on the Reaction Pathway for Isomerization of Tetrahydrotricyclopentadiene Using Ionic Liquid Catalyst

“…주성분이 exo-tetrahy- 독성과 폭발성 그리고 허용 가능한 인화점의 특성을 필요로 한다 [2]. 차세대 HEDF를 개발하기 위하여 높은 체적에너지 함량과 낮은 어는 점을 가지는 물질에 대한 많은 연구가 진행되어 왔다 [3][4][5][6][7]. THTCPD의 이성화를 위한 촉매로는 Lewis acid계 촉매인 AlCl3 (aluminum chloride)가 알려져 있다 [3,4].…”

“…THTCPD의 이성화를 위한 촉매로는 Lewis acid계 촉매인 AlCl3 (aluminum chloride)가 알려져 있다 [3,4]. AlCl3를 촉매로 사용한 THTCPD 의 이성화 전환율이 87%로 우수하고 온화한 반응조건에서 반응이 진행되 는 장점 [3]을 가지고 있으나, 반응 후 촉매를 재사용 할 수 없고, 촉매를 제거하기 위한 후처리 공정에서 부식성 폐기물이 생성된다는 단점을 가지 고 있다 [5,[10][11]. 최근에 친환경 용제 및 촉매로 많은 관심을 받고 있는 이온성 액체(Ionic Liquid; IL)는 상온에서 액체상을 가지는 이온성 염 화합 물이다 [12].…”

One-Pot Catalytic Transformation of Dicyclopentadiene to High Energy Density Fuel Exo-tetrahydrotricyclopentadiene

“…It has been widely used in land-, ship-and air-launched missiles [3][4][5][6][7]. Recently, researchers are exploring fuels with higher volumetric energy content [8][9][10][11][12][13][14]. This can be achieved by fabricating compact hydrocarbons with a polycyclic structure and high C/H ratio.…”