TPR profiles

Fig. 2. TPR profiles of I-VOx/Ti02 catalysts Fig. 3. TPR profiles of P-VOx/TiOa catalysts...

Figure 1. H2-TPR profiles of catalysts Figure 2. NHj-TPD spectra of catalysts...

Fig. 1. TG spectra of carbon particulates with Fig. 2. TPR profiles measured for various Lao.gCso MnOj catalyst heating rate=l K/min. perovskite type oxides heating rate=10 K/min,...

Figure 2 shows the TPR profiles of the calcined phosphate precursors of the Ni2P/Si02, Ni2P/Al203, and NiaP/C-ALOj catalysts. 

Physical properties of the prepared catalysts were measured by an adsorption analyzer [Quantachrome Co., Autosorb-lC]. The structure of prepared catalysts were investigated by XRD [Simmazdu Co., XRD-6000] with a Cu-Ka radiation source (X = 1.54056 A), voltage of 40.0 kV, ciurent of 30.0 mA and scan speed of 5.0 deg/min. Also, temperature-programmed reduction (TPR) profiles of the samples were investigated by a sorption analyzer [Micromeritics Co., Autochem II] and obtained by heating the samples from room temperature to 1100°C at a rate of lOTl/min in a 5 % H2/Ar gas flow (50 ml/min). 

Fig.3 H2-TPR profiles of LiNiLaOx catalysts with different Li content (a)LaNiOx (b) Li/Ni=0.2 ...

Fig.6 H2-TPR profiles of LiFTiLaOx (Li/Ni=l. 6) and LaNiOx catalysts after reaction (a) LaNiOx (b) LiNiLaOx(Li/Ni=l. 6)...

Fig.7 H2-TPR profiles of LiNiLaOx/AI2O3 catalyst after O2 pretreatment...

Fig.8 H2-TPR profiles of LiNiLa0x/Al203 and LiNiLaOx catalysts after reaction (a) LiNiLaOx (b) LibriLa0x/Al203...

The TPR profiles of the zirconia and silica series are shown in Fig 1 The silica series showed that the sulfated Ni catalysts are more difficult to reduce than the unsulfated ones The position of the maxima shifted 30-50°C to higher temperatures as sulfate was added As opposed to the silica series (see sample 6SSi), the zirconia series exhibited H2 consumption... 

The effect of sulfur addition on the TPR profiles for some of these catalysts is reported in Table 5. The saturation of the solid by SO2 shifts the TPR profiles to higher temperatures and a second reduction peak appears at high temperature. The maximum temperatures measured for this second high temperature peak are reported in Table 5 (column 6). The effect of sulfur addition depiends on the nature of the support, and zeolites appear less sensitive to SO2. 

TPR experiments were performed at different amounts of sulfur on a Cu/Zr02 (Fig. 2). SO2 addition induces a modification of the TPR profile the reduction peaks are shifted toward higher temperatures. The total hydrogen consumption is decreased by 50% for the Qrst SO2 dose, then remains constant. 

H2 TPR measurements are used to probe the reducibility and may reveal more information on the nature of vanadium and molybdenum species. The assignment of the TPR peaks has been based on the literature study [9, 10] but also by using two reference samples V1-Z15 and Mol-Z15 prepared by solid-state ion exchange. TPR thermograms of V-Mo-Zeolite systems can be divided into two zones of H2 consumption (/) Mo-Zeolites exhibit two reduction peaks at 600 and 850°C corresponding to the reduction of Mo6+ into Mo4+ through the Mo5+ step and to the reduction of Mo4+ into Mo°, respectively while (ii) V-Zeolites led to a broad asymmetric feature around 710°C, which has been previously attributed to the reduction of V5+ into V3+. Finally, the TPR profiles of V-Mo-Zeolite catalysts seem more like a superposition of both Mo and V-catalysts TPR profiles. 

Figure 1 shows the H2-TPR profiles of Co- and Co/Pd-HFER catalysts. The H2-TPR profile of Co-HFER shows the presence of two peaks at 340 °C and 670 °C corresponding to the reduction peaks of particles of cobalt oxides (Co304 and CoOx respectively). Normally, Co304 are on the external surface while CoOx is inside the zeolite cavities [11-13], At 960 °C, the reduction of the cationic species Co2+ occurs [14]. 

FIGURE 2.2 TPR profiles of carbon nanomaterial Fischer-Tropsch catalysts (gas mixture 10% H2 in Ar heating rate 10 K/min). 

Amount of hydrogen consumption on Ru reduction in TPR profiles at 380-600 K, where H2-TPR... 

FIGURE 6.3 TPR profiles of calcined (thick line) and reduced (thin line) catalysts (a) Co(20)/CyDTA/SiO2, (b) Co(5)/CyDTA/Si02, (c) Co(20)/SiO2, and (d) Co(5)/Si02. Heating rate 5 Kmin-1. 

Temperature-programmed reduction (TPR) profiles of fresh catalyst samples were obtained using a Zeton Altamira AMI-200 unit. Calcined fresh samples were first heated and purged in flowing argon to remove traces of water. TPR was performed using 30 cc/min 10% H2/Ar mixture referenced to argon. The ramp was 5°C/min from 50 to 1,100°C, and the sample was held at 1,100°C for 30 min. 

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. 

Most recently, we have attempted to use this procedure to alter the dispersion of cobalt particles over the more strongly interacting 25% Co/A1203 catalyst. However, as shown in Table 8.5, the cluster size was not found to change significantly, and the TPR profiles (not shown for the sake of brevity) were observed... 

FIGURE 14.2 TPR profiles of the Co/A1203 catalysts prepared by the slurry phase impregnation method. 

The presence of two peaks in the TPR profile for the Co/Ti02 system suggested that two cobalt oxide species were present on the calcined catalyst. Using XPS, these species were identified as C03O4 and Co+. The Co V /2 xpS spectrum of the calcined Co/Ti02 catalyst had a satellite peak due to a Co+ ... 

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