锂在嵌入物LixTio2中的扩散行为

本文利用电化学方法测定了薄膜电极Li_xTiO₂中锂离子的化学扩散系数,室温下其数量级为10^-11～10^-12cm²·S^-1(x=0.10～0.20)。通过₄-T关系,测得其扩散激活能E≈0.59eV,频率因子₀≈O.54cm²·s^-1.故其一般式可表为:₄=O.54exp(-6785/T)cm²·s^-1(t=15～50℃).利用D₄值和库仑滴定曲线测得了Li⁺在Li_xTiO₂薄膜电极中的迁移率和电导率分别为10^-10cm²·V^-1·s^-1和10^-7～10^-8Ω^-1·cm^-1数量级。比较了Li_xTiO₂体系与其他锂嵌入物的₄值,发现其与隧道化合物Li_xWO₃的₄值相近,而比层状化合物Li_xTiS₂的₄值小3～4个数量级。D₄值较大的嵌入物在作为锂电池的正极时,可以经受较大的充放电流。     

异苯橡胶环化反应动力学研究及产物微细结构表征

本文采用红外光谱法研究了前无报导的聚异苯橡胶环化反应动力学,测定了标题反应的动力学参数:反应级数n=1;活化能E_a=53.2kJ·mol^-1;指前因子A=2.24×10⁶min^-1,确立了该反应速率常数k_T与s反应温度T之间的函数关系为:Ln(k_T/min^-1)=14.62-6.40×10³K/T并采用核磁共振法分析了标题反应的产物环化异苯橡胶的微细结构,提出了标题反应的可能机理,并对活化能及指前因子进行了分析讨论。     

1-乙基-3-甲基咪唑丙氨酸离子液体热力学性质的研究

用中和法合成了氨基酸离子液体1-乙基-3-甲基咪唑丙氨酸([C₂mim][Ala]),并利用恒温环境的溶解反应热量计,在(288.15±0.01) K-(308.15±0.01) K温度范围内每隔5 K,测定不同质量摩尔浓度离子液体在水中的溶解焓(Δ_solH_m^θ).根据Archer的方法,通过线性拟合得到了该离子液体的标准摩尔溶解焓(Δ_sol),并计算了其相对表观摩尔溶解焓(^ΦL).在298.15 K下,根据Glasser经验方法得到了格子能U_POT = 566 kJ·mol^-1,并计算了其阴阳离子水化焓值(ΔH⁺ + ΔH^-) = -620 kJ·mol^-1及阴离子水化焓ΔH^-([Ala]^-) = -387 kJ·mol^-1.此外,估算了[C₂mim][Ala]水溶液的热容(C_p(sol))和表观摩尔热容(^ΦC_p).     

脂族酰基过氧化物分解动力学研究 Ⅰ.过氧化月桂酰在苯中的分解动力学

进行了过氧化月桂酰(1)在脱氧的苯中的分解动力学研究,当起始浓度0.1～0.2克分子·升^-1,温度30℃、40℃时,1不是严格地按一级反应分解的.在50℃下起始浓度0.04～0.34克分子·升^-1时,实验结果符合一级加二分之三级的反应规律:-(da/dt)=k₁a+k₁a^3/2.求出的自发分解速率常数k₁=0.0115小时^-1,诱导分解速率常数k₁=0.014克分子^-1.2·升^1/2·小时^-1.     

