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Calcined catalysts

An increasing intensity of the diffraction peaks of hematite is observed when comparing the dried and calcined catalyst as shown in Fig. 2(a), indicating that hematite forms at M er temperatures. No obvious diffraction peaks to lithium such as lithium iron oxide (LiFcsOg) could probably be ascribed to the small fraction of lithium or overlapped peaks betwem hematite and lithium iron oxide. The diffraction peak intensity of magnetite in tested catalysts increases significantly. [Pg.743]

Resolution of Che Mo 3p peaks showed molybdenum Co be present as Mo" for the calcined catalysts, and a mixture of Mo" " and Mo" for sulfided catalysts. The Mo 3p peaks were used since both arsenic and sulfur peaks interfere with the Mo 3d doublet. Although some authors have been able to resolve a peak attributed to Mo" "5 on sulfided catalysts (8-9), we were able to resolve our peaks using only two component peaks. Curve resolving consistently showed that about 70% of the molybdenum signal in the sulfided catalysts was due to Mo". ... [Pg.9]

X-ray dififtaction (XRD) analysis of the freshly calcined catalysts as well as samples used for several hours in the isomerization reaction, only presented the peaks corresponding to the tetragonal form of zirconia. At the same time, for the silica series, XRD confirmed the presence of NiO on the unsulfated catalysts and NiS04 on the sul ted ones. However, XRD did not show any evidence of any of these species for the zirconia series, probably due to their high state of dispersion. Similarly, the XPS data clearly showed the presence of NiO and NiS04 on the unsulfated and sulfated silica-supported catalysts, respectively, but they were not conclusive in the case of zirconia series since both sulfate and oxide species were observed. [Pg.556]

Therefore, we attempted to regenerate the catalyst by calcination at 773 K for 6 h the calcined catalyst showed a slight decrease in the surface area (450 m g versus 530 m g of the fresh catalyst) and recovered its activity significantly, although proving less stable with time-on-stream than the fresh one. [Pg.351]

Physical properties of calcined catalysts were investigated by N2 adsorption at 77 K with an AUTOSORB-l-C analyzer (Quantachrome Instruments). Before the measurements, the samples were degassed at 523 K for 5 h. Specific surface areas (,S BEX) of the samples were calculated by multiplot BET method. Total pore volume (Vtot) was calculated by the Barrett-Joyner-Halenda (BJH) method from the desorption isotherm. The average pore diameter (Dave) was then calculated by assuming cylindrical pore structure. Nonlocal density functional theory (NL-DFT) analysis was also carried out to evaluate the distribution of micro- and mesopores. [Pg.99]

Figure 6.10 shows Fourier transforms of Co K-edge EXAFS spectra of these calcined catalysts and polycrystalline Co oxides. Three peaks are clearly observed in EXAFS spectra of calcined Co(X)/Si02 catalysts at almost the same... [Pg.110]

Coordination Number (N) and Interatomic Distance (R) of Co-O and Co-Co Shells Calculated from Co K-edge EXAFS Spectra of Calcined Catalysts, and Polycrystalline Co304 and a-Co2Si04 (Figure 6.10)... [Pg.114]

In agreement with the TPR results, the hydrogen chemisorption/pulse reoxidation data provided in Table 8.3 indicate that, indeed, the extents of reduction for the air calcined samples are -20% higher upon standard reduction at 350°C (compare 02 uptake values). Yet in spite of the higher extent of reduction, the H2 desorption amounts, which probe the active site densities (assume H Co = 1 1), indicate that the activated nitric oxide calcined samples have higher site densities on a per gram of catalyst basis. This is due to the much smaller crystallite that is formed. The estimated diameters of the activated air calcined samples are between 27 and 40 nm, while the H2-reduced nitric oxide calcined catalysts result in clusters between 10 and 20 nm, as measured by chemisorption/pulse reoxidation. [Pg.155]

Turning to the XANES results (Figure 8.4), upon reduction at 350°C, the extent of reduction is found to be higher for the H2-activated air calcined catalysts. This is evident in the shoulder at the edge (-7,709 eV), which is a measure of metallic content, as well as the lower white line intensity for the activated air calcined catalyst at -7,725 eV. The catalysts appear to contain a combination of mainly Co metal and CoO, in agreement with the interpretation of TPR profiles previously discussed. [Pg.155]

FIGURE 8.7 CO conversion vs. time on stream in the CSTR (220°C, 280 psig, H2/CO = 2.5) at (squares) 10 NL/g.at/h and (circles) 20 NL/g.at/h for H2-activated (filled circles) air calcined and (unfilled circles) NO calcined catalysts, including (top) 15% Co/Si02 and (bottom) 25% Co/Si02. The NO calcined catalysts clearly exhibit higher CO conversion rates on a per gram of catalyst basis. [Pg.161]

The results confirm that the novel metal nitrate conversion method using nitric oxide in place of air advocated by Sietsma et al. in patent applications WO 2008029177 and WO 2007071899 leads to, after activation in H2, catalysts with smaller cobalt crystallites, as measured by EXAFS and hydrogen chemisorption/ pulse reoxidation. In spite of the lower extent of cobalt reduction for H2-activated nitric oxide calcined catalysts, which was recorded by TPR, XANES, EXAFS,... [Pg.161]

The surface area was calculated using the BET equation,36 while the total pore volume and the average pore size were calculated from the nitrogen desorption branch applying the Barrett-Joyner-Halenda (BJH) method.37 BET and BJH adsorption measurements were carried out with a Micromeritics Tri-Star system on both the supports and the calcined catalysts. Prior to measurements, the samples were evacuated at 433 K to approximately 50 mTorr for 4 h. [Pg.248]


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See also in sourсe #XX -- [ Pg.99 ]




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Calcine

Calcined

Calciner

Calciners

Calcining

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