Search

Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived α-hydroxyl acids into α-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supported on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH 3 on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components., Competing Interests: The authors declare no conflict of interest., (Copyright © 2018 the Author(s). Published by PNAS.)

The article in ChemCatChem discusses how Pd nanoparticles can enhance the reverse water-gas shift (RWGS) activity of Mn-substituted SrTiO3 in the Mars-van Krevelen (MvK) mechanism, with some contribution from the Langmuir-Hinshelwood mechanism. The MvK mechanism utilizes lattice oxygen and oxygen vacancies for the RWGS reaction, providing an alternative catalytic approach. The study emphasizes the effectiveness of combining metal and MvK-type catalysts to improve the efficiency of the RWGS reaction, offering valuable insights for catalytic strategies. [Extracted from the article]

In this work, the performances of Ag-loaded commercial Ga 2 O 3 (composite of α - and β -Ga 2 O 3), pure α -, and β -Ga 2 O 3 were examined for the photocatalytic conversion of CO 2 by H 2 O. Ag-loaded β -Ga 2 O 3 exhibited high selectivity for CO evolution if the proper loading methods and Ag nanoparticle contents were controlled. Using the chemical reduction method with NaH 2 PO 2 , 2 wt% Ag nanoparticles on β -Ga 2 O 3 produced CO with an activity of 201.3 μmol h−1 and selectivity of 83.5%. However, 8 wt% Ag nanoparticles were required to achieve the same selectivity when prepared using the photodeposition method. By varying the amount of Ag-loaded β -Ga 2 O 3 for the reaction, it was found that the selectivity toward CO evolution was largely dependent on the amounts of Ag-loaded β -Ga 2 O 3. The active sites where H 2 molecules are formed are poisoned by the oxygen reduction reaction (ORR) at high amounts of Ag-loaded β -Ga 2 O 3 , resulting in a high selectivity for CO evolution. [Display omitted] • Selectivity of CO over Ag-loaded Ga 2 O 3 depended on phase of Ga 2 O 3 very much. • Selectivity of CO over Ag-loaded Ga 2 O 3 depended on the loading method of Ag very much. • Oxygen reduction reaction (ORR) was probably critical to the selective evolution of CO over Ag-loaded Ga 2 O 3. [ABSTRACT FROM AUTHOR]

Heteronuclear Au-Pd nanoparticles were prepared and immobilized in the functionalized ionic liquid [C2OHmim][NTf2]. The structural and electronic properties of the nanoparticles were characterized by a range of techniques and the surface of the nanoparticles was found to be enriched in Pd. Moreover, the extent of Pd enrichment is easily controlled by varying the ratio of Au and Pd salts used in the synthesis. The heteronuclear nanoparticles were found to be effective catalysts in dehalogenation reactions with no activity observed for the pure Au nanoparticles and only limited activity for the pure Pd nanoparticles. The activity of the heteronuclear nanoparticles may be attributed to charge transfer from Pd to Au and consequently to more efficient reductive elimination. [ABSTRACT FROM AUTHOR]

The article presents information on nanocatalyst-stabilizer that enhances both catalytic activity and nanoparticle stability. It informs that nitrogen donor ligands based on pyridine, phenanthroline, and bipyridine (bipy) are effective nanocatalyst-stabilizers. It informs that a series of ruthenium-nanoparticle ( Rh NPs) is prepared with modified bipy ligand stabilizers.

Tetradentate thioacetyl porphyrin ligand ( 1) was synthesized to protect gold nanoparticles. 1-protected gold nanoparticles were characterized by UV-vis spectroscopy and XPS. Analysis by XPS showed that all of four thioacetyl groups of 1 were dissociated and bound to the surface of gold nanoparticles in thiolate form. The size of 1-protected gold nanoparticles ( GN:1) was controlled by thioacetyl group/HAuCl4 molar ratio and approached to 2 nm. Compared with a protecting ligand without porphyrin plane ( 2) or dodecanethiol, 1 can control the size of gold nanoparticles efficiently probably due to the tetradentate ligation effect. [ABSTRACT FROM AUTHOR]

Invited for this month's cover is the group of Dr. Katsutoshi Sato and Prof. Dr. Katsutoshi Nagaoka (Kyoto University) and collaborators at Oita and Kyushu Universities. The cover picture shows the proposed mechanism for automotive exhaust purification over a Pt–Co alloy nanoparticle catalyst with an extremely low Pt/Co molar ratio. In the catalyst, the isolated electron‐rich Pt atoms are present on the surface of the nanoparticles and play an important role in NOx capture and activation, which are important elementary steps in exhaust purification. Read the full text of the article at 10.1002/cplu.201800542. [ABSTRACT FROM AUTHOR]

A picture of ligand-coated nanoparticle is presented.

