Impregnation and calcination

To determine any structure modification to the Degussa C-aluminoxide support during wet impregnation and calcinations, adsorption/desorption isotherms obtained before and after modifications were compared. The results as presented in Figure 14.1 are in agreement with our previous results.39 It is found that the... 

Normally, the best activities observed during the development process are found for catalysts prepared in the laboratory where special attention is paid to each preparation step and where better control of e.g. impregnation and calcination temperature history can be achieved. This should be kept in mind when comparing activities of new lab-prepared catalysts with standard products from a production facility. As a consequence, it is seldom worth the effort to continue with a test production if the activity of the lab-prepared catalyst fails to meet the requirements. Important results for the test-produced catalysts are activity measurements covering the full range of operating conditions in the industrial converter and the mechanical strength. 

The carriers were impregnated and calcinated in the laboratory, and the activity was subsequently measured in the set-up shown in Fig. 9. The vanadium content was varied in the range 2-5 wt% and the molar ratios between alkali promoter and vanadium were varied in the ranges 0-4 for K/V, 0-2 for Na/V, and 0-3 for Cs/V. The sulphur content was about the same in all impregnations. The measured activities for 3 catalyst compositions A, B, and C impregnated on the same carrier and with the same vanadium content and molar ratios of K/V and Na/V are given in Table 1. The extrudates are made in the 9 mm Daisy form, which is the special 5-finned ring offered by Haldor Topsoe (Fig. 3). The observed pellet activity is reported as a pseudo-1st order rate constant calculated from... 

Figure 8. Luminescence spectra of tin loaded LaY at 77 K after vanadyl porphyrin impregnation and calcination (A) was taken before and (B) after steam aging. The excitation wavelength was set at 300 nm.

Zr/Si ratio, by using a model, for example the one published by Kuipers et al. [22]. When applied to the spectra of Fig. 10.8, Kuipers model indicates that the ZrC>2 dispersion of the three impregnated and calcined catalysts is 5 to 15%, whereas the dispersion of the catalyst from ethoxide is around 75%. 

Fig. 10.10. Auger spectra of a conducting ZrC>2/SiC>2/Si(100) model catalyst after impregnation and calcination (from Eshelman et al. [25]).

Zr02 dispersion of the three impregnated and calcined catalysts is 5 to 15%, whereas the dispersion of the catalyst from ethoxide is around 75%. 

A 4 wt% Na/Si02 catalyst and a 4 wt% K/Si02 catalyst were prepared by an impregnation method using nitrate salts. Fuji QIO silica spheres (2-3 mm) were used which have a surface area of 359 m g and a pore volume 1.01 cm g. Both catalysts were dried overnight at 100 °C after impregnation and calcined at 450 °C for 3 hours. 

Figure 16.5 FT-IR spectra of 0.5% Ru-TEA/Si02 impregnate and calcined intermediate.

---