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1.
复杂水盐体系存在稳态和介稳固液相平衡以及复杂的成盐规律。为了解固液平衡状态下液相的结构特征,本文采用拉曼光谱技术并结合高斯-洛伦兹去卷积分峰拟合程序对Na +, Mg 2+//SO 42-, Cl -, H 2O四元体系及其二元和三元子体系中 ν1-SO 42-的离子缔合结构特征进行了分析。研究结果表明:SO 42-在Na 2SO 4-H 2O体系存在自由态SO 42-和SO 42-离子簇两种结构,在MgSO 4-H 2O, MgSO 4-MgCl 2-H 2O及Na +, Mg 2+//SO 42-, Cl -, H 2O等含镁体系中,还有Mg 2+-H 2O-SO 42-和Mg 2+-OSO 32-两种缔合结构。在二元和三元体系中 ν1-SO 42-的离子缔合结构以自由态SO 42-为主,随着SO 42-离子总浓度的变化,上述四种结构所占比例会发生规律性变化。Na +, Mg 2+//SO 42-, Cl -, H 2O四元体系在NaCl减少及等温蒸发过程中,自由态SO 42-结构比例逐步降低, Mg 2+和SO 42-相结合形成Mg 2+-H 2O-SO 42-或Mg 2+-OSO 32-结构的机会增多,在复盐区还会形成SO 42-离子簇结构。由此判断溶液结构的适应性变化是导致介稳现象的重要原因。进一步的相关分析表明:SO 42-的浓度和耶涅克指数 J与 ν1-SO 42-峰的峰强度和峰面积存在正相关关系, Mg 2+浓度是影响 ν1-SO 42-峰中四种缔合结构的比例发生变化的主要因素。 相似文献
2.
硫代嘧啶碱基是光动力疗法潜在的重要光敏剂,其最低单重激发态的光物理研究已有广泛报道。然而,其较高激发态的跃迁性质和反应动力学研究较为稀少。因此,本文采用共振拉曼光谱和密度泛函理论计算方法研究2,4-二硫代尿嘧啶的紫外光谱和几个较高单重激发态的短时结构动力学。首先,基于共振拉曼光谱强度与电子吸收带振子强度f的关系,将紫外光谱去卷积成四个吸收带,分别为358 nm(f=0.0336)中等强度吸收带(A带),338 nm(f=0.1491)、301 nm(f=0.1795)和278 nm(f=0.3532)强而宽的吸收带(B、C和D带)。这一结果既吻合密度泛函理论计算结果,又符合共振拉曼光谱强度模式对紫外光谱带的预期。据此,去卷积得到的四个吸收带被分别指认为S0→S2跃迁、S0→S6跃迁、S0→S7跃迁和S_0→S_8跃迁。同时,分别对B,C和D带共振拉曼光谱进行了详细的指认,获得了短时动力学信息。结果表明,S_8态短时动力学的显著特征是在Franck-Condon区域或附近发生了S8(ππ~*)/S(nπ~*)势能面交叉引发的、伴随超快结构扭转的非绝热过程。S7和S6态短时动力学的主要特征是反应坐标的多维性,它们分别沿C_5C_6/C_2S_8/C_4S_(10)/N_2C_3+C_4N_3H_9/N_1C_2N_3/C_2N_1C_6/C_6N_1H_7/C_5C_6H_(12)和C_5C_6/N_3C_2/C_4S_(10)/C_2S_8+C_6N_1H_7/C_5C_6H_(12)/C_5C_6N_1/C_5C_6H_(12)/C_2N_1C_6/N_1C_2N_3/C_4N_3H_9/N_1C_2N_3等内坐标演化。 相似文献
3.
