Ruthenium/zeolite hydrogenation, selective

There are several examples of one-pot reactions with bifunctional catalysts. Thus, using a bifunctional Ru/HY catalyst, water solutions of corn starch (25 wt.%) have been hydrolyzed on acidic sites of the Y-type zeolite, and glucose formed transiently was hydrogenated on ruthenium to a mixture of sorbitol (96%), mannitol (1%), and xylitol (2%) [68]. Similarly a one-pot process for the hydrolysis and hydrogenation of inulin to sorbitol and mannitol has been achieved with Ru/C catalysts where the carbon support was preoxidized to generate acidic sites [69]. Ribeiro and Schuchardt [70] have succeeded in converting fructose into furan-2,5-dicarboxylic acid with 99% selectivity at 72% conversion in a one-pot reaction... 

Blackmond et al. compared the selectivities of ruthenium, platinum, and rhodium supported on NaY and KY zeolites with those supported on carbon, in the hydrogenation of cinnamaldehyde and 3-methylcrotonaldehyde in isopropyl alcohol at 100°C (for rhodium and ruthenium) or 70°C (for platinum) and 4 MPa H2.52 Good selectivities to unsaturated alcohols were obtained over zeolite-supported ruthenium and platinum with... 

Another pertinent example is provided by the manufacture of caprolactam [135]. Current processes are based on toluene or benzene as feedstock, which can be converted to cyclohexanone via cyclohexane or phenol. More recently, Asahi Chemical [136] developed a new process via ruthenium-catalysed selective hydrogenation to cyclohexene, followed by zeolite-catalysed hydration to cyclo-hexanol and dehydrogenation (Fig. 1.49). The cyclohexanone is then converted to caprolactam via ammoximation with NH3/H202 and zeolite-catalysed Beckmann rearrangement as developed by Sumitomo (see earlier). 

Catalysis by Metal Ousters in Zeolites. There is an increasing interest in the use of metal clusters stabilized in zeolites. One objective of such work is to utilize the shape and size constraints inherent in these support materials to effect greater selectivities in typical metal-catalysed reactions. Much work has been concerned with carbon monoxide hydrogenation, and although the detailed nature of the supported metals so obtained is not well understood, there is clear evidence of chain limitation in the Fischer-Tropsch process with both RuY zeolites and with HY and NaY zeolites containing Fe3(CO)22- In the former case there is a drastic decline in chain-growth probability beyond C5- or C10-hydrocarbons depending upon the particle size of the ruthenium metal. 

Transition metal complexes, zeolites, biomimetic catelysts have been widely used for various oxidation reactions of industrial and environmental importance [1-3]. However, few heterogenized polymeric catalysts have also been applied for such purpose. Mild condition oxidation catalyzed by polymer anchored complexes is attractive because of reusability and selectivity of such catalysts. Earlier we have reported synthesis of cobalt and ruthenium-glycine complex catalysts and their application in olefin hydrogenation [4-5]. In present study, we report synthesis of the palladium-glycine complex on the surface of the styrene-divinylbenzene copolymer by sequential attachment of glycine and metal ions and investigation of oxidation of toluene to benzaldehyde which has been widely used as fine chemicals as well as an intermidiate in dyes and drugs. 

Silica-supported hydrogenation catalysts show less substrate selectivity than polystyrene-supported catalysts (Michalska and Webster, 1975 Ichikawa, 1976 Sinfelt, 1977). The rates of hydrogenation with silica-supported catalysts are high, although they are still lower than the equivalent homogeneous catalysts. It also appears that, unlike polystyrene, the reactive groups are confined only to the surface of silica. Ruthenium has also been immobilized in a zeolite matrix (Coughlan et al., 1977). 

HDS purposes, for example, ruthenium sulfide, but their high cost hampers their utilization in industrial processes. Phosphorus is also sometimes added to the alumina support to increase the acidity character. It hardly influences HDS catalytic properties [4-7] but has a beneficial effect on HDN enhancing the selectivity toward hydrogenolysis (removal of heteroelements) versus hydrogenation. Finally, more acidic supports (Si02-Al203, Y-zeolite) are preferred only for hydrocracking reactions. 

Mishra DK, Dabbawala AA, Park JJ, Jhung SH, Hwang J-S. Selective hydrogenation of D-gJueose to D-sorbitol over HY zeolite supported ruthenium nanoparticles catalysts. Catal Today 2014 232 99-107. 

Mishra DK, Dabbawala AA, Hwang J-S. Ruthenium nanoparticles supported on zeolite Y as an efficient catalyst for selective hydrogenation of xylose to xylitol. J Mol Catal A Chem 2013 376 63-70. 

---