Finishing, catalyst drying supported catalysts

In many cases drying operations are critical to the production of successful commercial catalysts. Close control of the drying process is necessary to achieve the proper distribution of the catalyst precursor within the pore structure of the support. Drying also influences the physical characteristics of the finished catalyst and the ease with which subsequent pelleting or extrusion processes may be carried out. 

This method involves the repeated dipping of porous support materials into a solution containing the desired catalytic agent. It is then dried and calcined to transform the metal into insoluble form. The agent must be applied uniformly in a predetermined quantity to a preset depth of penetration. The metal loading in the finished catalyst is typically 1-5%, Fig. 6.5. 

The advantage of using a phosphine complex is that it contains no chloride, and the counter-ion is easily decomposed or eliminated. The complex has to be synthesised (not easy or cheap), and nonaqueous solutions are needed, which means that the support must be dehydrated, the solvent dried, and the finished catalyst stored in ampoules sealed under vacuum. 

The metallocene is added to the supported MAO as a solution in toluene or aliphatic hydrocarbon. Subsequently subjecting the mixture to microwaves has been claimed to fix the metal component on the support and reduce reactor fouling (adhesion of polymer to reactor surfaces). The metallocene can also be dry-blended with the support, avoiding solubilization of the finished catalyst. ... 

Two final words of caution are necessary, (i) It is essential to analyse the finished cafalysf chemically, because nol all of the active components will have ended up where you would like - on the support, (ii) It is desirable to measure the total surface area and porosity of the finished catalyst, because they may have been changedby the preparation. This is particularly necessary when silica is the support, because it readily undergoes hydrothermal sintering during drying, calcination and reduction, leading to the sealing off of internal pores. 

Lipases are manufactured by fermentation of selected microorganisms followed by a purification process. The enzymatic interesterification catalysts are prepared by the addition of a solvent such as acetone, ethanol, or methanol to a slurry of an inorganic particulate material in buffered lipase solution. The precipitated enzyme coats the inorganic material, and the lipase-coated particles are recovered by filtration and dried. Various support materials have been used to immobilize lipases. Generally, porous particulate materials with high surface areas are preferred. Typical examples of the support materials are ion-exchange resins, silicas, macroporous polymers, clays, etcetera. Effective support functionality requirements include (i) the lipase must adsorb irreversibly with a suitable structure for functionality, (ii) pore sizes must not restrict reaction rates, (iii) the lipase must not contaminate the finished product, (iv) the lipase must be thermally stable, and (v) the lipase must be economical. The dried particles are almost inactive as interesterification catalyst until hydrated with up to 10% water prior to use. 

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