锂硫电池的实际能量密度不高和多硫化物(LiPSs)的穿梭效应等问题严重影响了该电池的实际应用。本文通过将二维的Ti 3C 2T x Mxene纳米片与碳黑/硫(CB/S)材料进行混合,制备了Ti 3C 2T x-CB/S正极材料并将其涂覆在商业隔膜(PP)上,最终获得了Ti 3C 2T x-CB/S-PP一体式电极并用于锂硫电池。利用Ti 3C 2T x纳米片对CB/S进行修饰,不仅能提高活性物质硫的导电性,还能对扩散的LiPSs进行物理阻挡和化学吸附。而一体式电极的设计有利于提高电池的能量密度。恒流充放电测试结果表明,Ti 3C 2T x-CB/S-PP电极在0.1 C电流下的初始放电容量为1028.8 mAh·g -1,高于不含Ti 3C 2T x的CB/S-PP电极的896.8 mAh·g -1。Ti 3C 2T x-CB/S-PP电极还展示出了比基于传统铝箔集流体的Ti 3C 2T x-CB/S-Al电极更好的循环稳定性,前者在0.5 C下400圈长循环测试中的每圈衰减率为0.072%,而后者则为更高的0.10%。本文利用Ti 3C 2T x-CB/S构建一体式电极的策略为实现高性能和高能量密度的锂硫电池提供了新的研究方向。 相似文献
4.
采用浸渍提拉法制得TiO 2,ZnO,Fe 2O 3,ZnO/TiO 2,TiO 2/ZnO,Fe 2O 3/TiO 2和TiO 2/Fe 2O 3石英玻璃基底负载膜.光催化降解亚甲基蓝实验表明,TiO 2和ZnO具有良好的光催化活性,Fe 2O 3活性较差.但形成异质结后,TiO 2和Fe 2O 3的光催化降解能力发生明显的变化.用254nm紫外光光照后,TiO 2,ZnO和Fe 2O 3等3种氧化物膜与水的接触角均有不同程度的降低,TiO 2表现出超亲水性,ZnO/TiO 2和Fe 2O 3/TiO 2膜与水的接触角小于对应的单纯ZnO和Fe 2O 3膜与水的接触角,其中Fe 2O 3/TiO 2表面出现超亲水性.瞬态光电导谱的少数载流子寿命的测定表明,异质结势垒电场能有效地增强光生电子-空穴对的分离效率.根据能带理论建立的两组异质结能带模型可合理地解释实验结果. 相似文献
5.
Excess molar enthalpies HE and excess molar volumes VE have been measured, as a function of mole fraction x1, at 298.15 K and atmospheric pressure for the five liquid mixtures ( x11,4-C 6H 4F 2 + x2n-C lH 2l+2), l = 7, 8, 10, 12 and 16. In addition, HE and excess molar heat capacities CPE at constant pressure have been determined for the two liquid mixtures ( x1C 6F 6 + x2n-C lH 2l+2), l = 7 and 14, at the same temperature and pressure. The instruments used were flow microcalorimeters of the Picker design (the HE version was equipped with separators) and a vibrating-tube densimeter, respectively. The excess enthalpies of the five difluorobenzene mixtures are all positive and quite large; they increase with increasing chain length l of the n-alkane from HE(x1 = 0.5)/(J mol−1) = 1050 for l = 7 to 1359 for l = 16. The corresponding excess volumes VE are all positive and also increase with increasing l: VE(x1 = 0.5)/(cm3 mol−1) = 0.650 for l = 7 and 1.080 for l = 16. Interestingly, the excess enthalphies of the corresponding mixtures with hexafluorobenzene are only about 5% larger, whereas the excess volumes of (x1C6F6 + x2n-ClH2l+2) are roughly twice as large as those of their counterparts in the series containing 1,4-C6H4F2. Specifically, at 298.15 K HE(x1 = 0.5)/(J mol−1) = 1119 for (x1C6F6 + x2n-C7H16) and 1324 for (x1C6F6 + x2n-C14H30), and for the same mixtures VE(x1 = 0.5)/(cm3 mol−1) = 1.882 and 2.093, respectively. The excess heat capacities for both systems are negative and of about the same magnitude as the excess heat capacities of mixtures of fluorobenzene with the same n-alkanes (Roux et al., 1984): CPE(x1 = 0.5)/(J K−1 mol−1) = −1.18 for (x1C6F6 + x2n-C7H16), and −2.25 for (x1C6F6 + x2n-C14H30). The curve CPE vs. (x1 for x1C6F6 + x2n-C14H30) shows a sort of “hump” for x1 0.5, which is presumed to indicate emerging W-shape composition dependence at lower temperatures. 相似文献
6.
