一元强碱滴定混合一元弱酸的林邦滴定曲线方程及pHsp的计算

用物料平衡式MBE、质子条件式PBE、副反应系数和条件稳定常数等知识,推导出一元强碱滴定混合一元弱酸溶液的林邦滴定曲线方程并用其推导出第一、第二化学计量点pHsp1和pHsp2的计算公式.     

可逆对称的氧化还原滴定的林邦滴定曲线方程及其化学计量点E_(sp)值的计算

用物料平衡式MBE、副反应系数和条件稳定常数等知识,推导出可逆对称的氧化还原滴定的林邦滴定曲线方程并用其推导出化学计量点Esp值的计算公式。     

用滴定突跃的绝对值推导四大滴定分析的直接准确滴定条件

建立了四大滴定分析"滴定突跃绝对值"的概念;用滴定突跃绝对值推导出四大滴定分析直接准确滴定的条件。     

沉淀滴定的离子强度允许范围

用离子强度副反应系数、条件稳定常数和准确滴定的条件推导出沉淀滴定的离子强度允许范围。     

利用滴定曲线方程和Origin精确绘制滴定曲线*

滴定曲线是滴定分析原理的重要内容。它显示了滴定过程中平衡体系性质的变化,可以获知化学计量点和滴定突跃信息,从而指导准确滴定判别或指示剂的选择。滴定曲线方程是滴定过程中体系的某种性质X(例pH)与滴定分数a(或滴定剂体积V)的关系方程,解析方程可获得函数X=f(a)的表达式。对一些较复杂的体系,推导函数X=f(a)较困难,但多数情况下反函数a=g(X)的推导更容易,表达式也更简洁。本文对酸碱、配位、氧化还原和沉淀滴定曲线方程进行了系统总结,并对不同情况下的函数X=f(a)或反函数a=g(X)进行了推导,拓展了教材内容。根据函数关系,在Origin中利用其函数绘图功能可直接绘制出滴定曲线,不用先生成数据点再绘图,方便快捷。用反函数绘图时增加数据点即可获得高精度的滴定曲线,可直接从滴定曲线上查找化学计量点和滴定突跃信息。     

沉淀滴定终点误差的计算公式

滴定分析中的终点误差计算,学者们在配位滴定、酸碱滴定中多采用林邦误差公式,陶德祥等在氧化还原滴定中也推导出类似公式。本文就林邦误差公式在沉淀滴定中的应用进行了探讨,推导出了林邦误差公式形式表示的沉淀滴定终点误差计算公式,现介     

配位滴定的离子强度允许范围

用离子强度副反应系数、条件稳定常数和准确滴定的条件推导出配位滴定的离子强度允许范围。     

多元弱酸的准确滴定

用二元弱酸滴定的林邦滴定曲线方程推导第一和第二滴定突跃绝对值,用第一和第二滴定突跃绝对值推导二元弱酸第一和第二级解离的H+准确滴定的条件,并将其应用于多元弱酸的准确滴定.     

混合离子的沉淀准确滴定

用沉淀滴定的林邦滴定曲线方程推导滴定突跃的绝对值,用滴定突跃的绝对值推导混合离子准确滴定的条件。     

一元强碱滴定一元弱酸溶液的林邦滴定曲线方程及其应用

以林邦副反应思想为基础,用质子条件式PBE、物料平衡式MBE、滴定分数和条件稳定常数等知识推导出一元强碱滴定一元弱酸溶液的林邦滴定曲线方程,并用滴定曲线方程讨论了滴定开始至化学计量点时任意一点p H的计算。     

