噻吩和苯并噻吩在原位氢存在下的还原脱硫

研究了噻吩和苯并噻吩在原位氢和硼化镍存在下的还原脱硫。实验对操作条件进行了优化;研究了可能的反应机理。结果表明,六水合氯化镍与还原剂于质子溶剂中反应的对硫化物脱硫,产生的原位氢脱硫活性较高;还原剂用量为0.64 g时,脱硫率可达99%以上。噻吩和苯并噻吩脱硫主要发生直接氢解反应;少量苯并噻吩脱硫经由加氢途径进行,硫化物主要通过S原子"端连吸附"在硼化镍表面。推测反应机理为,反应中大量原位氢吸附在硼化镍表面并活化;硼化镍中富电子镍介入硫化物分子中C—S键形成加合物,与活性原位氢进一步作用,使C—S和C—C键断裂。     

硫化物在OTA催化剂上催化转化性能

考察了催化裂化(FCC)汽油中硫化物和模型硫化物在OTA(Olefin To Aromatics)催化剂上的催化转化性能.结果表明FCC汽油硫化物总脱硫率为86.3 %,其中,硫醚和四氢噻吩的转化率都达到100 %,硫醇硫转化率96.6 %,噻吩硫转化率78.8 %,烷基噻吩转化率85.8 %,苯并噻吩转化率81.4 %.3-甲基噻吩在OTA催化剂上的转化产物中含有小分子(噻吩),异构硫化物(2-甲基噻吩),以及大分子异构硫化物(如2,5-二甲基噻吩、2,4-二甲基噻吩和2,3-二甲基噻吩).烷基噻吩和苯并噻吩硫化物在OTA催化剂上脱硫反应网络一方面含有直接加氢脱硫反应,另一方面经历歧化、异构化和裂解等反应.     

吸附法脱除柴油中噻吩类含硫化合物的研究进展

综述了吸附法脱除柴油中噻吩类含硫化合物的常用吸附剂、吸附脱硫的机理及吸附脱硫过程动力学研究的最新进展。阐述了近来研究较多的吸附剂主要有分子筛、活性炭和金属有机骨架（MOFs）材料。目前传统的加氢脱硫（HDS）技术虽然可以满足当前柴油中硫含量的国家标准,但是其需要高温高压、成本高且对二苯并噻吩类硫化物脱硫率低,而吸附脱硫技术由于成本低、操作条件温和、易脱除加氢脱硫难以脱除的硫化物、对油品品质影响小等优点成为当前柴油脱硫的研究热点。吸附脱硫主要包括反应型吸附脱硫和非反应型吸附脱硫,反应吸附脱硫关键是有旧键的断裂与新键的生成,而非反应吸附脱硫则是通过分散力使硫化物上的硫原子与吸附剂之间相互作用,从而达到吸附脱硫的作用。本文对吸附脱硫机理和吸附脱硫过程的动力学加以讨论,为以后的研究提供一定的理论基础,并提出了脱硫吸附剂今后的研究方向。     

吸附法柴油脱硫技术进展

本文从吸附剂改性、吸附脱硫机理和吸附剂再生等方面综述了以活性炭、金属氧化物、分子筛等为吸附材料吸附脱除柴油中硫化物的最新进展。柴油中的含硫化合物主要包括无机硫和有机硫,其中有机硫占80％以上。在活性炭表面,金属氧化物或分子筛上负载过渡金属都可提高其对硫的吸附能力,π键配位吸附脱硫技术是脱除噻吩类硫化物的有效方法。吸附脱硫是一项具有发展潜力的脱硫技术,然而,要加速这一技术的工业化进程,开发对稠环噻吩类硫化物具有高选择性、高吸附量、易再生的吸附剂是当前面临的重要挑战。     

金属离子改性HY-KIT-1脱除柴油中硫化物

以介孔分子筛KIT-1与微孔分子筛HY机械混合作为载体,负载活性组分Ce、Ni、Co,对柴油中的含硫化合物进行吸附分离,采用气相色谱-硫化学发光检测分析柴油脱硫前后噻吩类硫化物的分布.结果表明,柴油中所含的硫化物主要为苯并噻吩和二苯并噻吩,其中苯并噻吩占总含量的51.15％,二苯并噻吩占总含量的48.85％.Ce/HY-KIT-1吸附剂的吸附效果最好.     

