钴配合物催化的乙烯与三烷基铝置换反应动力学研究

研究了用钴配合物催化的乙烯与三异丁基铝的置换反应动力学. 置换反应速率相对于烷基铝浓度、配合物浓度及乙烯压力呈一级关系. 置换反应速率的动力学方程为r=1.4 ×106[R3Al][Cat.][pC2H4]. 反应的活化能为71.9 kJ/mol.     

改性甲基铝氧烷和烷基铝活化的新癸酸钕催化剂催化异戊二烯聚合

 考察了改性甲基铝氧烷(MMAO,溶于庚烷)和烷基铝(AlR3)活化的新癸酸钕(Nd(vers)3)催化剂对异戊二烯(IP)聚合反应的催化性能. 结果表明,以Al(i-Bu)2H替代部分MMAO,可在较低的MMAO用量(n(MMAO)/n(Nd)=20,总铝量n(Al)/n(Nd)=40)下明显提高Nd(vers)3-MMAO催化剂的活性,但所得聚合物中顺式-1,4结构的含量较低(约90%). Nd(vers)3, MMAO, Al(i-Bu)2H和Al(i-Bu)2Cl可在少量单体(n(IP)/n(Nd)=10)存在下配制成稳定的均相催化剂,该催化剂能在相对较低的MMAO用量(n(MMAO)/n(Nd)=15,总铝量n(Al)/n(Nd)=30)及较宽的Al(i-Bu)2Cl用量范围(n(Cl)/n(Nd)=0.5～7.0)内聚合异戊二烯,其活性明显高于单独以MMAO或Al(i-Bu)2H组成的催化剂,所得聚合物中顺式-1,4结构含量可达96%. 调节MMAO和Al(i-Bu)2H用量可控制聚合产物的分子量. 初步推测了该四元均相催化剂活性中心的生成过程.     

CrOx/SiO2催化剂对C10+芳烃加氢脱烷基反应的催化性能

 采用等体积浸渍法制备了一系列不同组成的CrOx/SiO2催化剂样品,并用XRD,FT-IR,UV-Vis,TPR和N2吸附等技术对催化剂样品进行了表征,考察了催化剂对C10+重芳烃加氢脱烷基反应的催化性能. 结果表明,CrOx/SiO2催化剂对C10+重芳烃加氢脱烷基反应的催化性能与催化剂的表面结构有关,脱烷基活性主要来自载体表面的CrOx物种. 当催化剂中n(Cr)/n(Si)=1%～2%时,CrOx在SiO2表面达到单层分散; 当n(Cr)/n(Si)=2%～20%时,表面CrOx物种含量的变化不大,催化剂的活性及选择性基本不变.     

不同结构烷基铝催化异戊二烯齐聚与聚合行为研究

烷基铝（AlR₃）作为Ziegler-Natta催化剂体系的助催化剂组分,起到烷基化、还原主金属化合物、参与活性中心形成与演变、链转移剂等重要作用.然而烷基铝自身对二烯烃单体也具有催化作用.本工作采用不同结构烷基铝如三乙基铝（AlEt₃）、三异丁基铝（Al（i-Bu）₃）、氢化二异丁基铝（AlH（i-Bu）₂）、一氯二乙基铝（AlEt₂Cl）、二氯一乙基铝（AlEtCl₂）,研究了烷基铝的种类和浓度对异戊二烯催化行为的影响.采用核磁共振氢谱（¹H NMR）、凝胶渗透色谱（GPC）、气相色谱-质谱联用（GC-MS）等对产物的微观结构（顺式-1,4-和反式-1,4-含量）和分子量及分布等进行了表征,探讨了不同结构烷基铝的催化行为.发现烷基铝不仅可以催化异戊二烯齐聚,与微量水作用后还可以引发异戊二烯阳离子聚合,得到顺反混合结构的线性聚合物.烷基铝浓度对其催化行为有较大影响.当n（Al）/n（M）=1050×10^-5时,AlEtCl₂的催化活性显著提高,产物主要为线性聚合物;而其他结构烷基铝的催化活性较低.当n（Al）/n（M）≤350×10^-5,烷基铝自身催化异戊二烯齐聚及聚合能力极弱.过低和过高的烷基铝浓度都不利于获得高分子量聚合物.这为深入理解Ziegler-Natta催化剂体系烷基铝组分的催化作用及其对聚合物的影响提供依据.     