用中和法合成了氨基酸离子液体(AAIL)1-己基-3-甲基苏氨酸盐[C 6mim][Thr],并用核磁共振氢谱( 1H NMR)和核磁共振碳谱( 13C NMR)进行了表征。以苯甲酸为参考物质,用恒温热重法确定了AAIL[C 6mim][Thr]的蒸汽压和在平均温度下( Tav= 438.15 K)的蒸发焓(Δ glHm? ( Tav) =128.5 ± 6.0 kJ·mol -1)。利用Verevkin等人提出的方法计算得到AAIL[C 6mim][Thr]气态和液态的恒压热容差(Δ glCpm? = -70.8 J·K -1·mol -1),进而计算了不同温度的蒸发焓,其中参考温度(298.15 K)下的蒸发焓Δ glHm? (298.15 K) = 138.4 kJ·mol -1,只比应用我们提出的蒸发焓理论模型估算值大1.6 kJ·mol -1,小于恒温热重法的实验误差3.0 kJ·mol -1,说明这个蒸发焓的理论模型有一定的合理性。借助Clausius-Clapeyron方程估算了AAIL[C 6mim][Thr]的假想的正常沸点 Tb= 522.07 K,以及沸点的蒸发熵Δ glSm? ( Tb) = 228.5 J·K -1·mol -1,进一步得到了不同温度的蒸发熵和蒸发自由能Δ glGm? ( T),其结果表明蒸发自由能随着温度的上升而减小,达到沸点温度 Tb时变为零,而蒸发熵则随着温度上升而增大,是AAIL[C 6mim][Thr]蒸发过程的驱动力。 相似文献
7.
The structures of alkali halide clusters Na nF n, Li nF n and Na nCl n, and their metal-excess clusters Na nF n−1+, Li nF n−1+ and Na nCl n−1+ were investigated by the ab initio molecular orbital method for cluster sizes from 1 to 14. The magic numbers for the neutral clusters Na nF n, Li nF n and Na nCl n are 4, 6, and 8. The most stable structure for these cluster sizes is a perfect crystallite for Na nF n and Na nCl n, and a double ring for Li nF n. The magic numbers for the metal-excess clusters are 5 and 8, which are near ideal cuboids with (100) facets. 相似文献
8.
A superoxochromium(III) ion, Cr aqOO 2+, acts as a catalyst for the co-oxidation of alcohols and nitrous acid with molecular oxygen according to the stoichiometry: CH 3OH+HNO 2+O 2→CH 2O + NO 3− + H 2O+H +. The kinetics are second order in [HNO 2] and independent of the concentrations of the superoxochromium catalyst, substrate, and O 2. The proposed mechanism features the disproportionation of HNO 2 to NO and NO 2, both of which react rapidly with Cr aqOO 2+. The Cr aqOO 2+/NO reaction generates another equivalent of NO 2 and a mole of Cr aqO 2+, the active oxidant. The two-electron oxidation of the alcohol by Cr aqO 2+ produces Cr aq2+, which reacts rapidly with O 2 to regenerate the catalyst, Cr aqOO 2+. The NO 2/Cr aqOO 2+ reaction yields the peroxynitrato complex, Cr aqOONO 22+, in a dead-end equilibrium process that has no effect on the catalytic reaction. The disproportionation of NO 2 yields the final nitrogen-containing product, NO 3−, and regenerates an equivalent of HNO 2. Under a fixed set of conditions, the relative catalytic efficiency (CE) of Cr aqOO 2+ decreases as its concentration increases owing to the competition between O 2 and Cr aqOO 2+ for the intermediate Cr aq2+. 相似文献
9.
