催化化学课件英文版

1、多相催化研究方法多相催化研究方法 实际催化剂实际催化剂模型催化剂模型催化剂合成表征反应反应动力学探索催化反应本质引导实际催化材料的发展真空表面分析技术Pressure GapMaterials Gap发展高效催化剂催化反应动力学稳态动力学技术稳态动力学技术瞬态动力学技术瞬态动力学技术建立反应速率和操作条件参数间的定量关系， 提出正确的反应机理， 预测反应条件时的速率变化。LHHW型： 吸附-表面反应-脱附稳态同位素瞬态动力学稳态同位素瞬态动力学-SSITKA一个或多个快速变化的状态变量引如系统并跟踪发生的系统变化。温度温度-程序升温技术程序升温技术同位素示踪同位素示踪产物瞬时分析技术（产物瞬时

2、分析技术（TPA）瞬变应答技术（瞬变应答技术（Transient Response)光谱跟踪技术光谱跟踪技术Monitoring of Reactions Mid Infrared Spectroscopy The idea is that the characteristic peak for each compound that is IR active changes with time and this change can then be used to follow the reaction Near Infrared Spectroscopy One problem with N

3、IR is that compounds often do not exhibit highly characteristic peaks, and often the changes are more subtle and in small regions of the spectrum UV/vis spectroscopyRaman spectroscopy Raman spectroscopy probes have become fashionable. This technique is an alternative to MIR, but the relative intensi

4、ties of bands differ in the two techniques, however, many of the same methods can be employed to analyse the data.Summary of main data analysis techniquesThe following data analytical techniques are most common for the analysis of on-line spectroscopic data from reactions using different spectroscop

5、ies. 1.MIR and Raman. Generally conventional kinetic curve fitting of peak areas, but some deconvolution necessary if overlapping peaks. 2.NIR. Usually multivariate calibration such as PLS and a number of related classical chemometrics methods. 3.EAS. Deconvolution using MLR (multiple linear regress

6、ion) and pure standards, plus multivariate calibration. Of course life is never so simple and some quite sophisticated approaches have been developed in recent years to extract more information from these highly informative but sophisticated data matrices as will be discussed in the next article. It

7、 is of interest to consider the ways in which the presence of zirconia either as a support or an additive enhances the rate of methanol synthesis. zirconia promotes the rate of methanol formation occurring on the surface of Cu, or alternativelyCu promotes the synthesis of methanol over zirconia. Whi

8、ch of these two options offers the most plausible explanation.In-SituInfrared Study of Methanol Synthesis from H2/CO2 over Cu/SiO2 and Cu/ZrO2/SiO2 Ian A. Fisher and Alexis T. Bell, JOURNAL OF CATALYSIS 172, 222237 (1997)Infrared spectra taken during exposure of Cu/SiO2 to 0.16 MPa CO2 and 0.49 MPa

9、H2.Infrared spectra taken for Cu/SiO2 at 523 K after switching the feed from 0.65MPa H2 to 0.16 MPa CO2 and 0.49 MPa H2 at 523 K.Temporal Resolution of Surface SpeciesTransient spectra were obtained after switching the feed fromH2 to 3/1H2/CO2 at a total pressure of 0.65MPa while maintaining the tem

10、perature of the Cu/SiO2 catalyst at523 K. The results are shown in Fig. 3. b-HCOOCu (2927,2849, 1540, 1350 cm1), and weak features for adsorbedCO onCu(2128, 2094, 2077cm1, not shown) form immediately upon switching and the intensities of the bands for these species remain relatively constant during

11、the 22.6 h transient. At 2.7 min into the transient, a peak at 2959 cm1 begins to grow in and increases in intensity during the remainderof the transient. This feature is ascribable to CH3OSi and the companion peak at 2856 cm1 is evidenced by the asymmetry of the peak at 2849 cm1 (shoulder on the le

12、ft).CH3OSi is also evidenced by the shoulder at 2994 cm 1and the bending mode observable at 1464 cm1 at longer times. These features forCH3OSi have been observed during methanol adsorption on Cu/SiO2.Infrared spectra taken during exposure of ZrO2/SiO2 to 0.16 MPa CO2 and 0.49 MPa H2The principal fea

13、tures at 323 K are those for b-HCO3Zr (1619 cm1) and i-CO3Zr (1442cm1).Asmall amount of m-CO3Zr (1382cm1) and b-CO3Zr (1351 cm1(sh) are also present. As the temperatureis increased, the concentrations of b-HCO3Zr and i-CO3Zr decrease and bands appear that are characteristic of b-HCOOZr (2974, 2892,

14、1565, 1386, 1369 cm1). At 523 K bands appear at 2942, 2842, and 1463 cm1 which areattributable to methoxide species on zirconia (CH3OZr)region (not shown), peaks for CO on Cu (2131, 2094,2077 cm1) are present at 323 K. The peak at 2131 cm1is gone at 373 K, while those at 2077 and 2094 cm1 arepresent

15、 at all temperatures, but decrease in intensity withtemperature.Infrared spectra taken during exposure of Cu/ZrO2/SiO2 to 0.16 MPa CO2 and 0.49 MPa H2At 323 K the spectrum is comprised of features attributable to b-HCO3Zr (1606, 1465 cm1), m-CO3Zr (1490, 1383 cm1), b-CO3Zr (1576 cm1), and weak featu

