Inhibition of melanin production and promotion of collagen production by the extract of Kuji amber.

Kuji amber is fossilized tree resin of the Late Cretaceous in Japan. In this study, new biological activities of ethanol extract of Kuji amber (EtOH ext.) and supercritical carbon dioxide fluid extract of Kuji amber (scCO2 ext.) were examined. Both EtOH ext. and scCO2 ext. inhibited melanin production in B16 mouse melanoma cells and promoted collagen production in human skin fibroblast SF-TY cells. The scCO2 ext. had more potent activity than that of EtOH ext. and may depend on the efficiency of the extraction. The main new biologically active compound in Kuji amber, kujigamberol had no activities against melanin production, however, it promoted collagen production at low concentrations. A biologically active compound having a different structure, spirolactone norditerpenoid, showed both the inhibition activity against melanin production and the promotion activity of collagen production in a dose dependent manner. EtOH ext. and scCO2 ext., which include both kujigamberol and spirolactone norditerpenoid, have not only anti-allergy activity, but also inhibit melanin production and promote collagen production.

Platinum Nanosheets between Graphite Layers.

Two-dimensional platinum nanosheets were obtained by the hydrogen reduction of platinum tetrachloride intercalated between graphite layers, the latter was prepared by the treatment of the mixture of platinum tetrachloride and graphite powder under chlorine atmosphere. The size of platinum nanosheets was 1-3 nm in thickness with a width in the range of 5-300 nm. These nanosheets contain a number of hexagonal holes and edges with an angle of 120°. This review discusses the reduction and oxidation behavior of platinum species and structure of platinum nanosheets between graphite layers. The selective hydrogenation catalyzed by these platinum nanosheets entrapped between the graphite layers is also demonstrated.

Selective Hydrogenation of Cinnamaldehyde Over Platinum Nanosheets Intercalated Between Graphite Layers.

Platinum nanosheets between graphite layers were prepared by a thermal treatment of the mixture of platinum chloride (IV) and graphite powder under 0.3 MPa of chlorine at 723 K for 7 days, followed by the reduction under 40 kPa of hydrogen at 573 K for 1 h. Two-dimensional platinum metal nanosheets of 1-3 nm thickness and of 100-200 nm width were intercalated between graphite layers (Pt-GIC). The platinum nanosheets had a number of hexagonal holes and edges with angle of 120°. Liquid phase hydrogenation of cinnamaldehyde (CAL) was studied over Pt-GIC which was compared with that over platinum metal particles supported on graphite layers (Pt/Gmix). The conversion of cinnamaldehyde over Pt-GIC was lower than that over Pt/Gmix; however, the selectivity to cinnamyl alcohol (COL) was higher than that over Pt/Gmix. For similar CAL conversion of around 25% (in 60 min over Pt-GIC and 15 min over Pt/Gmix), the COL selectivities over 5 and 10 wt% Pt-GIC (56 and 54%) were higher than those over 5 and 10 wt% Pt/Gmix (33 and 19%).

Intramolecular dehydration of biomass-derived sugar alcohols in high-temperature water.

The intramolecular dehydration of biomass-derived sugar alcohols d-sorbitol, d-mannitol, galactitol, xylitol, ribitol, l-arabitol, erythritol, l-threitol, and dl-threitol was investigated in high-temperature water at 523-573 K without the addition of any acid catalysts. d-Sorbitol and d-mannitol were dehydrated into isosorbide and isomannide, respectively, as dianhydrohexitol products. Galactitol was dehydrated into anhydrogalactitols; however, the anhydrogalactitols could not be dehydrated into dianhydrogalactitol products because of the orientation of the hydroxyl groups at the C-3 and C-6 positions. Pentitols such as xylitol, ribitol, and l-arabitol were dehydrated into anhydropentitols. The dehydration rates of the pentitols containing hydroxyl groups in the trans form, which remained as hydroxyl groups in the product tetrahydrofuran, were larger than those containing hydroxyl groups in the cis form because of the structural hindrance caused by the hydroxyl groups in the cis form during the dehydration process. In the case of the tetritols, the dehydration of erythritol was slower than that of threitol, which could also be explained by the structural hindrance of the hydroxyl groups. The dehydration of l-threitol was faster than that of dl-threitol, which implies that molecular clusters were formed by hydrogen bonding between the sugar alcohols in water, which could be an important factor that affects the dehydration process.

Platinum Nanosheets Intercalated into Natural and Artificial Graphite Powders.

