提高烃类燃料热沉的研究进展

吸热型烃类燃料是一种热安定性好、可以利用其化学热沉的燃料,其热沉能够满足高超音速飞行的需要.本文论述了燃料热安定性、催化脱氢、催化裂解、引发裂解、超临界裂解等对吸热型烃类燃料热沉的影响,重点论述了引发裂解在吸热型烃类燃料中的裂解优势,提出引发裂解在高超音速飞行器上具有诱人的应用前景.     

提高烃类燃料热沉的研究进展

吸热型烃类燃料是一种热安定性好、可以利用其化学热沉的燃料，其热沉能够满足高超音速飞行的需要。本文论述了燃料热安定性、催化脱氢、催化裂解、引发裂解、超临界裂解等对吸热型烃类燃料热沉的影响，重点论述了引发裂解在吸热型烃类燃料中的裂解优势，提出引发裂解在高超音速飞行器上具有诱人的应用前景。     

高超音速推进用吸热型烃类燃料的热稳定性研究Ⅰ.热氧化与热裂解沉积

考察了作为高超音速飞行器冷却剂的吸热型烃类燃料挂式四氢双环戊二烯exo-THDCPD、甲基环己烷MCH以及对比样航煤RP－3的热稳定性能。结果表明，三种燃料的热氧化沉积在某温度下存在波峰，热裂解沉积随温度升高迅速增加，基本呈指数关系。RP－3的热稳定性能最差，THDCPD与MCH较为接近，在高温时优于MCH。随进料流量的增加，热裂解沉积不断增加，热氧化沉积先增加，在高流量时趋于定值。Philips XL30 ESEM环境扫描电子显微镜分析表明，三者的热氧化沉积及热裂解沉积有着不同的形态。热裂解沉积均发现了含有金属微粒长条状的细丝碳，这一现象在MCH热裂解沉积中最为显著。     

吸热型碳氢燃料五环[6.3.1.02,7.03,5.09,11]十二烷的催化合成

吸热型碳氢燃料是为解决高超音速飞行器冷却难题而研制的一类新型燃料[1].其最突出的优点是作为性能优良燃料的同时,还能满足飞行器的冷却要求,可减小飞行器的体积和质量,提高飞行速度,是高超音速飞行器的理想燃料.其冷却及燃烧原理是:大分子碳氢燃料在进入燃烧室前吸收飞行系统产生的热量气化、再裂解为小分子,产物进入燃烧室燃烧并释放出吸收的热量,从而在对系统冷却的同时提高了能源的利用率,减少了高超音速飞行器的负载,满足了燃烧室壁面和机身温度控制等要求.因此,吸热型碳氢燃料已成为各国研发的热点,但目前研究多限于原油调配燃料的催化裂解和脱氢,对新燃料的合成报道较少[2,3].……     

碳氢燃料热裂解机理及化学动力学模拟

发动机设计中,燃烧室的热管理问题日益突出.其根源必然涉及到碳氢燃料的化学机理模型.讨论了大分子烃类燃料热裂解反应的反应类型,分析了各反应类型的详细动力学以及对热裂解反应的灵敏度、重要性.根据热裂解反应类型有限和基于物质的一维表示,开发了大分子烃类反应机理的自动生成程序ReaxGen.建立了相应的热、动力学数据库,探讨了如何建立碳氢燃料的详细热裂解化学动力学模型.最后我们建立了正庚烷热裂解反应的详细机理,并用该机理模型模拟预测了产物分布和转化率,理论上计算了热沉值.所得结果与文献结果进行对比讨论.     

吸热型碳氢燃料模型化合物在超临界条件下的裂解及热沉测定

建立了一套热量计, 用于吸热型碳氢燃料及其模型化合物在超临界条件下的吸热能力测定及裂解机理的探索. 测定了正庚烷和JP-10在不同温度和压力下的热沉数据, 结合色谱分析结果讨论了压力、温度等对热沉、气相产物分布的影响. 测得正庚烷在873 K, 3.4 MPa条件下的热沉为3.14 MJ•kg－1, JP-10在903 K, 3.2 MPa条件下的热沉为3.08 MJ•kg－1, 对应的热裂解转化率分别为32%和4.7%, 该热沉值可以达到速度为5～6马赫数的飞行器的冷却要求.     