Bimetallic Au–Pd nanoparticles were prepared in the functionalized ionic liquid [C2OHmim][NTf2] by the thermal decomposition of Pd(OAc)2 and Au(OAc)3. The Au atoms are mostly located in the NP core, leaving the Pd atoms ENriched at the surface. Moreover, the Pd atoms are electropositive, which leads to high activity in catalytic dehalogENation reactions. The activity of the heteronuclear nanoparticles may be attributed to charge transfer from Pd to Au and consequENtly to more efficiENt reductive elimination. For more details, see the Full Paper by N. Yan et   al. on page   1227   ff. [ABSTRACT FROM AUTHOR]

Through in situ time-resolved X-ray absorption spectroscopy (XAS), we observed the dynamic behavior of the formation of two-dimensional low-coordinated Pt particles through reduction of PtO x particles by H 2 , which were under metal-support interaction (MSI) with the γ -Al 2 O 3 support. The relatively stabilized PtO x species were reduced below 373 K, and the interfacial PtO x species on γ -Al 2 O 3 surface were reduced above 373 K. The time-resolved Pt L 3 -edge XAS revealed that the morphology changed from three-dimensional PtO x particles to two-dimensional low-coordinated Pt particles during the in situ reduction of PtO x /Al 2 O 3 at 473 K, whereas at 373 K, the interfacial PtO x species remained after its reduction. This study demonstrated that in situ time-resolved XAS is one of the most definitive techniques to unveil the MSI effect during the reductive formation process of Pt nanoparticle catalysts loaded on γ -Al 2 O 3. [Display omitted] • Dynamic reduction behavior of supported PtO x particles was observed by in situ time-resolved XAS. • Reduction temperature of PtO x species on γ -Al 2 O 3 was higher than that on SiO 2. • Two-dimensional Pt particles formed on γ -Al 2 O 3 after 773 K reduction. • Interfacial PtO x species between γ -Al 2 O 3 was retained after low temperature reduction. [ABSTRACT FROM AUTHOR]

Surface decoration strategy is applied to design NP catalyst for the selective hydrogenolysis of C O bond without hydrogenating benzene ring, which is critical in lignin conversion under hydrogen treatment. The synthesized NiO x /Rh NPs are featured with Rh core whose surface is partially blocked by NiO x , which segregated the surface terrace zones into smaller segments, preventing the coordination and hydrogenation of benzene rings. Moreover, the NiO x shows no electronic modification to the Rh core, thereby the blockage effect of NiO x only inhibits the hydrogenation of benzene ring but not affect the hydrogenolysis activity of Rh core. [ABSTRACT FROM AUTHOR]

Nb 2 O 5 composed of nano-plate particles with the width of ∼35 nm and the length of ∼200 nm can be readily synthesized from the nanocrystalline niobium compound intercalating ethylene glycol obtained by the solvothermal reaction of niobium ethoxide in ethylene glycol. Thus-obtained Nb 2 O 5 nanoparticles have higher surface area and also higher catalytic activities of selective photooxidation of benzyl alcohol than Nb 2 O 5 synthesized from Nb 2 O 5 ·n H 2 O. We conclude that the crystallinity and surface area of Nb 2 O 5 are responsible to adsorption of the substrate, and the catalytic activities obviously correlate with the amount of substrate adsorbed on nanocrystalline Nb 2 O 5 . [ABSTRACT FROM AUTHOR]

Ag-loaded NaTaO 3 was used for the photocatalytic conversion of CO 2 using H 2 O as the electron donor, and the effect of the nanoparticle size, Ag loading, and crystal structure on the photocatalytic activity and CO selectivity were investigated. The sizes of the Ag nanoparticles could be tuned by controlling the photodeposition time, and relatively larger Ag nanoparticles were found to show higher CO selectivity. During the photocatalytic reaction, the initially polycrystalline Ag nanoparticles became single crystalline owing to the dissolution and redeposition of Ag, and the change in morphology reduced the CO selectivity. To solve this problem, Ag-Cr dual cocatalysts having a core–shell structure were developed. Subsequently, the locations and sizes of the Ag nanoparticles on the surfaces of NaTaO 3 were maintained during the reaction because of the protection by the chromium shell, thus providing stable and selective CO production via the photocatalytic conversion of CO 2 by H 2 O. [Display omitted] • Morphologies of Ag nanoparticles were effectively tuned by a series of strategies. • Large size and polycrystalline of Ag nanoparticles were proved to provide high selectivity toward CO evolution. • Stability was significantly improved by construction of core/shell of Ag/Cr dual cocatalyst. [ABSTRACT FROM AUTHOR]

Tin hydroxide nanoparticles-embedded montmorillonite (Sn-Mont) was prepared by the simple treatment of sodium ion-exchanged montmorillonite (Na-Mont) with aqueous SnCl 4 , the physical and chemical properties of which were investigated by N 2 adsorption, XRD, TG, TEM, 119 Sn-MAS-NMR, and XAFS analyses. It was revealed that Sn-Mont was composed of Sn(OH) 4 -based nanoparticles ( nano -Sn(OH) 4 ) of less than 3 nm in diameter surrounded by delaminated montmorillonite aluminosilicate unit layers. The arrangement of each aluminosilicate unit layer in the Sn-Mont is not laminated like that of the parent Na-Mont, but almost completely disordered to make a porous structure with a high surface area and a large pore volume that embraces the tin hydroxide-based nanoparticles. The intrinsic solid acid catalysis of Sn-Mont was used for the cyanotrimethylsilylation of benzophenone with cyanotrimethylsilane in an excellent yield, which was ascribed to the smooth reactant/product transfers in the micro/meso pores as well as the acidic property of the nano -Sn(OH) 4 enwrapped by the delaminated aluminosilicate unit layers. [ABSTRACT FROM AUTHOR]

A popcorn-like transformation of graphite oxide (GO; obtained by a modified Hummers method) into large-volume graphene oxide sheets (PGO) is achieved by heating differently oxidized graphite granules (quartz tube, 190-200 °C, 30-60 sec). [ABSTRACT FROM AUTHOR]