Mei-Yu Huang

Catalytic hydrogenation of aromatic nitro compounds by non-noble metal complexes of chitosan

Silica-supported mono-metal (such as Ni, Cu) complexes and mixed metal (such as Cu/Zn, Cu/Cr) complexes of chitosan have been prepared. It is found that these non-noble metal complexes could be used as efficient catalysts for the hydrogenation of aromatic nitro compounds. The effects of type of metal, reaction temperature and pressure, solvent, nitrogen/metal molar ratio in the complex catalysts on the yields from nitrobenzene to aniline have been examined. It was also found that catalysts are active for the catalytic hydrogenation of other aromatic nitro compounds such as 2-nitroanisole, 2-nitroaniline, 2-nitrotoluene and 1-chloro-4-nitrobenzene.

Catalytic hydrogenation behaviours of palladium complexes of chitosan-polyacrylic acid and chitosan-polymethacrylic acid

Abstract Silica-supported palladium complexes of the bipolymers chitosan-polyacrylic acid and chitosan-polymethachrylic acid were shown to have a higher activity in the proper molar ratio of monomeric units of chitosan to polyacrylic acid or polymethacrylic acid in the hydrogenation of nitrobenzene to aniline or acrylic acid to propionic acid at room temperature and under atmospheric pressure. Such palladium complexes of bipolymers are very active, selective and stable in the hydrogenation. In the hydrogenation of acrylic acid to propionic acid, the turnover numbers were > 14 000 in 4–6 h, and no by-products were observed.

Liquid-phase oxidation of alcohols by dioxygen using oxide-supported platinum catalysts

Abstract Alkaline earth oxide (MgO, CaO, BaO)-supported platinum catalysts displayed higher activity in the oxidation of alcohols such as 1-butanol, 1-hexanol, cyclopentanol and cyclohexanol under mild conditions than neutral oxide (SiO2, Al2O3)-supported platinum catalysts. MgOPt catalyst could be recycled in the oxidation without noticeable decrease of its activity. Further investigation of MgOPt and SiO2Pt by TEM and XPS showed that lower valent (mainly Pt(O)) smaller, and more homogeneously dispersed platinum particles tended to form on MgO than on SiO2. This indicated that the oxide in the oxide—Pt catalysts played an important role in controlling the dispersion and valence of platinum, consequently strongly influencing the activity of oxide-Pt catalysts.

Aerobic epoxidation of cyclic alkenes catalyzed by poly(vinylbenzyl)acetylacetonato cobalt(II complex

Poly(vinylbenzyl)acetylacetonato complex of cobalt is an effective and stable catalyst for the epoxidation of cycloalkenes with molecular oxygen under 25°C with i-butyraldehyde as the sacrificial reductant. The acetylacetone ligand/Co mole ratio, the reaction time, and the strain and electronic nature of cycloalkenes all affect the conversions of alkenes and selectivities to the corresponding epoxides. The catalyst can be recycled at least seven times without loss of its activity.

Magnesium oxide-supported polytitazane cobalt(III) complex for catalytic epoxidation of α-pinene with molecular oxygen

SummaryMagnesium oxide-supported polytitazane cobalt complex has been prepared and found to be a very effective catalyst for the epoxidation of α-pinene in the presence of an aldehyde as a reductant. XPS data show that the high valent cobalt(III) was stabilized by the mutidentate nitrogen ligand of polytitazane. The α-pinene oxide can be obtained in 96.0% yield with 96.6% selectivity at 25°C under an atmospheric pressure of molecular oxygen. Isobutyraldehyde is an effective reductant and only 1.2 equivalent of isobutyraldehyde to α-pinene is needed to ensure high yield of α-pinene oxide. The catalyst is also very stable and can be reused at least eight times without loss of its activity.

Hydroformylation of styrene to 2-phenylpropionaldehyde catalyzed by silica-supported poly-γ-aminopropylsiloxane-ruthenium-cobalt bimetallic complex

Abstract Selective hydroformylation of styrene to iso-aldehyde, 2-phenylpropionaldehyde in higher than 90% yield has been achieved catalyzed by silica-supported poly-γ-aminopropylsiloxane-ruthenium-cobalt bimetallic complex catalysts (SiNH 2 RuCo) in the presence of acetic acid. The Ru Co mole ratio, the amount of acetic acid and total pressure greatly influenced the reaction. The catalyst was stable and could be used repeatedly without any remarkable changes in activity and selectivity.

