Hydrogen activation, with immobilized

Figure 16. The processes involved in hydrogen activation with immobilized hydrogenase.

Selenium-catalysed epoxidations have been carried out using a perfluo-roalkylated phenylselenide together with hydrogen peroxide, as shown in Scheme 9.6 [13]. The catalyst could be recycled 10 times with no loss of activity, with the toxic selenide immobilized in the perfluorinated solvent. 

It is known that Ir-complexes in the presence of hydrogen can form catalytically inactive hydrogen-bridged dimers. The finding that the activities of immobilized catalysts increase with decreasing catalyst loading (Scheme 2.1) indicates that the dimer formation can be prevented by a site-isolation effect. 

Three different organic bases, imidazole (IM), triazole (TZ) and hydrogenated 1,8-diaza-bicyclo(5.4.0) undecene-7 (DBU) were immobilized on mesoporous materials. Immobilized state of organic bases and their catalytic activities in Knoevenagel condensation between ethylcyanoacetate and benzaldehyde was studied. Organic bases immobilized mainly on mesopore still retained their catalytic activities with an inevitable loss due to immobilization. Imidazole catalyst immobilized on KIT-1 disordered mesoporous material with three-dimensional channels showed a sufficient activity for multi-repeated use. 

A special electrochemical cell was often employed to detect the photosynthetic activity of immobilized thylakoids. " " With this electrochemical micro-cell, it was possible to detect a photocurrent of free or immobilized thylakoid membranes in the absence of exogenous artificial electron acceptor. The photosynthetic origin of the photocurrent was demonstrated by an inhibition in the presence of the photosynthetic inhibitor diuron. The inhibition of the photocurrent by catalase, an enzyme that degrades hydrogen peroxide, demonstrated that dissolved oxygen was involved. " The ability of oxygen to act as an electron acceptor for the photosynthesis membrane was initially demonstrated by Mehler. This process, known as pseudocyclic electron transport or Mehler... 

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