甲烷在SrO-La2O3/CaO催化剂上的氧化偶联Ⅱ.反应动力学的研究

在２０％Ｌａ２Ｏ３／ＣａＯ（ＬＣ）催化剂中添加ＳｒＯ（添加ＳｒＯ的ＬＣ以ＳＬＣ表示）明显地提高了反应活性和Ｃ２选择性。反应动力学研究表明，ＬＣ和ＳＬＣ催化剂在甲烷氧化偶联反应中，在表观活化能和表观反应级数上存在很大的差异。ＬＣ催化剂在ＣＨ４转化以及Ｃ２和ＣＯｘ形成过程中，表观活化能大于ＳＬＣ催化剂，而ＳＬＣ催化剂的指前因子小于ＬＣ体系，两者存在着补偿形象。ＳＬＣ催化剂的反应速率常数比ｋｃ２／ｋＣＨ     

Hydraulic activity of C4A3Cr in presence of C4A3S

This paper deals with synthesis and assessment of the hydraulicity of C₄A₃Cr, analog phase C₄A₃S to , relevant to the phase chemistry and properties of sulfoaluminate cements. C₄A₃Cr, synthesized at 1250 °C is well crystallized phase, latently hydraulic, with hydration accelerated in the presence of C₄A₃S, or CS. Calorimetric curves show reciprocal influence of sulfate and chromate phase in hydration of C₄A₃S-C₄A₃Cr system. The total heat expressed at hydration is nearly the same for all specimens, but the rate of heat evolution depends on the ratio of C₄A₃S/C₄A₃Cr phases. X-ray diffraction pattern and DTA curves showed that, increasing content of C₄A₃Cr in hydrating mixture results in a coexistence of two types of ettringite (chromate and sulfate ettringite) hydrogarnet, gibbsite and monosulfate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Apparent molar volumes of aqueous calcium chloride to 250°C, 400 bars,and from molalities of 0.242 to 6.150

Relative densities of CaCl ₂ (aq) with 0.22ml(mol-kg^–1)6.150 were measured with vibrating- tube densimeters between 25 and 250°C and near 70 and 400 bars. Apparent molar volumes V calculated from the measured density differences were represented with the Pitzer ioninteraction treatment, with appropriate expressions chosen for the temperature and pressure dependence of the virial coefficients of the model. It was found that the partial molar volume at infinite dilution V ^o , and the second and third virial coefficients B ^V and C ^V , were necessary to represent V near the estimated experimental uncertainty. The ionic-strength dependent ^(1)v term in the B ^V coefficient was included in the fit. The representation for V has been integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. The volumetric data indicate that the logarithm of the mean ionic activity coefficient, ln ±(CaCl ₂ ), increases by a maximum of 0.3 at 400 bars, 250°C, and 6 mol-kg^–1 as compared with its value at saturation pressure.     

Microgels and ionic associations in solutions of cellulose diacetate

Solutions of cellulose diacetate (CDA) from two sources (cotton linters and wood pulp Floranier) were analysed in various solvents by size exclusion chromatography (SEC). Without special precautions, the SEC chromatograms presented three peaks — or prehumps — before the main polymer peak. The first prehump which could be eliminated by ultracentrifugation corresponded to microgels whose sugar composition was determined. These microgels were also investigated by electron microscopy, X-ray and electron diffraction analysis. They corresponded mainly to cellulose triacetate (CTA-II) in the case of CDA from cotton linters and a mixture of CTA-II and xylan diacetate (XDA) in the case of CDA from the wood pulp Floranier. The second and third prehumps could be attributed to ionic effects corresponding to the association of remaining sulfate groups on the CDA molecules with residual calcium. It was found that these ionic effects could be eliminated by the addition of LiBr or LiCl to the elution solvents. This led to chromatograms devoid of prehumps.Presented in part at the Cellulose '91 meeting in New Orleans.     