富马酸单正烷基酯的合成和表征

马来酸酐(1)和C1～C8正烷基醇(2a～2h)发生醇解反应生成马来酸单正烷基酯,后者接着在无水AlCl3存在下加热发生异构化反应,得到富马酸C1～C8单正烷基酯(3a～3h),醇解反应和异构化反应的总收率79.2%～87.3%。其结构经ESI-MS,IR和1H NMR表征。     

溴化十六烷基吡啶自盐酸溶液中在铝表面上的吸附及其缓蚀作用

用失重法研究了溴化十六烷基呲啶对铝在盐酸溶液中的缓蚀作用, 应用吸附理论和Sekine方法处理实验数据~[4], 发现溴化十六烷基吡啶自盐酸溶液中在铝表面上产生了吸附, 且基本服从Langmuir吸附等温式。求得吸附热为35.4 kJ mol~(-1), 认为这种吸附是产生缓蚀作用的重要原因。实验还表明, 缓蚀率随温度升高而增大, 根据这些结果讨论了吸附与缓蚀作用之间的关系。     

二氟亚烷基卡宾与甲醛环加成反应机理的理论研究

用二阶微扰理论研究单重态二氟亚烷基卡宾与甲醛发生的环加成反应机理,采用MP2/6-31G^*方法计算了势能面上各驻点的构型参数、振动频率和能量.结果表明,单重态二氟亚烷基卡宾与甲醛的环加成反应主要有两种反应通道,通道1中,两个反应物经a,b和c三条反应途径生成三元环构型的产物P1,其中途径c是主反应途径,该途径有两步组成:(Ⅰ)二氟亚烷基卡宾与甲醛生成了1个富能中间体(INT1c),是无势垒放热反应,放出能量为219.18kJ/mol;(Ⅱ)中间体(INT1c)异构化为产物二氟亚烷基环氧乙烷,其势垒为134.71kJ/mol.通道2的反应途径由三步组成:(Ⅰ)反应物首先生成了1个富能中间体(INT1b),为无势垒的放热反应,放出的能量142.77kJ/mol;(Ⅱ)中间体(INT1b)异构化成另一中间体(INT2),其势垒为22.31kJ/mol;(Ⅲ)中间体(INT2)异构化成四元环构型产物P2,其势垒为11.98kJ/mol.     

亚烷基锗烯与环氧乙烷及环硫乙烷抽提氧和硫反应的量子化学研究

用量子化学密度泛函理论(DFT)的B3LYP和从头算MP2方法在6-311G(d, p)水平上对亚烷基锗烯与环氧乙烷的氧转移及环硫乙烷的硫转移的反应机理进行了系统的研究, 计算了势能面上各驻点的构型参数、振动频率和能量; 并用CCSD(T)/6-311G(d)方法进行了单点能校正. 结果表明, 亚烷基锗烯与环氧乙烷和环硫乙烷抽提氧和硫的反应存在顺反两种反应方式, 分别生成锗杂烯酮(P1)、硫代锗杂烯酮(P4)以及锗杂环氧乙酮(P2)、锗杂环硫乙酮(P5), 环状产物P2和P5能继续与环氧乙烷或环硫乙烷反应, 进一步生成更稳定的产物甲醛(P3-1)、一氧化锗(P3-2)及锗烯的二硫化物(P6), 且反式反应是主要的反应通道. 同时还研究了该反应中环氧乙烷C—O键和环硫乙烷C—S键的解离过程, 并与亚烷基卡宾和环氧乙烷及环硫乙烷的抽提反应进行了比较.     

异烷基膦酸单烷基酯萃取分离稀土的研究

研究了异烷基膦酸单烷基酯系列萃取剂色层分离稀土的性能。结果表明,以八碳异烷基膦酸-1-甲基庚基酯分离稀土的性能最佳,体系酸度均较目前使用的萃取剂低,用1.73 mol/L HNO_3可将Tm、Yb、Lu完全分离,用它制成的负载树脂分离稀土,其柱效高,动力学性能好。另外,对萃取反应机理作了一些探讨。     

