化工学报2024，Vol.75Issue(2)：626-636,封4,12.DOI:10.11949/0438-1157.20231190
热通道内典型碳氢燃料的热解结焦行为
Pyrolysis and coking behavior of typical liquid hydrocarbon fuels in hot pipe
摘要
Abstract
The fuel molecular structure is an important factor affecting the pyrolysis coking process in the active cooling channel.Stripping the effect of turbulent diffusion on pyrolysis coking,the pyrolysis coking patterns of typical aviation kerosene components such as n-heptane(n C7H16),iso-heptane(i C7 H16),methylcyclohexane(MCH),n-dodecane(n C12 H26),and toluene(A1 CH3)were compared in a pre-oxidized STS304(Φ3.0 mm×0.5 mm×1.0 m,outer diameter×wall thickness×length)flow reactor tube at 600-800℃,1.0 MPa,and under a laminar near-chemical kinetic state.The normalized molar fraction distributions of pyrolysis gas-liquid products of the five typical fuels were quantitatively obtained,and the unsteady-state coking characteristics and along-range coking distribution patterns of the fuels were compared by weighing method.The results show that the conversion of chain alkanes is higher at the lower temperature of 650℃,the conversion of MCH as well as A1 CH3 is lower due to the stabilized cyclic structure,and the conversion of A1 CH3 increases abruptly above 775℃.The hydrogen(H2),methane(CH4)content of i C7 H16 and MCH is significantly higher due to the presence of branched methyl groups.Straight-chain alkanes have higher contents of ethylene(C2 H4)and ethane(C2 H6)through β-scission.Propylene(C3 H6)is a by-product of C—C bond breakage.The content of C3 H6 is higher at lower temperatures,while the content of C2 H4 and C3 H6 tends to decrease due to the secondary reaction of coking at high temperatures.The main products in the liquid phase included benzene,A1 CH3,naphthalene and other diphenyl aromatic hydrocarbons.The content of polycyclic aromatic hydrocarbons(PAHs)increased at high temperatures,and tetraphenyl aromatic hydrocarbons such as perylene,phenanthrene,and anthracene were detected by GC-MS,but they accounted for a very low molar fraction of the bulk phase.The coking rates of MCH and n C12 H26 were low at lower temperatures,and the coking rates of MCH and A1 CH3 increased significantly at higher temperatures.Branched and long straight-chain alkanes favor high-temperature coking inhibition.Straight-chain alkane coking peaks at the beginning of the thermostatic zone,with coking by addition of unsaturated light hydrocarbons.MCH and A1 CH3 coking peaks are closer downstream,with coking by deposition of aromatic polymerization.Straight-chain alkanes have the highest content of cracked C2 H4 and C3 H6,which is conducive to providing high heat sink.The cleavage of n C12 H26 firstly produces 1-olefins such as 1-dodecene,1-undecene,1-decene,1-octene,1-hexene,1-pentene etc.,and the deep cleavage of these 1-olefins produces C2 H4 and C3 H6 etc.Since the depth of pyrolysis of long carbon-chain n C12 H26 is lower than that of the short-chain n C7 H16,it exhibits the heat sink that is even lower at high temperatures.Branched-chain alkanes are more stable than straight-chain alkanes and have a weaker tendency to form carbon deposition,but the presence of methyl group makes the product alkylated to a higher degree.The coking rates of the five typical hydrocarbon fuels were closely related to the temperature,showing a three-stage unsteady-state growth pattern,with differences in the location of the peak coking along the process.The coking rate of straight-chain alkanes was larger at low temperatures,and the contribution of MCH and A1 CH3 coking was significantly higher at high temperatures.关键词
碳氢化合物/分子结构/热解/焦化/热沉Key words
hydrocarbons/molecular structure/pyrolysis/coking/heat sink分类
化学化工引用本文复制引用
李浩文,兰昊,郑幼丹,孙勇辉,杨子昕,宋谦石,汪小憨..热通道内典型碳氢燃料的热解结焦行为[J].化工学报,2024,75(2):626-636,封4,12.基金项目
中国科学院稀土重点实验室前沿基础项目(E32PF00116) （E32PF00116）
国家自然科学基金项目(51976219) （51976219）
中国科学院赣江创新研究院自主部署项目(E155D00101,E355B0020) （E155D00101,E355B0020）
江西省引进培养创新创业高层次人才"千人计划"项目(jxsq2023101058) （jxsq2023101058）
