Analysis of Acidic Properties of Zeolitic and Non-Zeolitic Solid Acid Catalysts Using Temperature-Programmed Desorption of Ammonia

A method of ammonia temperature-programmed desorption (TPD) for analysis of acidic property of a solid was improved by introduction of a water vapor treatment method and development of a theory for calculation of ammonia adsorption heat from the TPD profile. The improved method was applied to various solid acid catalysts to establish relationships between the acidic properties and catalytic performances for various acid-catalyzed reactions. Here, examples of the applications to some important acid catalysts are reviewed. The exact analysis of acidic property of Y zeolite and its change by such modifications as steaming and ethylenediaminetetraacetic acid (EDTA) treatment gave a new interpretation on the generation of alkane (paraffin) cracking activity on an ultra stable Y (USY) zeolite. The surface density and strength of acid sites on WO₃/ZrO₂ and SO₄ ^2–/ZrO₂ catalysts were determined, and their relations with catalytic activities for Friedel–Crafts type alkylation and skeletal isomerization of alkane were found.     

A deprotection procedure using SO3H silica gel to remove non-silyl protecting groups

Protecting groups are indispensable in organic synthesis and there is a great need for a variety of deprotection methods. Here, we investigated the scope of the application of a deprotection procedure using SO₃H silica gel, which we have previously reported as a desilylation procedure. Under these conditions, -OMOM, -OSEM, -OTHP, and -OAc groups and dimethyl acetal were cleaved. Pivaloyloxy, benzyloxy and methoxy carbonyl groups remained intact and selective deprotection of TBS groups in the presence of other protecting groups was accomplished. We succeeded in cleaving an acetyl group on a secondary alcohol in a highly polar nortropine derivative. Our findings here provide another deprotection option and would be helpful in the synthesis of multifunctional compounds.     

High-resolution solid-state NMR study of the crystallization of hydroxysodalite

The crystallization of hydroxysodalite has been studied by means of high-resolution solid-state NMR of ²⁹Si, ²⁷Al and ²³Na nuclei with the magic-angle sample-spinning technique. Information has been obtained on the crystallization process, and the mechanism is discussed.     

1,3-Dipolar cycloaddition reaction of benzodiazinium and naphthyridinium N-imines with acetylenic esters

1,3-Dipolar cycloaddition of N-imines derived from mono-N-amino salts of phthalazines, 2-phenylquinoxaline, 1,5- and 1,8-naphthyridines with dimethyl acetylenedicarboxylate: and methyl propiolate resulted in the formation of new tricyclic: heterocyclic ring systems with bridgehead nitrogen.     

Synthesis and catalytic activity of gold-silver binary nanoparticles stabilized by PAMAM dendrimer

Gold-silver binary nanoparticles, which feed atomic ratios of gold to silver were 3:1, 1:1, and 1:3, were prepared. These particles were stabilized by amine-terminated (generation (G) 3.0 and 5.0) and carboxyl-terminated (G 3.5 and 5.5) poly(amidoamine) (PAMAM) dendrimers in water. UV-vis spectra indicate that the particles are not mere physical mixtures of monometallic particles or core/shell type but alloy. According to transmission electron microscope (TEM) observation, the mean diameters of the particles were 7-10 nm for silver particles and 3-4 nm for both gold and alloy particles, respectively. Catalytic activities for reduction of p-nitrophenol were investigated by monitoring the absorbance at 400 nm during the reaction. They were proportional to the feed ratio of gold in the particles and showed a maximum at the ratio of Au:Ag=3:1.     

Decomposition kinetics of 2-propylphenol in supercritical water

The decomposition of 2-propylphenol (PP) at 673 K and a water density of 0–0.5 g cm⁻³ yielded 2-isopropylphenol (IPP), phenol and 2-cresol. Gas products were methane, carbon dioxide, ethylene and propene. The decomposition was found to occur through rearrangement and alkylation, that is, (1) rearrangement of the propyl functional group from PP to IPP, (2) dealkylation of PP to phenol, (3) dealkylation of PP to 2-cresol. The decomposition probably occurred by a free-radical mechanism. The reaction rate constants of each pathway were determined and it was found that these were invariant over all the water densities studied at the given temperature.     

Thallium(III) salt-induced olefinic cyclization of o-prenylphenols

Olefinic cyclization of $\text{o}$-prenylphenols ($\text{1}$), ($\text{4}$) and ($\text{6}$) induced by thallium(III) trifluoroacetate was performed.     

On the rate of soapless emulsion polymerization of methyl methacrylate

The rate of soapless emulsion polymerization is studied experimentally and theoretically. The soapless emulsion polymerization of methyl methacrylate (MMA) in water is carried out with potassium persulfate as initiator. It is shown that the soapless emulsion polymerization of MMA gives different time-conversion and time-average molecular weight curves from those of bulk and emulsion polymerizations. Comparing the experimental results with those of the other types of polymerization, features of the rate of soapless emulsion polymerization are discussed and a kinetic model is proposed to apply the soapless emulsion polymerization of MMA in water. The experimental results can be well expressed by this model.     

Construction and characterization of alkoxy-derived (Y,Yb)MnO<Subscript>3</Subscript>/HfO<Subscript>2</Subscript>/Si structures for FeRAM application

(Y,Yb)MnO₃ and HfO₂ films were prepared using alkoxy-derived precursor solutions, and (Y,Yb)MnO₃/HfO₂/Si structures were fabricated. The thickness, surface uniformity and crystallinity of the HfO₂ film affect the crystallization of Y_0.5Yb_0.5MnO₃ films. The degree of c-axis orientation and crystallinity of the Y_0.5Yb_0.5MnO₃ films were changed with preparation conditions of HfO₂ films. It was difficult to obtain Y_0.5Yb_0.5MnO₃ films with high crystallinity and high degree of c-axis orientation on the HfO₂ films thinner than 10 nm. The degree of c-axis orientation and crystallinity of the Y_0.5Yb_0.5MnO₃ films on HfO₂ films were improved by using diluted HfO₂ precursor solution in the case of 10 nm-thick HfO₂ film. Following this, the capacitance-voltage (C-V) characteristics were improved.