银基活性炭对废轮胎热解油的吸附脱硫机理研究

废轮胎经热解制备得到热解油和热解炭,热解炭活化制得活性炭,并利用Ag⁺对活性炭进行改性制得Ag⁺改性活性炭（Ag/AC）,将Ag/AC用于热解油的吸附脱硫实验,并利用GC/MS对热解油中的含硫化合物进行了分析。研究结果表明：活性炭吸附脱硫的合适温度和时间分别为20℃和12 h,此时未改性活性炭的脱硫率为15.33%;而Ag/AC的脱硫率提高到了38.6%。GC/MS分析发现热解油中有机硫的主要存在形式为噻吩、2-甲基噻吩、苯并噻吩、二苯并噻吩和4,6-二甲基二苯并噻吩,其中二苯并噻吩（DBT）的GC含量最高,为2.57%。利用原位红外、核磁共振氢谱、ICP-OES和元素分析等检测手段,进一步探究了Ag⁺与二苯并噻吩模型化合物在溶液中的反应机理,研究发现：二苯并噻吩分子上存在S原子和苯环2个反应位点,当Ag⁺加入二苯并噻吩溶液后,Ag⁺与二苯并噻吩分子上的S原子或者苯环发生配位数为1的配位反应生成2种配合物,分子式分别为Ag（D_S）NO₃和Ag（D_C6H6）NO₃。     

活性炭催化氧化脱除汽油和柴油中噻吩类硫化物的选择性

研究了活性炭催化氧化脱除汽油和柴油中噻吩类硫化物的选择性。采用气相色谱-硫化学发光检测器（GC-SCD）分析了汽油和柴油中噻吩类硫化物的分布及浓度;以活性炭作为催化剂,以30％过氧化氢溶液为氧化剂,在甲酸存在条件下考察了汽油和柴油中噻吩类硫化物催化氧化脱除的选择性,讨论了硫化物中硫原子电子密度对硫化物氧化选择性的影响。结果表明：汽油中噻吩类硫化物主要有噻吩（T）及其烷基衍生物（T alkylated derivatives）和苯并噻吩（BT）;而柴油中噻吩类硫化物主要分布有苯并噻吩(BT)及其烷基衍生物(BT alkylated derivatives)和二苯并噻吩（DBT）及其烷基衍生物（DBT alkylated derivatives）;硫原子电子密度大于5.716的含3个C烷基噻吩（C3-T）、BT、BT alkylated derivatives、DBT 和DBT alkylated derivatives 能被催化氧化脱除,硫原子的电子密度越大,其被氧化的速率越快,被脱除的选择性也越大;被脱除选择性顺序为：DBT alkylated derivatives > DBT > BT alkylated derivatives> BT> C3-T;然而硫原子电子密度小于5.716的T,含1个烷基噻吩（C1-T）和含2个C烷基噻吩（C2-T）则不能被氧化脱除。采用此方法,能将初始硫浓度为1200 μg•g^-1的柴油降低至小于10 μg•g^-1,可将初始硫浓度为320 μg•g^-1的汽油降低至155 μg•g^-1。     

银基吸附剂脱除噻吩类含硫化合物机理的研究进展

噻吩类含硫化合物因其稳定的共轭结构是油品中较难脱除的含硫化合物,银基吸附剂对其有较好的脱除性能。对银基吸附剂上活性组分银与噻吩间3种类型的作用机理进行了综述,3种类型的作用方式为π络合,S-Ag键及软酸Ag(Ⅰ)和软碱噻吩的相互作用。脱硫过程中,作用方式的类型及其强弱不仅受到噻吩类含硫化合物分子尺寸、共轭程度及硫原子电负性的影响,还与银的存在形态及其与载体间作用有关。π络合作用对芳烃/烯烃和噻吩硫的吸附存在竞争作用,适合于不含芳烃和烯烃体系中硫化物的脱除;S-Ag键主要是金属的空轨道与硫原子的孤对电子之间的作用,相对而言更适合于芳烃存在体系中噻吩硫的脱除。针对不同的脱硫体系,需要借助最适合的作用机理对吸附剂上银的存在形态和分布进行精准的定向调控。     

