| Popis: |
Recently, biocatalysis has become an interesting alternative for conventional industrial processes. Enzyme reactions are highly selective and fast, and can be performed under ambient conditions. A drawback of the use of enzymes is their fragile nature. Stirring, high temperature, or solvents can cause deactivation. Also separation of the free enzyme from the reaction medium is difficult. Therefore, enzymes are generally used in an immobilized form on particulate carriers. This can still cause problems regarding mechanical strength and separation, or additional problems associated with the use in packed beds (pressure drop) or mass transport limitations inside the support-particle (possible pH-gradients). In the present study, different enzymes were immobilized onto ceramic monoliths. Monoliths can be seen as a bundle of small channels, and were originally developed for gas-phase applications. Advantages of the monoliths compared to conventional reactor types include a low pressure drop over the reactor, high mechanical strength, high available surface area, easy separation. Two types of monoliths were employed: the classical cordierite monolith and the ACM monolith, with a porous channel wall. It can be concluded that different enzymes can be (reversible) immobilized onto the monolithic support, to yield active biocatalysts. The monolithic biocatalysts were applied in different reactors; the monolithic stirrer reactor and the monolithic loop reactor. Finally, a new carrier material was explored, consisting of carbon nano fibers (CNF) on the monolith channel wall, which could also be promising for metal catalysts. |
