Pt-Sn/MgAl2O4催化剂的TPR和H2-TPD研究

Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0～2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover.     

A study of metals supported on active carbon with a temperature programmed reduction (TPR) technique

The influence of active carbon as support on the reducibility of supported metals (Ni, Cu, Cd, Zn) has been studied by means of a temperature programmed reduction (TPR) technique. The TPR profiles indicate that active carbon behaves as a dispersion agent and the supported metal is dispersed in a disordered phase rather than as a stoichiometric compound. The hydrogen consumed in the reduction indicates that the metal residues are present in monovalent and divalent forms. High-temperature reduction peaks were also observed and are explained on the basis of metal-surface interactions and the porosity of the active carbon. Nitrogen adsorption reveals that the active carbon porosity decreases due to progressive closure of the pores when metals are supported on the surface of active carbon.     

镁铁和镁铝双羟基复合金属氧化物的结构和性能差异

Layered Double Hydroxides MgFe-LDH and MgAl-LDH have been prepared by the method involving separate nucleation and ageing steps. The structure analyses for these two materials show that the values of the parameters both a and c of MgAl-LDH are smaller than that of MgFe-LDH though their structures are similar, and MgAl-LDH with higher crystallinity is more easily formed than MgFe-LDH in the same preparing conditions. The IR analyses manifest that the structures of layer sheets and the orderings of the anions in the interlayer regions of MgAl-LDH are more regular than that of MgFe-LDH. The temperature programmed XRD analyses reveal that the diffraction peak of 003 reflections for MgAl-LDH could be seen after calcining at 300℃, while this peak for MgFe-LDH disappears after calcining at 200℃. Together with the TG-DTA analysis it can be concluded that the thermal stability of MgAl-LDH is obviously higher than that of MgFe-LDH.     

助剂CeO2对Co/Al2O3催化剂上F-T合成反应性能的影响

 在用于F－T合成的Co／Al2O3催化剂中加入少量助剂,能够提高CO转化率和C5＋烃选择性．主要考察了助剂CeO2添加量和催化剂焙烧温度等因素对F－T合成反应的影响,并通过程序升温还原、程序升温氧化及X射线衍射等手段对催化剂进行了表征．结果表明,在Co／Al2O3催化剂中加入少量CeO2（n（Ce）／n（Co）＝0．1～0．14）,能够有效提高催化剂的催化活性和C5＋烃选择性;焙烧温度则以相反的趋势控制F－T反应活性和链增长几率;助剂的加入降低了催化剂的起始还原温度,改善了催化剂的还原性能．但是,催化剂的积碳量有所增加,经10h反应后,催化剂上存在两种类型的积碳．     

不同方法制备的Cu－Co低碳醇含成催化剂的比较研究Ⅱ．H_2－TPD，CO－TPD及CO／H_2TPSR的研究

本文采用Ｈ２－ＴＰＤ，ＣＯ－ＴＰＤ及ＣＯ／Ｈ２ＴＰＳＲ技术对三种方法（ＳＭＡＤ、浸渍、共沉淀）制备的Ｃｕ－Ｃｏ催化剂进行了表征，并与低碳醇合成选择性进行了关联．Ｃｕ－Ｃｏ催化剂上Ｈ２－ＴＰＤ谱中共有四个脱附峰（Ａ，Ｂ，Ｃ，Ｄ），其中Ｃ峰对应于低配位Ｃｏ中心上的活化吸附氢，其面积百分数随不同催化剂的变化规律与醇选择性的变化规律一致．与ＣＯ－ＴＰＤ谱对比，Ｃｏ及Ｃｕ－Ｃｏ催化剂上ＣＯ／Ｈ２ＴＰＳＲ谱中都出现一个新的甲烷析出峰（４７３～５７３Ｋ），归属为活化吸附氢与表面活泼碳物种之间的反应，其面积百分数随不同催化剂的变化规律与醇选择性的变化一致。基于上述结果，就ＣＯ插入中心问题进行了讨论．     