L-谷氨酸、甘氨酸二元、三元体系中铽(Ⅲ)、钙(Ⅱ)的化学形态研究

在模拟生理条件下 (37℃ ,I=0 .1 5mol/ L Na Cl) ,用 p H电位法研究了铽 ( )、钙 ( )与 L-谷氨酸、甘氨酸二元、三元体系。确定了体系存在的物种 ,测定了体系中配合物的稳定常数。讨论了上述二元、三元体系中铽 ( )、钙 ( )的物种分布特点。     

甲烷氧化偶联催化反应的特征

应用程序升温反应（ＴＰＲ）及质谱分析表征了ＣａＯ，Ｓｍ２Ｏ３，０．５－１０％Ｓｍ／ＣａＯ催化剂上的甲烷氧化偶联反应特性。谱图分析表明，在４００－１０００℃范围内，甲烷氧化偶联反应产物的变化呈现三个反应温度区域：（１）完全氧化区，反应主要为ＣＨ３·在催化剂表面完全氧化形成ＣＯｘ和Ｈ２：（２）偶联区，主要为ＣＨ３·的氧化和偶联竞争反应，Ｈ２谱线出现明显的低温峰；（３）氧耗尽区，反应为高温气相反应，产物     

周岁内幼儿头发中锌钙含量的动态分析

对合肥市16671名1－12个月幼儿的发锌，钙含量进行了测定，并对测定值进行了统计分析。结果表明，锌，钙的含量随着月龄的增加呈直线递减。并给出了发锌，钙含量的趋势线方程，丰富了目前文献给出的发锌，钙的标准值，为及时准确判断周岁内幼儿微量元素锌，钙缺乏程度提出依据。     

CaO和NaCl焙烧混合稀土精矿过程中的分解反应

用XRD和TG-DTA热分析技术, 研究了含独居石和氟碳铈镧矿的混合稀土精矿在100～1000 ℃焙烧过程中, 添加CaO, NaCl时, REPO4和REFCO3的分解反应. 研究结果表明: 不添加CaO和NaCl时, 仅在377～450 ℃范围内存在REFCO3的分解反应, 其产物是REOF, RE2O3, 以及Ce2O3进一步的氧化产物CeO2, 而REPO4不分解; 添加CaO后在660～750 ℃之间, CaO有3种分解作用: (1) CaO分解REPO4, 其产物是RE2O3和Ca3(PO4)2. (2) CaO分解REOF, 其产物是RE2O3和CaF2. (3) CaO和REOF的分解产物CaF2共同作用分解REPO4, 其分解产物为RE2O3, Ca5F(PO4)3; 添加CaO, NaCl后, 混合精矿的分解率明显提高, NaCl的作用是为反应体系提供了液相, 促进了固相反应物间的传质过程, 加快了反应速度. 与此同时NaCl还可能参加了CaO分解REPO4的反应.     

Control of calcium carbonate polymorphism and morphology through biomimetic mineralization by means of nanotechnology

In vitro biomimetic mineralization by means of nanotechnology allows the formation of calcium carbonate polymorphs at low temperatures (<25 degrees C) under a CO(2) atmosphere of 500-1500 ppm. A two-dimensional zinc-ion ordered array (zinc array), which acts as an active-site mimic of carbonic anhydrase, has been prepared by immersing the self-organized monolayer of 3-(2-imidazolin-1-y)propyltriethosilane on mica (ImSi substrate) into aqueous zinc solution. The zinc array mounted on the ImSi substrate catalyzed the conversion from CO(2) to HCO(3) (-), and accelerated the formation of calcium carbonate. In situ X-ray diffraction data of the formed calcium carbonate on the poly(L-aspartate)-coated chitin substrate (pAsp substrate), with calcium ion-recognition sites, demonstrated that the interaction between the zinc array and pAsp substrates formed both vaterite and calcite at low temperature (15 degrees C) and mainly vaterite at 25 degrees C; this interaction also controlled the morphology of calcium carbonate formed on pAsp substrate.