电化学阻抗谱可用于诊断多孔电极内电荷转移反应,即界面电荷集聚和电荷传导,以及反应物质输运。本文采用复相量方法,在同态假设条件下,重新推演多孔电极阻抗谱模型,厘清传统多孔电极阻抗谱模型中的模糊性表述。(1) 定义多孔电极表征输入参数,包括电极基体电子电导率 σ1 、电解质离子电导率 σ2、界面电荷传递电导率 gct、单位面积界面电容 C、固相扩散系数 D、速度常数 k、电极厚度 d、特征孔深 Lp 和单位体积表面积 Sc;(2) 解析阻抗谱特征输出参数,包括场扩散常数 K,特征频率 ω0、 ω1、 ω2、 ω3和 ωmax,它们分别相关于界面传导反应、有限场扩散、氧化还原反应、孔内扩散和最小特征孔尺寸,以及分别对应于从传导到扩散和从扩散到饱和的转折频率 fk1 和 fk2;(3) 当参数 X和 Z同时变化时( X = σ1和 Z = d, Sc, Lp, C, gct, D, k),通过阻抗谱特征参数的演变规律,分析了电荷转移反应中 X和 Ζ参数耦合竞争;(4)为深入分析电荷转移反应中参数 X和 Z的耦合竞争,引入了分叉频率 fXZ和 fZX 。 fXZ和 fZX所处位置可以用于表征参数 X和 Z影响电荷转移反应的深度和广度。当分叉频率 fXZ和 fZX不存在时,表明电荷转移反应中参数 X和 Z在全频率范围内存在耦合竞争。总之,借助于特征频率和分叉频率,本文一方面研究了动力学参数和微观结构参数对多孔电极中电荷转移反应的影响,另一方面分析谱图的变化及其背后的阻抗谱特征演化规律。本文研究结果可为阻抗谱的系统仿真和辨识提供理论基础,可为多孔电极内电荷转移反应的竞争分析提供技术支撑,还可为电化学储能系统的优化设计提供诊断工具。 相似文献
10.
采用沉淀法制备了Fe(OH)_3和Fe_2O_3。通过硫酸化处理得到SO_4~(2-)/Fe(OH)_3和SO_4~(2-)/Fe_2O_3两种催化剂,并将其应用于氨选择性催化还原NO_x(NH_3-SCR)反应,研究了SO_4~(2-)功能化处理对Fe_2O_3催化剂上NH_3-SCR脱硝性能的促进机理。结果表明,与纯的Fe_2O_3相比,硫酸化处理得到的催化剂上SCR活性得到显著提升;其中,SO_4~(2-)/Fe(OH)_3表现出更加优异的催化性能,在250-450℃时NO_x转化率高于80%,且具有优异的稳定性和抗H_2O+SO_2性能。XRD、Raman、TG、FT-IR、H_2-TPR、NH_3-TPD和in situ DRIFTS等表征结果显示,硫酸功能化处理能抑制Fe_2O_3的晶粒生长,同时SO_4~(2-)与Fe~(3+)结合形成硫酸盐复合物,提高了催化剂表面酸性位点的数量和酸强度,抑制了Fe_2O_3上的氨氧化反应,从而提高了其脱硝催化性能。 相似文献
11.
The addition of electrons to form gas-phase multiply charged anions (MCAs) normally requires sophisticated experiments or calculations.In this work, the factors stabilizing the MCAs, the maximum electron uptake of gas-phase molecules, X, and the electronic stability of MCAs X Q-, are discussed. The drawbacks encountered when applying computational and/or conceptual density functional theory (DFT) to MCAs are highlighted. We develop and test a different model based on the valence-state concept. As in DFT, the electronic energy, E( N, vex), is a continuous function of the average electron number, N, and the external potential, vex, of the nuclei. The valence-state-parabola is a second-order polynomial that allows extending E( N, vex) to dianions and higher MCAs. The model expresses the maximum electron acceptance, Qmax, and the higher electron affinities, AQ, as simple functions of the first electron affinity, A1, and the ionization energy, I, of the "ancestor" system. Thus, the maximum electron acceptance is Qmax, calc = 1 + 12 A1/7( I -A1). The ground-state parabola model of the conceptual DFT yields approximately half of this value, and it is termed Qmax, GS = ${}^{1}\!\!\diagup\!\!{}_{2}\; $ + A1/( I -A1). A large variety of molecules are evaluated including fullerenes, metal clusters, super-pnictogens, super-halogens (OF 3), super-alkali species (OLi 3), and neutral or charged transition-metal complexes, AB mL n0/+/-. The calculated second electron affinity A2, calc = A1-(7/12)( I -A1) is linearly correlated to the literature references A2, lit with a correlation coefficient R = 0.998. A2 or A3 values are predicted for further 24 species. The appearance sizes, nap3-, of triply charged anionic clusters and fullerenes are calculated in agreement with the literature. 相似文献
12.
