一國 伸之

TiO4-deposited mesoporous silica (TDMS) was studied as a water-tolerant solid Lewis acid catalyst. TDMS prepared by a simple postgrafting technique using Ti(i-pro)4 has a large BET surface area (ca. 450 m2 g-1) and ordered mesoporous structure. Ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray absorption near edge structure (XANES), and CO adsorption measurements with Fourier transform infrared (FTIR) spectroscopy revealed that isolated TiO 4 tetrahedra on TDMS have Lewis acidity, even in the presence of water. Lewis acid centers on TDMS exhibit higher catalytic performance for the hydride transfer of pyruvaldehyde to lactic acid and the Mukaiyama-aldol condensation of benzaldehyde with 1-trimethylsilyloxy-cyclohexene in water than that of conventional heterogeneous and homogeneous Lewis acids, including scandium(III) triflate (Sc(OTf)3), which also works even in water. The high catalytic performance of TDMS can be attributed to Lewis acid catalysis of isolated TiO4 tetrahedra in water. © 2014 American Chemical Society.

A very simple synthetic procedure was developed for the preparation of Ni-Sn alloy catalysts that were uti-lised for chemoselective hydrogenation of furfural, producing furfuryl alcohol almost exclusively. The mix-ture of nickel nanoparticles supported on aluminum hydroxide (R-Ni/AlOH) and a solution containing tin was treated under hydrothermal condition, producing the as prepared nickel-tin alloy supported on alumi-num hydroxide (Ni-Sn/AlOH). H2 treatment at range of temperature of 673-873 K for 1.5 h to the as pre-pared Ni-Sn/AlOH produced nanoporous Ni-Sn alloy catalysts. XRD patterns and SEM images revealed that the formation of Ni-Sn alloy of Ni3Sn and Ni3Sn2 phases and the transformation of crystalline gibbsite and bayerite into amorphous alumina were clearly observed after H2 treatment at 873 K. The formation of the Ni-Sn alloy may have played a key role in the enhancement of the chemoselectivity. © 2014 BCREC UNDIP.

メソポーラスシリカの骨格表面に形成された配位不飽和チタン種（4配位チタン）は水中で機能するルイス酸であり、水溶液内でのヒドリド移動反応および向山アルドール反応に高い触媒活性を示した。

A series of Pd-incorporated titanate catalysts (Pd/KSTO) were synthesized by the intercalation of Pd(NO3)(2) into layered potassium titanate (KTO), which proceeded via a cation-exchange reaction in molten salts. Perovskite phases of Pd/KSTO for catalysis were synthesized at 600 degrees C and above, whereas a lepidocrocite-type layered titanate structure, similar to that of the parent KTO, was retained when a lower temperature of 400 degrees C was used during synthesis. In both cases, the Pd species exists as divalent Pd. The synthesized Pd/KSTO catalysts were then applied to the liquid-phase oxidation of alcohols using molecular oxygen without any additives. The perovskite-type Pd/KSTO catalyst displayed superior activity when compared to that of the lepidocrocite-type, yielding a high turnover number of 800 in the aerobic oxidation of 1-phenylethanol with no loss of catalytic activity after three runs in catalyst recycling experiments.

Three types of Co-porphyrin complexes differing in their porphyrin-ring substituents and nonionic or cationic structure were intercalated into lithium taeniolite (LiTN) using a simple cation exchange method. All the intercalated catalysts displayed expanded clearance spaces (in the range of 0.30-0.51 nm) compared with that of the parent LiTN (0.24 nm). The catalysts were applied for the oxidative cleavage of isoeugenol to vanillin with molecular oxygen as the sole oxidant, and the reaction proceeded effectively under mild reaction conditions. The highest vanillin selectivity of 72% was obtained with CoTPyP/TN, which had the widest clearance space among the three Co-porphyrin catalysts. These intercalated catalysts showed high stability during oxidation, enabling their recycling for at least three runs. (c) 2012 Elsevier B.V. All rights reserved.

A novel method was applied for the preparation of Ni-Sn alloy catalysts that were utilized for chemoselective hydrogenation of unsaturated carbonyl compounds, producing unsaturated alcohols almost exclusively. The formation of the Ni-Sn alloy may have played a key role in the enhancement of the chemoselectivity.