L-丙交酯与环氧氯丙烷共聚物的合成与表征

以系列烷基铝为催化剂,制得丙交酯与环氧氯丙烷的共聚物。分别考察了Al(Oct)_3、Sn(Oct)_2·4Al(Oct)_3、Al(Oct)_3·0.5H_2O、AlEt_3、AlEt_3·0.5H_2O催化下聚合的情况,结果表明:认为在烷基铝的催化下,丙交酯和环氧氯丙烷可以共聚,其中部分水解烷基铝催化效果较好。聚合反应的最佳温度为100℃。在此温度下,随着反应时间的增加,共聚物的分子量和产率皆提高。环氧氯丙烷用量增加,聚合物的产率和分子量呈下降趋势。用~1H-NMR、GPC、DSC对产物进行测试和表征。     

乳酸酯氧化脱氢制备丙酮酸酯的研究进展

生物质资源替代化石资源制取燃料和化学品已成为发展可再生能源化工的重要研究方向之一。本文综述了近年来以生物质平台分子乳酸酯为原料制备丙酮酸酯的研究工作,主要涉及的反应包括气相催化反应、液相催化反应和光催化反应。详细讨论了各种类型的催化剂对反应性能的影响;最后,对乳酸酯催化转化制取丙酮酸酯的发展前景进行了展望。     

Mild Copper‐Catalyzed Fluorination of Alkyl Triflates with Potassium Fluoride

A chemoselective catalytic fluorination of alkyl triflates is described using potassium fluoride as a fluoride source. Excellent yields of the desired alkyl fluorides are obtained after one hour at 45 °C using 2 mol % of the copper catalyst. With 10 mol % of the catalyst, full conversion can be achieved in less than 10 minutes at 45 °C, and thus makes this procedure potentially suited for the preparation of ¹⁸F‐labeled PET probes. As a result of the mild reaction conditions, only the substitution products are observed with no evidence of common side reactions, such as elimination. Reported is a preliminary study of the reaction scope, which demonstrates that the fluorination can be performed in the presence of a wide range of functional groups. Evidence suggests an unusual role of the [IPrCuOTf] catalyst as a phase‐transfer catalyst and points to [IPrCuF] as the active fluorinating reagent (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene).     

Alkyl vinyl esters of brassylic (tridecanedioic) acid

Brassylic acid was partially esterified at 77°C. in toluene solution with ethyl, 2-methylpentyl, or nonyl alcohol and with p-toluenesulfonic acid used as catalyst. Half-esters were isolated from the respective reaction mixtures in yields of 28, 34, and 32% after reaction times of 2,6, and 8 hr. Both recovered brassylic acid and byproduct dialkyl ester were successfully used as starting materials in subsequent esterifications. Consequently, conversion of starting materials to half-ester would be increased in a process that involved continuous recycling of byproducts. Alkyl hydrogen brassylates were vinylated at 165°C. for 8 hr. with acetylene at 360 psig. The zinc salt generated in situ from zinc oxide served as catalyst and toluene as solvent. Yields were 80–88% and purities of products were 94–95%. Samples of 2-methylpentyl vinyl brassylate and nonyl vinyl brassylate of much higher purity were obtained by preparative gas–liquid chromatography or molecular distillation. Physical properties and experimental conditions for gas–liquid chromatographic analyses of both the alkyl hydrogen and alkyl vinyl brassylates are reported.     

Oxidative decarboxylation of levulinic acid by silver(I)/persulfate

The oxidative decarboxylation of levulinic acid (LA) by silver(I)/persulfate [Ag(I)/S?O?2?] has been investigated in this paper. The effects of buffer solution, initial pH value, time and temperature and dosages of Ag(I)/S?O?2? on the decarboxylation of LA were examined in batch experiments and a reaction scheme was proposed on basis of the reaction process. The experimental results showed that a solution of NaOH-KH?PO? was comparatively suitable for the LA decarboxylation reaction by silver(I)/persulfate. Under optimum conditions (temperature 160 °C, pH 5.0, and time 0.5 h), the rate of LA conversion in NaOH-KH?PO? solutions with an initial concentration of 0.01 mol LA reached 70.2%, 2-butanone (methyl ethyl ketone) was the single product in the gas phase and the resulted molar yield reached 44.2%.     

