Ketones from carboxylic acids over supported magnesium oxide and related catalysts

Silica-supported alkaline earth oxides revealed excellent activity to convert acetic acid selectively into acetone in a vapor-phase fixed-bed flow system. Acetone was obtained through the cyclic formation of alkaline earth acetate followed by decomposition. Magnesium oxide should be supported on the silica surface without formation of magnesium silicate, which was inactive for the present reaction. Attempted syntheses of benzophenone and acetophenone are also described.     

Synthesis,Characterization, and Application of Mesoporous Silica Functionalized with Alkyl‐Hydroperoxides

A variety of alkyl hydroperoxides such as tert‐butyl‐, tert‐octyl‐, 1‐cyclopentyl‐, 1‐cyclohexyl‐, 3,4‐disubstituted‐1‐cyclohexyl‐, n‐propyl, and n‐undecyl‐hydroperoxides have been functionalized onto ordered mesoporous silica, SBA‐15, from the corresponding covalently anchored synthons. All the tert‐hydroperoxides are prepared by autoxidation using molecular O₂ and an initiator, whereas other hydroperoxides are obtained by reaction with H₂O₂. For autoxidation, the use of a combination of an azoinitiator (AIBN) and N‐hydroxyphthalimide increased the hydroperoxide yield compared with using the azoinitiator alone. Synthons containing two or more tert‐ and sec‐hydrogens lead to higher peroxide yield compared to synthons with a single reactive site. Oxidation of Si–OH (silanol groups) with acidic H₂O₂ at low temperature produces Si–OOH. Reusability of these alkyl hydroperoxides is carried out by oxidation of alcohols obtained from the corresponding alkyl hydroperoxides using H₂O₂. Both the covalently anchored synthons and the resulting hydroperoxides are thoroughly characterized by powder X‐ray diffraction, ¹³C cross‐polarized magic angle spinning NMR, TG/DTA, Fourier transform IR spectroscopy, sorption, and surface area measurements. The quantification of the amount of alkyl hydroperoxide was carried out by iodometric titration using a thio solution. The hydroperoxides exhibit high activity for the epoxidation of styrene to styrene oxide and exhibit reasonably high efficiency for oxygen transfer.     

Nanoscale Membrane Strips for Benign Sensing of HgII Ions: A Route to Commercial Waste Treatments

The integration of actively‐functional receptors into nanoscale networks outperformed competent detection devices and other ion‐sensing designs. Synthesis of azo chromophores with long hydrophobic tails showed an ecofriendly sensing and an extreme selectivity for divalent mercury analytes. In order to tailor the tip to Hg^II ion‐sensing functionality, we manipulated the chromophores into nanoscale membrane discs, which led to small, easy‐to‐use optical sensor strips. The design of these hydrophobic probes into ordered pore‐based membranes transformed the ion‐sensing systems into smart, stable assemblies and portable laboratory assays. The nanosensor membrane strips with chemical and mechanical stability allowed for reversible, stable and reusable detectors without any structural damage, even under rigorous chemical treatment for several numbers of repeated cycles. The optical membrane strips provided Hg^II ion‐sensing recognition for both cost‐ and energy‐saving systems. Indeed, the synthetic strips proved to have an efficient ability for various analytical applications, targeting especially for on‐site and in situ chemical analyses, and for continuous monitoring of toxic Hg^II ions. On the proximity‐sensing front, these miniaturized nanomembrane strips can revolutionize the consumer and industrial market with the introduction of the probe surface‐mount naked‐eye ion‐sensor strips.     

Re-crystallization of silicalite-1 crystals from a crystalline layered silicate using nanosized seeds

Crystallization of silicalite-1 guided by nanosized seeds has been carried out from a crystalline layered silicate. The crystallization process was investigated by crystallinity of silicalite-1 obtained by hydrothermal treatments of the seeds/crystalline layered silicate mixtures with H₂O/Si ratios of 2, 6, and 12, respectively, at 423 K. Time courses of the crystallinity revealed the improved crystallization rate: the crystallization with the seeds was completed for 24 h although it spent more than 48 h without the seeds. SEM observation of the products showed well-crystallized particles with a coffin-like shape reflecting the crystal growth of the seeds. The particles sizes were 2-4 μm for the products by the treatment with the H₂O/Si ratio of 6 and 12, although the size was < 2 μm for the product with the H₂O/Si ratio of 2, suggesting that less H₂O content brings about the limited growth. As a result, we have succeeded to control the crystallization process of silicalite-1 from the crystalline layered silicate by impregnation of the seeds.     

