In-situ spectroscopy and catalysis

12-P-05 - Study of relationship between mordenite acidity and structure with calcination temperature 

Shanghai Research Institute of Petrochemical Technology, China, zhuzhirong yahoo.com 

12-P-06 - Infrared observation of the stable carbenium ions formed by adsorption of olefins on zeolite Y at low temperatures 

Chemical Resources Laboratory, TITech, Yokohama, Japan. E-mail kdomen res. titech. ac.jp. 

The formation of alkenyl carbenium ions, characterized by an IR band at ca. 1510 cm , was successfully observed by adsorption of 1-methylcyclopentene, methylenecyclopentane and 1-methylcyclopentanol on zeolite Y. At temperatures as low as 150 K, the carbenium ions were formed soon after introducing the olefins. The characteristic band at ca. 1510 cm increases in intensity with the elevation of temperature and is stable up to 373 K. For MCPOH, the characteristic band appears at temperatures above 245 K after its dehydration. The formed species were assigned to be dimerized alkenyl carbenium ions by calibrating the acid sites of HY using 1-butene at 235 K. UV-vis spectroscopic studies confirm the formation of momoenylic and dienylic carbenium ions, with bands at 323 and 400 nm, respectively. 

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SUMMARIES of ORAL PRESENTATIONS 12 - In-Situ Spectroscopy and Catalysis (Monday am)... 

This paper reviews our recent work dealing with designed active structures at oxide surfaces and their spectroscopic characterizations in an atomic or molecular scale. The paper also provides the information on the key issues in catalytic research such as behavior of adsorbed active species during catalysis which are well characterized by recent in-situ spectroscopy and also by traditional spectroscopy. The paper also presents a concept of surface design relevant to supported oxide catalysis, which world allow us to move toward the ulitmate goals of more rational catalyst design. 

Chen, P. and Somorjai, G.A (2002) In situ catalysis and surface science methods, In-Situ Spectroscopy in Heterogeneous Catalysis (ed. J.F. Haw), Wiley-VCH Verlag, Weinheim, pp. 15-52. 

Phosphites have been used as ligands in Rh-catalyzed hydroformylation from the early days since their introduction in 1969.205 206 Identification of complexes occurred more recently. Ziolkowski and Trzeciak have studied extensively the use of phosphite ligands in the Rh-catalyzed hydroformylation of alkenes.207-210 The ligand tris(2-/er/-butyl-4-methylphenyl) phosphite (65) leads to extremely fast catalysis and in situ spectroscopy showed that under the reaction conditions only a mono-ligated complex [Rh(H)(CO)3(65)], (66), is formed due the bulkiness of the ligand.211-213... 

The growing interest in physical characterization of solid catalysts as they function has stimulated a new series of congresses, the first held in Lunteren (The Netherlands) in 2003 and the second in Toledo in 2006. The subject has been documented in recent books (B. M. Weckhuysen, Ed., In situ Spectroscopy of Catalysts, American Scientific Publishers, 2004, and J. F. Haw, Ed., In situ Spectroscopy in Heterogeneous Catalysis, Wiley-VCH, 2002) and in topical issues of journals Top. Catal. 15 (2001) Phys. Chem. Chem. Phys. 5, issue 20 (2003) and Catal. Today 113 (2006). It is our intention that our set of volumes be more nearly comprehensive than these publications, as well as providing many newer results. 

Elsevier, C.J. (1994) NMR at elevated gas pressures and its application to homogeneous catalysis./. Mol. Catal., 92, 285. Weckhuysen, B.M. (2002) Snapshots of a working catalyst possibilities and limitations of in situ spectroscopy in the field of heterogeneous catalysis. Chem. Commun., 97. 

XAS, and particularly its application to catalysis, has been the subject of several previous reviews and books. In 1988, Koningsberger and Prins published the book "X-ray absorption principles, applications, techniques of EXAFS, SEXAFS and XANES" (Koningsberger and Prins, 1988). In this monograph there is a thorough description of the technique together with a chapter on its application to catalysis. Iwasawa in 1996 published "XAFS for catalysts and surfaces" (Iwasawa, 1996), which focused solely on XAFS spectroscopy as applied to catalyst characterization. This volume includes a chapter by Bazin, Dexpert, and Lynch about measurements of catalysts in reactive atmospheres, and several other chapters allude to examples of such characterization. Recently a book entitled In situ Spectroscopy of Catalysts" (Weckhuysen, 2004) was published that contains three chapters focused on XAFS of catalysts in reactive atmospheres one on XANES, one on EXAFS, and one on time-resolved XAFS. 