烃及含硫模型化合物在ZSM-5催化剂上的催化转化性能

以正己烷、环己烷、1-己烯3种烃类和噻吩、3-甲基噻吩和苯并噻吩三种硫化物为模型化合物,考察了烃及含硫模型化合物在ZSM-5分子筛催化剂上的催化转化性能。结果表明,在催化剂作用下,烃类模型化合物都具有芳构化和异构化转化性能,芳构化率高低顺序为：烯烃〉环烷烃〉正构烷烃,异构化率高低顺序反之;高温、低压有利于芳构化反应,低温、高压有利于异构化反应;模型硫化物都较易被脱硫,其加氢脱硫活性高低顺序为：噻吩〉烷基取代噻吩〉苯并噻吩,高温、高压有利于他们的脱硫。     

超临界甲醇中氧化脱除模型物中噻吩硫的研究

传统加氢脱硫往往难以脱除重油中的噻吩类硫化物。利用噻吩类硫化物氧化后的极性增加,在超临界甲醇条件下强化其在极性溶剂中的溶解度,可深度脱除重油中的噻吩硫。以二苯并噻吩(DBT)与十四烷为模型油,甲醇为超临界介质,考察了无催化时反应条件对超临界氧化脱硫性能的影响,不同催化氧化体系的脱硫效率。利用红外光谱、气相色谱-质谱联用对反应产物进行分析以研究脱硫机理。结果表明,在无催化时,反应温度260℃、反应压力8.5～9.0 MPa、反应时间3 h、过氧化二叔丁基作氧化剂且氧硫摩尔比为3:1时,噻吩模型物的脱硫率最高,达42%。在催化氧化体系中,催化剂用量与硫的摩尔比为1:10时催化剂使用效率最高,3种脱硫效果较好的催化氧化体系脱硫率分别达到了47%、45%、45%。FTIR、GC-MS结果表明二苯并噻吩被氧化为相应亚砜并转移至甲醇相,从而实现了硫化物的脱除。     

Oxidation Behavior of Titanium Boride at Elevated Temperatures

The oxidation behavior of dense TiB₂ specimens was investigated. Hot-pressed TiB₂ with 2.5 wt% Si₃N₄ as a sintering aid was exposed to air at temperatures between 800° and 1200°C for up to 10 h. The TiB₂ exhibited two distinct oxidation behaviors depending on the temperature. At temperatures below 1000°C, parabolic weight gains were observed as a result of the formation of TiO₂( s ) and B₂O₃( l ) on the surface. The oxidation layer comprised two layers: an inner layer of crystalline TiO₂ and an outer layer mainly composed of B₂O₃. When the oxidation temperatures were higher than 1000°C, gaseous B₂O₃ was formed along with crystalline TiO₂ by the oxidation process. In this case, the surface was covered with large TiO₂ grains imbedded in a highly textured small TiO₂ matrix.     

Combustion synthesis of ultra-high-temperature solid solutions (ZrxNb1-x)B2. Part 1: The mechanisms of combustion and structure formation

The self-propagating high-temperature synthesis (SHS) in Zr–Nb–B system has been thoroughly investigated with a focus on its macrokinetics and phase formation mechanisms. The activation energies were determined by analyzing the relationship between the combustion rate and temperature. For compositions NbB₂–40%ZrB₂ and NbB₂–50%ZrB₂, the increase in the initial temperature has resulted in a significant change in combustion rate's dependence on temperature, signifying a possible shift in the reaction mechanisms. The quenched combustion front technique (QCF) method in conjunction with thermodynamic and ab initio calculations were used to analyze the sequence of phase formation events, including the formation of niobium and zirconium borides through gas transport reactions involving volatile boron suboxide BO in the heating zone, followed by the emergence of a zirconium-boron melt in the combustion zone and formation of main fraction of niobium and zirconium borides. Interactions between the primary niobium and zirconium borides and the melt result in the formation of solid solutions; however, at sub-optimal combustion conditions multiple non-equilibrium solid solutions are retained in the products. To address this issue, a machine learning model was developed, attaining coefficients of determination (R²) of 89% for combustion temperature and rate predictions, thus enabling the fine-tuning of macrokinetic parameters of the SHS process in the system.     

Combustion synthesis of ultra-high-temperature solid solutions (ZrxNb1-x)B2. Part 2: Fine-tuning the mechanical properties and thermal conductivity of Zr–Nb–B diboride solid solutions for ultra-high temperature applications

In Part 1 of this study, we investigated the macrokinetic parameters and phase formation mechanism in the combustion front of Zr–Nb–B mixtures. In the second part, we produced consolidated samples of solid solutions NbB₂-(0.100%)ZrB₂ by hot pressing the combustion-derived powders at 1900 °C. By measuring the crystallographic parameters, mechanical and thermophysical properties of the produced bulk samples, we obtained valuable insights into the behavior of the solid solutions. Our results pave the way for the application-specific fine-tuning of the mechanical properties and thermal conductivity of diboride solid solutions in the Zr–Nb–B system for ultra-high temperature applications. Our findings have significant implications for the development of advanced materials with outstanding performance in extreme environments.     