HS+HO2气相反应机理及主通道速率常数的理论研究

采用CCSD(T)/6-311++G(3df, 2pd)//B3LYP/6-311+G(2df, 2p)双水平计算方法构建了HO₂+HS反应体系的单、三重态反应势能面,并对该反应主通道的速率常数进行了研究。研究结果表明,标题反应经历了八条反应通道,其中三重态反应通道R1是标题反应主通道。此通道包含路径Path 1 (R → ³IM1 → ³TS1 → P1(³O₂+H₂S))和Path 1a (R → ³IM1a → ³TS1a → P1(³O₂+H₂S))两条路径。利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了主路径Path 1和Path 1a在200-800 K温度范围内的速率常数k^TST、k^CVT和k^CVT/SCT,在此温度区间内路径Path 1和Path 1a具有负温度系数效应。速率常数计算结果显示,对主路径Path 1和Path 1a而言,变分效应在计算温度段内有一定影响,与此同时量子力学隧道效应在低温段有显著影响。路径Path 1和Path 1a的CVT/SCT速率常数的三参数表达式分别为k₁^CVT/SCT(200-800 K) = 1.54×10^-5T^-2.70exp(1154/T) cm³ ·molecule^-1·s^-1和k_1a^CVT/SCT(200-800 K) = 5.82×10^-8T^-1.84exp(1388/T) cm³·molecule^-1·s^-1。     

2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物的酸催化Smiles重排反应动力学

研究了酸催化下的2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物Smiles重排反应的动力学,考察了盐酸的初始浓度、溶剂、反应温度和取代基对反应速率的影响。结果表明,盐酸的初始浓度增加,重排反应速率加快;在单一溶剂中反应速率的顺序为:甲醇>乙醇>二甲基亚砜>乙腈,而在甲醇/水(1:1, V/V)的混合溶剂中反应速率明显增加,其表观反应速率常数(k_obs)值是甲醇溶剂中的5.27倍;在25-45 ℃温度范围内,各衍生物的反应速率随着温度的升高而加快,其活化能(73.99-76.92 kJ·mol^-1)、活化焓(71.57-74.38 kJ·mol^-1)及Gibbs自由能(81.51-85.77 kJ·mol^-1)数值相近,仅活化熵(-24.38 --47.11 J·K^-1·mol^-1)有一定的差别;取代基常数和表观速率常数之间呈现一定的线性关系,环上吸电子基团的存在有利于反应速率的提高;实验验证了反应机理的合理性。     

微量热法研究过氧化氢酶反应

利用微量热法和热动力学方程研究了过氢化氢酶反应.该反应遵循Michaelis-Menten动力学,298.15K和pH7.0时,其米氏常数、酶转换数以及摩尔反应焓分别为2.36×10^-2mol/L、1.20×10⁴s^-1和-83.67kJ·mol^-1.过氧化氢酶反应后期对底物是一级反应,其总反应速度常数和一级速度常数分别为k_o=6.31×10⁵L·mol^-1·s^-1和k₁=6.31×10⁵/[E_o]s^-1.该反应服从Ogura机理,其酶-底物三元复合物的分解速度常数为6.00×10³s^-1.     

微量热法研究燃料电池PtRu/C催化剂的CO微分吸附热

用微量热法技术测量CO的微分吸附热以探测碳负载的单金属Pt,Ru及双金属Pt-Ru催化剂的CO表面吸附位.结果表明,单金属Pt催化剂显示出最高的初始微分吸附热(q_initial=125 kJ·mol^-1);单金属Ru催化剂具有最低的初始微分吸附热(q_initial=109 kJ·mol^-1);三种双金属PtRu催化剂的初始微分吸附热(q_initial=124～112 kJ·mol^-1)界于两种单金属之间.当双金属PtRu催化剂Pt:Ru原子比为1:2时,催化剂Pt原子表面上的强CO吸附位(> 112 kJ·mol^-1)被Ru原子所覆盖而完全消失.     

4,6-二甲氧基-2-嘧啶氨基甲酸甲酯的热力学研究

用精密自动绝热量热计测定了自行合成并提纯的4,6-二甲氧基-2-嘧啶氨基甲酸甲酯在80～380 K温区的摩尔热容.实验结果表明,在345～360 K温区,该化合物有一固-液熔化过程.经两次重复测定,得其熔化温度、摩尔熔化焓以及熔化熵分别为:(357.201±0.080) K, (26.289±0.029) kJ·mol^-1和(73.597±0.070) J·mol^-1·K^-1.通过分步熔化法得到该物质绝对纯样品的熔点为357.449 K.根据热力学关系和热容数据,计算出了该化合物相对于标准参考温度298.15 K的热力学函数.用DSC和TG热分析技术在300～500 K温区对该物质的热力学性质作了进一步研究,得到与绝热量热法一致的固-液熔化过程热力学参数,并得到该化合物蒸发过程的热力学参数:沸点为488.06 K,摩尔蒸发焓为81.73 kJ·mol^-1.     