N2O Decomposition Catalyzed by K+-doped Bi0.02Co

K⁺-doped Bi_0.02Co was investigated as catalyst for N₂O decomposition. It was found that the catalytic performance of the Bi_0.02Co catalyst, which was prepared by coprecipitation method, can be effectively modified by potassium cations via impregnation. The optimized K_0.01Bi_0.02Co catalyst exhibited much higher activity compared with Bi_0.02Co and K_0.01Co for the reaction in feed gas 0.2% N₂O/Ar, irrespective of the presence or absence of impurity gas(volume fraction) 5%O₂, 2%H₂O, 0.12%NO and 10%CO₂. Characterization of the catalysts with H₂ temperature programmed reduction(H₂-TPR) and O₂ temperature programmed desorption(O₂-TPD) indicate that the Co-O bond in Bi_0.02Co was weakened by the K⁺doping, and hence the K_0.01Bi_0.02Co catalyst has much higher turnover frequency(TOF) than Co₃O₄ spinel and Bi_0.02Co for the reaction.     

A new high temperature gas chromatograph incorporating a temperature programmable direct injector

A high temperature gas chromatograph has been developed which is capable of operating at column oven temperatures up to 500°C. In addition, the detector can operate at temperatures up to 500°C, and the injector up to 450°C. The injector on this instrument is a temperature programmable direct injector, designed specifically to introduce labile or high molecular weight samples into the GC without molecular weight discrimination. The design of this GC and injector will be described, and high temperature applications will be discussed.     

Hydrogen occluded in sulfide catalysts: evidence from the temperature programmed heating technique

Strongly bonded hydrogen is found in alumina supported sulfide Co, Ni, Mo, (Co, Mo) and (Ni, Mo) catalysts. This hydrogen is desorbed from the catalysts in the temperature range of 500-750^oC and seems to be occluded in the corresponding sulfide matrix. Possible sites of its localization in the sulfide crystal lattice are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

沸石分子筛上程序升温脱附谱的Monte Carlo模拟研究Ⅱ．不同晶粒的沸石分子筛

沸石分子筛上程序升温脱附谱的ＭｏｎｔｅＣａｒｌｏ模拟研究＊Ⅱ．不同晶粒的沸石分子筛王建国李永旺陈诵英彭少逸（中国科学院山西煤炭化学研究所，太原０３０００１）关键词沸石分子筛，程序升温脱附，ＭｏｎｔｅＣａｒｌｏ模拟沸石分子筛被广泛用作吸附剂和催化剂的根...     

含铜MFI分子筛的H2-TPT和O2-TPD研究

 采用H2－TPR和O2－TPD手段考察了不同金属离子交换的ZSM－5分子筛催化剂上的氢还原性能和氧脱附性能．发现Cu－ZSM－5催化剂的储氧能力及氧脱附性能优于Co－ZSM－5和Fe－ZSM－5催化剂;储氧能力强、低温下氧脱附性能好的催化剂,对NO分解反应的催化活性就高．铜离子是反应的活性中心．添加Ag和Ce可使Cu－ZSM－5催化剂上氧的脱附温度大大降低．Cu－ZSM－5／堇青石整体式催化剂上Cu的存在形式与单纯的Cu－ZSM－5有差异,整体式催化剂上的一价铜数量少,但较稳定．     

β－Mo2N0．78的合成及其对噻吩加氢脱硫反应的催化性能

 以N2－H2混合气为反应气，与三氧化钼进行多段程序升温反应制得了氮化钼．考察了反应气组成和氮化温度等条件对氮化钼结构组成的影响．结果表明，在n（N2）／n（H2）＝0．25～1，θ＝650～750℃的条件下，生成的氮化钼结构组成为β－Mo2N0．78．其生成机理与γ－Mo2N有类似之处．β－Mo2N0．78催化噻吩加氢脱硫反应的结果表明，β－Mo2N0．78催化剂对该反应有较高的催化活性，在360℃下，其活性比硫化钼催化剂高一倍左右．     

汽车尾气净化用Pt/ZrO2-CeO2催化剂的表征与性能

汽车尾气净化用三效催化剂是一个多元复合型催化剂.以氧化铈或氧化铝为载体的催化剂其物理化学性质及催化性能已有报道[1,2],但载体氧化铈中添加氧化锆对催化剂性能影响的报道并不多.本文利用H2-TPR,CO-TPD和贮氧量测定等技术表征了CeO2中加入ZrO2后载体及催化剂的还原、吸附选择性及贮氧能力,并与三效反应进行了关联.     

Calculation of retention indices in temperature-programmed gas chromatography

Summary A new method is presented for the calculation of the retention indices under linear temperature programming with or without an initial isothermal period. The data calculated by the method are in good agreement with the isothermal retention indices.     