Determination of the enthalpy change for anabolism by four methods

The enthalpy change for anabolism is needed to model the growth/respiration relation in plants. If all CO₂ production is assigned to catabolism, the anabolic reaction becomes C_substrate→C_products+xO₂ with an enthalpy change, ΔH_b. Four methods are proposed for determining ΔH_b: (a) From the difference in the heats of combustion of substrate and anabolic products (i.e. newly grown tissue). (b) From the composition of newly grown tissue and application of Thornton’s rule. (c) From independently measured values of the specific growth rate, R_SG, and of the product (R_SG ΔH_b). The product (R_SG ΔH_b) equals (−ΔH_CO2R_CO2−R_q) where R_CO2 is the specific rate of CO₂ production by respiration, ΔH_CO2 is the heat of combustion of respiratory substrate per mole of CO₂ and R_q is the specific metabolic heat rate. ΔH_b is then calculated as the ratio (R_SG ΔH_b)/R_SG. (d) From (ΔH_b=−(R_q/R_CO2+ΔH_CO2) [(1−)/] where is the substrate carbon conversion efficiency obtained from a total carbon balance. The first three methods have been tested and compared on oat seedlings and the last on corn seedlings. ΔH_b values from all four methods are in reasonable agreement despite the different assumptions involved.     

CeTiOx脱硝催化剂的抗硫中毒性能

分别以Ce₂(C₂O₄)₃和Ce(SO₄)₂为Ce前驱体, 采用固相球磨法制备了Ce基选择性催化还原(SCR)脱硝催化剂CeTiO_x-A[以Ce₂(C₂O₄)₃为前驱体]和CeTiO_x-B[以Ce(SO₄)₂为前驱体]. 将2个催化剂分别在体积分数为0.15%的SO₂的气氛下反应40和60 h, 得到高硫条件下SCR反应后的CeTiO_x催化剂, 分别记为40CeTiO_x-A, 60CeTiO_x-A, 40CeTiO_x-B和60CeTiO_x-B. 考察了反应前后催化剂的NH₃-SCR反应活性. 采用X射线衍射(XRD)、 X射线荧光光谱(XRF)、 比表面积(BET)测试、 H₂程序升温还原(H₂-TPR)、 X射线光电子能谱(XPS)、 NH₃程序升温脱附(NH₃-TPD)及SO₂程序升温脱附(SO₂-TPD)等技术对样品进行了表征. 结果表明, CeTiO_x-A系列催化剂比CeTiO_x-B系列催化剂具有更高的NH₃-SCR反应活性和更好的抗硫抗水性能. 与CeTiO_x-B系列催化剂相比, CeTiO_x-A系列催化剂具有更大的比表面积和孔容, 更多的Ce³⁺和吸附氧(O_α)物种有助于NO的吸附和活化; CeTiO_x-A系统催化剂还具有更多的Lewis强酸性位数量, 可以吸附更多的NH₃分子, 有利于催化剂上NH₃-SCR反应的进行, 提高了CeTiO_x-A系列催化剂的NO转化率.     

核-壳结构多酸/磁性铈铁纳米复合氧化物@SiO2吸附-氧化脱硫性能

水热法合成了铈铁纳米复合氧化物,采用化学沉积法在其表面包裹SiO₂制备核-壳结构磁性材料,以其为载体负载H₂O₂结合Keggin结构磷钼酸(HPMo)制备了HPMo-H₂O₂/CeFe_xO_y@SiO₂吸附-氧化脱硫催化剂。 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线粉末衍射(XRD)、氮气吸附脱附(BET)、³¹P魔角核磁共振(MAS-NMR)和X射线光电子能谱(XPS)等对催化剂的结构进行表征。 结果表明,SiO₂将CeFe_xO_y包裹形成核-壳结构纳米复合材料,以其为载体负载HPMo-H₂O₂后Keggin型多酸的骨架结构保持,并产生少量过氧化磷钼酸盐活性物种。 不同催化剂对有机硫化物二苯并噻吩(DBT)的吸附脱硫和氧化脱硫性能,均呈现出HPMo-H₂O₂/CeFe_xO_y@SiO₂＞CeFe_xO_y@SiO₂＞CeFe_xO_y的活性顺序,多酸的引入大大提升了其对大分子有机硫化物的吸附和氧化脱除性能,催化氧化脱硫活性的提高源于多酸分子“假液相”反应过程的结果。 在反应温度60 ℃,反应3 h,m(油)∶m(催化剂)=35∶1,n(O)∶n(S)=10∶1的条件下,对DBT氧化脱除率达到99.4%。 制备的磁性核-壳结构氧化脱硫剂有理想的氧化脱除DBT的循环使用性能,并且可通过外加磁场进行简单分离,是一类制备方法简单、催化活性高且稳定性好的绿色环保型催化剂。     