合成黑索今中副产物3, 5-二硝基-1-氧-3, 5-二氮杂环己烷的晶体结构及热分解动力学

直接法硝解乌洛托品制备黑索今的过程中合成了一种新型的环形副产物,采用硅胶柱层析法分离得到3, 5-二硝基-1-氧-3, 5-二氮杂环己烷,洗脱剂为:丙酮/二氯甲烷,梯度洗脱.以丙酮为溶剂培养得到了3, 5-二硝基-1-氧-3, 5-二氮杂环己烷单晶,用元素分析、傅里叶变换红外(FTIR)光谱、核磁共振氢谱(NMR)以及质谱(MS)对其结构进行了表征,用X射线单晶衍射仪测定了其晶体结构.结果表明,晶体C₃H₆N₄O₅分子量为178.12,属于单斜晶系,空间群P121/n1,晶胞参数: a = 0.58128(13) nm, b = 1.72389(14) nm, c = 0.71072(6) nm, β =112.056°, V = 0.66006(16) nm³, Z = 4, D_C= 1.792 g·cm^-3, μ = 0.17 mm^-1, F(000) = 368.0,最终偏差因子R =0.0397.用同步热分析仪技术研究了3, 5-二硝基-1-氧-3, 5-二氮杂环己烷的热行为, DSC曲线上在383.15和519.05 K分别有一个尖锐的熔化吸热峰和分解放热峰.另外,根据Kissinger方程及Flynn-Wall-Ozawa方程和不同升温速率下的TG曲线计算得到了该化合物的热分解动力学参数(活化能和指前因子),利用Coats-Redfern法研究了该物质的热分解机理.结果表明: 3, 5-二硝基-1-氧-3, 5-二氮杂环己烷是一种低熔点、热稳定性好的化合物. Kissinger方程计算其活化能为212.32 kJ·mol^-1,指前因子为6.20×10²⁰ s^-1, Flynn-Wall-Ozawa方程计算其活化能为210.39 kJ·mol^-1,该物质的热分解动力学方程为G(α) = (1-α)^-1-1,反应级数为2.     

Electrochemistry of CeCl3 in Molten LiCl-KCl Eutectic

The electrochemical properties of CeCl3, dissolved in LiCI-KCI eutectic melt, were investigated by electrochemical techniques, such as cyclic voltammetry and square wave voltammetry on Mo electrode. It was shown that Ce（Ⅲ） is reduced to Ce（0） based on a three-step mechanism. In a temperature range of 833-923 K, the diffusion coefficient of Ce（Ⅲ） is lgDceoH）=-2.49-1704/T determined by means of the Berzins-Delahay equation with two different expressions under reversible and irreversible conditions. The apparent standard potential of a Ce（Ⅲ）/Ce（0） redox system is ECE^3＋0^＊/Ce^0 =3.551＋0.0006132T（K） vs. Cl2/Cl^-. Some thermochemical properties of CeCl3 solutions were also derived from the electrochemical measurements, such as the enthalpy, entropy, Gibbs free energies and the activity coefficients of Ce（Ⅲ）. The Gibbs free energy of a dilute solution of CeCl3 in this system was determined to be △G^0CeCl3/（kJ·mol^-1）=-1027.9＋0.178T（K） And the activity coefficients, γCeCl3 , range between （7.78-9.14）×10^-3. Furthermore, the standard rate constant of kinetic reaction was calculated to be （4.94-9.72）× 10^-3 cmZ/s and the reaction was regarded as a quasi-reversible reaction under the present experimental conditions at 833 K.     