The aerobic oxidation of alpha-hydroxy ketones into alpha-diketones catalyzed by CaO is compared with the same reaction catalyzed by other metal oxides. The catalytic activities of the various metal oxides were proportional to their surface basicities. The direct conversion of alpha-hydroxy ketones into quinoxalines via CaO-catalyzed aerobic oxidation followed by in situ reaction with 1,2-diaminoaromatics is also achieved. Various types of quinoxalines were synthesized in the presence of the CaO catalyst and molecular oxygen. It was also found that the CaO catalyst was reusable without any loss of its catalytic activity.

Monodisperse PVP-stabilized Pt nanoparticles (PtNPs) with an average diameter of 1.4 +/- 0.3 nm were efficiently produced via the complete reduction of Pt4+ ions by BH4- in a micromixer. Because of microfluidic mixing, hydrolytic decomposition of BH4- by the PtNPs formed in the initial stage of the reaction was suppressed, and hence, the PtNP yield was higher than that in the conventional batch mixing. The results of various spectroscopic analyses including EXAFS, FTIR of CO and XPS revealed that the microfluidically synthesized PtNPs were negatively charged and had a high population of edges and vertices on their surface. (C) 2011 Elsevier B. V. All rights reserved.

The structure of allophane heat-treated at 623, 773, and 973 K was characterized by Al-27 cross-polarization magic-angle-spinning (CP-MAS) and Al-27 multiple-quantum magic-angle-spinning (MQMAS) NMR. From these spectra, the structural change of allophane was observed over 623 K, i.e., the formation of five-coordinated Al from the original six-coordinated Al in allophane was confirmed after heat treatment. We concluded that Al atoms in the five-coordinated species have been formed by the OH elimination from six-coordinated Al in allophane. In addition, aluminosilicate layer deformation also took place to form silica and alumina thin layers separately. The results of P-31 MAS NMR studies indicate the Lewis acid sites rather than Bronsted acid sites increased with a rise in the treatment temperature.

A series of tris(β-diketonato)zirconium(IV) complexes was immobilized into a synthetic clay structure of Taeniolite by an ion-exchange method to generate organic/inorganic hybrid compounds. The hybrid compound served as a good catalyst for ring-opening reactions of methyl, ethyl, and dimethyl oxiranes with various alcohols to generate primary alkoxy alcohols in appreciable selectivity. This method describes a technique to immobilize cationic zirconium complexes without losing selectivity. © 2012 Published by LPPM ITB.

Inexpensive Ni-Sn-based alloy catalysts, both bulk and supported, exhibited high selectivity in the hydrogenation of a wide range of unsaturated carbonyl compounds and produced unsaturated alcohols almost exclusively. For the bulk Ni-Sn alloy catalysts, a relatively high reaction temperature of 453 K was required to achieve an efficient hydrogenation of C=O rather than C=C. The catalyst that consisted of the Ni-Sn alloy dispersed on TiO2 allowed a remarkable reduction of the reaction temperature to 383 K. Both the Ni3Sn2 and Ni3Sn alloy phases were found to be responsible for the enhancement of the chemoselectivity. The Ni-Sn alloy catalysts were reusable without any significant loss of selectivity.

Organogold clusters Au-54(C2Ph)(26) were selectively synthesized by reacting polymer-stabilized Au clusters (1.2 +/- 0.2 nm) with excess phenylacetylene in chloroform.

Clay-intercalated Sn catalysts were prepared by a conventional cation-exchange method and used for the Baeyer-Villiger oxidation of various ketones with hydrogen peroxide as an oxidant. The intercalation of monomeric Sn species into the clay interlayer was monitored by solid-state Li-7 MAS NMR. Solid-state Sn-119 MAS NMR and Sn K-edge XAFS analysis revealed that an isolated Sn species, such as [Sn-IV(OH)(x)(H2O)(5-x)]((4-x)+) (x = 0 3), was formed in the clay interlayers. Our clay-intercalated Sn catalysts showed extremely high performance in Bayer-Villiger oxidation and were also reusable without any significant loss of activity or selectivity.

