Water purification catalyst immobilization

When making pharmaceuticals, one critical issue is to control and minimize metal impurities in the product, often to less than 10 ppm. Each product requires a different work-up and purification protocol, and it is difficult to describe a general solution. On some occasions washing removes the catalyst, but at other times the product is crystallized and the catalyst remains in the mother liquors occasionally, the product is volatile and can be distilled. Sometimes the catalyst is carried forward to the next stage and is removed at this point. In our experience, residual metal has not been problematic, but if it is then either immobilized or water-soluble catalysts, as described in this chapter, can be employed. 

To study the stability of immobilized C. antarctica lipase in methanolysis of waste edible oil, the three-step methanolysis was repeated by transferring the enzyme to a fresh substrate mixture. The conversion was maintained during 50 cycles (100 days) (Watanabe et al., 2001), showing that contaminants in waste oil do not affect the stability of the lipase preparation. In a chemical alcoholysis with an alkaline catalyst, FFAs in a waste edible oil convert to alkaline soap the water present disturbs an efficient reaction. Hence, FFAs and water should be removed before the reaction, and a small amount of alkaline soap generated must be removed by washing with water after the reaction. But the enzymatic process does not need the pretreatment and downstream purification. 

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. 

Enzymes have been used in a variety of biotechnological, biomedical and pharmaceutical applications due to their high specificity, non-toxicity, and water solubility, which are major advantages over inorganic catalysts (/). Because separation and purification of enzymes often requires complicated processing and retrieving them can be costly, immobilization of enzyme has attracted a lot of research 1-4). 

Substituted acrylic monomers. The reactants (methyl acrylate plus alcohol or amine) were added neat or in a non-aqueous solvent together with Novozym 435 immobilized lipase from Candida antarctica as a catalyst. Molecular sieves (4A) were used to remove water in order to shift the reaction equilibrium to product formation, and also to eliminate side reactions due to Michael addition that was usually enhanced by the presence of water or methanol. Unreacted starting materials were removed by evaporation, and the monomer products obtained without further purification. TLC analysis indicated that the desired products had formed. The purity of the products was confirmed by NMR and IR analysis. The two monomers were successfully polymerized in a separate step. 

An addition of activated carbon powder to photocatalytic Ti02 suspension improves water purifying ability (for selected papers, da Silva, 2003 Arana, 2003 Melian, 2003). J.L. Faria insisted that the presence of the activated carbon enhanced the photoefficiency of the Ti02 catalyst for photodegradation of an azo dye in aqueous solution. S.C. Lee et al. have reported air purification by Ti02 immobilized on activated carbon and they... 

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