微量热法研究γ-Mo2N催化剂表面氢的微分吸附热

近年来,人们发现高比表面积的过渡金属氮化物催化剂,尤其是γＮｏ2Ｎ催化剂对一些涉及加氢的反应,如ＣＯ加氢、乙烷氢解及加氢精制等反应呈现出优良的催化活性[1-7],因而成为多相催化领域研究的前沿课题之一.γＮｏ2Ｎ是体积较小的Ｎ原子嵌入金属Ｍｏ原子的间隙位而形成的一种“间充化合物”.由于非金属原子的价电子参与成键,故对金属原子的4ｄ能带和费米能级产生影响;反映在晶体结构上,γＮｏ2Ｎ不仅具有Ｐｄ,Ｐｔ,Ｒｈ,Ｉｒ的面心立方(ｆｃｃ)结构,而且在一些催化加氢反应中,具有贵金属Ｐｄ,Ｐｔ等催化剂的特征[8].Ｈ2ＴＰＤ研究结果发现,…     

微量热法研究γ-Mo2N催化剂表面氢的微分吸附热

Differential heats of H 2 adsorption on γ-Mo2N catalysts were studied by using microcalorimetry. Samples with high and medium surface areas (90 and 17 m2•g -1 ) present a homogeneous energetic distribution of surface sites, which corresponds with the preferential orientation of their (200) planes. Molybdenum nitride with low surface area (8 m2•g -1 ) displays a heterogeneous energetic distribution of H 2 adsorption sites. The higher initial differential heat of hydrogen adsorption observed for the low surface Mo nitride was attributed to species adsorbed on surface sites associated with the (111) plane.     

适于脉冲法和连续法两用的气／固吸附量热装置

适于脉冲法和连续法两用的气／固吸附量热装置周立幸（中国科学院大连化学物理研究所，１１６０１２）吸附热是表面热力学研究中的一个重要数据，在催化、吸附现象的基础研究和有关工业的应用等都很有意义。获得吸附热数据的方法很多，但最准确可靠的还是用量热法直接测定...     

微量吸附量热技术研究Pd-Cu/SiO2的表面吸附

应用微量吸附量热技术研究了室温Ｈ２,ＣＯ,Ｏ２和Ｃ２Ｈ４在ｍ（Ｐｄ）／ｍ（ＳｉＯ２）＝２％,ｍ（Ｐｄ,Ｃｕ）／ｍ（ＳｉＯ２）「ｎ（Ｐｄ）／ｎ（Ｃｕ）＝１／１」＝２％,ｍ（Ｐｄ,Ｃｕ）／ｍ（ＳｉＯ２）「ｎ（Ｐｄ）／ｎ（Ｃｕ＝１／４」＝２％和ｍ（Ｃｕ）／ｍ（ＳｉＯ２）＝８％催化剂表面的吸附性能,并考察了Ｏ２对Ｃ２Ｈ４吸附性能的影响,结果表明,Ｐｄ－Ｃｕ／ＳｉＯ２具有与Ｐｄ／ＳｉＯ２数量相近的表面Ｐｄ原子,加入Ｃｕ可使Ｐｄ对Ｈ２和ＣＯ的强吸附位数目相对减少,弱吸附位数目相对增加Ｐｄ增加了Ｈ２在Ｃｕ／ＳｉＯ２催化剂表面的吸附量,加速了Ｏ２在Ｃｕ表面的吸附速率,Ｐｄ原子和Ｃｕ原子在Ｐｄ－Ｃｕ／ＳｉＯ２混合均匀且分散良好,乙烯在Ｐｄ／ＳｉＯ２表面吸附有乙川,ｄｉ－σ和π吸附态。Ｃｕ的加入可抑制乙类在Ｐｄ表面吸附氧发生氧化反     

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.     

Cr/C催化剂的催化性能与表面酸性的微量吸附热技术分析

以NH3作为吸附探针分子，定量地分析了Cr／C固体表面酸性中心的强度、数量和分布状态，并探讨了表面酸性对催化性能的影响关系。结果表明适当强度的酸性位有利于CO2氧化乙烷脱氢制乙烯反应。     

气相色谱法测定气固表面的吸附停留时间

提出了一个用气相色谱测定气体在固体表面上吸附停留时间的方法. 经推导, 得到了测定公式.用八种烷烃及苯在硅胶上的吸附实验数据进行验证和研究, 得到了满意的结果.     

二组分气体在固体上吸附的研究(Ⅰ)──新的快速迎头色谱测定吸附等温线系统

本文提出了一个新的二组分气固吸附的色谱测定系统。该系统由迎头色谱系统及普通色谱系统联合组成;通过各种阀门的转换,可以分别测得吸附到达平衡时,吸附相和气相中各组分的吸附量和蒸气压。并详细探讨了影响吸附数据测定的各主要因素。     

B-E-T吸附等温式的另一种建立方法

将多分子层气固吸附等效地视为链状分子的单分子层吸附,然后通过一个所谓的气固吸附Szyszkowski公式,同样能够建立起B-E-T吸附理论,并导出各种多分子层吸附的气固吸附等温式.     

热重分析技术测定二苯并呋喃在活性炭上的吸附相平衡

以吸附动力学为基础,建立了热重分析技术测定难挥发性有机物吸附等温线的方法.通过热重分析实验测定了不同升温速率下二苯并呋喃从Norit RB1和Chemviton BPL活性炭上脱附速率曲线,及对应的脱附峰温度.运用所提出的方法,对二苯并呋喃在Norit RB1和ChemvironBPL活性炭上的Langmuir吸附等温线方程进行了估算.估算结果与静态吸附实验测定结果相比,误差不超过10%.     

