Drying and calcination steps

Role of CyDTA during Drying and Calcinations Steps.107... 

Pt-Re Pt-Rh coimpregnation on A1203 / - / Not reduced. A study of drying and calcination steps. EXAFS... 

The microstructure of a sol, in terms of the nature and concentration of sol particles, significantly affect a membrane s properties such as average pore diameter and pore size distribution. Other critical parameters are the temperature and rate of evaporation used in the drying and calcination steps. Even though it is economical to obtain the final product form quickly, too rapid a drying rate forms cracks in the membrane. Crack formation is also dependent on thickness of the membrane. The work of Cini et al. [49], who prepared supported microporous y-A C membranes as catalyst supports, illustrates many of these effects. 

Fig. 2 Selected preparation parameters. Impregiiation, drying and calcination steps are described by the following parameters impregnation time (tj), ratio iKtween volume of solution and pore volume of support (V.A p), pH of solution, stiriit speed (n), and corresponding temperature (T), heating ramp (s) and time (t) of drying and calcination with subscription d and c, respectively.

During the drying and calcination steps, the adsorbed Fex-COy mixed hydroxides can be transformed by a solid state reaction into Fe and Co mixed phases containing CoxFcyOz nano-particles supported on yAlaOs. This hypothesis was confirmed in another study carried out in our laboratories when using different sequences of impregnation of Co and Fe ions. The same carbon yield was observed when Fe ions were incorporated first into the support and then the Co ions vs the co-impregnation route. On the contrary. 

The drying and calcination steps, where the metal salts are dehydrated and/or converted to oxides, are very critical. The optimum conditions are required... 

After the deposition, drying and calcinations steps usually follow, the latter being a temperature treatment in air or other gases for a defined duration. Normally the dried samples are not immediately put into a hot furnace but rather heated up gradually. The final temperature of calcination needs to ensure that organic materials such as binders are completely removed. 

The overall manufacturing process of /3"-alumina tubes can be subdivided into the production stages powder preparation, forming, and sintering. The main production routes are shown in Figure 21.13. The powder preparation includes mainly milling, spray drying, and calcination steps. These are described in detail by Duncan et al. [23]. 

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