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Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling [1]. The recycling of metal catalysts is important from economic and environmental points of view. When supported and bulk metal catalysts are used in liquid-phase organic reactions, there is a possibility that active metal species are leaching away into the liquid phases [2,3]. The metal leaching would make it difficult for the catalysts to maintain their desired initial performance for repeated batch reactions and during continuous ones. The metal leaching would also cause some undesired contamination of products by the metal species dissolved in the reaction mixture, and the separation of the metal contaminants would be required to purify the products. Therefore, various novel methods have been proposed so far to immobilize/stabilize the active metal species and to separate/collect/reuse the dissolved metal species [4]. In addition, knowledge on the heterogeneous and homogeneous natures of organic reactions using heterogeneous catalysts is important to discuss their reaction mechanisms and catalytically working active species. [...] Full article

Hydrogen production through steam reforming of ethanol was investigated with conventional supported nickel catalysts and a Ni-containing smectite-derived catalyst. The former is initially active, but significant catalyst deactivation occurs during the reaction due to carbon deposition. Side reactions of the decomposition of CO and CH₄ are the main reason for the catalyst deactivation, and these reactions can relatively be suppressed by the use of the Ni-containing smectite. The Ni-containing smectite-derived catalyst contains, after H₂ reduction, stable and active Ni nanocrystallites, and as a result, it shows a stable and high catalytic performance for the steam reforming of ethanol, producing H₂. Full article

Hydroformylation of cyclohexene was studied with a catalyst system ofRu₃(CO)₁₂ and LiCl using H₂ and CO₂ instead of CO in NMP. The influence of H₂ andCO₂ pressures on the total conversion and the product distribution was examined. It wasshown that increasing total pressure of H₂ and CO₂ promoted the reverse water gas shiftreaction and increased the yield of cyclohexanecarboxaldehyde. Its hydrogenation tocyclohexanemethanol was promoted with increasing H₂ pressure but suppressed withincreasing CO₂ pressure. Cyclohexane was also formed along with those products and thisdirect hydrogenation was suppressed with increasing CO₂ pressure. The roles of CO₂ as apromoter as well as a reactant were further examined by phase behavior observations andhigh pressure FTIR measurements. Full article

Several ionic liquids were applied as catalysts for the synthesis of cyclicurethanes from amino alcohols and pressurized CO2 in the presence of alkali metalcompounds as promoters. A comparative study was made for the catalytic performanceusing different ionic liquids, substrates, promoters, and pressures. The optimum catalyticsystem was BMIM-Br promoted by K₂CO₃, which, for 1-amino-2-propanol, produced cyclicurethane in 40% yield with a smaller yield of substituted cyclic urea and no oligomericbyproducts. For other amino alcohols, cyclic urethanes, cyclic ureas, and/or undesiredbyproducts were produced in different yields depending on the substrates used. Possiblereaction mechanisms are proposed. Full article