采用分步浸渍法制备了系列Mg改性的Co/γ-Al_2O_3-TiO_2催化剂,通过X射线衍射(XRD)、紫外可见漫反射光谱(DR-UV-vis)、N_2吸附-脱附(BET)、X射线光电子能谱(XPS)和H_2程序升温还原(H_2-TPR)等技术对催化剂进行表征,并考察了其对丙烷燃烧的催化性能。结果表明,Co在原始γ-Al_2O_3-TiO_2载体和Mg改性MgO/γ-Al_2O_3-TiO_2载体上均以Co_3O_4的形式存在;Mg掺入后与Al_2O_3作用形成MgAl_2O_4尖晶石,改善了载体的织构性质,提升了Co_3O_4在催化剂载体表面的暴露数量和分散程度。此外,MgAl_2O_4与Co_3O_4相互作用提升了Co_3O_4颗粒表面Co~(3+)/Co~(2+)和O_(ads)/O_(latt)的比例,并削弱了Co-O键键能,从而提升了其对丙烷的催化燃烧活性。当Mg负载量为15%(质量分数)时,在Co/MgO(15%)/γ-Al_2O_3-TiO_2催化剂上进行丙烷燃烧,丙烷90%转化率的温度比无Mg掺杂的Co/γ-Al_2O_3-TiO_2催化剂的降低了45℃,并且连续反应40 h其活性保持稳定。 相似文献
13.
Closo-B nH n−2(CO) 2 ( n = 5–12), isolobal analogues of closo-C 2B n−2H n, have been investigated at the B3LYP/6-311+G **density functional level of theory. The most stable isomers of closo-B nH n−2(CO) 2 are similar to those of closo-C 2B n−2H n in geometric patterns apart from closo-B 6H 4(CO) 2, and closo-B nH n−2(CO) 2 is much less strained than closo-C 2B n−2H n. Energetic analysis identifies closo-B 6H 4(CO) 2, closo-B 12H 10(CO) 2 and closo-B 10H 8(CO) 2 to be most stable, of which the latter two cages have been prepared experimentally. On the basis of the negative and rather large nucleus independent chemical shifts (NICS), closo-B nH n−2(CO) 2 are aromatic. To aid further experimental study, the CO stretching frequencies have been computed. 相似文献
14.
采用酶动力学方法研究了5种钒取代的Dawson型磷钼酸H 7[P 2Mo 17VO 62]、H 8[P 2Mo 16V 2O 62]、H 9[P 2Mo 15V 3O 62]、H 8[P 2Mo 14V 4O 62H 2]和H 9[P 2Mo 13V 5O 62H 2](分别简写为P 2Mo 17V、P 2Mo 16V 2、P 2Mo 15V 3、P 2Mo 14V 4和P 2Mo 13V 5)对蘑菇酪氨酸酶二酚酶的抑制作用,结果表明,效应物P 2Mo 17V、P 2Mo 16V 2和P 2Mo 15V 3能够明显地抑制酪氨酸酶的活性,其半抑制浓度(IC 50)值分别为0.409、0.386和0.386 mmol/L,且均表现为可逆的竞争型抑制,效应物P 2Mo 17V、P 2Mo 16V 2和P 2Mo 15V 3对游离酶的抑制常数K I分别为0.234、0.391和0.249 mmol/L。 而效应物P 2Mo 14V 4在0~1.0 mmol/L浓度范围内,对酪氨酸酶二酚酶无明显抑制作用,效应物P 2Mo 13V 5对酪氨酸酶二酚酶表现为激活作用。 相似文献
15.
