UV Raman spectroscopy

An interesting and powerful new development in Raman spectroscopy of catalysts is the use of a UV laser to excite the sample. This has two major advantages. First, the scattering cross section, which varies with the fourth power of the frequency, is substantially increased. Second, the Raman peaks shift out of the visible region of the spectrum where fluorescence occurs. The reader is referred to Li and Stair for applications of UV Raman spectroscopy on catalysts [40]. 

Li, et al. (2003), Phase Transformation in the Surface Region of Zirconia and Doped Zirconia Detected by UV Raman Spectroscopy , Phys. Chem. Chem. Phys., 5, 5326-5332. 

The investigation of liquids, gases, or solids in reactive atmospheres requires the use of vials or cells that have to be transparent to the radiation. Glass or quartz is suitable for the construction of cells, making Raman spectroscopy very versatile with respect to the media and conditions that can be used, particularly in comparison to IR spectroscopy. FT Raman spectroscopy uses IR radiation and shares the limitations inherent to IR radiation. UV-Raman spectroscopy uses UV radiation and shares the limitations inherent to UV radiation. 

Source Trout, C.C. and Kubicki, J.D., UV Raman spectroscopy and ab initio calculations of carboxylic acids-Al solutions, Abstr. Pap. Am. Chem., 224 012-Geoc,... 

The Application of UV Raman Spectroscopy for the Characterization of Catalysts and Catalytic Reactions... 

Similar tests of the fiuidized-bed method have been successful with a variety of molecular adsorbates and catalysts (other zeolites, supported oxides, naphthalene, pyridine, methanol, alkanes, alkenes, acetonitrile, ammonia, etc.) (25). We believe that this fiuidized-bed method is a major step forward for measurements of working catalysts with UV Raman spectroscopy. It should also be a useful method for measurements of catalytic kinetics by reducing heat and mass transfer effects that arise when catalysts are used in the form of pellets. In the limit of low conversions... 

These results motivated an exploration of the interaction of Fe/MFI with molecular oxygen with UV Raman spectroscopy (51). The results and interpretation of this investigation are summarized below and in Table II. 

The formation of peroxide and superoxide in Fe/MFI, prepared by sublimation of FeCla into H-MFI, was observed by UV Raman spectroscopy (52). Peroxide produced a distinct peak at 730cm and the presence of superoxide was identified by a complex band in the region of 1050-1160cm The position and intensity of these bands and their behavior as a function of temperature and O2 pressure depend on the catalyst pretreatment. Three types of pretreatment after FeCl3 sublimation but prior to placing the catalyst into the fluidized-bed cell can... 

The formation of hydrocarbons from methanol catalyzed by zeolite H-MFI has been investigated extensively 60,61). As with many hydrocarbon conversions, the catalytic activity of the methanol-to-hydrocarbons reaction decreases over time as a result of the buildup of high-molecular-weight carbonaceous deposits (coke). UV Raman spectroscopy was employed to characterize the accumulation and chemical nature of deposited hydrocarbons as a function of time and reaction temperature with both methanol and dimethyl ether as reactants and with zeolite MFI of various Si/Al atomic ratios as catalysts the first account of this work reported results for a zeolite MFI with low acid content (Si/Al = 90) (62). Both polyolefin and a cyclopentadienyl species were observed as intermediates during the formation of polyaromatic retained hydrocarbons. These observations strongly confirm the mechanism of coke formation proposed by Schulz and Wei (63) involving aromatic formation via a five-membered ring... 

Ogura A, Yamasaki K, Kosemura D, Tanaka S, Chiba 1, Shimidzu R (2006) UV-Raman spectroscopy system for local and global strain measurements in Si. Jpn J Appl Phys 45 3007... 

UV Raman Spectroscopy of Nanoscale Ferroelectric Thin Films and Superlattices 589... 

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