Direct coal liquefaction oil hydrogenation to produce high energy density fuel

With the continuous development of supersonic aircraft, the demand for energy performance is also increasing. Traditional petroleum-based fuels are difficult to meet the requirements. Direct coal liquefaction oil is rich in polycyclic aromatic hydrocarbons (partially saturated aromatic hydrocarbons) and is an ideal candidate for high-energy-density fuels. Through hydrogenation, cycloalkanes can be obtained, which have advantages such as high calorific value and good thermal oxidation stability. Currently, most studies on the hydrogenation of direct coal liquefaction oil use model compounds. There are few studies on the production of high-energy-density fuels through the hydrogenation of direct coal liquefaction distillate oil. To investigate the feasibility of preparing high-energy-density fuels from direct coal liquefaction oil, Al-SBA15-modified USY-supported Pt was used as the catalyst to hydrogenate direct coal liquefaction oil (220−350 ℃). A fixed-bed reactor was first used to explore the optimal hydrogenation temperature, pressure, and space velocity. The product distribution and carbon number distribution were studied through gradient experiments. The results showed that higher temperatures were not conducive to the hydrogenation reaction and cracking and alkylation reactions occurred. The optimal reaction temperature was 360 ℃. Higher pressure was beneficial to the hydrogenation reaction. When the space velocity was low, the contact time between the reactants and the catalyst was short. Only the outer surface was contacted, which could not complete the reaction. When the space velocity increased, the amount of reactants increased, and the amount of catalyst was insufficient to completely convert the reactants. Therefore, the optimal reaction space velocity was 6 h⁻¹. A high-pressure autoclave was used to prepare high-energy-density fuels. The analysis of the hydrogenation products by comprehensive two-dimensional gas chromatography coupled with mass spectrometry showed that the main components were cycloalkanes, among which bicyclic and tricyclic cycloalkanes accounted for about 80%. The fuel properties of the hydrogenation products were determined. The density was 0.88 g/cm³, the calorific value was 45.26 MJ/kg, the flash point was 67.00 ℃, the pour point was −42.00 ℃, the aromatic hydrocarbon mass fraction was 0.5%, and the sulfur volume fraction was less than 3 ppm, meeting the national standard requirements. The thermal oxidation stability was determined by the JFTOT method at 355 ℃ for 5 hours, with a maximum pressure drop of 0 Pa, a pipeline grade rating of < 1, a minimum ignition temperature of 271 ℃, and an ignition delay time of 1 402 ms. These results show that the prepared fuel is an excellent high energy density fuel.