Calculation of activation energies using the sinusoidally modulated temperature

Activation energy is calculated from a single curve of a derivative of mass loss perturbed by a sinusoidal modulation of a temperature-time relationship. The method is based on a prediction of a hypothetical derivative of mass loss that corresponds to the absence of this modulation (perturbation). Simple considerations show that the unperturbed derivative coincides with the modulated derivative at inflection points of the modulated temperature-time relationship. The ratio of the perturbed and unperturbed derivatives at the points of time corresponding to maxima and minima of the sinusoidal component of the modulated temperature immediately leads to activation energy. Accuracy of the method grows with decreasing in the amplitude of the modulation. All illustrations are prepared numerically. It makes possible to objectively test the method and to investigate its errors. Two-stage decomposition kinetics with two independent (parallel) reactions is considered as an example. The kinetic parameters are chosen so that the derivative of mass loss would represent two overlapping peaks. The errors are introduced into the modulated derivative by the random-number generator with the normal distribution. Standard deviation for the random allocation of errors is selected with respect to maximum of the derivative. If the maximum of the derivative is observed within the region from 200 to 600°C and the amplitude of the temperature modulation is equal to 5°C, the error in the derivative 0.5% leads to the error in activation energy being equal to 2-6 kJ mol^-1. As the derivative vanishes, the error grows and tends to infinity in the regions of the start and end of decomposition. With the absolute error 0.5% evaluations of activation energy are impossible beyond the region from 5 to 95% of mass loss. This revised version was published online in August 2006 with corrections to the Cover Date.     

溶胶-凝胶法制备的铑基CO加氢制C2含氧化合物催化剂

用XRD,FT-IR,吸附CO的程序升温脱附(TPD),吸附CO的程序升温表面加氢反应(TPSR)等技术,并结合高压下CO加氢反应研究了用溶胶-凝胶法制备的铑基催化剂.结果表明,用溶胶-凝胶方法制备的催化剂中,Rh以极高的分散状态(主要以单原子形式)存在.与文献报道的浸渍法催化剂不同,CeO2的加入使甲醇选择性显著提高,但降低了催化剂的活性.CeO2对Rh的促进作用可能主要是CeO2与Rh产生了电子效应,即CeO2向Rh转移了电子.     

载体对负载PdO催化剂的CO氧化活性的影响

由于催化燃烧比传统的热力燃烧法有反应温度低和能量消耗低的优点，因而广泛用于挥发性有机物和CO的消除．把和铂是最常用的催化剂，但是载体对催化性能的影响很大【‘’‘］．本文制备了系列负载把催化剂，发现载体的性质对催化剂的CO氧化活性影响很大．本文所用载体为CeO。，TIO。，SnO。，AI。O。，ZAI。，ZSM－5和SIO。催化剂制备采用浸渍法，把负载量为5％（质量分数）．催化剂经120C烘干后，于650’C空气气氛焙烧4h制成．在常压固定床流动反应装置上考察催化剂的CO氧化活性，反应气组成为CO2．4％，O。1．2％，N。96．4…     

Activation of CuSi and CuZnSnSi contact masses for the direct synthesis of methylchlorosilanes

The temperature-programmed-activation (TPA) of CuSi, CuSi(H) (prepared using CuCl and CuCl 2H2O, respectively), and CuSi copromoted with zinc and tin have been investigated. The main effect of promotion was to increase the activation temperature suggesting that zinc may inhibit the transfer of chlorine from CuCl to surface silicon atoms. The sample prepared using hydrated cuprous chloride initially exhibited reduced activity for the Direct Reaction relative to CuSi, apparently, due to oxidation of the contact mass surface inhibiting the formation of -Cu₃Si.     

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.

     

NO气体在TiO2表面的吸附行为

采用TPD (Temperature Programmed Desorption)试验方法测定了NO在TiO₂表面吸附后的脱附谱, 揭示了气体脱附量的变化规律. 结果表明, NO在TiO₂表面吸附后可在两个峰值温度450和980 K脱附出N₂气体, 其活化能分别是0.48 和2.5 eV. TiO₂表面经预覆氧处理后, N₂的脱附量降低. N₂的脱附量随NO气体暴露量增加而增加, 但当气体覆盖度超过一定值后, 脱附量趋于定值. 脱附峰值温度随气体暴露量的增加而降低.