Preparation of New Solid Bases Derived from Supported Metal Nitrates and Carbonates

A highly basic solid catalyst was obtained by dispersing nitrates or carbonates of alkali metals such as KNO₃, CsCO₃ over alumina and zirconia at the surface density of 10-15 × 10¹⁸ cations m^-2 and heating them at 773-873 K in an inert atmosphere. The temperature is far below the decomposition temperatures of the nitrates and the carbonates. Based on the temperature-programmed decomposition (TPD) experiments, two types of decomposition process are suggested; a bulk decomposition and an anion decomposition. Generation of a strong basicity relates to the anion decomposition. The basic center may be composed of the oxygen anions liberated from the decomposition of the nitrate or carbonate anions that are dissociatively adsorbed on the support surface during the preparation. These catalysts effectively catalyzed the double bond isomerization of aliphatic hydrocarbons and bicyclic hydrocarbons at moderate temperature.     

ZrO2酸碱性质的TPD表征 II. NH3和CO2共吸附研究

用NH_3和CO_2双组分并吸附TPD-MS和IR技术对ZrO_2催化剂表面酸中心和碱中心的相互关系进行了表征. 先吸附NH_3（或CO_2）对在其后吸附的CO_2（或NH_3）不仅无阻碍，反而导致后吸附CO_2（或NH_3）在最高程脱峰温区（＞510 K）的脱附量增加．这种双组分并吸附效应在IR谱图上表现为NH_3共吸附诱发生成了一种新的CO_2吸附态，即在碱中心上形成单齿碳酸根物种．同时CO_2共吸附又强化NH_3与Zr~(4＋)（Lewis酸中心）的配位键合．这表明ZrO_2表面存在相互邻接的酸中心和碱中心，它们通过表面键诱导极化而令酸－碱相互作用加强．这类双组分共吸附效应可归结为表面键诱导酸－碱相互作用．     

The study of diffusion processes in the thermodesorption results

A consecutive model of surface reaction, consisting of two steps (desorption and diffusion) was applied. It was concluded that diffusion modifies the temperature programmed desorption spectra, although the single peak curves appear. The differential method for calculation of kinetic parameters based on thesT _M shift give values close to predicted ones only in the cases when particular steps are rate limiting. Generally, the desorption process have to be considered as a complex reaction, with the overall kinetic parameters. As a consequence of diffusion influence, the overall kinetic parameters are smaller than those for desorption step was obtained.

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Zusammenfassung Ein konsekutives Modell für Oberflächenreaktionen, bestehend aus zwei Schritten (Desorption und Diffusion) wird angewendet. Dabei zog man die Schlußfolgerung, daß das temperaturabhängige Desorptionsspektrum durch Diffusion modifiziert wird, wenn sich auch Single-Peak-Kurven ergeben. Die auf der Verschiebung von T_M basierende Differentialmethode zur Berechnung der kinetischen Parameter liefert nur in denjenigen Fällen Werte, die mit den prognostisierten übereinstimmen, in denen Einzelschritte geschwindigkeitsbestimmend sind. Ganz allgemein ist der Desorptions-vorgang als komplexe Reaktion mit kinetischen Bruttoparametern zu berücksichtigen. Als Folge des Einflusses der Diffusion sind die kinetischen Bruttoparameter kleiner als die für den Desorptionsschritt.

     

Synthesis of layered double hydroxides and their reactivities in 1-butene isomerization after calcination

Layered double hydroxides were synthesized and their catalytic activities tested in 1-butene isomerization after calcination at 723 K. The heat treatment destroyed the hydrotalcite-like structure creating mixed oxides with wide-ranging acid-base properties as revealed by temperature-programmed desorption of carbon dioxide and the double bond isomerization of 1-butene.     

TPD of oxygen from La?Sr?Ni?Co perovskite catalysts doped with Fe or Mn

Perovskites are interesting catalysts for hydrocarbon oxidation. TPD spectra of oxygen from La_0.66Sr_0.34Ni_0.3Co_0.7O₃, alone or doped with Fe or Mn, show the presence of two oxygen states related to the catalytic activity of these catalysts.     

基于偏振干涉成像光谱仪的视场增强和相位热漂移补偿关键技术的研究

偏振干涉成像光谱技术以傅里叶变换光谱学为理论基础,以一系列起偏/检骗器、剪切分束器和延时晶体等双折射晶体材料为主要结构,较之传统光栅式色散型光谱仪具有多通道、图谱合一、大光通量、高信噪比和抗环境振动干扰等一系列优点,并且结合多普勒光谱学相关原理和技术,已被广泛应用在各种天文学和天体物理学测试与计量领域如空间遥感、视向速度、宇航飞行、月球探测等。但是许多前人研究工作中仍然存在两个尚未妥善解决的问题：(1) 视场受限。普通型偏振干涉成像光谱仪存在远场条纹的弯曲而使系统视场角限制在±2°以内,严重影响傅里叶变换后的光谱重构精度;(2) 相位热漂移。晶体的热胀冷缩和双折射率之差随温度变化的特性导致像面干涉条纹发生随机抖动误差,将严重影响以多普勒频移为原理的视向速度等测量精度。因此,首先引入一块半波片构成增强型的Savart剪切分束器实现主动的视场展宽,可以使增强后的观察视场角达到±10°左右。这一改进不仅提高了傅里叶光谱变换的算法精度,同时也大幅增加光通量从而实现对微光光谱进行高信噪比的探测与标定。另外,为了消除环境温度造成的相位热漂移误差,选用偏硼酸钡(α-BBO)和铌酸锂(LiNbO₃)两种晶体进行精密组合匹配。该关键技术利用这两种晶体的双折射率之差随温度变化的相反特性,从而实现相位热漂移误差补偿。实验证明,在实验室环境温度下热相位漂移误差不超过0.02 rad。通过这些方案改善偏振干涉成像光谱仪的测试精度,拟实现对天文光梳以及其他大型天文光谱仪器快速而精确的标定与测试。     