Structural and Transport Characteristics of UCl3 in Molten LiCl-KCl Mixture: a Molecular Dynamics Simulation Study

To obtain suitable data for the pyrometallurgical post-processing in the fusion-fission hybrid reactor, the structure and transport characteristics of molten LiCl-KCl mixture containing UCl₃ were studied by molecular dynamics simulation. The radial distribution functions, densities, and self-diffusion coefficients were investigated at various molar fractions of UCl₃. In the molten LiCl-KCl-UCl₃ salt mixture, the first peak for g_U-Cl(r) was located at 0.266 nm, which was slightly left-shifted than the X-ray diffraction data, i.e., 0.285 nm for pure molten UCl₃. The preexponential factors for U³⁺ decreased from 46.2×10^-5 cm²/s to 32.2×10^-5 cm²/s as the molar fraction of U³⁺ increased from 0.005 to 0.05.     

聚羟基丁酸-戊酸的非等温热分解反应动力学

用非等温TG-DTA技术, 在5.0、10.0、15.0和20.0 K•min^-1线性升温条件下, 研究聚羟基丁酸-戊酸(PHBV)的热分解反应动力学. 结果表明, 分解过程分三个阶段：分解初期、分解中期和分解后期. 分解初期的机理函数为Avrami-Erofeev方程(n=1/2), 对应随机成核和随后生长机理, 表观活化能E_a(β→0)为69.44 kJ•mol^-1, 指前因子A(β→0)为106.27 s^-1；分解中期的机理函数为Avrami-Erofeev方程(n =2/5), 对应随机成核和随后生长机理, 表观活化能Ea(β→0)为117.64 kJ•mol^-1, 指前因子A(β→0)为10^11.48 s^-1；分解后期的机理函数为Mampel Power法则(n=1/3), 对应机理为幂函数法则, 表观活化能Ea(β→0)为116.64 kJ•mol^-1, 指前因子A(β→0)为10^8.68 s^-1.     

氯化钾介质中铈(Ⅲ)的荧光特性及应用研究

Ce³⁺在pH<6.2的KCl介质中受252.4nm的紫外光激发时,发射出的353.8nm荧光可用于痕量铈的测定.在pH5～6时,用Al₂(SO₄)₃可消除Fe³⁺的干扰.在0～3.0×10^-6mol/L范围内,荧光强度与Ce³⁺的浓度遵守ΔF=2.37×10⁶C-0.001方程(n=10,r=0.9999),检测限为6.0×10^-9mol/L.用于GWB07103(GSR-1)岩石成分分析的回收率为95.0％～103.2％,变异系数是4.18％(n=10);用于水系沉积物和土壤标准物质中铈含量分析,结果与标准值无显著差异.     

