航空燃料超临界热裂解过程中焦炭的形成

Formation of Coke in Thermal Cracking of Jet Fuel Under Supercritical Conditions

采用连续流动反应装置研究了国产航空燃料RP-3在超临界热裂解条件下焦炭形成的规律和性质,总结了焦炭的形成机理和形成过程。示差扫描量热仪测定结果显示,5MPa下RP-3燃料的起始裂解温度为471.8℃;程序升温氧化和扫描电子显微镜的分析结果显示,沉积焦炭中有3种不同的焦炭,分别为富氢吸附碳、无定形碳和纤维焦炭;超临界流体对焦炭前体和沉积的焦炭有较强的萃取及溶解能力,可携带90%以上的焦炭;用X射线能谱分析剥离下来焦炭的结果显示,焦炭中含有质量分数为17.09%和11.12%的铁、铬原子,说明金属发生了渗碳现象;用气相色谱-质谱联用仪对RP-3燃料及其裂解液的分析结果显示,裂解液中烷基苯和烷基萘含量的增加最为显著。

Study of coke formation in thermal cracking of home-made jet fuel RP-3 under supercritical conditions was carried out in a continuous flow reactor system. Mechanism and process of coke formation was stated. The initial cracking temperature of RP-3 jet fuel was determined to be 471.8 ℃ under 5 MPa by means of DSC. Temperature programmed oxidation analysis （TPO） and SEM examination of reaction tube showed that there are three different species of coke in the solid deposits including chemisorbed carbon,amorphous carbon and filamentous coke. More than 90% of coke deposition amount are carded away by supercdtical fluid which is highly capable in extraction of coke precursors and dissolution of coke deposits. By means of EDS, 17.09% （mass fraction）of iron and 11.12% （mass fraction）of chromium were detected and founded in coke layer stripped from tube inner surface, which proved carburation of alloy. RP-3 jet fuel and its cracking liquids were analysed by means of GC-MS. Contents of alkyl benzene and alkyl naphthalene increased evidently in cracking liquids after thermal cracking.