FTIR-TPD

For the generation of the FTIR-TPD profiles (A vs. T), the decrease in the intensity (absorbance) of one of the selected bands was monitored, during heating at a constant rate [97]... 

The FTIR-TPD profiles (A vs. T) for the desorption of benzene, toluene, and ethylbenzene from high-silica H-ZSM-5 is reported in Figure 4.40 [97], These results were fitted with the complementary error function, that is,... 

In FTIR-TPD, we are not reporting the desorption rates, dN/dt, as is customary in TPD practice, we are reporting A, which is proportional to N, the amount adsorbed. In this sense, it is evident that [97]... 

The CO-TPD technique together with DFT calculations were previously successfully used to characterize monovalent copper positions in Cu-ZSM-5 and Cu-Na-FER catalysts[4, 5]. Recently it was observed that the CO molecule can also form adsorption complexes, where the CO molecule is bonded between two extra-framework cations [6]. It is likely that the formation of similar species between the Cu+ and K+ ions can also occur. The presence of adsorption complexes on such heterogeneous dual cation site was evidenced by the FTIR experiments [7]. The formation of CO complexes on dual cation sites was not considered in our previous TPD models where three types of Cu+ sites were taken into account. 

Alkaline earth oxides (AEO = MgO, CaO, and SrO) doped with 5 mol% Nd203 have been synthesised either by evaporation of nitrate solutions and decomposition, or by sol-gel method. The samples have been characterised by chemical analysis, specific surface area measurement, XRD, CO2-TPD, and FTIR spectroscopy. Their catalytic properties in propane oxidative dehydrogenation have been studied. According to detailed XRD analyses, solid solution formation took place, leading to structural defects which were agglomerated or dispersed, their relative amounts depending on the preparation procedure and on the alkaline-earth ion size match with Nd3+. Relationships between catalyst synthesis conditions, lattice defects, basicity of the solids and catalytic performance are discussed. 

The chemical composition of the samples was determined using an inductively Coupled plasma atomic emission spectrometer (ICP-AES) JY 38 from Jobin Yvon. Specific surface area values were determined by BET method using a Micromeritics Instrument Corp. FlowSorb 2300. The basicity of the materials was studied by temperature programmed desorption (TPD) of C02 used as a probe molecule. The equipment was described in a previous work [7]. FTIR spectra of pellets pressed at 2.5xl08 Pa were recorded with a Vector 22 spectrometer from Brucker. The samples were diluted with KBr (lOOmg KBr - 1.5mg of the sample). 

Both preparation procedures (Ev and SG) aimed at fine distribution of the elements and at obtaining solid solutions. However, the sol-gel methods are known to be particularly powerful to achieve molecular scale dispersion in mixed oxides. The studied samples are shown in Table 1. Taking into account the fact that SrO was easily carbonated, that the surface of SrNd-Ev was covered by carbonate and SrNd-SG was partly composed of bulk carbonate (as it was shown by CO2 TPD, FTIR, and XRD), SrC03 was used instead of SrO. 

Cr-ZSM-5 catalysts prepared by solid-state reaction from different chromium precursors (acetate, chloride, nitrate, sulphate and ammonium dichromate) were studied in the selective ammoxidation of ethylene to acetonitrile. Cr-ZSM-5 catalysts were characterized by chemical analysis, X-ray powder diffraction, FTIR (1500-400 cm 1), N2 physisorption (BET), 27A1 MAS NMR, UV-Visible spectroscopy, NH3-TPD and H2-TPR. For all samples, UV-Visible spectroscopy and H2-TPR results confirmed that both Cr(VI) ions and Cr(III) oxide coexist. TPD of ammonia showed that from the chromium incorporation, it results strong Lewis acid sites formation at the detriment of the initial Bronsted acid sites. The catalyst issued from chromium chloride showed higher activity and selectivity toward acetonitrile. This activity can be assigned to the nature of chromium species formed using this precursor. In general, C r6+ species seem to play a key role in the ammoxidation reaction but Cr203 oxide enhances the deep oxidation. 

Three series of LaCoi. CuxOs, LaMni.xCuxOs, LaFei x(Cu, Pd)x03 perovskites prepared by reactive grinding were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) of O2, NO + O2, and CsHg in the absence or presence of H2O, Fourier transform infrared (FTIR) spectroscopy as well as activity evaluations without or with 10% steam in the feed. This research was carried out with the objective to investigate the water vapor effect on the catalytic behavior of the tested perovskites. An attempt to propose a steam deactivation mechanism and to correlate the water resistance of perovskites with their properties has also been done. 

It is important to understand the catalyst characteristics in detail, which in turn helps to understand the catalyst better and correlate the structure and composition of the catalysts with its performance, so that further improvement of the catalyst is possible. Acidity is an important property which influences the overall activity of the alkylation catalysts and the same was studied for Cui.xZnxFc204 by IR and TPD methods. The changes in acidity with respect to catalyst composition and temperature were studied through pyridine adsorption followed by IR measurements. In situ FTIR spectra of pyridine adsorbed on Cui xZnxFe204 between 100 and 400°C (Figme 23) indicated Lewis acidity is the predominant active centers available on the surface [14]. 

The possible accumulation of intermediates during the photocatalytic oxidation of aromatic contaminants has been studied with a variety of techniques, including temperature-progranuned desorption (TPD), oxidation (TPO), and hydrogenation (TPH), Fourier transform infrared analysis (FTIR), and extraction of adsorbed species with a variety of solvents. 

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