ZnO逆修饰小尺寸Cu/SiO2催化剂及其在CO2加氢制甲醇中的应用

Cu-ZnO is broadly used as a catalyst in CO₂ reduction to produce methanol, but fabricating small-sized Cu-ZnO catalysts with strong Cu-ZnO interactions remains a challenge. In this work, a simple, low-cost method is proposed to synthesize small-sized Cu-ZnO/SiO₂ with high activity and controllable Cu-ZnO interactions derived from copper silicate nanotubes. A series of Cu-ZnO/SiO₂ samples with different amounts of ZnO were prepared. The activities of the as-prepared catalysts for methanol synthesis were tested, and the results revealed a volcano relationship with the weight fraction of ZnO. At 523 K, the methanol selectivity increased from 20% to 67% when 14% ZnO was added to the Cu/SiO₂ catalyst, while the conversion of CO₂ increased first and then decreased with the addition of ZnO. The optimum space time yield (STY) of 244 g·kg^-1·h^-1 was obtained on C-SiO₂-7%ZnO at 543 K under 4.5 MPa H₂/CO₂. Furthermore, the synergistic effect of Cu and ZnO was studied by high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), and temperature-programmed reduction (TPR) analyses. The HRTEM images showed that the Cu particles come in contact with ZnO more frequently with increased addition of ZnO, indicating that the catalysts with higher ZnO contents have a greater probability of formation of the Cu-ZnO interface, which promotes the catalytical activity of Cu-ZnO/SiO₂. Meanwhile, the HRTEM images, XRD patterns, and TPR results showed that the addition of excess ZnO leads to an increase in the size of the Cu particles, which in turn decreases the total number of active sites and further degrades the activity of the catalysts. The activation energy (E_a) for methanol synthesis and reverse water gas shift (RWGS) was calculated based on the results of the catalytical test. With the addition of ZnO, E_a for methanol synthesis decreased from 72.5 to 34.8 kJ·mol^-1, while that for RWGS increased from 61.3 to 102.7 kJ·mol^-1, illustrating that ZnO promotes the synergistic effect of Cu-ZnO. The results of XPS and in situ DRIFTS showed that the amount of Cu⁺ species decreases with the addition of ZnO, indicating that the Cu-ZnO interface serves as the active site. The Cu surface area and the turnover frequency (TOF) of methanol were calculated based on the H₂-TPR curves. The TOF of methanol on the Cu-ZnO/SiO₂ catalysts at 543 K increased from 1.5 × 10^-3 to 3.9 × 10^-3 s^-1 with the addition of ZnO, which further confirmed the promotion effect of the Cu-ZnO interface on the methanol synthesis. This study provides a method to construct Cu-ZnO interfaces based on copper silicate and to investigate the influence of ZnO on Cu-ZnO/SiO₂ catalysts.     

Low Temperature Molten Salt Synthesis of Perovskite-type ACeO3(A=Sr,Ba) in Eutectic NaCl-KCl

A molten salt method was developed for the synthesis of ACeO₃(A=Sr, Ba) with perovskite structure at 750 ℃(SrCeO₃) and 850 ℃(BaCeO₃) in the eutectic NaCl-KCl. The synthetic temperature was much lower than that of the conventional method(generally>1000 ℃). The structure and morphology of the product were characterized by means of X^-ray diffraction(XRD), field emission scanning electron microscopy(FESEM) and transmission electron microscopy(TEM). The results show that the synthesized octahedral SrCeO₃ crystallizes in the orthorhombic system with the unit cell parameters of a=0.85855 nm, b=0.61523 nm, c=0.60059 nm, and the synthesized cuboid BaCeO₃ crystallizes in the cubic system with the unit cell parameter of a=0.43962 nm. The result of X^-ray photoelectron spectroscopy(XPS) analysis indicates that both Ce⁴⁺ and Ce³⁺ exist in the two structures, and the Ce⁴⁺/Ce³⁺ peak area ratios for SrCeO₃ and BaCeO₃ are 1.93 and 2.12, respectively. Meanwhile, the adsorbed/lattice oxygen ratios(1.87 for SrCeO₃ and 3.04 for BaCeO₃) indicate the existence of a lot of oxygen vacancies in the structures of SrCeO₃ and BaCeO₃, which indicates a far-reaching significance to study the corresponding physicochemistry performance.     

铜催化内炔的硅羧基化反应机理及区域选择性的密度泛函理论研究

用CO₂作为原料,在过渡金属催化下生成新的碳碳键是很重要的.在这类反应中,杂原子官能团和CO₂同时与不饱和的底物被催化生成高功能化的羧酸衍生物已经越来越受到人们的关注.本文采用密度泛函理论(DFT)方法,研究了金属铜催化剂催化内炔的硅羧基化反应机理.根据炔烃上甲基和苯环两个取代基的相对位置,提出了两条反应路径(path I:甲基和path II:苯环).计算结果表明炔烃插入Cu－Si键既是速率决速步骤也是区域选择决速步骤.在path I中,炔烃插入Cu－Si键的自由能为112.8 kJ·mol^-1,而在path II中为127.6kJ·mol^-1.显然, path I比path II在动力学上更有利,这与实验上两条路径对应产物的产率97: 3是一致的.分析表明区域选择性是由炔烃取代基甲基和苯环的电子效应决定的.