Infrared spectroscopy monoxide

Whereas ATR spectroscopy is most commonly applied in obtaining infrared absorption spectra of opaque materials, reflection-absorption infrared spectroscopy (RAIRS) is usually used to obtain the absorption spectrum of a thin layer of material adsorbed on an opaque metal surface. An example would be carbon monoxide adsorbed on copper. The metal surface may be either in the form of a film or, of greaf imporfance in fhe sfudy of cafalysfs, one of fhe parficular crysfal faces of fhe mefal. 

The first anhydride plant in actual operation using methyl acetate carbonylation was at Kingsport, Tennessee (41). A general description has been given (42) indicating that about 900 tons of coal are processed daily in Texaco gasifiers. Carbon monoxide is used to make 227,000 t/yr of anhydride from 177,000 t/yr of methyl acetate 166,000 t/yr of methanol is generated. Infrared spectroscopy has been used to foUow the apparent reaction mechanism (43). 

Chang SC, Hamelin A, Weaver MJ. 1991. Dependence of the electrooxidation rates of carbon monoxide at gold on the surface crystallographic orientation A combined kinetic-surface infrared spectroscopy study. J Phys Chem 95 5560-5567. 

Corrigan DS, Weaver MJ. 1988. Mechanisms of formic acid, methanol, and carbon monoxide electrooxidation at platinum as examined by single potential alteration infrared spectroscopy. J Electroanal Chem 241 143-162. 

Kizhakevariam N, Weaver MJ. 1994. Structure and reactivity of bimetaUic electrochemical interfaces Infrared spectroscopy studies of carbon monoxide adsorption and formic acid electrooxidation on antimony-modified Pt(lOO) and Pt(lll). Surf Sci 310 183-197. 

Leung L-WH, Wieckowski A, Weaver MJ. 1988. In situ infrared spectroscopy of well-defined single-crystal electrodes Adsorption and electrooxidation of carbon monoxide on plati-nuk(lll). J Phys Chem 92 6985-6990. 

Villegas I, Weaver MJ. 1994. Carbon monoxide adlyaer structures on platinum (111) electrodes A synergy between in-situ scanning tunneling microscoy and infrared spectroscopy. J Chem Phys 101 1648-1660. 

Chang SC, Roth JD, Ho YH, Weaver MJ. 1990. New developments in electrochemical infrared-spectroscopy— Adlayer structures of carbon-monoxide on monocrystalline metal-electrodes. J Electron Spectrosc Relat Phenom 54 1185-1203. 

Zhu YM, Uchida H, Watanabe M. 1999. Oxidation of carbon monoxide at a platinum him electrode studied by Fourier transform infrared spectroscopy with attenuated total rehection technique. Langmuir 15 8757-8764. 

Zou S, Gomes R, Weaver MJ. 1999. Infrared spectroscopy of carbon monoxide and nitric oxide on palladium(lll) in aqueous solution unexpected adlayer structural differences between electrochemical and ultrahigh-vacuum interfaces. J Electroanal Chem 474 155-166. 

Chang SC, Hamelin A, Weaver MJ. 1990. Reactive and inhibiting adsorbates for the catal34ic electrooxidation of carbon-monoxide on gold (210) as characterized by surface infrared-spectroscopy. Surf Sci 239 L543-L547. 

Tethwisch, D.G. and Dumesic, J.A. (1986) Effect of metal-oxygen bond strength on properties of oxides. 1. Infrared spectroscopy of adsorbed carbon monoxide and carbon dioxide, Langmuir, 2, 73. 

Carbon monoxide on metals forms the best-studied adsorption system in vibrational spectroscopy. The strong dipole associated with the C-O bond makes this molecule a particularly easy one to study. Moreover, the C-0 stretch frequency is very informative about the direct environment of the molecule. The metal-carbon bond, however, falling at frequencies between 300 and 500 cm1, is more difficult to measure with infrared spectroscopy. First, its detection requires special optical parts made of Csl, but even with suitable equipment the peak may be invisible because of absorption by the catalyst support. In reflection experiments on single crystal surfaces the metal-carbon peak is difficult to obtain because of the low sensitivity of RAIRS at low frequencies [12,13], EELS, on the other hand, has no difficulty in detecting the metal-carbon bond, as we shall see later on. 

