Catalysis of Organic..

178 Hydrogenation of Dehydrolinaloolcase DiHL (3,7-dimethyl-6-octaene-3-ol, dihydrolinalool) is an unfavorablebyproduct of the reaction.OH+H 2OH+H 2OHDHLLNDiHLFigure 1. Hydrogenation of DHL to a completely saturated product DiHLLinalool is one of the most widely used fragrant substances in cosmetic andpharmaceutical industry (as a composite of many cosmetics and perfumes and as anintermediate in synthesis of vitamins (A, E)) (1). But natural resources can’t supplythe growing needs, so the necessity in synthetic LN has been increasing. Therefore thereaction of selective catalytic hydrogenation of DHL to LN is one of the mostsignificant reactions in the chemistry of fragrant substances (2), and the main problemof this research is the development of modern catalytic technology for preparation oflinalool.Catalytic hydrogenation of DHL by various catalysts such as bulk metals andmetals deposited on the carbon, oxides and salts has been studied since the 70-s of thelast century (3). The disadvantages of such catalysts are the low surface area and thehigh content of the noble metals, which result in their high cost price.In contrast, modern catalysts on the base of metal nanoparticles have largesurface area-to-volume ratio of the metal, which allows effectively utilizing expensivemetals (4). However, without a suitable support the metal nanoparticles aggregatereducing the surface area and restricting the control over the particle size. Toovercome this problem, catalytic nanoparticles have been immobilized on solidsupports, e. g., carbon (5), metal oxides (6) and zeolites (7), or stabilized by cappingligands that ranged from small organic molecules to large polymers (8, 9). Theencapsulation by polymers is advantageous because in addition to stabilizing andprotecting the particles, polymers offer unique possibilities for modifying both theenvironment around catalytic sites and access to these sites (10-12). So, the protectivepolymer not only influences particle sizes but can also have a tremendous influenceon catalytic activity and selectivity (13). Besides, polymers, which contain complexesor metal nanoparticles, combine the advantages both of homogeneous (high activityand selectivity) and heterogeneous catalysts (easy recovery from the reaction mixtureand possibility of regeneration). Catalytic properties of such systems may be changedby varying the type of polymeric matrix and characteristics of metal nanoparticles(14).