Sentaro Ozawa

Effect of vanadium on USY zeolite destruction in the presence of sodium ions and steam—studies by solid-state NMR

Abstract The effect of deposited vanadium on the thermal destruction of ultra stable Y (USY) zeolite in the presence of sodium ions and steam was investigated by solid-state NMR. When USY zeolite containing few sodium ions was heated in a dry atmosphere, SiOH groups, which corresponded to defect sites, and strong adsorption sites were formed by the dealumination. The former mainly caused an increase in the mean void volume per supercage and the latter originated from cationic extra framework Al in the supercages. Furthermore, in the dry atmosphere, the sodium ions inhibited the dealumination; the effect of the deposited vanadium on the structural change was not large. After the heat treatment in 100% steam, in case of USY zeolite containing few sodium ions, the crystallinity and the supercage structure hardly changed although the dealumination occurred remarkably. This process did not depend on the deposited vanadium. Data suggested that the heat treatment in 100% steam causes the framework stabilization. In case of USY zeolite containing a number of sodium ions, the synergistic effect between a few deposited vanadium ions and the sodium ions on the framework destruction in 100% steam was tremendous. We propose that the deposited vanadium functions as vanadic acid and catalyzes the conversion of the sodium ions into NaOH. Thus, an increase in the NaOH content promotes the ‘dissolution’ of the zeolite crystal, i.e. the framework destruction. In addition, when the sample containing both a few vanadium ions and a number of sodium ions was heated in 100% steam, the supercage was plugged partially. We believe that the blockage compounds in the supercage are sodium vanadates.

Applicability of MCM-41 as column packing in HPLC for the evaluation of aluminum species in partially neutralized aluminum solutions

Abstract Separation of Al ionic species in partially neutralized aluminum solution was studied using HPLC technique in order to elucidate the applicability of MCM-41 as promising column packing. Three peaks observed in HPCL chromatogram were assigned to mononuclear aluminum cation (Al(mono)), tridecameric polycation (Al(13)), and polynuclear precursors of Al(OH) 3 (Al(poly)) in the order of appearance. Overlapping of the peaks between Al(mono) and Al(13) was significant, however, these three Al species were quantitatively evaluated by using a curve fitting. A plausible mechanism for the present system does not obey the gel permeation chromatography principle, but it is suggested that the separation of Al species in the present system proceeds through the chemical interactions between the Al species and the surface of MCM-41. The structural changes in MCM-41 were observed due to the hydrolysis of silica framework of MCM-41 and the pressure during the HPLC operations.

The Adsorption of CHClF2 on NaY5.6 Zeolite

The adsorption of CHClF2 on NaY5.6 zeolite has been studied by measuring the H and F NMR of the adsorbed CHClF2, focusing in particular on the measurements of the chemical shift and longitudinal relaxation time, as well as the adsorption isotherm measurements. It is possible to determine the coordination structure of the CHClF2 adsorbed on NaY5.6 zeolite by measuring the adsorption amount dependence of the chemical shift. In addition, the motional activity of the adsorbed molecules in the super cage of the zeolite is discussed on the basis of observed longitudinal relaxation times for various adsorption amounts.

Transient Isotope Tracing of Methanation Over Nickel Catalyst

Transient isotope tracing of methanation over nickel catalyst was conducted in a gradientless recirculating reactor at low H 2 /CO ratios using 13 CO. Results indicate that hydrogenation of carbidic carbon and of chemisorbed hydrocarbon species is slower than the initial splitting of carbon monoxide.