Absorption spectra of both atomic and molecular species in the air-acetylene flame, which are produced when the aqueous solutions of indium dissolved in HNO 3, HF, HCl, HBr and HI were aspirated into the flame, have been investigated in the u.v. region. Numerous atomic absorption lines of indium have been observed in the absorption spectra. Most of these lines were previously listed only as emission lines. Those atomic lines have been ascribed to the electronic transitions from the ground states of 5 p 2P1/20 and 5 p 2P3/20 to the excited states such as ls 2S1/2, md 2D3/2, nd 2D5/2, 4 p2 4P1/2, 4 p2 4P3/2 and 4 p2 4P5/2, respectively, where 13 l 6 and 14 m, n 5. The molecular absorption bands for InF, InCl and InBr in the airacetylene flame have been also observed near 234 nm, 267 nm and 282 nm, respectively, as the electronic transition of 1Σ + → 1Π 1 Those absorption bands show fine structures due to the molecular vibrations. The spectral parameters for the molecular vibrations have been obtained from the simulations of the observed spectra. The molecular absorption band for InI was not observed because of the decomposition of the molecule in the flame. In addition, the molecular absorption band for InO has been observed near 273 nm and those for NO near 205 and 215 nm. 相似文献
16.
利用热天平对比研究了大同煤及煤焦在O 2/N 2、O 2/CO 2和O 2/H 2O/CO 2中的燃烧行为,探讨CO 2和H 2O气化反应对其富氧燃烧特性的影响。结果表明,在5%氧气浓度下,煤粉在O 2/N 2、O 2/CO 2和O 2/H 2O/CO 2中的燃烧速率按顺序依次降低。氧气浓度降低到2%,由于CO 2和H 2O气化反应的作用,煤粉在高温区的整体反应速率按顺序依次增大。当氧气浓度为5%时,煤焦在O 2/CO 2中的燃烧速率要低于O 2/N 2中的燃烧速率,但燃烧反应推迟后气化反应的参与使得煤焦在O 2/H 2O/CO 2中的整体反应速率显著升高。当氧气浓度降低到2%后,随着温度的升高,在CO 2气化反应的作用下,煤焦在O 2/CO 2中的整体反应速率逐渐高于O 2/N 2中的燃烧速率。在O 2/H 2O/CO 2中,由于H 2O在共气化中起主要作用,煤焦在O 2/H 2O/CO 2高温区的整体反应速率进一步升高。动力学分析表明,在5%氧浓度时,煤焦在O 2/N 2、O 2/CO 2和O 2/H 2O/CO 2中的表观活化能依次升高。随着氧气浓度的降低,在不同反应气氛中的表观活化能均有所下降。 相似文献
17.
基于微波水热法和微乳液法合成SnO2/TiO2纳米管复合光催化剂.通过X射线衍射(XRD)、配有能量色散X射线光谱仪(EDX)的透射电镜(TEM)和电化学手段对光催化剂进行表征.以甲苯为模型污染物,考察光催化剂在紫外光(UV)和真空远紫外光(VUV)下的性能及失活再生.结果表明,SnO2/TiO2纳米管复合光催化剂形成三元异质结(锐钛矿相TiO2(A-TiO2)/金红石相TiO2(R-TiO2)、A-TiO2/SnO2和R-TiO2/SnO2异质结),促使光生电子-空穴对的有效分离,提高光催化活性.SnO2/TiO2表现出最佳的光催化性能,UV和VUV条件下的甲苯降解率均达100%,CO2生成速率(k2)均为P25的3倍左右.但由于UV光照矿化能力不足,中间产物易在催化剂表面累积.随着UV光照时间的增加,SnO2/TiO2逐渐失活,20 h后k2由138.5 mg·m-3·h-1下降到76.1 mg·m-3·h-1.利用VUV再生失活的SnO2/TiO2,过程中产生的·OH、O2-·、O(1D)、O(3P)、O3等活性物质可氧化吸附于催化剂活性位的难降解中间产物,使催化剂得以再生,12 h后k2恢复到143.6 mg·m-3·h-1.UV和VUV的协同效应使UV降解耦合VUV再生成为一种可持续的光催化降解污染物模式. 相似文献
18.