The effect of terminal chain modifications on the mesomorphic properties of 4,4'-disubstituted diphenyldiacetylenes

A variety of terminal chain modifications (Y) were made on the diacetylenes in which X=C_nH_2n+1, C₁₂H₂₅O and F, and Y=CH₂CH(Me)C₂H₅, COCH₃, C≡CC₅H₁₁, C_nF_2n+1C_nH_2n+1 and CH=CHCO₂C₃H₇. Mesomorphic properties were determined by hot stage polarizing microscopy and DSC. These were compared with those for the dialkyl analogues (X=C_mH_2m+1, Y=C_nH_2n+1) and a series of 1- and 2-olefins (Y=CH=CHC_nH_2n+1 and CH₂CH=CHC_nH_2n+1). The 1-olefin series showed wider range nematics than the dialkyl compounds, whereas the above modifications showed either narrow range nematic phases, no mesophase or higher melting temperatures. New transition temperature and enthalpy data are provided for some of the dialkyl and F-alkyl compounds previously reported, for comparisons. Preliminary birefringence data are also included along with the results of some heat and UV stability studies.     

Peculiarities of CaCO3, SrCO3 and BaCO3 decomposition in CO2 as a proof of their primary dissociative evaporation

The results of thermogravimetric experiments on the decompositions of CaCO₃, SrCO₃ and BaCO₃ in the presence of CO₂ and some data reported in the literature were used for the determination of the E parameter of the Arrhenius equation by the third-law method. The values obtained (495, 569 and 605 kJ mol⁻¹) are twice as much compared with the values of the E parameter obtained for these carbonates earlier in the absence of CO₂. This fact together with the invariance of the E parameter with partial pressure of CO₂ (P_CO2) and a hyperbolic dependence of the rate of decomposition on P_CO2 is in excellent agreement with the theoretical predictions deduced from the mechanism of decomposition that includes the primary stage of dissociative evaporation of reactant.     

Free surface-induced bilayer smectic A phase in polar liquid crystals

Here the influence of the free surface on both a thick (semi-infinite) layer and a thin freely suspended film of a polar liquid crystal is investigated. It is shown that within the temperature range of the monolayer smectic A phase (S_A1) the interaction between polar molecules and the free surface of the liquid crystal gives rise to a bilayer smectic A, a structure with long range antiferroelectric order (S_A2) in the surface region of the semi-infinite layer. The dependence of the bilayer smectic order parameter on the strength of the interaction between the constituent molecules and the free surface as well as temperature and the distance to the free surface are determined. Sufficiently far from the S_A1-S_A2 transition the latter dependence has an exponential character and the depth of the S_A2 phase penetration into bulk liquid crystal is equal to the longitudinal correlation length for the bilayer smectic A structure fluctuations in the S_A1 phase. However, near the S_A1-S_A2 transition the bilayer smectic order parameter decays non-exponentially and more rapidly with increasing distance to the free surface. In addition, it is found that the bilayer S_A2 phase can form several smectic layers at the free surface of a semi-infinite polar liquid crystal layer with the S_A1 phase. Finally, it is shown that in a freely suspended film the free surface-induced S_A2 phase can completely occupy the volume of the sample. Hence in a freely suspended polar liquid crystal film the S_A1-S_A2 transition occurs with decreasing film thickness.     