The structure of supported rhodium catalysts has been the subject of intensive research during the last decade. Rhodium is the component of the automotive exhaust catalyst (the three-way catalyst) responsible for the reduction of NO by CO [1], In addition, it exhibits a number of fundamentally interesting phenomena, such as strong metal-support interaction after high temperature treatment in hydrogen [21, and particle disintegration under carbon monoxide [3]. In this section we illustrate how techniques such as XPS, STMS, EXAFS, TEM and infrared spectroscopy have led to a fairly detailed understanding of supported rhodium catalysts. 

Infrared spectroscopy can be used to obtain a great deal of information about zeolitic materials. As mentioned earlier, analysis of the resulting absorbance bands can be used to get information about the structure of the zeolite and other functional groups present due to the synthesis and subsequent treatments. In addition, infrared spectroscopy can be combined with adsorption of weak acid and base probe molecules to obtain information about the acidity and basicity of the material. Other probe molecules such as carbon monoxide and nitric oxide can be used to get information about the oxidation state, dispersion and location of metals on metal-loaded zeolites. 

R. Ryberg, Carbon-Monoxide Adsorbed on Cu(100) Studied by Infrared-Spectroscopy, Surf. Sci. 114 (1982), 627 641. 

Infrared Spectroscopy. Infrared (1R) spectroscopy is also used for understanding the structure of the bimetallic nanoparticles. Carbon monoxide can be adsorbed on the surface of metals, and the 1R spectra of the adsorbed CO depend on the kind of metal. These properties are used for analyzing the surface structure of metal nanoparticles. The inverted core/shell structure, constructed by sacrificial hydrogen reduction, was probed by this technique (44). 

Direct reaction of iron pentacarbonyl with trimethylsilyl isocyanide ( C=N—SiMe3) at 65°-75° yields an air-sensitive substitution product Me3Si—N=C Fe(CO)4 in 93% yield, with elimination of carbon monoxide (152). It was shown by infrared spectroscopy (38) that complex formation lowers the N=C bond order for Me3Si—N=C , whereas it raises the N=C bond order for Me3C—N=C , presumably as a result of interaction between dv orbitals of silicon with the metal d orbitals. 

Infrared Spectroscopy. The spectrum of the solid C showed only weak and unresolved hydroxyl bands (Figure 5). The introduction of CO under an equilibrium pressure of 50 torr did not modify the i>oh bands. After evacuation of the carbon monoxide at room temperature, the IR spectrum showed two bands at 2135 and 2110 cm-1 caused by strongly chemisorbed... 

Hitherto, in the form of reflection-absorption infrared spectroscopy (RAIRS), the infrared method had been capable of detecting single monolayers only in the exceptionally favorable (strong absorption) cases of carboxylate ions [Francis and Ellison (14)] or carbon monoxide [Chesters, Pritchard, and Sims (15)] adsorbed on flat metal surfaces. The new challenge from VEELS provided the motivation for a search for improvements in RAIRS sensitivity, and this was very successfully achieved by M. A. Chesters and his colleagues through the introduction of Fourier-transform-based interferometric infrared spectroscopy (16). 

A major objective of the work employing infrared spectroscopy is the identification of the species involved in the reactions that gold is adept at catalysing ((selective) oxidation of carbon monoxide, water-gas shift, etc.),... 

I. Mirsojew, S. Ernst, J. Weitkamp, and H. Knozinger, Characterization of acid properties of [Al] - and [Ga] - HZSM - 5 zeolites by low temperature Fourier transform infrared spectroscopy of adsorbed carbon monoxide, Catal. Lett. 24, 235-248 (1994). 

Equilibration with carbon monoxide at room temperature and low pressure (a few torr ) yielded the rhodium(I)-dicarbonyl compound (13) in addition to the Rh(I)(C0) paramagnetic complexe (11). The structure of this complex was elucidated by ESCA and UV measurements (13) which showed that the trivalent rhodium was indeed reduced to the monovalent state and by infrared spectroscopy which provided evidence for a gem dicarbonyl (14). Use of 1 1 C0 ... 

Because of our previous success In applying Fourier-transform infrared spectroscopy to the study of the rhodium carbonyl clusters under high pressures of carbon monoxide and hydrogen 2. A, we have applied the same technique and equipment in this work. 3. The temperature has been kept In all these experiments below 200° with maximum pressures of 832.0 atm to maximize the trend towards fragmentation of clusters. The absence of bases, e.g., salts or amines, in the systems under evaluation in this work was desirable to eliminate the ambiguity that would result from the enhancement of the fragmentation of clusters by carbon monoxide In a basic medium. . ... 

---