High efficiency ester condensation using hydrophobic zeolite membranes

We successfully developed zeolite membranes with hydrophilic character, by choosing appropriate zeolites in terms of hydrophilicity and high acid tolerance. We evaluated thus developed membranes by their pervaporation (PV) performance, dehydration from acidic organic solvent. The zeolite membranes we developed, based on merlinoite (MER), chabazite (CHA) or phillipsite (PHI), are shown to exhibit stable dehydration performance, respectively. We successfully applied the membranes to the selective removal of water in an ester condensation reaction starting from a stoichiometric mixture of a carboxylic acid and an alcohol. The availability of pervaporation-assisted ester condensation reaction was validated by various kinds of combinations of carboxylic acid and alcohols, which implies the general availability of pervaporation-assisted process intensification by zeolite membranes. This paper was presented at the 11th Korea-Japan Symposium on Catatysis held at Seoul, Korea, May 21–24, 2007.     

Vacuum fluorescent displays: from single digits to colour TV

Physical principles and operational characteristics of various vacuum fluorescent displays are outlined. A VFD history and details of construction are also given. Displays of various resolutions for different applications are described up to a 256 × 256 dot matrix unit. Uniform brightness and precise switching operation are realized using improved anode and grid electrode construction, anode baseplate processing, and grid configuration and its fixing processes. A scrolling VFD and a MOS FET switching array VFD are introduced. The latter uses an integrated circuit of 241 × 246 elements to produce a picture 23 × 23 mm. Prospects for the development of VFDs are given in conclusion.     

Incorporation of tin in different types of pores in SBA-15: Synthesis, characterization and catalytic activity

Mesoporous Sn-SBA-15 has been synthesized by three different methods such as conventional hydrothermal route, using cocatalyst NH₄F and in the presence of organosilane precursor. All the materials are thoroughly characterized by powder X-ray diffraction (XRD), SEM, TEM, N₂ sorption and surface area measurements, diffuse-reflectance UV–visible and FTIR spectroscopy, TG–DTA and elemental analysis through ICP. Nitrogen adsorption data, XRD patterns, and TEM observations suggests that the textural properties are retained during the isomorphous substitution of silicon by tin. ICP chemical analysis indicates that tin can be substituted in the range of Si/Sn = 69–162. UV–visible spectra of samples synthesized by the cocatalytic approach exhibit unique absorption band at 213 nm characteristics of tin atom substituted in the smaller pores (2–3 nm) located inside the walls of mesopores. Further, an additional band at 224 nm can be assigned to Sn atoms located in the distorted tetrahedral position along the primary mesopores. In contrary, only one absorption band centered at 224 nm is observed for all the samples synthesized by conventional hydrothermal as well as in the presence of organosilane precursor. ¹⁹F NMR spectra confirmed (no signal) the absence of occluded F⁻ ions in the samples made with NH₄F. Observed high catalytic activity in Baeyer–Villiger oxidation and Meerwin–Pondorf–Verly reduction under the liquid-phase conditions suggest the incorporation of a portion of tin in the smaller pores for the Sn-SBA-15 materials synthesized through cocatalyst method.     

Heterogeneous catalytic activity of NiO-silica composites designated with cubic Pm3n cage nanostructures

The fabrication of nanomaterials with the active network sites has led to efficient transport and easier diffusion of guest species in the catalytic application. In this regard, the NiO-supported cage monoliths show evidence to act as effective catalysts toward the oxidation of organic pollutants. Here, the cage-like NiO-silica catalyst with large particle size, cage-like pores, and ordered cubic Pm3n (HOM-9) structures could be fabricated by a simple, in short period (5 min), and direct strategy in which microemulsion liquid crystalline phase of Brij 56 (C₁₆EO₁₀) surfactant was used as a template. Our synthetic strategy revealed that the nickel oxide nanoparticles were wrapped onto the pore surface matrices of the cubic Pm3n monoliths, indicating the simplicity and flexibility to control the geometry, morphology and dispersion of particles. No significant change in the cubic Pm3n (NiO/HOM-9) phase structures was evident by using this synthetic manipulation; however, high nickel contents up to Si/Ni ratios 1 were added to the phase composition domains. Results from the analysis techniques including XRD, N₂ isotherms, TEM, XPS, and EDX revealed that the NiO nanoparticles with irregular sizes might be embedded, to some extent, into the pore cavity, particularly with low content of NiO. In turn, with low Si/Ni ratios, The NiO crystallite particles underwent the anisotropic growth to larger sizes (15 nm) resulted from the aggregation effect, leading to the difficulty to be wrapped into the pore cavity. Practically important results were that the NiO-supported cage monoliths were used as effective catalysts for the oxidation of aminophenols in aqueous solution. However, among all NiO-supported amorphous and ordered silica materials, the NiO/HOM-9 catalyst with open, uniform pore-cage architectures, high surface area and large pore volumes allowed efficient adsorption and diffusion of aminophenols to the active site of NiO clusters, leading to high degree of conversion and reaction rate. On such heterogeneous catalytic systems, the reaction affinity of aminophenols was substantially affected by the structural feature of the catalysts, amount and degree of dispersion NiO particles onto the cubic cage pore surfaces, and the controlled temperature conditions.