银、镧改性混合型吸热碳氢燃料裂解分子筛催化剂的研究

为提高吸热型碳氢燃料的吸热能效,制备了吸热型碳氢燃料NNJ-150和银、镧 离子交换改性USY,ZSM-5分子筛及混合分子筛,考察了NNJ-150在USHY,HZSM-5和 二者混合物以及银、镧改性混合分子筛催化剂上的裂解情况。结果表明,NNJ-150 在Ag-LaUSY + Ag-LaZSM-5（75：25）混合分子筛上裂解时,低碳烯烃选择性较高 （600 ℃,47.92%）,催化剂寿命较长(35 min以上）,催化性能比较稳定,可满 足冷却高超音速飞行器的要求。     

高热安定型碳氢燃料的理论设计与制备

结合碳氢燃料的组成-性质关系和喷气燃料的基本理化性质指标,建立了高热安定性碳氢燃料的设计方法.通过碳氢燃料烃族组成(直链烷烃、异构烃、环烷烃、芳烃)和性质关系的三角相图,确定符合吸热型碳氢燃料基本理化性质(密度、闪点、冰点、热值与热安定性)的烃族组成域.对4种燃料样品的热安定性研究表明,在确定的组成域内燃料的热安定性优于RP-3,证实了燃料理论设计方法的可靠性.     

吸热型碳氢燃料在银、镧改性混合分子筛上的裂解研究

为进一步提高吸热型碳氢燃料的吸热能效，考察了吸热型碳氢燃料NNJ－150在USHY和HZSM－5混合分子筛以及银、镧改性混合分子筛催化剂上的催化裂解。结果表明，在Ag-LaUSY Ag-LaZSM-5(75:25)混合分子筛催化NNJ－150裂解反应中，低碳烯烃选择性较高，催化剂寿命较长。采用此催化剂，能较好满足吸热型碳氢燃料裂解的需要。     

Pd/HZSM-5涂层催化吸热燃料超临界裂解

超临界催化裂解反应是实现吸热燃料功能的关键途径.采用气体辅助涂层和化学镀方法在ψ3管内壁制备了Pd/HZSM-5双功能涂层催化剂.利用SEM、XRD和XPS等对涂层进行了表征,结果显示催化剂涂层表面平整,涂层厚度为12μm～16μm,催化剂粒径为1μm～5μm;Pd颗粒分散均匀,主要以零价态存在.考察了模型吸热燃料正十二烷在反应管内的超临界催化裂解反应,结果表明,Pd/HZSM-5涂层能显著促进裂解反应,在温度640℃、压力4 MPa、停留时间10 s下,吸热燃料裂解率为55.5%,产氢率为3.1%,热沉为3 470 kJ/kg,较HZSM-5涂层分别提高了8.5%,58.7%和10.5%;较热裂解分别提高了17.3%,78.1%和13.5%.     

Monomolecular endothermic reaction of n-decane catalyzed by HZSM-5 films

Summary This paper reports the possibility of in situ synthesis of HZSM-5 zeolites films on tubular steel substrate for the improved potential chemical heat sink of fuels, and the performance of prepared membrane catalysts in the endothermic, catalytic cracking of n-decane. Through hydrothermal crystallization, a zeolite / steel composite was obtained which consists of a continuous zeolite film that strongly attaches to the substrate surface. The membrane catalysts are active enough for the n-decane catalytic cracking to provide endothermal ability, and also can suppress the formation of carbon deposits compared with thermal cracking.     

Nikolay Zelinsky (1861–1953): Mendeleev's Protege,a Brilliant Scientist,and the Top Soviet Chemist of the Stalin Era

This Essay outlines the life path and scientific achievements of Nikolai Zelinsky to testify to his contributions to organic chemistry, catalysis, and petrochemistry. His legacy includes four name reactions (the Hell–Volhard–Zelinsky reaction, 1887; the Zelinsky–Stadnikov reaction, 1906; Zelinsky irreversible catalysis, 1911; the Zelinsky–Kazansky acetylene trimerization, 1924), pioneering contributions to the main oil-refining processes (thermal cracking, catalytic cracking, hydrodesulfurization, reforming, and oxidative regeneration of coked catalysts), the coal gas mask, Pd/C and other supported catalysts, and a very large scientific school.     

硫氰基/有机铜锂体系引发MMA阴离子聚合研究

采用有机锂为引发剂,以甲基丙烯酸酯（MMA）类为单体进行阴离子聚合,其副反应较严重,因为在此类单体分子中存在卢碳和羰基碳两个亲核点,引发剂进攻羰基碳则会使链终止,在聚合过程中发生各种副反应,以碱金属（Li,Na,K）为反离子的有机碳负离子化合物,其亲核性较强,倾向于进攻羰基碳,因此甲基丙烯酸酯类单体的阴离子聚合除了采用较大立体阻碍引发剂外。     

Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4‐Dioxane

A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4‐dioxane as reagents and 1,10‐phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.     

Determination and perturbation of the electronic potentials of solid catalysts for innovative catalysis

Concerns about energy and the environment are motivating a reexamination of catalytic processes, aiming to achieve more efficient and improved catalysis compatible with sustainability. Designing an active site for such heterogeneous catalytic processes remains a challenge leading to a next level breakthrough. Herein, we discuss a fundamental aspect of heterogeneous catalysis: the chemical potential of electrons in solid catalysts during thermal catalysis, which directly reflects the consequent catalytic reaction rate. The use of electrochemical tools during thermal catalysis allows for the quantitative determination of the ill-defined chemical potentials of solids in operando, whereby the potential–rate relationship can be established. Furthermore, the electrochemical means can also introduce the direct perturbation of catalyst potentials, in turn, perturbing the coverage of adsorbates functioning as poison, promoters, or reactants. We collect selected publications on these aspects, and provide a viewpoint bridging the fields of thermal- and electro-catalysis.