1.053μm激光照射金平面靶产生的散射光谱实验研究

 测量了1.053μm激光照射金平面靶时产生的3ω_0/2谐波散射光的时间积分谱,由红移峰和蓝移峰的波长推算出双等离子体衰变区域的电子温度以及nc/4 区域的等离子体膨胀速度,即离子声速。实验结果和不稳定性饱和机制预言的结果有良好的自洽性。     

Adsorption Behavior of Nitrogen Monoxide on KxGaxSn8−xO16 Hollandite

Fine powder of K _x Ga _x Sn_8–x O₁₆ hollandite was prepared by the sol-gel process using metal alkoxides, and the adsorption behavior of nitrogen monoxide (NO) on it was examined by temperature programmed desorption (TPD) method and in situ diffuse reflectance fourier transform infrared spectroscopy. Any species other than nitrogen monoxide were not detected in the TPD measurement, and the profile showed three stages between 420 and 880 K which were regarded as the desorption of chemically adsorbed NO _x species. This desorption behavior seems well consistent with the spectral changes in the FT-IR measurement. The absorption band at 1270 cm^–1 was decayed in the first stage from 420 to 640 K, and the bands at 1235 and 1570 cm^–1 in the second stage from 640 and 770 K. In the third stage above 770 K, the strong band at 1340 cm^–1 disappeared. These NO _x species on the hollandite were estimated to have a form of NO₃ ^– in the first and second stages and a form of NO₂ ^– in the third stage, considering the data on adsorption of nitrogen oxides on La₂O₃ and CaO.     

同时脱除烟气中硫和硝的V2O5/AC催化剂研究

通过在固定床微反应器上对同时脱硫脱硝催化剂的研究,发现将V2O5担载在活性焦(AC)上制得的V2O5/AC催化剂可在200 ℃同时脱除烟气中的SO2和NO,其活性明显高于纯AC。V2O5/AC催化剂的脱硫脱硝活性与催化剂中钒的质量分数有关,随着V2O5质量分数从0.5%增至9%,硫容从3%增加到12%,脱硝率在V2O5质量分数为0.5%到3%时脱硝率稳定在60%左右,继续增加V2O5质量分数,脱硝率降低。程序升温脱附 (TPD) 和红外光谱 (FTIR) 表征结果显示在脱硫脱硝过程中,催化剂表面有H2SO4, 铵盐和VOSO4生成, VOSO4的质量分数随催化剂中V2O5质量分数的提高而升高。使用后的催化剂可通过5%NH3在300 ℃再生,再生后催化剂的脱硝活性明显增加,NO转化率从新鲜样的67%提高到接近100%,对SO2的吸附也比新鲜样有所增加。     

Surface chemistry and catalysis of oxide model catalysts from single crystals to nanocrystals

Fundamental understandings of surface chemistry and catalysis of solid catalysts are of great importance for the developments of efficient catalysts and corresponding catalytic processes, but have been remaining as a challenge due to the complex nature of heterogeneous catalysis. Model catalysts approach based on catalytic materials with uniform and well-defined surface structures is an effective strategy. Single crystals-based model catalysts have been successfully used for surface chemistry studies of solid catalysts, but encounter the so-called “materials gap” and “pressure gap” when applied for catalysis studies of solid catalysts. Recently catalytic nanocrystals with uniform and well-defined surface structures have emerged as a novel type of model catalysts whose surface chemistry and catalysis can be studied under the same operational reaction condition as working powder catalysts, and they are recognized as a novel type of model catalysts that can bridge the “materials gap” and “pressure gap” between single crystals-based model catalysts and powder catalysts. Herein we review recent progress of surface chemistry and catalysis of important oxide catalysts including CeO₂, TiO₂ and Cu₂O acquired by model catalysts from single crystals to nanocrystals with an aim at summarizing the commonalities and discussing the differences among model catalysts with complexities at different levels. Firstly, the complex nature of surface chemistry and catalysis of solid catalysts is briefly introduced. In the following sections, the model catalysts approach is described and surface chemistry and catalysis of CeO₂, TiO₂ and Cu₂O single crystal and nanocrystal model catalysts are reviewed. Finally, concluding remarks and future prospects are given on a comprehensive approach of model catalysts from single crystals to nanocrystals for the investigations of surface chemistry and catalysis of powder catalysts approaching the working conditions as closely as possible.