With respect to in situ spectroscopy, there is no attempt here to give a detailed overview of the ongoing activities in this field. The interested reader is directed to excellent articles describing applications of MR spectroscopy in catalysis that have been published elsewhere (Baba and Ono, 1999 Dybowski et al., 1991 Fraissard, 1999 Haw, 1999 Hunger and Weitkamp, 2001 Packer, 1996 Parker 2000 Roe et al., 1998 van der Klink, 2000). Instead, we focus on the nature of... 

Figure 10 Typical ultrahigh vacuum system used for surface science studies of catalytic reactions on model systems. The combined development of new preparation methods for realistic catalytic samples and in situ spectroscopies for the molecular level characterization of surface species during catalysis promises to advance the basic understanding of catalytic processes...

Various forms of spectroscopy have been applied to in situ studies of catalysis, and it is appropriate to cite a few examples. FT-IR is frequently employed for in situ investigations. The experimental configurations used can be either transmission studies of free-standing catalyst wafers [2] or diffuse reflectance measurements on samples in catalytic reaction chambers 13]. In situ Raman spectroscopy has also been applied [4]. X-rays have been used to study catalysts in situ, either by powder diffraction methods [5,6] or XAFS [7]. In situ imaging techniques are beginning to be applied to the measurement of spatial distributions and residence times in catalytic reactors. A recent example of this method employed positron-emission tomography [8]. 

The advantages of the radiolysis/EPR method for studying mechanisms of zeolite catalysis are due to the sensitivity and structural specificity of EPR, surpassing that of other in situ spectroscopies, such as FTIR and NMR, and the ability to identify products at low temperature. It is often the case that at high temperatures needed to evolve products from the zeolite for ex situ analysis, a... 

Since the subjects of two of the subsequent sections, viz. catalysis on and diffusion in zeolites will be extensively treated in later volumes of the present series Molecular Sieves - Science and Technology , including the application of spectroscopic techniques in these fields, the reviews under Sects. 5.6.3 and 5.6.4 may be rather brief. They will just provide a few examples, where in-situ IR and Raman spectroscopy were employed with respect to problems of catalysis and diffusion. 

In the field of catalysis, it is essential to achieve a better understanding of the physical and chemical properties of various well-defined crystalline orientations of catalyst particles over a wide range of temperature and pressure. Such insights permit us to interpret the catalytic behavior of small particles at the atomic and molecular level. Surprisingly, SERS is also a suitable in-situ spectroscopy for well-defined surfaces. This was recently demonstrated for oxygen on faceted Ag surfaces, which are not smooth but locally well ordered along the facets (over 10-1000 nm) [44]. 

In situ spectroscopy is the only approach to obtain reliable information on mechanisms and the role of intermediates in chemical reactions as well as on structure-reactivity relationships in catalysis [1-5]. Especially, in heterogeneous catalysis, the application of a variety of in situ methods has gained a lively development during the recent two decades. But also in homogeneous catalysis, as well as in catalytic multiphase systems, in situ characterization methods are increasingly applied. A survey of techniques, which are most commonly applied in gas/soUd and multiphase systems and the method-specific information, is presented in Table 3.1. 

The fundamental studies of the catalytic reactions mechanisms that occur near the three-phase boundary in the anode of a solid oxide fuel cell still deserving attention and investigation. Many in situ sp>ectroscopies such as Raman and infrared spectroscopy are routinely used in catalysis research to characterize surface intermediates and reaction mechanisms. It is very difficult to apply in situ spectroscopy techniques to an operating SOFC anode (Atkinson et al., 2004). Recently research groups (Liu et al., 2002 Guo et al., 2010) presented their methodologies on the possible ways to apply the infrared emission spectroscopy to characterize working SOFC anodes. 

Weckhuysen, B.M. Snapshots of a working catalyst PossihUities and limitations of in situ spectroscopy in the field of heterogeneous catalysis. Chem. Commun. 2002,97-110. 

Mossbauer spectroscopy is a specialist characterization tool in catalysis. Nevertheless, it has yielded essential information on a number of important catalysts, such as the iron catalyst for ammonia and Fischer-Tropsch synthesis, as well as the CoMoS hydrotreating catalyst. Mossbauer spectroscopy provides the oxidation state, the internal magnetic field, and the lattice symmetry of a limited number of elements such as iron, cobalt, tin, iridium, ruthenium, antimony, platinum and gold, and can be applied in situ. 

Meunier, F. and Daturi, M. (2006) Recent developments in in situ and operando spectroscopy for catalysis - Preface, Catal. Today, 113, 1. 

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