Catalyst elemental analysis

Samples for catalyst elemental analysis were prepared as follows After taken from the continuous stirred tank (CST), they were let settle down overnight. 

Catalyst Elemental Analysis [Found(Calc)] Atomic Absorption Anchoring... 

Composition. The results of elemental analyses are almost always included among the specifications for a commercial catalyst. Depending on the accuracy desired and whether or not the catalyst can be rendered soluble without great difficulty, elemental analysis may be performed by x-ray methods, by one of the procedures based on atomic absorption, or by traditional wet-chemical methods. Erequentiy it is important to determine and report trace element components that may have an effect on catalyst performance. 

The mesoporous character of MCM-41 overcomes the size limitations imposed by the use of zeolites and it is possible to prepare the complex by refluxing the chiral ligand in the presence of Mn +-exchanged Al-MCM-41 [34-36]. However, this method only gives 10% of Mn in the form of the complex, as shown by elemental analysis, and good results are only possible due to the very low catalytic activity of the uncomplexed Mn sites. The immobihzed catalyst was used in the epoxidation of (Z)-stilbene with iodosylbenzene and this led to a mixture of cis (meso) and trans (chiral) epoxides. Enantioselectivity in the trans epoxides was up to 70%, which is close to the value obtained in solution (78% ee). However, this value was much lower when (E)-stilbene was used (25% ee). As occurred with other immobilized catalysts, reuse of the catalyst led to a significant loss in activity and, to a greater extent, in enantioselectivity. 

TEM observation and elemental analysis of the catalysts were performed by means of a transmission electron microscope (JEOL, JEM-201 OF) with energy dispersion spectrometer (EDS). The surface property of catalysts was analyzed by an X-ray photoelectron spectrometer (JEOL, JPS-90SX) using an A1 Ka radiation (1486.6 eV, 120 W). Carbon Is peak at binding energy of 284.6 eV due to adventitious carbon was used as an internal reference. Temperature programmed oxidation (TPO) with 5 vol.% 02/He was also performed on the catalyst after reaction, and the consumption of O2 was detected by thermal conductivity detector. The temperature was ramped at 10 K min to 1273 K. 

The TEM images of 12 wt.% Co/MgO calcined at 873 K (Catalyst I) before and after reduction are shown in Fig. 1 (a) and (b), respectively. Although Co metal phase was detected in reduced Co/MgO by X-ray diffraction measurements (XRD) [7, 8], no Co metal particle was observed on both catalysts. EDS elemental analysis showed that primary particles contain both Mg and Co elements, whose concentrations were about the same as loaded amounts. Figure 2 shows TEM image of 12 wt.% Co/MgO calcined at 1173 K (Catalyst II). 

The TEM images of deposits observed on Catalyst I used for the steam reforming of naphthalene are shown in Fig. 5. Two types of deposits were observed and they were proved to be composed of mainly carbon by EDS elemental analysis. One of them is film-like deposit over catalysts as shown in Fig. 5(a). This type of coke seems to consist of a polymer of C H, radicals. The other is pyrolytic carbon, which gives image of graphite-like layer as shown in Fig. 5(b). Pyrolytic carbon seems to be produced in dehydrogenation of naphthalene. TPO profile is shown in Fig. 6. The peaks around 600 K and 1000 K are attributable to the oxidation of film-like carbon and pyrolytic carbon, respectively [11-13]. These results coincide with TEM observations. 

The bidentate ligands were prepared by the Schiff-base condensation of two equivalents of the desired 2,6-dialkyl substituted anilines with acenaphthenequinone as in the scheme 1, The pre-catalysts, formed by addition of the ligand to (DME)NiBr2 are isolated and purified. The products were characterized by h, C NMR, GPC, DSC and Elemental Analysis. 

In this chapter we have limited ourselves to the most common techniques in catalyst characterization. Of course, there are several other methods available, such as nuclear magnetic resonance (NMR), which is very useful in the study of zeolites, electron spin resonance (ESR) and Raman spectroscopy, which may be of interest for certain oxide catalysts. Also, all of the more generic tools from analytical chemistry, such as elemental analysis, UV-vis spectroscopy, atomic absorption, calorimetry, thermogravimetry, etc. are often used on a routine basis. 