Hydrogenation of aldehydes and ketones catalyzed by zeolite-supported polyvinyl alcohol–amino acid–platinum complex

Zeolite-supported polyvinyl alcohol–amino acid (alanine, proline, glutamine, leucine or lysine)–platinum complexes (Zeo-PVA-AA-Pt) have been prepared by a very simple method and have been found to catalyze the hydrogenation of some aldehydes and ketones such as hexanal, benzaldehyde, cyclohexanone, 2-pentanone, methyl acetoacetate, ethyl acetoacetate, 2,4-pentandione to 1-hexanol, cyclohexylmethanol, cyclohexanol, 2-pentanol, methyl 3-hydroxybutyrate, ethyl 3-hydroxybutyrate and 2,4-pentandiol, respectively, at 55°C and under an atmospheric hydrogen pressure. In several cases, the yield or selectivity amounted to 100%. Such catalysts were very stable in the hydrogenation, and could be reused several times without any remarkable change in the catalytic activity. The catalytic activity was greatly affected by molar ratios of monomer unit of polyvinyl alcohol to amino acid, amino acid to Pt in the complex, and the nature of the amino acids and solvent used in hydrogenation. In the hydrogenation of methyl acetoacetate to methyl 3-hydroxybutyrate, a small amount of optical active product was obtained. This result suggested that more effective catalysts for asymmetric hydrogenation may be found from such simple polymer–amino acid–metal complexes by selecting the proper amino acid and polymer. Copyright

Magnesium Oxide-Supported Polytitazane Copper(II) Complex Catalyzed Aerobic Baeyer-Villiger Oxidation of Ketones and Cyclohexanol in the Presence of Benzaldehyde

Abstract Magnesium oxide-supported polytitazane copper complex is prepared and found to be a very effective catalyst for the Baeyer-Villiger oxidation of ketones and cyclohexanol in the presence of an aldehyde as a reductant under an atmospheric pressure of oxygen at room temperature. The δ-valerolactone and δ-caprolactone can be obtained in high than 97% yield. The reactivity of ketones decreases as fellow: cycloketones > acetophenone > aliphatic ketone. It is found that cyclohexanol is selectively oxidized to e-caprolactone in 77% yield and 89% selectivity by the above combined catalytic system. The catalyst is also very stable and can be reused at least six times without loss of its activity.

Polycondensation catalyzed by polyvinyl pyrrolidone-supported metal complexes

Some polyvinyl pyrrolidone–metal complexes (abbreviated as PVP-M) have been prepared by the reaction of polyvinyl pyrrolidone with metal acetate, and have been characterized by its performance toward the polycondensation of glutaric acid and glycols to produce polyester oligomers under mild conditions. The molecular weight of the oligomers was influenced by the type of metal, the molar ratio of two metals (M1/M2), the molar ratio of the ligand atom to metal (N/M) in the complex, and the kind of glycol used in the reaction. Copyright

Isdmerization of Olefins Catalyzed by Silica-Polyalumazine-Palladium Complexes

Abstract A silica-supported polyalumazane-palladium complex (abbreviated Al-N-Pd) has been found to be an effective isomerization catalyst for olefins. It can catalyze pentene-1 to pentene-2 in 72% yield and hexene-1 to hexene-2 and hexene-3 in yields of 88 and 12%, respectively, at 0°C and under atmospheric pressure. In investigating the solvent effects on the isomerization of hexene-1 catalyzed by Al-N-Pd, it was found that alcohol probably plays a role as promoter. Kinetic studies on the isomerization of hexene-1 indicate that the rate equation is r = kCpd C hexene-1, where k = 0.82 ± 0.07 (mol Pd-min)−1. Al-N-Pd is very stable in air and relatively stable during the reaction. The turnover numbers in the isomerization of hexene-1 amount to above 1 000. These results show that the inorganic polymer-supported metal complex Al-N-Pd is more active, selective, and stable than other catalysts for isomerization of α-olefins.