Effect of sol–gel conditions on BET surface area,pore volume,mean pore radius,palladium dispersion,palladium particle size,and catalytic CO oxidation activity of Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> cryogels

Porous and homogeneous palladium-alumina cryogels were synthesized from aluminium sec-butoxide (ASB) and palladium nitrate through one-pot sol–gel processing in an aqueous system and subsequent freeze drying. In order to optimize the sol–gel conditions so that higher catalytic oxidation activity could be acquired after high temperatures heating, effects of H₂O/ASB, HNO₃/ASB, ethylenediamine/Pd, and urea/ASB ratios on BET surface area, pore volume, mean pore radius, Pd dispersion, Pd diameter, and catalytic CO oxidation activity of the Pd/Al₂O₃ cryogels were examined. It was revealed that optimized molar ratios were ASB:H₂O:HNO₃:urea?=?1:76:0.26:0.29 and ethylenediamine:Pd?=?3.4:1, at the ratios of which higher Pd dispersion and more superior catalytic activity were obtained. It was suggested that maintenance of as large BET surface area and pore volume as possible even after the heating was important to obtain high Pd dispersion, which consequently brought about superior catalytic activity. It was also suggested that porosity of the cryogel also played an important role in suppressing the sintering of palladium. The palladium-alumina cryogel prepared under the optimized sol–gel conditions was compared with corresponding commercial catalyst in regard to Pd particle size, Pd dispersion, PdO reducibility, catalytic CO oxidation activity. It was shown, after heating the cryogel at 800 °C for 5 h, that finer palladium particles with ca. 3.5 nm diameter were dispersed throughout alumina support with higher dispersion (ca. 32%), which was primarily responsible for higher catalytic oxidation activity on the cryogel.     

Infrared and near-infrared spectral evidence for water clustering in highly hydrated poly(methyl methacrylate)

First, we developed quantitative analytical methods of water in poly(methyl methacrylate) (PMMA) in various hydrated states by utilizing the first combination and OH stretching bands of water at about 5240 and 3630 cm-1, respectively. Next, we investigated how the state of water depended on its quantity or the mole ratio of water to the CO (denoted as the H2O/CO ratio), which only interacts with water in PMMA, mainly on the basis of the band feature of the OH stretching bands. Below the H2O/CO ratio of 0.032, the contained water, which shows two clear bands at about 3630 and 3550 cm-1, is hydrogen-bonded to two C=O groups as C=O::H-O-H::O=C to form "the hydration core". The spectrum of the water that exceeds the ratio in question shows one broader band only, the frequency of which shifts downward with the increasing hydration. From detailed analysis of the behavior of the OH stretching and combination bands in relation to the H2O/CO ratio, we have concluded that the water that exceeds the hydration ratio becomes mobile to aggregate or "cluster" around hydrated sites rather than nonhydrated ones in the PMMA matrix, although the latter is much larger in population.     

Development of sulfur tolerant catalysts for the synthesis of high quality transportation fuels

In this paper, results concerning the development of sulfur tolerant catalysts for Fischer–Tropsch synthesis (FTS), C₂₊ alcohol synthesis, methanol and/or DME synthesis are presented. In the FTS reaction on Fe using H₂-rich syngas such as the biomass-derived syngas, the composition of catalyst pretreatment gas and the addition of MnO on Fe had strong impacts on its sulfur resistance as well as activity. Especially the Fe/MnO catalyst pretreated with CO showed a much lower deactivation rate and a higher FTS activity than an Fe/Cu/K catalyst in the presence of H₂S. For C₂₊ alcohol synthesis a novel preparation method was developed for a highly active MoS₂-based catalyst that is well known as the sulfur tolerant catalyst. Besides some metal sulfides were found to show higher CO hydrogenation activities than MoS₂. In particular, both Rh and Pd sulfides were active and selective for the methanol synthesis. Modified Pd sulfide catalyst, i.e. sulfided Ca/Pd/SiO₂, showed an activity that was about 60% of that of a Cu/ZnO/Al₂O₃ catalyst in the absence of H₂S. This catalyst preserved 35% of the initial activity even in the presence of H₂S. The sulfided Ca/Pd/SiO₂ mixed with γ-Al₂O₃ was also available for in situ DME synthesis in the presence of H₂S.     

Degradation of Azo Compounds by Aeromonas hydrophila var. 24B

A bacterium which has the ability to degrade azo dyes has been isolated from a polluted environment and identified as Aeromonas hydrophilia. The specificity of azo dyes to the bacterium was examined. p-Acetamidoazobenzene, p-aminoazobenzene, acetanilide, aniline and p-phenylenediamine, which are produced as metabolites, were also isolated.