The compounds benzonitrile, p-methylbenzonitrile, /)-methoxybenzonitrile, p-trifluoromethyl-benzonitrile, /)-methoxycarbonylbenzonitrile, and triethoxysilane are commercial products and are degassed and stored under argon before use. Trimethylsilane was prepared according to a literature report [38]. The nitrile (9.8 mmol) and the hydrosilane (49 mmol) are added to the rhodium catalyst (0.1 mmol) contained in a Carius tube. When using trimethylsilane, the operation is performed at —20°C. The tube is closed and the mixture stirred at 100 °C for 15h. The liquid is separated by filtration and the excess of hydrosilane removed under vacuum to leave the N, Wdisilylamine derivative. If necessary, a bulb to bulb distillation is performed to obtain a completely colorless liquid. The yields obtained in the different runs are reported in Table 6. The product have been characterized by elemental analysis, NMR spectroscopy, and GC-MS analysis. 

Applications Over the last 20 years, ICP-AES has become a widely used elemental analysis tool in many laboratories, which is also used to identify/quantify emulsifiers, contaminants, catalyst residues and other inorganic additives. Although ICP-AES is an accepted method for elemental analysis of lubricating oils (ASTM D 4951), often, unreliable results with errors of up to 20% were observed. It was found that viscosity modifier (VM) polymers interfere with aerosol formation, a critical step in the ICP analysis, thus affecting the sample delivery to the plasma torch [193]. Modifications... 

Applications X-ray fluorescence is widely used for direct examination of polymeric materials (analysis of additives, catalyst residues, etc.) from research to recycling, through production and quality control, to troubleshooting. Many problems meet the concentration range in which conventional XRF is strong, namely from ppm upwards. Table 8.42 is merely indicative of the presence of certain additive classes corresponding to elemental analysis element combinations are obviously more specific for a given additive. It should be considered that some 60 atomic elements may be found in polymeric formulations. The XRF technique does not provide any structural information about the analytes detected the technique also has limited utility when... 

Thus the results from elution chromatography, extraction with acid and base and elemental analysis show that as the catalyst concentration used increases, the heteroatom content of the resultant oil decreases. 

Electrolysis of a solution of the catalyst at — 1.4 V to — 1.5 V vs. SCE in the absence of C02, giving le /Re atom, gave the sparingly soluble green dimer (as characterised by UV-visible, [R, nmr and elemental analysis on the isolated material) in agreement with the work of Lehn and colleagues (Hawecker, 1983) and showing that the first reduction is coupled to the formation of the dimer if chloride loss is allowed to occur. If the cyclic voltammetric scan was reversed when the potential reached —1.5 V, at a... 

Chemical composition was determined by elemental analysis, by means of a Varian Liberty 200 ICP spectrometer. X-ray powder diffraction (XRD) patterns were collected on a Philips PW 1820 powder diffractometer, using the Ni-filtered C Ka radiation (A, = 1.5406 A). BET surface area and pore size distribution were determined from N2 adsorption isotherms at 77 K (Thermofinnigan Sorptomatic 1990 apparatus, sample out gassing at 573 K for 24 h). Surface acidity was analysed by microcalorimetry at 353 K, using NH3 as probe molecule. Calorimetric runs were performed in a Tian-Calvet heat flow calorimeter (Setaram). Main physico-chemical properties and the total acidity of the catalysts are reported in Table 1. 

Table 1. Elemental analysis and textural properties of the MCM-22 catalysts.

Lupton et al. [69] studied delayed PL and EL of another ladder polyphenylene, PhLPPP (44). A pronounced phosphorescence at ca. 600 nm was observed at room temperature. Elemental analysis revealed the presence of 80ppm of Pd (that is one Pd atom per 1700 polymer units), as an unintentional impurity originating from the polymerization catalyst,... 

---