Insertion of sheet-type platinum particles (platinum nanosheets) between graphite layers was achieved by a thermal treatment of a mixture of platinum chloride (IV) and graphite powder (natural graphite or artificial graphite) under 0.3 MPa of chlorine at 723 K, followed by the treatment under 40 kPa of hydrogen pressure. Similar platinum nanosheets, which were 1-3 nm in thickness and 100-500 nm in width and had a number of hexagonal holes and edges with 120° angle, were formed between the layers of both natural graphite or artificial graphite; however, their location in the graphite layers depended on the type of graphite used. A number of platinum nanosheets were observed in the edge region of natural graphite particles which have flat surface. On the other hand, a number of platinum nanosheets were found inside and away from the edge of the artificial graphite particles especially in the vicinity of the cracks. Both the platinum nanosheet-containing artificial and natural graphite samples showed high selectivity to cinnamyl alcohol in cinnamaldehyde hydrogenation under supercritical carbon dioxide conditions, while spherical platinum particles, which were located on the surface of natural and artificial graphite, showed lower selectivity.

Kinetic analyses of intramolecular dehydration of hexitols in high-temperature water.

Intramolecular dehydration of the biomass-derived hexitols D-sorbitol, D-mannitol, and galactitol was investigated. These reactions were performed in high-temperature water at 523-573 K without added acid catalyst. The rate constants for the dehydration steps in the reaction networks were determined at various reaction temperatures, and the activation energies and pre-exponential factors were calculated from Arrhenius plots. The yield of each product was estimated as a function of reaction time and temperature using the calculated rate constants and activation energies. The maximum yield of each product from the dehydration reactions was predicted over a range of reaction time and temperature, allowing the selective production of these important platform chemicals.

Bond cleavage of lignin model compounds into aromatic monomers using supported metal catalysts in supercritical water.

More efficient use of lignin carbon is necessary for carbon-efficient utilization of lignocellulosic biomass. Conversion of lignin into valuable aromatic compounds requires the cleavage of C-O ether bonds and C-C bonds between lignin monomer units. The catalytic cleavage of C-O bonds is still challenging, and cleavage of C-C bonds is even more difficult. Here, we report cleavage of the aromatic C-O bonds in lignin model compounds using supported metal catalysts in supercritical water without adding hydrogen gas and without causing hydrogenation of the aromatic rings. The cleavage of the C-C bond in bibenzyl was also achieved with Rh/C as a catalyst. Use of this technique may greatly facilitate the conversion of lignin into valuable aromatic compounds.

Supercritical water decomposition of polyethylene samples for the determination of their trace cadmium content.

A novel pretreatment method has been developed for determination of toxic metals in plastic materials by their decomposition under supercritical water conditions. Particularly, quantitative analysis of cadmium in polyethylene has been demonstrated using inductively coupled plasma atomic emission spectrometry combined with supercritical water treatment. All the cadmium in a polyethylene sample was obtained as an aqueous solution by the treatment with supercritical water containing 12.4% of hydrogen peroxide at 673 K. Although a complete recovery of the aqueous solution from the reactors has not yet been attained, we verified that the present method was effective and promising for quantitative analysis of trace amounts of hazardous metals in plastic materials.

Catalytic ring hydrogenation of phenol under supercritical carbon dioxide.

A charcoal-supported rhodium catalyst was highly active for the ring hydrogenation of phenol and cresols under supercritical carbon dioxide.

Acetophenone hydrogenation over a Pd catalyst in the presence of H2O and CO2.

The addition of carbon dioxide and water enhances acetophenone hydrogenation activity over an activated carbon-supported palladium catalyst, and 1-phenylethanol can be easily recovered without distillation and neutralization. Two liquid phases (water and acetophenone) are indispensable for enhancement of the hydrogenation rate.

Gaseous fuel production from nonrecyclable paper wastes by using supported metal catalysts in high-temperature liquid water.

Paper wastes are used for the production of gaseous fuels over supported metal catalysts. The gasification of the nonrecyclable paper wastes, such as shredded documents and paper sludge, is carried out in high-temperature liquid water. The order of the catalytic activity for the gasification is found to be ruthenium>rhodium>>platinum>>palladium. A charcoal-supported ruthenium catalyst (Ru/C) is the most effective for the gasification of paper and cellulose. Paper wastes are gasified to a limited degree (32.6 carbon %) for 30 min in water at 523 K to produce methane and carbon dioxide, with a small amount of hydrogen. At 573 K, more complete gasification with almost 100 carbon % is achieved within 10 min in water. At 523 K, the gas yield of paper gasification over Ru/C is higher than that of cellulose powder. The gas yields are increased by ball-milling treatment of the recycled paper and cellulose powder. Printed paper wastes are also gasified at 523 K in water.