采用CCSD(T)/6-311++G(3 df, 2 pd)//B3LYP/6-311+G(2 df, 2 p)双水平计算方法构建了HO 2+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( 3O 2+H 2S))和Path 1a (R → 3IM1a → 3TS1a → P1( 3O 2+H 2S))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 kTST、 kCVT和 kCVT/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 k1CVT/SCT(200-800 K) = 1.54×10 -5T-2.70exp(1154/ T) cm 3 ·molecule -1·s -1和 k1aCVT/SCT(200-800 K) = 5.82×10 -8T-1.84exp(1388/ T) cm 3·molecule -1·s -1。 相似文献
19.
The proton-transfer between ammonia/water and HF/HBr without and with the stimulus of external electric fields(E ext) was investigated with the ab initio calculations. When external electric field is applied, the proton transfer occurs, resulting in ion-paired H 4N +X - and H 3O +X -(X=Br and F) from hydrogen-bonded complexes in view of the great changes of geometrical structures, dipole moments, frontier molecular orbitals and potential energy surfaces in the critical external electric fields(E c) of 1.131×107 V/cm for H 3N-HBr, 1.378×108 V/cm for H 3N-HF, 9.358×107 V/cm for H 2O-HBr and 2.304×108 V/cm for H 2O-HF, respectively. Furthermore, one or three excess electrons can trigger the proton transfer from H 3N-HBr and H 3N-HF to H 4N +Br - and H 4N +F -, while two and four excess electrons can induce the proton transfer from H 2O-HBr and H 2O-HF to H 3O +Br - and H 3O +F -, respectively. Compared with that of the analogous NH 3/H 2O-HCl systems, the strength of E c of proton transfer increases from HBr to HCl and HF for either H 3N-HX or H 2O-HX series, which is understandable by the fact that the acidity sequence is HBr>HCl>HF. And the larger of acidity of conjugated acid, the smaller of needed E c. On the other hand, the E c for the systems of NH 3 with a stronger basicity is generally smaller than that of H 2O systems for the same conjugated acid. 相似文献
20.
采用连续浸渍法制备了一系列非贵金属稀燃NO x阱(LNT)催化剂CuO-K 2CO 3/TiO 2,考察了Cu负载量对催化剂结构和NO x储存还原性能的影响.发现8% (w) CuO-K 2CO 3/TiO 2催化剂的催化性能最佳,其对NO x的储存量达到1.559 mmol·g -1,对NO x的还原效率高达99%,且在NO x还原过程中无副产物N 2O产生.应用粉末X射线衍射(XRD),高分辩透射电子显微镜(HR-TEM), CO 2程序升温脱附(CO 2-TPD),扩展X射线吸收精细结构(EXAFS),氢气程序升温还原(H 2-TPR)和原位漫反射红外光谱( in-situ DRIFTS)等技术详细表征了催化剂的结构.结果表明,不同Cu负载量的催化剂中,铜物种均主要以CuO相存在.铜的负载量直接影响铜物种、钾物种的存在状态,高分散的CuO相与表面K 2CO 3之间存在较强相互作用,这种相互作用不仅有利于NO x的储存,而且有利于增强催化剂的稳定性. in-situ DRIFTS结果表明, NO x储存过程中产生的两个负峰(1436和1563 cm -1)缘于碳酸盐的分解,这间接证明了碳酸盐作为储存介质参与到NO x储存反应中. EXAFS结果表明,经过15个稀燃/富燃循环测试,催化剂中的CuO相仍保持稳定.基于以上表征结果,提出了CuO和K 2CO 3在催化剂表面的分布模型,并探讨了NO x储存还原的可能机理. 相似文献
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