Catalysts highly active

Organometallic catalysis in biphasic aqueous/organic media is a novel and environmentally benign approach to combining the inherent advantages of homogeneous catalysts (high activity and selectivity) with the ease of separation... 

Another approach towards asymmetric heterogeneous catalysts is the immobilization of chiral homogeneous complexes via different methods. In this way the advantages of homogeneous catalysts (high activity and selectivity) and heterogeneous catalysts (easy recovery) can be combined. For a complete overview of this active research field the reader is referred to several reviews on this topic [50, 51]. The practical applicability of these catalysts is hampered by the fact that severe demands of recyclability and stability need to be obeyed. In certain cases promising results have been obtained as outlined here. 

Other catalysts, highly active in ethylene polymerization, have been obtained by co-milling MgCl2 with Ti compounds other than chlorides37). Even though these catalysts are active for the propylene polymerization, they are stereospecifically poor and have mainly been used to determine kinetic parameters at short polymerization times 38). 

For illustration, we may consider the preparation of a palladium/zirconia catalyst highly active for the oxidation of CO [4.47,71], the preparation of a copper/zirconia catalyst for the hydrogenation of C02 [4.23], and the preparation of iron/zirconia for ammonia synthesis [4.44]. 

Claisen-Schmidt condensation, and acetonylacetone cyclization Aryl coupling reactions (Suzuki, Heck, and Pd-exchanged mesoporous catalysts High activity and reusability avoiding the usual problem of Pd [184]... 

This feature should be beneficial for the catalytic performance of the relevant catalyst. High activity was observed in Rh-catalyzed hydroformylation of 1-octene... 

Deng, J., Zhang, L., Dai, H., et al. (2009). In situ Hydrothermally Synthesized Mesoporous LaCo03/SBA-15 Catalysts High Activity for the Complete Oxidation of Toluene and Ethyl Acetate, Appl. Catal. A Gen., 352, pp. 43 9. 

Low percent ring substitution is not critical for activity in all nucleophilic displacements. Brown and Jenkins found 40% to 100% ring substituted catalysts highly active for 0-alkylation of 2-naphthoxide ion with benzyl bromide. 

Deng, J. Zhang, L. Dai, H. et al. Single-crystalline Lao6Sro4Co03.5 nanowires/nanorods derived hydrothermally without the use of a template catalysts highly active for toluene complete oxidation. Catal. Lett. 2008, 123,294-300. 

El. Gao, 1999, Rhodium-amine complexes tethered on silica-supported metal catalysts. Highly active catalysts for the hydrogenation of arenes. New J. of Chem. 23, 6,633-640 F.R Hartley, 1985, Supported Metal Complexes, D. Reidel Publ. Co. Dordrecht... 

The preparation, stability and catalytic activity of non-stoichiometric spinel-type phases used in the synthesis of methanol were investigated as a function of the composition, heating temperature and atmosphere. It was shown that these phases formed mainly via amorphous chromates, especially for copper-rich catalysts. High activities in the synthesis of methanol were observed for zinc-rich samples (with a maximum for a catalyst in which 20% of the zinc ions were substituted by copper ions) and associated with the presence of a non-stoichiometric spinel-type phase, stable also in the reaction conditions. On the other hand, the low activity of copper-rich catalysts was attributed to the instability of the spinel-type phase where much of the copper segregates into well crystallized metallic copper, with a further poisoning effect by zinc and cobalt. 

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