Catalysts calcination temperatures

Hopkins (161) found that a steady decrease in n-heptane cracking activity occurred over La- and Ca-exchanged Y zeolites as the catalyst calcination temperature was increased from 350° to 650°C. The lanthanum form was about twice as active as the calcium form. Reduction in activity with increasing activation temperature was attributed to removal of acidic framework hydroxyl sites as dehydration becomes more extensive. The greater activity of La—Y with respect to the calcium form was thought to result from the greater hydrolysis tendency of lanthanum ion, which would require more extensive dehydration to result in the same concentration of acidic OH groups as found on Ca—Y. 

Catalyst (calcination temperature,°C) Highest acid strength (Ho value)... 

Isooctane 1.5% Pt/ Ceo gGdo.20i 9 750 3 0.5-3.5 Catalyst calcination temperature plays a crucial role for catalytic activity and sulfur tolerance. Catalyst calcined at 800 °C exhibit a better performance and sulfur tolerance due to improved catalyst stability and synergism Lu et al.135... 

Fio. 28. Frequency factor (A) for hydrogenation of benzene, size of crystallite (D ), and lattice defect (ij) of palladium on aluminosilicate catalyst prepared by cation exchange versus temperature of reduction of the catalyst. Calcined temperature before reduction was kept constant at 300°. 

Fig. 5. The relationship between specific activity for the formation of butadiene (solid line, gmol min ), surface antimony composition (broken line, at. %), and catalyst calcination temperature (a) 4 (b)20 (c)40 (d)68 (e)83 (f) lOOat. %Sb bulk composition. [Reproduced from H. Hemiman, D. Pyke, and R. Reid (74).]... 

The Cu-Zn/Al203 (Cu/Zn = 0.7) catalysts calcination temperature before reduction affected significantly its activity and stability as shown in Fig.3. The initial MOIP conversion was measured at 260 C and 6.2 h i and the deactivation rate (% conversion/hour) was calculated from the MOIP conversion decrease... 

Figure 123 provides a simple example illustrating this approach, and it again demonstrates the benefits of enhanced dehydroxylation. Cr/silica-titania (2.5 wt% Ti) was calcined at various temperatures for 3 h in a nonoxidizing atmosphere (N2, CO, or CS2), followed by 2 h in dry air at the same temperature. These catalysts were then tested for polymerization activity, and the resultant polymers were analyzed. In all the three cases, the polymer MI increased as the catalyst calcination temperature was raised, as would be expected. Because of enhanced dehydroxylation, calcination in CS2 resulted in higher MI values than calcination in CO, and it was better than in N2. Of course, the N2 treatment would be the equivalent of a one-step activation in air, because in this case both the primary and secondary steps were conducted at the same temperature. 

Catalyst Calcination temperature X-ray diffraction pattern Amount of noble metal Specific sui ce area (m /g)... 

Figure 2. DTA profiles obtained for soot-lCulOOCe mixture samples with different catalyst calcination temperatures.

The influence of catalyst calcination temperature was studied in the case of samarium phosphate as those products show a thermal phase transition between 600 and 700°C (ref. 10). Catalytic results are summarized in Table 3. 

Figure 2 Effect of calcination temperature on TPR of Ru-Sn/Al20j catalysts. Calcination temperature (A) - 250 °C (Jt) - 400 °C (A) - 450 °C. Preparation coimpregnation, Ru loading 5 wt.%, Sn Ru atomic ratio 2.

Type and amount of catalyst, calcination temperature, reaction conditions, conversion and selectivity with the catalytic alkylation of benzene with propylene to cumene. 

Kudus, M.H.A., Akil, H.M., Mohamad, H., Loon, L.E., 2011. Effect of catalyst calcination temperature on the synthesis of MWCNT—alumina hybrid compound using methane decomposition method. Journal of Alloys and Compounds 509, 2784—2788. 

Figure 5 depicts the effect of calcination temperature on subsequent catalyst activity after reduction at 300°C (572°F). Activity was measured in laboratory tubular reactors operating at 1 atm with an inlet gas composition of 0.40% CO, 25% N2, and 74.6% H2, and an inlet temperature of 300°C. Conversion of CO is measured and catalyst activity is expressed as the activity coefficient k in the first order equation ... 

Figure 4.11. Typical Tafel plots for Pt catalyst-YSZ interfaces during C2H4 oxidation on Pt the large difference in I0 values between the two Pt films (labeled R1 and R2) is due to the higher calcination temperature of Pt film R2 vs Pt film Rl.4 Reprinted with permission from Academic Press.

CO conversions over Au/Ce02 catalyst were measured in the dry and wet condition as shown in Fig. 1. Similar to other supported gold catalysts, Au/Ce02 catalyst showed higher CO conversions in the presence of water vapor than in the absence of it at the same temperature. Catalytic activities for CO oxidation over Au/Ce02 catalysts prepared at different calcinations temperature were compared in the dry and wet condition as shown in Fig. 2. Au/Ce02 catalyst calcined at 473 K showed the highest initial CO conversion in the absence of water vapor. However, the CO conversion decreased steadily and reached a steady-state value over this catalyst. 

Fig. 1. CO conversions at different reaction temperatures in the dry (open points) and wet condition (filled points) over 0.95wt% Au/CeOj catalyst calcined at 573 K. FAV = 1,000 ml/min/gcat..

Fig. 2. CO conversions at 363 K in the dry condition (open points) and 353 K in the wet condition (filled points) over lOOmg and 50 mg of Aa/CeOi catal) containing 0.95 wt% Au prepared at different calcination temperatures (373 K (circle), 473 K(square), 573 K(triangle up), 673 K (triangle down), 773 K (diamond), 873 K (hexagon)). The reactants of 100 ml/min, 1 vol% CO and 1 vol% O2 in He, were fed to the catalyst.

Extensive data on the charaaerization and the thermal evolution of the different catalysts have been reported elsewhere [9-14]. Phase composition, cell parameters and surface area of the final materials are summarized in Table 1. The XRD data indicate that for all the hexaaluminate-type samples the formation of the final phase begins at 1273 -1373 K and requires calcination temperatures of 1473-1573 K to be completed. 

PtWZ (Std) to obtain a reference catalyst. Prior to reaction, all samples were calcined for one hour at the chosen temperature (1096 K for WZ, Pt/Al203 and Pt/WZ (Std), and 773 K for Pt/WZ (acac)) and subsequently reduced for 1 h under a H2 flow of. 5 liter/ min g at 623 K. The choice of temperature for the second calcination cycle of the Pt/WZ (acac) sample is not in any way arbitrary. The idea is to use a non-aqueous scheme to keep the incorporation of moisture to a minimum, and a calcination temperature low enough to guarantee better metal dispersions. 

Larese, C., Cabello Galisteo, F., Lopez Granados, M. et al. (2004) Effects of calcination temperature on the stability of CeP04 detected in vehicle-aged commercial three-way catalysts, Appl. Catal. B Environ., 48, 113. 

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