The utilization of 5-(hydroxymethyl)furfural (HMF) for the large-scale production of essential chemicals has been largely limited by the formation of solid humin as a byproduct, which prevents the operation of stepwise batch-type and continuous flow-type processes. The reaction of HMF with 1,3-propanediol produces an HMF acetal derivative that exhibits excellent thermal stability. Aerobic oxidation of the HMF acetal with a CeO -supported Au catalyst and Na CO in water gives a 90-95 % yield of furan 2,5-dicarboxylic acid, an increasingly important commodity chemical for the biorenewables industry, from concentrated solutions (10-20 wt %) without humin formation. The six-membered acetal ring suppresses thermal decomposition and self-polymerization of HMF in concentrated solutions. Kinetic studies supported by DFT calculations identify two crucial steps in the reaction mechanism, that is, the partial hydrolysis of the acetal into 5-formyl-2-furan carboxylic acid involving OH and Lewis acid sites on CeO , and subsequent oxidative dehydrogenation of the in situ generated hemiacetal involving Au nanoparticles. These results represent a significant advance over the current state of the art, overcoming an inherent limitation of the oxidation of HMF to an important monomer for biopolymer production.

Süße Sache: Pt‐ oder Ru‐Komplexe auf anorganischen Oxiden sind sehr aktive Katalysatoren der Umwandlung von Cellulose in Zuckeralkohole (hauptsächlich Sorbitol) in Wasser unter Wasserstoffdruck; außerdem können die Katalysatoren mehrmals wiederverwendet werden. Glucose entsteht in niedrigen Ausbeuten, was dafür spricht, dass die Pt‐ oder Ru‐Oxide difunktionelle Katalysatoren der Cellulosehydrolyse und der anschließenden Reduktion zu Zuckeralkoholen sind.

The purpose of this study was to evaluate the short-term µTBS (Micro-tensile bond strength) and microscopic (SEM and TEM) observation of four recent adhesives. One adhesive was an experimental step-less 1-step system (LLB-2, Tokuyama Dental), which is an all-in-one system without the light-curing step in the application process. The other two were self-adhering light-cured flowable composite resin systems FLD (Fusio Liquid Dentin, Pentron Clinical Technologies) and VF (Vertise Flow Dental Restorative Materials, Kerr Corporation), which combine all the bonding steps together. A 2-step self-etching system MG (Clearfil MegaBond, Kuarary Medical) was employed as the control group in this study. The µTBS of MG was the highest (79.0 MPa) followed by that of LLB-2 (63.1 MPa), FLD (23.6 MPa), and VF (13.1 MPa). The microscopic observations showed that MG and LLB-2 had an approximately 20 µm and 5 µm adhesive layer respectively, without bubble or gap-formation at the resin-dentin interface, which were found in FLD and VF.

No abstract

Ethylene is a gaseous volatile organic compound (VOC) that works as a plant hormone to inhibit or promote plant growth. Ethylene released from fruits, vegetables, and flowers can accelerate aging and spoiling of plants even in refrigerators at low temperature. Consequently, the removal of trace amounts of ethylene at low temperature (ca. 0 8C) is imperative.Previously, biotechnological materials, such as soil bacteria, dry biobeds, and biofilters were applied for removal of ethylene. [1][2][3][4] However, high production costs and inefficiency in removing trace amounts of ethylene were drawbacks of these methods. Several photocatalysts have also been used, [5][6][7][8] but this resulted in limited application because of the more complicated working conditions required.Many attempts have been made by Hao et al. to develop gold catalysts supported on Co 3 O 4 for the removal of ethylene at low temperature. First, 2 wt % Au/Co 3 O 4 catalyst prepared by a deposition-precipitation method showed only 7.4 % conversion of ethylene at 20 8C from a relatively low concentration (1050 ppm). [9] A more active catalyst, 2.5 wt % Au nanoparticles supported on mesoporous Co 3 O 4 , was later prepared by a nanocasting method, but the catalytic activity was still insufficient for complete removal of trace (50 ppm) ethylene at 0 8C despite the complicated preparation method. [10] Gold nanoparticles supported on Co 3 O 4 rods recently prepared by a hydrothermal method solved the timeconsuming problem of catalyst preparation; however, the method afforded no significant improvement in catalytic activity. [11] Therefore, further catalyst screening is still necessary to find sufficiently active catalysts to remove low concentrations of ethylene.Herein, we report the catalytic performance of Pt nanoparticles supported on mesoporous silica MCM-41 for ethylene oxidation under low-temperature conditions. This study has revealed the influence of metals (Pt, Pd, Au, and Ag) and supports (MCM-41, SiO 2 , Al 2 O 3 , ZrO 2 , and TiO 2 ) on the catalytic performance. The Pt nanoparticles supported on MCM-41 exhibited the highest activity and demonstrated excellent durability in prolonged reaction time or recycle use.The conversion of 50 ppm ethylene over 1 wt % Pt/MCM-41 at 0 8C was over 99.8 %. To our knowledge, this is the highest conversion of ethylene oxidation at low temperature reported to date.All of the catalysts were prepared by using a typical wet impregnation method. Characterization of the catalysts was conducted by various physicochemical methods. The structural parameters are summarized in Table 1 and Table S1 (in the Supporting Information). The small-angle X-ray diffraction (XRD) patterns of MCM-41 and 5 wt % Pt/MCM-41 (Figure S1a) are consistent with the literature, [12] and peaks appeared at (100), (110), and (200), a characteristic of a typical two-dimensional hexagonal structure of mesopores in MCM-41. This result indicates that the mesoporous structure remains unchanged after the incorporation of Pt nanoparticles. However, n...