Diffraction patterns of catalysts

The catalysts, both fresh and used, were characterized as to BET surface area, pore size distribution, elemental analysis, x-ray diffraction and XPS. Some BET and pore volume data are given in Table 1. The diffraction pattern of Catalyst B gave some indication of a gamma-alumina phase, not well resolved All other peaks were well-resolved, suggesting the absence of amorphous or highly-dispersed phases. 

Figure 2. X-ray diffraction patterns of catalysts after the liquid-phase methanol synthesis...

Figure 4. X-ray diffraction patterns of catalysts with a V/Mo ratio of 0.4 calcined in air or nitrogen O Nbo.( Moo.9i02.8o, TeM30io, Te2M2o057, A M0O3, TeMosOis...

In the following discussion the X-ray diffraction (XRD) patterns of a series of six industrial catalysts are compared. High-resolution scans were obtained with monochromated Co radiation on a transmission Guinier diffractometer. Phase analyses were carried out on an automated Phillips APD 10 powder diffractometer using postmonochromated Cu radiation. In Fig. 2.2, relevant sections of the diffraction patterns of catalysts from three industrial sources are displayed. The observed reflections can be assigned to magnetite and wustite as the main components of the catalysts. The catalysts differ markedly in their content of crystalline wustite. It should be stressed here that XRD is not a suitable method for quantitative determination of the wustite content, since it depends on the crystallinity of the phase analyzed. The nonstoichiometric nature of wustite and its close structural... 

Figure 1 is a TEM photograph of the Cu (10wt%)/Al2O3 catalyst prepared by water-alcohol method, showing the dispersed state of copper and was confirmed the particle sizes from XRD data. Figure 2 is X-ray diffraction patterns of above-mention catalysts, was used to obtain information about phases and the particle size of prepared catalysts. Metal oxide is the active species in this reaction. Particle sizes were determined fix)m the width of the XRD peaks by the Debye-Scherrer equation. 

Table 1 shows that the physicochemical properties of the support material were modified by the pre-treatment process. The particle sizes. Dp, which are summarized in the Table 1 were calculated from the X-ray diffraction patterns of prepared catalysts and a commercial catalyst(30 wt% Pt-Ru/C E-TEK) by using Scherrer s equation. To avoid the interference from other peaks, (220) peak was used. All the prepared catalysts show the particle sizes of the range from 2.0 to 2.8nm. It can be thought that these values are in the acceptable range for the proper electrode performance[7]. For the prepared catalysts, notable differences are inter-metal distances(X[nm]) compared to commercial one. Due to their larger surface areas of support materials, active metals are apart from each other more than 2 3 times distance than commercial catalyst. Pt-Ru/SRaw has the longest inter-metal distances. 

In catalyst characterization, diffraction patterns are mainly used to identify the crystallographic phases that are present in the catalyst. Figure 6.2 gives an example where XRD readily reveals the phases in an Fe-MnO Fischer-Tropsch catalyst [7], The pattern at the top is that of an MnO reference sample. The diffraction pattern of the reduced Fe-MnO catalyst shows a peak at an angle 29 of 57°, corresponding to metallic iron, and two peaks which are slightly shifted and broadened in comparison with the ones obtained from the bulk MnO reference. The Mossbauer spectrum of the reduced catalyst contains evidence for the presence of Fe2+ ions in a mixed (Fe,Mn)0 oxide [7], and thus it appears justified to attribute the distortion of the XRD peaks to the incorporation of Fe into the MnO lattice. Small particle size is another possible reason why diffraction lines can be broad, as we discuss below. 

Figure 6.4 X-ray diffraction patterns of Rh-Mn catalysts on Si02. Left catalyst with atomic ratio Rh/Mn=l after calcination in air at the indicated temperatures right calcined Rh-Mn catalyst (atomic ratio Rh/Mn=2) after reduction in H2 at the indicated temperature (from Kunimori et a/.[12]). 

Nickel silicate, as catalyst, 20 106-109 differential thermogram of xerogel, 20 107 infrared spectra of, 20 108 preparation by SHCP method, 20 106 properties and structure of, 20 107-109 X-ray diffraction pattern of, 20 109 Nickel sulfate hexahydrate, dehydration of, dislocations and, 19 389 Nickel sulfides... 

Figure 1. X-ray powder diffraction patterns of Sn02, V2O5 and VaOs/SnOa catalysts.

Figure 3 X-Ray diffraction patterns of the VPO catalysts at room temperature after the in situ Raman cell run.

The X-ray powder diffraction patterns of the parent materials showed the hexagonal structure characteristic for MCM-41 and SBA-15, and the cubic structure for MCM-48, respectively. All the patterns matched well with the reported patterns, confirming the successful synthesis of the mesoporous molecular sieves. The intensity of the reflection did not change essentially upon loading the carrier with the organometallic complexes, nor after a catalytic cycle, showing that the mesoporous structures were not affected by incorporation of the catalyst. 

X-ray diffraction patterns of powdered catalysts were recorded with a Rigaku RINT 1200 diffractometer using a radiation of Ni-filtered Cu-Ka. BET surface area and pore size distribution were calculated from the adsorption isotherm of N2 at 77 K. The BJH method was used for the latter. Aluminum content was determined by ICP spectrometer. FTIR spectra of adsorbed NH3 were recorded with a JASCO FT/IR-300 spectrometer. The self-supporting wafer was evacuated at prescribed temperatures, and 25 Torr of NH3 was loaded at 473 K. After NH3 was allowed to equilibrate with the wafer for 30 min, non-adsorbed NH3 was evacuated and a spectrum was collected at 473 K. The differential heat of adsorption of NH3 was measured with a Tokyo-riko HTC-450. The catalyst was pretreated in the presence of 100 Torr oxygen and evacuated at 873 K. The measurements were run at 473 K. 

Powder X-ray diffraction (XRD) patterns of the catalysts were obtained using a Philips APD X-ray diffraction spectrometer equipped with a Cu anode and Ni filter operated at 40 kV and 20 mA (CuKa = 0.15418 nm). Iron phases were identified by comparing diffraction patterns of the catalyst samples with those in the standard powder XRD file compiled by the Joint Committee on Powder Diffraction Standards published by the International Center for Diffraction Data. 

Figure 5. X-Ray diffraction pattern of the catalyst after steaming in the presence of vanadium, a) REHY + silica-alumina b) REHY + sepiolite.

It has also been suggested that the strain associated with a high concentration of such microscopic precipitates could be described by paracrystallinity theory,51 which would imply that the diffraction pattern of a catalyst containing such precipitates would have a characteristic form which would... 

FIGURE 12 X-Ray diffraction pattern of a mixed oxide catalyst for methanol synthesis. The peaks marked C are cupric oxide Z, zinc oxide A, y-alumina. 

FIGURE 13 X-Ray diffraction patterns of a standard NaY zeolite (A) and a typical cracking catalyst containing the zeolite (B). 

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