Synthesis of renewable high-density fuel with isophorone

Abstract

1,1,3-Trimethyl-5-(2,4,4-trimethylcyclohexyl)cyclohexane, a renewable high density fuel, was first produced in a high overall carbon yield (~70%) with isophorone which can be derived from hemicellulose. The synthetic route used this work contains three steps. In the first step, 3,3,5-trimethylcyclohexanone was synthesized by the selective hydrogenation of isophorone. Among the investigated catalysts, the Pd/C exhibited the highest activity and selectivity. Over this catalyst, a high carbon yield (99.0%) of 3,3,5-trimethylcyclohexanone was achieved under mild conditions (298 K, 2 MPa H2, 1 h). In the second step, 3,5,5-trimethyl-2-(3,3,5-trimethylcyclohexylidene)cyclohexanone was produced in a high carbon yield (76.4%) by the NaOH catalyzed self-aldol condensation of 3,3,5-trimethylcyclohexanone which was carried out in a round bottom flask attached to the Dean–Stark apparatus. In the third step, the 3,5,5-trimethyl-2-(3,3,5-trimethylcyclohexylidene)cyclohexanone was hydrodeoxygenated under solvent-free conditions. High carbon yield (93.4%) of 1,1,3-trimethyl-5-(2,4,4-trimethylcyclohexyl)cyclohexane was obtained over the Ni/SiO2 catalyst. The 1,1,3-trimethyl-5-(2,4,4-trimethylcyclohexyl)cyclohexane as obtained has a density of 0.858 g mL−1 and a freezing point of 222.2 K. As a potential application, it can be blended into conventional fuels (such as RP-1, RG-1, etc.) for rocket propulsion.

Development of Intermediates for High‐Energy Content New Biomass‐Derived Jet and Diesel Fuels with a Robust Rapid Green Reaction

“…would have cyclic hydrocarbons structures, similar to the chemical structure of recently reported high‐density fuels . The densities of these cycloalkanes were calculated to be in the range of 0.711–0.964 g cm −3 , which is among the highest densities of current reported state‐of‐the‐art biofuels [5b,d,13,26b,36]. Furthermore, theoretical calculation indicates that the VNHOC value of these potential biofuels would increase to 39.06 MJ L −1 , which is comparable to that of most of the state‐of‐the‐art biofuels[5b,d,13,26b,36] and that of some commercial jet fuels such as RJ‐4 (39.0 MJ L −1 ), JP‐10 (39.6 MJ L −1 ), RF‐1 (38.9 MJ L −1 ), and RJ‐41(38.5 MJ L −1 ), etc.…”

“…The potential products from 3e‐a , 3f‐a , 3h‐a , 3h‐e , etc. would have cyclic hydrocarbons structures, similar to the chemical structure of recently reported high‐density fuels . The densities of these cycloalkanes were calculated to be in the range of 0.711–0.964 g cm −3 , which is among the highest densities of current reported state‐of‐the‐art biofuels [5b,d,13,26b,36].…”

“…4j‐g shows the highest VNHOC value of 39.06 MJ L −1 and the highest density of 0.964 g cm −3 . The VNHOC value of 4j‐g is comparable to that of most of the state‐of‐the‐art biofuels[5b,d,13,26b,36] and that of some commercial jet fuels such as RJ‐4 (39.0 MJ L −1 ), JP‐4 (32.9 MJ L −1 ), W‐5(34.8 MJ L −1 ), JP‐10 (39.6 MJ L −1 ), RF‐1 (38.9 MJ L −1 ), and RJ‐41(38.5 MJ L −1 ).…”

“…The densities of predicted biofuels were calculated to be in the range of 0.711–0.964 g cm −3 . The highest density of the predicted final cycloalkanes is 0.964 g cm −3 for 4j‐g , which is among the highest densities of the current reported state‐of‐the‐art biofuels [5b,d,13,26b]. The densities of most predicted final alkanes meet the requirements for high‐density fuels, which typically have a high density of over 0.9 g cm −3 , such as JP‐10 (0.94 g cm −3 ), RJ‐4 (0.94 g cm −3 ), RF‐1 (0.92 g cm −3 ), and RJ‐41 (0.94 g cm −3 ) .…”

“…Tri‐condensed products are typically minor products due to the steric hindrance of reactants . Products with C—C rings equal to or over three are very limited …”