激光拉曼光谱研究NiMoP浸渍液活性组分的结构 Ⅱ.不同有机添加剂的影响

采用激光拉曼光谱（LRS）技术对添加有乙二醇和柠檬酸的NiMoP浸渍液和用该浸渍液制备的NiMoP/Al₂O₃催化剂进行了表征,研究了乙二醇和柠檬酸含量对NiMoP浸渍液及浸渍过程中活性相组成、结构的影响。结果表明,乙二醇使NiMoP(0.063)浸渍液中H_{x\[PMo11O39\]⁽7-x)- 或Hx\[PMo9O31\]⁽3-x)-及Hx\[PMo12O40\]⁽3-x)- 杂多阴离子结构转化成Hx\[P2Mo5O23\]⁽6-x)- 结构,而柠檬酸能保持NiMoP(0.063)浸渍液中Hx\[P2Mo5O23\]⁽6-x)-、Hx\[PMo11O39\]⁽7-x)- 或Hx\[PMo9O31\]⁽3-x)-及Hx\[PMo12O40\]⁽3-x)-杂多阴离子结构共存,但导致Hx\[P2Mo5O23\]⁽6-x)-含量降低,Hx\[PMo12O40\]⁽3-x)-含量升高。相对乙二醇而言,柠檬酸有机添加剂能够更有效地阻止浸渍过程中各杂多阴离子结构在载体氧化铝孔道中的分解。}     

High-throughput model-building and screening of zeolitic imidazolate frameworks for CO2 capture from flue gas

To find potential zeolitic imidazolate frameworks(ZIFs)for CO2 capture from flue gas,we built 169,898 ZIF models from 84,949 hypothetical zeolite networks.By calculating their lattice energies,accessible volumes to CO2,the isosteric adsorption heat(Qst)of H2 O,Henry’s constant ratio(SKH)of CO2/N2,percent regenerability(R%),CO2 working capacity(ΔNCO2),CO2/N2 adsorption selectivity(SCO2/N2))and adsorbent performance score(APS),we identi fied 49 hydrophobic ZIF structures that might outplay already-realised ZIFs built from the same imidazolate linkers for CO2 capture from flue gas.     

Copolymerization of （10-oxo- 10-hydro-9-oxa- 10λ^5-phosphaphenanthrene-lO-yl）-methyl acrylate with styrene

A phosphorus-containing monomer (10-oxo-10-hydro-9-oxa-10λ⁵-phospha-phenanthrene-10-yl)-methyl acrylate (M₁) was copolymerized with styrene to give a potential flame retardant copolymer of high thermal stability. The structures of monomer and copolymer were characterized by FT-IR and ¹H NMR measurements. The reactivity ratios for free-radical of the monomer (M₁) and styrene (M₂) were studied. The calculated results are as follows:r₁=0.225, r₂=0.503; Q₁=0.413, e₁=0.476; azeotropic point=0.37. TGA and DTG curves indicated that M₁ is a potential flame retarding monomer for styrenic polymers.     

醋酸铅作为铅源合成CH3NH3PbBr3-xClx纳米晶体颗粒

Lead acetate, which is highly soluble in dimethylformamide, was used to synthesize mixed halide perovskite CH₃NH₃PbBr_3-xCl_x (MA = CH₃NH₃, 0 ≤ x ≤ 3) nanocrystals (NCs). This method provides an approach to address the low solubility of lead halides, especially lead chloride. Different Br/Cl ratios in MAPbBr_3-xCl_x lead to various optical properties. The photoluminescence emission peak can be tuned from 399 to 527 nm. Their full-widths at half-maxima (FWHM) are about 20 nm. MAPbBr_3-xCl_x NCs have an average diameter of ~(11 ± 3) nm and have uniform dispersion in toluene. The MAPbBr₃ NCs have a long average recombination lifetime (τ_ave = 97.4 ns) and a photoluminescence quantum yield (PLQY) of up to 73%.