Synthesis of Hard Materials by Field Activation: The Synthesis of Solid Solutions and Composites in the TiB2–WB2–CrB2 System

The synthesis of solid solutions of (Ti,W,Cr)B₂ from elemental reactants using the field-activated, pressure-assisted synthesis method and employing the SPS apparatus was investigated. The nature of the products depended on temperature; they were nearly pure solid solutions at 1900°C with minor amounts of β-WB. The product density and microhardness depended on the temperature of synthesis for the same value of applied pressure (64 MPa). Samples with the highest density (94%) corresponded to a hardness of 22.7 GPa. When annealed at 1500°C, the solid solutions decomposed, precipitating a (W,Ti,Cr)B₂ phase in a spinodal form. In addition, β-WB precipitates in the form of thin (0.4–5.3 nm) layers were observed. They existed in a 60°/120° orientation to the (Ti,W,Cr)B₂ matrix, in agreement with previous observations. Highly faceted, small (nanosized) pores associated with the β-WB precipitates were also observed.     

金属硼化物的合成与应用

论述了几种重要的金属硼化物合成工艺在高新技术及在其他领域的应用,展示了金属硼化物在国民经济各领域及其相关行业中的应用前景.     

Formation of Nanometric TiB2 from TiO2

Titanium diboride can be produced by ball-milling a mixture of TiO₂, B₂O₃, and Mg metal for between 10 and 15 h. The reaction was found to be completed during the milling with no evidence of residual Mg. The unwanted phase, MgO, was readily removed by leaching in acid. The leached powder obtained after 15 h milling had a particle size of <200 nm and was highly faceted. The particle size decreased to ∼50 nm after 100 h milling and seemed to be relatively monodisperse. Scherrer calculation of the crystallite size showed that the product particles were probably single crystal.     

The Microwave Sintering Technology and Its Application in the Synthesis of ZrB2

1 IntroductionThe microwave is a kind of high-frequency elec-tromagnetic wave, its wave-length is l ~1000mm, thefrequency scope is 0·3 ~300GHz. But in microwavesintering technology the required frequency is mainly2.45 GHz, though there were reports on 28GHz and60GHz.The microwave sintering is to make use of the mi-crowave energy to heat whole materials to sinteringtemperature and realize densifying.The microwave sintering and normal sintering havethe basic difference in principle. In norm…     

刚玉莫来石——ZrB2复合材料力学性能的研究

研究了不同含量的ZrB_2对刚玉莫来石材料力学性能的影响,进而分析了复合材料的强化韧化机制.     

ZrO_2增韧Al_2O_3－硼化物陶瓷性能研究

本文对原料配方研制的ＺｒＯ_２增韧Ａｌ_２Ｏ_３－硼化物陶瓷进行性能测试，并进行分析研究，得出了该陶瓷所具有的性能结论。     

B4C–(Ti0.9Cr0.1)B2 composites with excellent specific hardness and enhanced toughness

Dense and light B₄C–(Ti_0.9Cr_0.1)B₂ composites with excellent mechanical properties were designed and reactively densified from boron, TiC, and Cr₃C₂ powder mixtures by spark plasma sintering in this work. Due to solid solution effects, the as-obtained B₄C–(Ti_0.9Cr_0.1)B₂ composite exhibited obviously enhanced hardness (43.2 ± 3.0 GPa at 9.8 N) and higher specific hardness (12.82 GPa cm³ g⁻¹) together with improved flexural strength (663 ± 39 MPa) and fracture toughness (K_IC, 5.40 ± 0.25 MPa m^1/2), compared to the counterparts such as B₄C–TiB₂ composite and B₄C. Toughening contributions in the as-sintered ceramics were quantitatively analyzed, and higher K_IC in B₄C–(Ti_0.9Cr_0.1)B₂ was mainly due to their larger initial fracture toughness and compressive stress toughening. The combination of these properties makes B₄C–(Ti_0.9Cr_0.1)B₂ composites exhibit great potentials in the application as lightweight structural materials. This work provided an inspiration to achieve lightweight materials with high performance through doping minor-amount atoms into the matrix.