Supported NiO nanocluster was prepared by using Ni colloid. Alkoxide stabilized Ni nanocluster supported on SiO₂ was oxidized by exposing to air at room temperature to produce NiO nanocluster. The cluster size of NiO was estimated by XAFS analysis. Supported NiO nanocluster thus prepared showed the catalytic activity for oxidative coupling of thiophenol, whereas the conventional impregnation NiO catalyst did not. Remarkable NiO cluster size dependency on activity for oxidative coupling of thiophenol was observed.

This article summarizes our recent research on the size-controlled synthesis of Au clusters stabilized by a polymer or supported by a solid, and related work reported by others. Small Au clusters have excellent, size-specific catalytic activity in the aerobic oxidation of alcohols and alkanes.

Semiconductor TiO2 particles loaded with WO3 (WO3/TiO2), synthesized by impregnation of tungstic acid followed by calcination, were used for photocatalytic oxidation of alcohols in water with molecular oxygen under irradiation at lambda > 350 nm. The WO3/TiO2 catalysts promote selective oxidation of alcohols to aldehydes and show higher catalytic activity than pure TiO2. In particular, a catalyst loading 7.6 wt% WO3 led to higher aldehyde selectivity than previously reported photocatalytic systems. The high aldehyde selectivity arises because subsequent photocatalytic decomposition of the formed aldehyde is suppressed on the catalyst. The TiO2 surface of the catalyst, which is active for oxidation, is partially coated by the WO3 layer, which leads to a decrease in the amount of formed aldehyde adsorbed on the TiO2 surface. This suppresses subsequent decomposition of the aldehyde on the TiO2 surface and results in high aldehyde selectivity. The WO3/TiO2 catalyst can selectively oxidize various aromatic alcohols and is reusable without loss of catalytic activity or selectivity.

The structure of imogolite treated at 623, 773, and 973 K was characterized by Al-27 MAS and Al-27 multiple-quantum magic-angle-spinning (MQMAS) NMR. For comparison, Al-27 NMR spectra of imogolites, allophanes, and kaolinite heated at 623, 773, and 973 K were acquired to investigate the structural change of these clay minerals. From these spectra, the structural change of imogolite has been observed at 623 K as well as in the case of allophane, while that of kaolinite has been demonstrated at a higher temperature of 773 K. The formation of five-coordinated Al from the original six-coordinated Al in imogolite after heat-treatment was confirmed as well as in the case of kaolinite and allophane. Furthermore it is found that the peaks for five- and four-coordinated Al of imogolite shifted to lower field and that their quadrupolar products (P-Q) increased with treated temperature. It can be concluded that the five- and four-coordinated Al species are generated from the decomposition of six-coordinated Al. The chemical shifts of all peaks above 623 K indicate the increase of the structural strain in the heat-treated imogolite and the formation of amorphous phases by the decomposition of the original tubular structure.

Typical biomass in Japan (bamboo, Japanese cedar and rice straw) were decomposed by using sulfonated allophane catalyst and hemicellulose in bamboo was preferentially decomposed to xylose. The maximum xylose yield was 40.9% (on the base of hemicellulose) in the reaction at 150 degrees C for 4.0 h. Mannose and xylose were mainly produced from Japanese cedar and arabinose was mainly produced from rice straw. (C) 2010 Elsevier B. V. All rights reserved.

An anionic D-valine-Pd(II) complex intercalated into an anion exchangeable Ni-Zn mixed basic salt (NiZn), which is classified as a layered hydroxy double salt, was synthesised in situ via a simple anion exchange procedure. A Bronsted basic PO(4)(3-) anion was also intercalated into the NiZn interlayer along with the anionic D-valine-Pd(II) complex. The Bronsted basic clay-Pd(II) nanocomposite catalysed the aerobic oxidation of a wide variety of alcohols to the corresponding aldehydes and ketones. In the aerobic oxidation of 1-phenylethanol, for example, a turnover number (TON) of 2000 based on Pd was achieved. During the aerobic alcohol oxidation, the D-valine-Pd(II) complex in the NiZn interlayer maintained its original monomeric Pd(II) structure due to the strong electrostatic interaction between the NiZn host and the anionic Pd(II) complex. This catalyst could be reused without loss of either catalytic activity or selectivity for the aerobic oxidation of alcohols.