16、res for b-HCOOZr (2980, 2897, 1568, 1390, and 1370 cm1). In the temperature interval of 373523 K b-HCOOZr (2980, 2897, 1568, 1389, and 1370 cm1) becomes the dominant species. With increasing temperature the intensities of the bands for this species pass through a maximum at 423 K. At 373 K new featu

17、res appear at 2966 and 2861 cm1 due to bidentate methylenebisoxy on zirconia (b-CH2OOZr) (45, 4750), and at 2944 and 2846 cm1 due to CH3OZr. At 473 K bands appear at 2957 and 2856 cm1 due to CH3OSi. At 523 K, the features for b-CH2OOZr are not readily apparent. It is evident that the formation of b-

18、HCOOZr and CH3OZr are significantly faster in the presence of Cu.Intensities of b-HCOOZr and CH3OZr featuresformate and methoxide decay occurs much more readily on the copper containing catalyst and that methoxide decays only extremely slowly on ZrO2/SiO2.Proposed mechanism.CO2 is adsorbed on ZrO2 a

19、nd then undergoes stepwise hydrogenation to formate, ethylenebisoxy, and methoxide species, with atomic hydrogen being supplied by spillover from Cu. The final step in this sequence is the hydrolysis of the methoxide groups on ZrO2 via reaction with water produced as a co-product of methanol synthes

20、is and the reverse-watergas-shift reaction. The latter reaction is thought to occur exclusively on Cu and is not enhanced significantly by the presence of ZrO2.标记同位素方法标记同位素方法同位素质子数相等但中子数不等-电子结构和化学性质不变动力学同位素效应反应机理H和D在振动频率和穿越活化势垒的差异稳定性同位素放射性同位素13C， 18O，15N， D14C， 35S 等等稳定性同位素标记物的分析稳定性同位素标记物的分析原子质量数的差异

21、原子质量数的差异伸缩振动频率的红移伸缩振动频率的红移核自旋量子数不为零MSIRNMR标记同位素方法研究反应机理丙烯歧化反应丙烯歧化反应2C=C*-C C-C*-C-C-C*-C C=C* +C-C=C*-CCH2=14CH-CH32C=C*-CC-C*-CC-C*-C C=C +C-C*=C*-CRe2O7/Al2O3标记同位素方法研究反应机理CO+H2合成甲醇的反应机理Rh/TiO2CO C + OadCHn+Had CH （n+1） adCH3ad+OHad CH3OHH2 2HadHad + Oad OHadCO COadCOHn+Had COH （n+1） adCOH3ad+Had C

22、H3OHH2 2HadCO离解的反应机理离解的反应机理CO非离解的反应机理非离解的反应机理标记同位素方法研究反应机理CO+H2合成甲醇的反应机理合成甲醇的反应机理Rh/TiO23234Mass number33Mole fraction / %13CH316OHProducts50%13CO+50% 14CO as C18O sourceCO非离解的反应机理非离解的反应机理12CH316OH13CH318OH12CH318OH35154442CO离解的反应机理离解的反应机理产物的分布各25%标记同位素方法研究反应机理丙烯丙烯氧化的反应机理氧化的反应机理CH3-CH=CH2 + O2 CH2=C

23、H-CHOH2C CH CH2HCH2D-C-H=CH2CH3-CH=CHDCD3-CD=CD2CH3-CH=CH2RDSH14CH3-CH=CH214CH2 = CH - CH350%CH2 = 14CH - CH30%H & D kinetic effectCarbon Isotopic Tracer18CH2=CH-CH16OCH2=CH-CH18OConvincing evident for the involving of Lattice Oxygen Selective Oxidation of propylene to AcroleinOxygen activationT

24、OSSteady-State Isotopic-Transient Kinetic Analysis-SSITKAS.L.Shannon et al., Chem, Rev., 95(1995)677-695- 稳态同位素瞬变动力学稳态同位素瞬变动力学同位素示踪技术同位素示踪技术瞬变动力学技术瞬变动力学技术IR技术技术根据产物分布推测中间物种直接观察催化剂表面吸附物种的变化吸附，基元反应，脱附MS和IR检测技术的结合提供更深入的反应信息Typical Reaction System for SSITKA ExperimentalGas Feed SystemReaction SystemPro

25、duct AnalysisIR cell稳态同位素瞬变技术动力学参数的测定稳态同位素瞬变技术动力学参数的测定反应稳态反应稳态反应体系的流速，压力，温度，催化剂表面状态反应体系的流速，压力，温度，催化剂表面状态以及反应物和产物的浓度不随时间发生变化。以及反应物和产物的浓度不随时间发生变化。同位素瞬变同位素瞬变在反应稳态条件下进行反应物在反应稳态条件下进行反应物A和其同位素和其同位素A*的理的理想切换或脉冲，想切换或脉冲， 但仍然保持体系的稳定。但仍然保持体系的稳定。瞬变响应信息瞬变响应信息反应物在催化剂表面的吸附和反应导致了同位素反应物在催化剂表面的吸附和反应导致了同位素A*的瞬变响应和惰性失踪剂的瞬变响应的差别。的瞬变响应和惰性失踪剂的瞬变响应的差别。表面中间物种的量和寿命A*A P*P瞬变响应曲线的积分求瞬变响应曲线的积分求得表面物种的停留时间得表面物种的停留时间Typical normalized step-input transient responses from A to *A/He反应处于稳定状态时， 产物P的生成速率可以根据流量和含量直接获得， 除以停留时间即得到中间物种的表面浓度。化学吸附法确定的表面暴露的原子总数表面