B-P-O系催化剂表面酸性的吸附量热研究

制备了不同P／B比的W-P-O系催化剂，XRD和Raman光谱表明各样品中P和B都处于四面体结构中，但Raman光谱显示P／B＜1的样品表面有B的三配位物相B2O3。存在．用吸附量热法考察了NH3、H2O及二甲醚（DME）等探针分子的吸附行为，研究了样品的表面酸性，NH3在P／B＞1的样品上发生解离吸附，而在P／B＜1的样品上，其起始吸附热与在γ-Al2O3上的相似．进一步的研究表明，二甲醚可以作为合适的探针分子表征B-P-O系催化剂的表面酸性．     

氨基酸在固体表面的吸附*

介绍了氨基酸在固体表面吸附的常见吸附模式和吸附等温线类型。在常见的等温式中Sips等温式能处理液相中吸附质浓度从低到高、吸附剂表面从均匀到不均匀等各种情形下的固/液吸附体系,得到的等温线一般归属4类：S型、L型、H型和C型;总结和讨论了各吸附参数对氨基酸吸附的影响,具体考察了氨基酸种类、固体表面的性质、溶剂种类、介质的pH、介质离子强度和温度等因素对氨基酸吸附的影响,指出通过优化各吸附参数,可以调整氨基酸和固体吸附剂之间的静电吸引力或疏水作用,达到最好的吸附效果;对氨基酸的固体吸附剂进行了分类阐述。     

Co/SiO2催化剂的表征和吸附量热研究

用溶胶-凝胶法制备了Co/S iO2系列的担载型催化剂,采用SBET、TPR、XRD、O2滴定及室温H2、O2、CO和C2H4微量吸附量热等技术进行了研究.结果表明:Co很好分散,S iO2的含量越高,样品的SBET越大;Co是经由Co3 →Co2 →Co0的还原过程;Co/S iO2系列催化剂上,CO、H2、O2和C2H4的初始吸附热数值均比较接近、饱和覆盖度以50Co/50S iO2最高,O2为多层吸附而H2、CO和C2H4为单层吸附,CO为线式吸附并发生歧化反应生成了C和CO2,C2H4吸附解离生成了H2、乙川(C2H3)和C2H6.     

A Thermodynamic Model for Gas Adsorption Isotherms

In this paper based on the principle of solution thermodynamics for gas–solid equilibrium, a relation is developed to express gas adsorption isotherms. An activity coefficient model based on weight fraction of sorbate in the solid phase has been derived that well describes the behavior of various gases on different types of adsorbents. The proposed model has been evaluated and compared with four other models commonly used for gas adsorption isotherms in the literature. For 12 different systems at various isotherms for the temperature range −128 to 100°C and the pressure range 0.02 to 1219 kPa for 689 data points, the proposed model predicts equilibrium pressure with an average deviation of 5.3%, which is about half of the error obtained from other methods. The proposed model clearly outperforms other available methods such as the vacancy solution theory, the ideal adsorption solution model, and other various modified forms of the Langmuir isotherm. Unique features of the proposed model are its simplicity, generality, and accuracy over the entire pressure and temperature ranges.     

Adsorption of Nitrogen on Silica Gel Over a Large Range of Temperatures

To study the mechanism of physical adsorption of supercritical gases, the adsorption equilibria of N₂ on silica gel for 103–298 K using 20 K increments and pressures up to 10 MPa were measured. A transition of the adsorption mechanism was proven on crossing the critical temperature, but the transition way observed is different from that observed with activated carbon. This causes a difference in the locations of the linear section of the n- _g isotherm at the near-critical temperature. Although the isotherm type is different on silica gel and on activated carbon in the sub-critical region, all isotherms in the supercritical region can be well modeled by a single model. It leads to the argument that the adsorption mechanism of supercritical gases is identical no matter what kind of adsorbent is used.     

微量吸附量热技术在ZnxCo1-xCr2O4催化剂筛选上的应用

采用共沉淀法制备了一系列ZnxCo1-xCr2O4催化剂,并将其进行了微量吸附量热技术测定,及苯酚与甲醇邻位烷基化反应的应用性实验。结果证明,ZnxCo1-xCr2O4催化剂上苯酚和甲醇邻位烷基化反应的活性中心应是酸碱的协同作用产生的,ZnxCo1-xCr2O4系列催化剂中的Zn／Co的最佳比例为Zn／Co=1。运用微量吸附量热技术实现了对ZnxCo1-xCr2O4系列催化剂的优化。     

Calculation of Adsorption Isotherms on Hard Solid Surfaces Using Measurements of Surface Tensions and Contact Angles

The adsorption excess isotherms of binary mixtures adsorbed on hard solids were calculated by means of surface tension and contact angle measurements using the Gibbs adsorption isotherm equation. The calculation procedure is described in detail using the authors' own measurements of mixtures containing ethylene glycol(1)/water(2) on Teflon and poly(vinyl chloride), and water(1)/n-propanol(2) on Teflon. On the basis of these results and also from surface tensions and contact angles on hard solids published by other authors, all types of isotherms were found as given for porous adsorbents in the classification of Schay and Nagy. In addition to those, new isotherm types are proposed.