1、2003. 1. 14,申 文 杰,催 化 反 应 化 学 课 题 组,Catalytic Reaction Chemistry Group,固体催化剂的研究方法 催化反应的动态监测技术,多相催化研究方法,实际催化剂,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 Gap,Materials Gap,发展高效催化剂,催化反应动力学,稳态动力学技术,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-SSITKA,一
2、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-程序升温技术,同位素示踪,产物瞬时分析技术（TPA）,瞬变应答技术（Transient Response),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 I
3、nfrared Spectroscopy,One problem with NIR 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 spectroscopy,Raman spectroscopy,Raman spectroscopy probes have become fashionable. This technique is an alte
4、rnative to MIR, but the relative intensities 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 techniques,The following data analytical techniques are most common for the analysis of on-line spectroscopic data
5、from reactions using different spectroscopies. MIR and Raman. Generally conventional kinetic curve fitting of peak areas, but some deconvolution necessary if overlapping peaks. NIR. Usually multivariate calibration such as PLS and a number of related classical chemometrics methods. EAS. Deconvolutio
6、n using MLR (multiple linear regression) 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
7、be discussed in the next article.,It 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 alternatively Cu promotes the syn
8、thesis of methanol over zirconia. Which 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 o
9、f Cu/SiO2 to 0.16 MPa CO2 and 0.49 MPa 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 Species Transient spectra were obtained after switching the feed fromH2 to 3/1H2/CO2 at a total pre
10、ssure of 0.65MPa while maintaining the temperature of the Cu/SiO2 catalyst at 523 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
11、 species remain relatively constant during 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 remainder of the transient. This feature is ascribable to CH3OSi and the companion peak at 2856 cm1 is evidenced by the asymmetry
12、 of the peak at 2849 cm1 (shoulder on the left). 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
13、 0.16 MPa CO2 and 0.49 MPa H2,The principal features 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 temperature is increased, the concentrations of b-HCO3Zr and i-CO3Zr decrease and bands appear t
14、hat are characteristic of b-HCOOZr (2974, 2892, 1565, 1386, 1369 cm1). At 523 K bands appear at 2942, 2842, and 1463 cm1 which are attributable 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 cm1 is gone a
15、t 373 K, while those at 2077 and 2094 cm1 are present at all temperatures, but decrease in intensity with temperature.,Infrared spectra taken during exposure of Cu/ZrO2/SiO2 to 0.16 MPa CO2 and 0.49 MPa H2,At 323 K the spectrum is comprised of features attributable to b-HCO3Zr (1606, 1465 cm1), m-CO
16、3Zr (1490, 1383 cm1), b-CO3Zr (1576 cm1), and weak features 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 spe
17、cies pass through a maximum at 423 K. At 373 K new features 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
18、readily apparent.,It is evident that the formation of b-HCOOZr and CH3OZr are significantly faster in the presence of Cu.,Intensities of b-HCOOZr and CH3OZr features,formate and methoxide decay occurs much more readily on the copper containing catalyst and that methoxide decays only extremely slowly
19、 on ZrO2/SiO2.,Proposed mechanism.,CO2 is adsorbed on ZrO2 and 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 reac
20、tion with water produced as a co-product of methanol synthesis 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,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
21、同位素,13C， 18O，15N， D,14C， 35S 等等,稳定性同位素标记物的分析,原子质量数的差异,伸缩振动频率的红移,核自旋量子数不为零,MS,IR,NMR,标记同位素方法研究反应机理,丙烯歧化反应,2C=C*-C C-C*-C-C-C*-C C=C* +C-C=C*-C,CH2=14CH-CH3,2C=C*-C,C-C*-C,C-C*-C,C=C +C-C*=C*-C,Re2O7/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/TiO2,CO离解的反应机理,CO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,Rh/TiO2,3
22、2,34,Mass number,33,Mole fraction / %,13CH316OH,Products,50%13CO+50% 14CO as C18O source,CO非离解的反应机理,12CH316OH,13CH318OH,12CH318OH,35,1,54,44,2,CO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,丙烯氧化的反应机理,CH3-CH=CH2 + O2 CH2=CH-CHO,H,RDS,H,14CH3-CH=CH2,14CH2 = CH - CH3,50%,CH2 = 14CH - CH3,0%,H & D kinetic effect,Car
23、bon Isotopic Tracer,18,CH2=CH-CH16O,CH2=CH-CH18O,Convincing evident for the involving of Lattice Oxygen,Selective Oxidation of propylene to Acrolein,Oxygen activation,TOS,Steady-State Isotopic-Transient Kinetic Analysis-SSITKA,S.L.Shannon et al., Chem, Rev., 95(1995)677-695,- 稳态同位素瞬变动力学,同位素示踪技术,瞬变动力
24、学技术,IR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 Experimental,Gas Feed System,Reaction System,Product Analysis,IR cell,稳态同位素瞬变技术动力学参数的测定,反应稳态,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。,同位素瞬变,在反应稳态条件下进行反应物A和其同位素A*的理想切换或脉冲， 但仍然保持体系的稳定。,瞬变响应信息,反
25、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。,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,表面中间物种的覆盖度,推测催化剂表面反应机理,Product responses of *CO pulse into a CO gas flow durin
26、g C2H4 hydroformylation,对生成产物P的中间产物停留时间较长的反应也可以用脉冲的方法确定,C2H4+H2+CO C2H5CHO,10ml 98%*CO/2%Ar,Mn-Rh/SiO2,非稳态同位素瞬变技术,La2O3 -Ni/Al2O3 催化剂性能的影响,La2O3 通过电子相互作用使镍金属中心稍带正电荷， 适当降低了镍金属中心的反应活性， 提高了Ni/Al2O3 催化剂抗积炭性能。,CH4 C + 2H2,2CO C + CO2,La2O3 -Ni/Al2O3抑制了：,Response of switch Ar CH4/*CO Ar at 600 ,非稳态同位素瞬变技术
27、,Rh/SiO2催化剂上CO加氢反应机理,2040 cm-1 1993 cm-1,1767 cm-1 1737 cm-1,CO *CO,线式吸附,桥式吸附,通过对反应温度压力的考察确定生成CH4， C2等产物的机理。,产物瞬时分析技术（Temporal Analysis of Products, TAP）,基元反应的顺序和动力学常数,一个很窄的反应气脉冲射入催化剂床层的入口，在出口处检测脉冲的峰形， 由此观察反应的结果和多峰形的数学模拟取得反应常数。,时间宽度200-600 微秒 脉冲量 1016个分子（通常为2x1018分子）,时间分辨图像,Mo/ZSM-5甲烷无氧芳构化,诱导期的变化主要是氧化钼被还原为碳化钼,乙烯很可能是芳构化的中间体,多脉冲实验(Pump-Probe),CH4部分氧化反应机理,先射入某一种被探讨的气体分子，在设定时间后射入第二种分子的脉冲。,氧的浓度是影响催化剂选择性的主要因素。,随着间隔时间的增加，H2和CO的量逐渐增加。,(1) O2 injection,(2) CH4 injection,