The interlayer space of layered Ni-Zn mixed basic salt (NiZn) can be controlled precisely by the intercalation of various carboxylate anions with long alkyl chains via simple anion exchange. Expansion of interlayer space in the anion-exchanged NiZn depends on the alkyl chain lengths of pillar molecules. The butyrate anion-exchanged NiZn (C3H7COO-/NiZn) catalyst promoted effectively various base-catalyzed Knoevenagel reactions in water with remarkably high yield. This C3H7COO-/NiZn catalyst was reusable without any loss of catalytic activity or selectivity.

Bamboo biomass was hydrolyzed by using sulfonated allophane catalyst and hemicellulose in bamboo was preferentially decomposed to xylose and xylo-oligosaccharides in the range from 130 to 160 degrees C.

Au clusters smaller than 1.5 nm and stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) showed higher activity for aerobic oxidation of alcohol than those of larger size or stabilized by poly(allylamine) (PAA). X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy of adsorbed CO, and X-ray absorption near edge structure measurements revealed that the catalytically active Au clusters are negatively charged by electron donation from PVP, and the catalytic activity is enhanced with increasing electron density on the Au core. Based on similar observations of Au cluster anions in the gas phase, we propose that electron transfer from the anionic Au cores of Au:PVP into the LUMO (pi*) of O-2 generates superoxoor peroxo-like species, which plays a key role in the oxidation of alcohol. On the basis of these results, a simple principle is presented for the synthesis of Au oxidation catalysts stabilized by organic molecules.

SiO2-Supported Fe-NbN catalysts were prepared by temperature programmed reaction (TPR) method from Fe-Nb/SiO2 oxide precursor under a N-2-H-2 gas stream. As raising the intermediate temperature-maintaining (ITM) step temperature during the TPR, Fe species in the Fe-Nb/SiO2 catalyst was reduced to zero-valent, confirmed by Fe K-edge XAFS analysis. Although the Fe-Fe coordination number increased by elevating ITM temperature, the size of Fe cluster was still small. The Nb-N coordination number became larger, as higher the ITM temperature. The reduced Fe species effectively assisted the nitridation process of Nb.

An active Pd(II) catalyst supported on the Ni-Zn mixed basic salt (NiZn), which is classified by the anion-exchangeable layered hydroxy double salts, was synthesized by simple intercalation of the anionic Pd(II) hydroxyl complex. The divalent Pd species in the interlayer of NiZn maintained their original monomeric structure during the aerobic alcohol oxidation, due to the strong electrostatic interaction between the NiZn host and anionic Pd(II) species. This catalyst could be reused without any loss of the catalytic activity and selectivity in the aerobic alcohol oxidation.

Two series of palladium(II)-alkylamine (Pd(Me(2)NCn)(2)(OAc)(2), Me(2)NCn: N,N'-dimethylalkylamine, n = 4, 8, 12, and 16) and palladium(II) N,N'-dialkylamine (Pd(Cn(2)NH)(2)(OAc)(2), Cn(2)NH: N,N'-dialkylamine, n=4,8, and 12) were prepared. These homogeneous Pd complexes catalyzed the aerobic oxidation of wide range of alcohols into the corresponding aldehydes and ketones efficiently. For example, a benzylalcohol oxidation proceeded rapidly by means of Pd(Me(2)NCl2)(2)(OAc)(2) with an excellent turnover frequency of up to 96 h(-1). (C) 2007 Elsevier B.V. All rights reserved.

Lowering the carburization temperature of Ti-oxide into TiC down to 1173 K could be achieved by the addition of Co. Co-promoted TiC/Si-2 catalysts were prepared by the temperature programmed reaction (TPR) method. Co-Ti/SiO2 precursors were prepared by use of the successive impregnation method (sc) and the co-impregnation method (co). Samples were characterized by X-ray absorption fine structure (XAFS) measurements and X-ray diffraction (XRD) results. The carburization degree of TiC was affected by the method of Co addition. The carburization degree of sc Co-TiC/SiO2 was better than that of co Co-TiC/SiO2. The activity of thiophene hydrodesulfurization reaction at 693 K on sc Co-TiC/ SiO2 was higher than that on co Co-TiC/SiO2. The HDS activity was related to the carburization degree of TiC. (C) 2007 Elsevier B.V. All rights reserved.

