Yoshinobu Yokomori

The crystal structure of analcime

Abstract Crystals of analcime were synthesized; the size was about 200 μm. The diffraction data were collected with both cubic system and trigonal system from the same crystal. The crystal parameters were completely cubic and the space group was Ia 3 d , but the R -factor only dropped to about 10%. The R -factor was lowered to 0.048 with the trigonal system. This result shows that every pseudo-cubic or average cubic analcime is really trigonal ( R 3¯). The unit cell size is a half of the cubic cell size, i.e. Na 8 [Al 8 Si 16 O 48 ] · 8H 2 O, a = 11.909(5) A, α = 109.51(3) °.

Structure of toluene6.4-ZSM-5 and the toluene disproportionation reaction on ZSM-5

The structure of a high-loading complex of ZSM-5 with 6.4 toluene molecules per unit cell has been determined by single-crystal X-ray diffraction. At least three kinds of toluene molecules were identified in the unit cell. Two disordered toluene molecules were located at the intersection of the straight and sinusoidal channels, the third in the sinusoidal channel. One (TOL1) of the two toluene orientations at the intersection was similar to that of p-dichlorobenzene at the intersection in high-loaded H-ZSM-5/p-xylene (hereafter 8PARA) and high-loaded H-ZSM-5/p-dichlorobenzene (hereafter 8PDCB) complexes, respectively. The other toluene orientation (TOL2) at the intersection was similar to those of p-xylene or p-dichlorobenzene at the intersection in the low-loaded p-dichlorobenzene complex (hereafter 2.6PDCB). A third toluene orientation (TOL3) existed in the sinusoidal channel; its orientation was similar to those of p-xylene and p-dichlorobenzene in the sinusoidal channels in 8PARA and 8PDCB complexes, respectively. If the occupancy of TOL2 at the intersection increases with temperature, TOL2 will connect with TOL3 in the sinusoidal channel and form the intermediate diphenylmethane.

Determining the structure of a benzene7.2-silicalite-1 zeolite using a single-crystal X-ray method.

An orthorhombic benzene-silicalite-1 single crystal was obtained from a monoclinic twin crystal, and the structure was determined by a single-crystal method for the first time.

Final storage of radioactive cesium by pollucite hydrothermal synthesis

The Fukushima nuclear accident has highlighted the importance of finding a better final storage method for radioactive cesium species. Cs is highly soluble in water, and can easily exchange with other alkali ions in zeolites or clays to form stable complexes. However, Cs+ is released from Cs+ complexes into water when surrounded by an excess of water. Pollucite may be the best final storage option for Cs+, but its typical synthesis requires heating to about 1200°C in air. Here, we show that the hydrothermal synthesis of pollucite can be completed at 300°C in three hours from any zeolite or clay. Furthermore, our procedure does not require ion exchange before synthesis. Radioactive Cs is usually found in complexes with clays. At that time, this method only requires calcium hydroxide, water, and three hours of hydrothermal synthesis, so the process is both inexpensive and practical for large-scale application. Pollucite is an analog of analcime zeolite, and contains a channel system 2.8 Å in diameter, which is formed by 6-oxygen rings. As the diameter of Cs+ is 3.34 Å and each Cs+ exists independently within a separate portion of the channel, Cs+ cannot exit the pollucite framework without breaking it.

m-chloroperbenzoic acid oxidation of 1,2-dithietes: First synthesis and characterization of 1,2-dithiete s-oxides and ethane-1,2-dithione S,S′-Dioxides (α-Disulfines)

Oxidation of 1,2-dithietes with 1 equiv of MCPBA gives the corresponding 1,2-dithiete S-oxides, while oxidation with more than 2 equiv of MCPBA affords three geometrical isomers of ethane-1,2-dithione S.S′-dioxides (α-disulfines) with opening of the four-membered ring.

Structure and Brønsted acid sites of ferrierite

Abstract The structure of natural ferrierite (from Kamloops Lake) is determined. The space group is not Immm but I222 (no. 23) and its R-factor is 8.6%. All 18 H2O molecules, Na+, and Mg2+ ions are successfully assigned [Mg1.6(Ca0.1Ba0.1Na1.6K0.4)Al5.8Si30.2O72·18H2O]. The angle of T(41)–O(5)–T(42) is 168° because the O5 site is not located on an inversion center in I222 space group. We also determined Bronsted acid sites. The Al atom distribution in the framework is also discussed and the T(1), T(2), and T(42) [or T(41)]-sites are the most probable sites.

Large-quantity single crystal synthesis of TPA-ZSM-5 using KOH as a mineralizer

Single crystals of TPA-ZSM-5 were synthesized using KOH as a mineralizer instead of NaOH. The size of the TPA-ZSM-5 crystals after 120 h was approximately 100 μm. When KOH was used, the quantity of TPA-ZSM-5 crystals formed was increased, and Al distribution in the crystal was uniform. The form and quality of these crystals were suitable for single crystal X-ray diffraction. Nucleation of the analcime by-product, which is formed in the presence of NaOH, is inhibited when KOH is used, because the potassium ion does not act as a template for the analcime structure. Instead, zeolite W was observed as a by-product. However, compared to analcime, the amount of zeolite W was lower, and it was easier to separate from TPA-ZSM-5. Thus, potassium ions play an important role in the production of large quantities of high-quality ZSM-5 with a uniform Al distribution.

Crystal structure of pollucite

Abstract The crystal structure of pollucite (ANA) (Cs,Na)AlSi2O6 is characterized by single-crystal X-ray diffractometry. The space group C2/c, monoclinic, is found to be the most probable space group for this mineral based on the systematic absences of reflections. Cesium ions or water molecules are disordered at the center of a channel and are slightly apart from the special position. This is the origin of symmetry breaking and the space group becomes lower from Ia-3d (analcime) to C2/c. Sodium ions or vacancies are located at the contact point of the channel. No ordering of aluminum is observed in the pollucite structure.

Regioselective synthesis of bicyclic diselenides by the reaction of phosphoniump ylides with elemental selenium

Selenabicyclo[2.2.1]heptenes reacted with elemental selenium to produce unusual bicyclic diselenides in 30-40% yield. The reaction of phosphonium ylides with excess of elemental selenium also afforded bicyclic diselenides in good yields. The reactions might proceed via biradical intermediates

Synthesis of large single crystals of CoAPO-5 molecular sieves

Abstract Large single crystals of CoAPO-5 have been synthesized using 2-diethylaminoethanol (DAE) as a template reagent, at the mole ratio of Al 2 O 3 :P 2 O 5 :(0.1–0.4)DAE:18H 2 O:0.045CoCl 2 , after aging at various temperatures (25, 50, 100, 150°C) for 1 day and heating hydrothermally at 200°C for 72 h. The optimum synthetic conditions for large single crystals of CoAPO-5 are a DAE ratio of 0.2–0.25 and an aging temperature of around 50°C. The average size of the crystals is 230 μm length and 75 μm width. The maximum size is 400 μm length and 150 μm width.