Mechanically Initiated Reaction of Aluminum with Alkyl Halides

Mechanochemical reactions of aluminum with alkyl halides were examined at room temperature. The reaction was initiated by mechanical activation of vibromilling without any activator. It was found that the initiation was not due to the temperature rise at mechanical contact but the active sources formed on aluminum surface by vibromilling. The reactivity of milled aluminum was well correlated with the intensity of exoelectron emission. Both the reactivity and the emission intensity increased sharply after 60 min of milling. The decaying characteristics by exposure of preactivated aluminum were observed for both the reactivity and the emission intensity. The role of exoelectron on the reaction was discussed.     

用ab initio方法研究NaN_3的几何构型、电子结构和热力学、动力学性质

用ａｂｉｎｉｔｉｏＭＯ方法，在ＭＰ２（ｆｕｌ）／６３１１Ｇ水平下，全优化计算了叠氮化钠（ＮａＮ３）分子的线状和环状两种稳定构型及其转化过渡态的几何参数、电荷分布、分子总能量和振动频率，并研究了它们的热力学性质及转化速率常数和平衡常数．结果表明，线状比环状构型稍稳定（能量低６．０４ｋＪ／ｍｏｌ）；两者相互转化的能垒分别为１３．１５ｋＪ／ｍｏｌ（线型→环状）和７．１１ｋＪ／ｍｏｌ（环状→线型）．热力学和动力学计算均表明：ＮａＮ３通常主要以线型结构存在（占８５％以上），且随温度升高而增多（在１０００Ｋ大于９１％）．     

Cross‐Electrophile Coupling of Vinyl Halides with Alkyl Halides

An improved method for the reductive coupling of aryl and vinyl bromides with alkyl halides that gave high yields for a variety of substrates at room temperature with a low (2.5 to 0.5 mol %) catalyst loading is presented. Under the optimized conditions, difficult substrates, such as unhindered alkenyl bromides, can be coupled to give the desired olefins with minimal diene formation and good stereoretention. These improved conditions also worked well for aryl bromides. For example, a gram‐scale reaction was demonstrated with 0.5 mol % catalyst loading, whereas reactions at 10 mol % catalyst loading completed in as little as 20 minutes. Finally, a low‐cost single‐component pre‐catalyst, (bpy)NiI₂ (bpy=2,2′‐bipyridine) that is both air‐ and moisture‐stable over a period of months was introduced.     

Kinetics of hydrogen production of methanol reformation using Cu/ZnO/Al2O3 catalyst

The catalytic performance of methanol reformation using Cu/ZnO/Al2O3 was investigated at low temperature. The operation conditions, such as composition of Cu, Zn, and Al, temperature, molar ratio of H2O/CH3OH, weight hourly space velocity, catalyst weight, and kind and flow rate of carrier gas (helium and air), were evaluated to obtain the optimum reaction condition. The catalysts were prepared by oxalic coprecipitation, coprecipitation, and polyol method. The weight composition of Cu, Zn, and Al prepared by oxalic coprecipitation was 15:15:5 by high-throughput screening of combinatorial chemistry method, which was the best Cu/ZnO/Al2O3 catalyst. The prepared catalysts showed high activity and selectivity towards hydrogen formation. The methanol conversion, production rate, and volumetric percentage of hydrogen using this best catalyst were larger than 95%, 0.65 mol/h x g and 59%, respectively, and the CO volumetric percentage was smaller than 0.22% when the reaction temperature was 240 degrees C. The size and dispersity of copper, and the activity and turnover frequency of the catalyst were calculated as well.     

用铝灰生产聚氯化铝的反应动力学研究

本文对以工业废渣铝灰与盐酸反应制取聚氯化铝的反应进行了动力学研究。在0.5～3N的盐酸浓度范围内,反应速度与盐酸浓度的1.5次方成正比,反应的表观活化能为48kJ/mol-H₂。以某厂提供的铝灰为试样,测得动力学方程式为 dH₂/dt=6.2×10²·exp(-5.8×10³/T)·W·C_Hcl^1.5(mol/s)。     

Rate Study of Samarium Diiodide Reduction of Alkyl Halides and 2-Heptanone

Rate constants directly measured from GC-analyzed method for SmI₂ reduction of alkyl halides were obtained. The rates increase in the orders of primary, secondary, tertiary RX and RCl < RBr < RI as expected. 2-Heptanone was chosen as the partner of alkyl halide in the samarium Barbier reaction. In the absence of HMPA, the reaction orders of alkyl halide and ketone were determined as first and zero order, respectively.