Carbonate-derived catalysts

Rapoport s findings have been confirmed in the authors laboratory where the actions of carbon-supported catalysts (5% metal) derived from ruthenium, rhodium, palladium, osmium, iridium, and platinum, on pyridine, have been examined. At atmospheric pressure, at the boiling point of pyridine, and at a pyridine-to-catalyst ratio of 8 1, only palladium was active in bringing about the formation of 2,2 -bipyridine. It w as also found that different preparations of palladium-on-carbon varied widely in efficiency (yield 0.05-0.39 gm of 2,2 -bipyridine per gram of catalyst), but the factors responsible for this variation are not knowm. Palladium-on-alumina was found to be inferior to the carbon-supported preparations and gave only traces of bipyridine,... 

The commercial process for the production of vinyl acetate monomer (VAM) has evolved over the years. In the 1930s, Wacker developed a process based upon the gas-phase conversion of acetylene and acetic acid over a zinc acetate carbon-supported catalyst. This chemistry and process eventually gave way in the late 1960s to a more economically favorable gas-phase conversion of ethylene and acetic acid over a palladium-based silica-supported catalyst. Today, most of the world s vinyl acetate is derived from the ethylene-based process. The end uses of vinyl acetate are diverse and range from die protective laminate film used in automotive safety glass to polymer-based paints and adhesives. 

Bifunctional catalysts have proven to be very powerful in asymmetric organic transformations [3], It is proposed that these chiral catalysts possess both Brpnsted base and acid character allowing for activation of both electrophile and nucleophile for enantioselective carbon-carbon bond formation [89], Pioneers Jacobsen, Takemoto, Johnston, Li, Wang and Tsogoeva have illustrated the synthetic utility of the bifunctional catalysts in various organic transformations with a class of cyclohexane-diamine derived catalysts (Fig. 6). In general, these catalysts contain a Brpnsted basic tertiary nitrogen, which activates the substrate for asymmetric catalysis, in conjunction with a Brpnsted acid moiety, such as urea or pyridinium proton. 

The asymmetric cyclopropanation of a-bromocyclohexenone with cyanoacetate 31 has been achieved under phase-transfer conditions by the use of cinchona alkaloid-derived catalyst, which constructs chiral quaternary carbons on the cyclopropane... 

Oxazolinones are not so stable and 2-oxazolin-5-ones (166), for example, react with sodium borohy-dride to yield 2-hydroxyamides (167), and their alkylidene derivatives (168) are converted into the corresponding alkyloxazolinones (169) by hydrogenation over palladium on carbon as catalyst. These... 

Fig. 25. Carbon efficiencies of oxygenated products in the CO + H2 reaction and ethanol selectivities on bimetallic RhCo cluster-derived catalysts impregnated on Zr02 (0.2 wt% metal) (CO/H2 ratio 20/45 cmHg, 200°C). O.C. represents oxygenated products on a carbon basis.

Data for both hydrogen and carbon monoxide chemisorption for the series of reduced [Rhe Ir,]/NaY (x = 0,2,4, and 6) are presented in Table XXV. It was found that, in particular, the CO/M values on Rh-rich cluster-derived catalysts were higher than those for Ir-rich clusters. The trend of CO chemisorption amounts is in good agreement with the decreasing order of electron deficiency on the clusters inside zeolites which has been estimated from XE NMR chemical shifts (SS). 

Hydrqformylation of Ethylene on Carbon-Supported Ru, RujCo, and Co Carbonyl Cluster-Derived Catalysts"... 

COClj reacts vigorously with 1,2-epoxides to give either chloroformate or carbonate derivatives depending upon the reaction conditions. In the absence of a catalyst [1309], or in... 

Due to the accumulation of the oligomerized products of PO and carbonate-derived intermediates, the propylene conversion tended to decrease sharply soon after the reaction and then after 10-20 min, it gradually decreased with time onstream. Quasi-steady-state conversions were usually obtained after 30-60 min. The selectivity to PO and hydrogen conversion reached steady state much earlier. The used catalysts could be almost completely recovered by treating at 523 K in a stream of air, which allowed repeated experiments. 

XRD and LRS were used to characterize both supported and unsupported catalysts derived from V0(H2P04)2. Supported V0(H2P04)2-derived catalysts were found to be more active but slightly less selective in butane oxidation to maleic anhydride than unsupported samples, but the difference in selectivity could be eliminated by adding a small amount of phosphorus to the supported samples. For butane oxidation, the activity of the catalysts was much enhanced by the presence of a,-VOP04- The relative rates of oxidation of propane, butcme, and pentane were consistent with alkane activation occurring predominantly at the secondary carbon. 

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