Two series of zirconium beta-diketonates: tris(benzoylacetonato)zirconium (IV) perchlorate (3b) and tris(dibenzoylmethanato)zirconium (IV) perchlorate (3c) were synthesized. The complexes were synthesized by a reaction of zirconium tetrachloride with corresponding ligands in a 1:3 molar ratio, followed by a reaction with silver perchlorate. Characterization was by elemental analyses, UV-Vis, FTIR and H-1 NMR spectroscopies. The complexes were prospective to serve as Lewis acid catalysts for ring opening reactions of oxiranes with alcohols for synthesizing primary alkoxyalcohols. Previously reported tris(acetylacetonato)zirconium (IV) chloride (2a) was used as comparison. The effect of phenyl ring on ligand frame towards enhancement of Lewis acidity of zirconium is focused. Other factors, such as nucleophile strength of alcohols and alkyl substituent of oxiranes are also discussed. (c) 2005 Elsevier B.V. All rights reserved.

2-Methoxy-1-propanol has been selectively synthesized using clay supported tris(2,4-pentanedionato)zirconium(IV), prepared by facile ion-exchange process. The tris(2,4-pentanedionato)zirconium(IV) cation was synthesized by refluxing zirconium chloride with acetylacetone in chloroform. The heterogenized complex showed an increase in conversion rate and selectivity compared to the homogeneous one. Selectivity of 58% towards primary methoxypropanol was achieved under mild reaction condition. The clays selected as supporting materials were synthetic taeniolite and natural bentonite. It was observed that natural bentonite showed similar activity to synthetic taeniolite as a catalyst support. (C) 2004 Elsevier B.V. All rights reserved.

Novel nano-structured clays were synthesized from cation exchange reaction by the intercalation of rhodium complexes with ligand spacers into clay. Expansion of interlayer space of the modified clays depends on the spacers. A unique conformation of pillar complexes was detected by cross polarization magic angle spinning (CP MAS) NMR.

New solid acid catalysts have been synthesized by immobilization of zirconium complex into clay materials. The catalyst precursor was tris(acetylacetonato)zirconium(IV) cation ([Zr(acac)₃]⁺), which was synthesized by refluxing zirconium chloride with acetylacetone in chloroform. Characterization of the complex was carried out using FT-IR, ¹H NMR and CH analysis. Two types of clay, taeniolite and bentonite, possessing cation exchange capacity (C.E.C) of 268.2 meq/100 g and 82.0 meq/100 g, respectively were employed in the work as supporting materials. The ion complex was intercalated into interstitial layer spaces of the clays using facile ion-exchange method. The synthesized organic/inorganic hybrid was then characterized using UV-Vis, FT-IR and powder XRD. The catalysts demonstrated better catalytic performance for ring-opening and esterification reactions under mild conditions compared to previous works.

A palladium(II)-aminosilane complex supported on MCM-41 (Pd-AEAPSi/MCM (1)) was prepared by the complexation of palladium(II) acetate to 3-(2-aminoethyl)aminopropyl (AEAPSi) groups grafted on MCM-41. FT-IR and C-13 CP MAS NMR studies indicated that AEAPSi chelated to palladium(II) to form the Pd(II)-AEAPSi complex. Regioselective hydrogenation of dienes was carried out by the obtained 1 as a catalyst. Pd-AEAPSi/MCM exhibited remarkably high reaction rates for the dienes with a hydroxyl group such as geraniol and linalool, while for limonene without OH group the reaction rate, was notably low. The MCM-supported catalyst also showed noticeably high regioselectivity in the hydrogenation of dienes with OH group. These results indicate that the hydrophilic interaction between the MCM-41 surface and the substrates plays an important role in the rate-determining step. (C) 2002 Elsevier Science B.V. All rights reserved.