Concerns about energy and the environment are motivating a reexamination of catalytic processes, aiming to achieve more efficient and improved catalysis compatible with sustainability.     

超临界条件下正庚烷的裂解与结焦

以正庚烷为碳氢燃料模型化合物, 考察其在超临界条件下的裂解和结焦情况, 着重探讨了裂解温度和雷诺数(Re)对裂解反应的影响. 在4.0 MPa和500～650 ℃范围内, 随着反应温度升高, 正庚烷的裂解转化率大幅度提高, 裂解反应及其产物的二次反应使结焦前驱物增加, 最终导致结焦严重; 在超临界条件下, 提高流体的湍动程度, 有利于抑制结焦. 采用扫描电镜(SEM)、透射电镜(TEM)、差示扫描量热(DSC)和X射线衍射(XRD)等技术分析固体焦的形貌特性, 结果表明正庚烷裂解结焦主要以金属催化作用产生的丝状焦为主, 丝状焦的生长是不锈钢发生渗碳现象的重要原因.     

Effects of fuel additives on the thermal cracking of n-decane from reactive molecular dynamics

Thermal cracking of n-decane and n-decane in the presence of several fuel additives are studied in order to improve the rate of thermal cracking by using reactive molecular dynamics (MD) simulations employing the ReaxFF reactive force field. From MD simulations, we find the initiation mechanisms of pyrolysis of n-decane are mainly through two pathways: (1) the cleavage of a C-C bond to form smaller hydrocarbon radicals, and (2) the dehydrogenation reaction to form an H radical and the corresponding decyl radical. Another pathway is the H-abstraction reactions by small radicals including H, CH(3), and C(2)H(5). The basic reaction mechanisms are in good agreement with existing chemical kinetic models of thermal decomposition of n-decane. Quantum mechanical calculations of reaction enthalpies demonstrate that the H-abstraction channel is easier compared with the direct C-C or C-H bond-breaking in n-decane. The thermal cracking of n-decane with several additives is further investigated. ReaxFF MD simulations lead to reasonable Arrhenius parameters compared with experimental results based on first-order kinetic analysis. The different chemical structures of the fuel additives greatly affect the apparent activation energy and pre-exponential factors. The presence of diethyl ether (DEE), methyl tert-butyl ether (MTBE), 1-nitropropane (NP), 3,6,9-triethyl-3,6,9-trimethyl-1,2,4,5,7,8-hexaoxonane (TEMPO), triethylamine (TEA), and diacetonediperodixe (DADP) exhibit remarkable promoting effect on the thermal cracking rates, compared with that of pure n-decane, in the following order: NP > TEMPO > DADP > DEE (～MTBE) > TEA, which coincides with experimental results. These results demonstrate that reactive MD simulations can be used to screen for fuel additives and provide useful information for more comprehensive chemical kinetic model studies at the molecular level.     

Thermal polymerization mechanism of thitsiol separated from Gluta usitata

Thitsiol separated from Gluta usitata lacquer sap was polymerized by thermal catalysis, and the dimers were purified by HPLC. The dimer chemical structures were characterized by NMR and field desorption mass spectrometry spectroscopy. Almost all dimers have biphenyl nuclear–nuclear (C–C) structure that is somewhat different to the thitsiol dimer obtained from laccase catalysis. Based on these results, the thermal polymerization mechanism of thitsiol was discussed.     

Cracking of n‐octadecane: A molecular dynamics simulation

Despite the extensive research studies, the understanding of the fundamental mechanisms of chemical transformations at the cracking of hydrocarbons remains unexplored. In the present study, the initial stages of both thermal and catalytic cracking of n‐octadecane C₁₈H₃₈ (with a nickel Ni₄₉ particle as a catalyst) were investigated using the ReaxFF force field (the ReaxFF software package). The initial cracking mechanism of n‐octadecane was simulated at four different temperatures 1,800, 1,900, 2,000, and 2,200 K on a large interface system (2,849 atoms) consisting of 49 nickel atoms surrounded by 50 hydrocarbon molecules. Analysis of trajectories, according to the simulations, reveals a complex mechanism for initiating thermal and catalytic cracking of C₁₈H₃₈. Thermal cracking of C₁₈H₃₈ is initiated by breaking the C–C bond and proceeds via a free‐radical mechanism, whereas catalytic cracking is preferentially activated by deprotonation and protonation of the C–C bond. This work demonstrates that the ReaxFF force field can be actively used in the study of complex chemical transformations that occur at the cracking of hydrocarbons.