Hiroshi Kominami

Glycothermal synthesis of rare earth aluminium garnets

The reaction of a stoichiometric mixture of aluminium isopropoxide and yttrium acetate in 1,4-butanediol at 300 °C yielded crystalline yttrium aluminium garnet having an approximate particle size of 30 nm. No other phases were detected. Similarly, all the lanthanide elements from Nd to Lu gave essentially single-phase aluminium garnets. Samarium and europium aluminium garnets were also formed by this method, but the products contained corresponding lanthanide acetate oxide. The use of ethylene glycol instead of 1,4-butanediol afforded amorphous products.

Novel synthetic method for the catalytic use of thermally stable zirconia: thermal decomposition of zirconium alkoxides in organic media

Abstract Thermal treatment of zirconium n-propoxide in glycol at 300°C yielded microcrystalline tetragonal zirconia (ZrO2). The crystallite size of the product depended on the carbon number of the glycol and increased in the following order (carbon number of glycol): 2

Synthesis of large pore-size and large pore-volume aluminas by glycothermal treatment of aluminium alkoxide and subsequent calcination

Aluminas were prepared by calcination of the products obtained by glycothermal treatment of aluminium alkoxides, and their pore structures investigated by means of the nitrogen adsorption technique and mercury porosimetry. The product had a honeycomb-like texture which developed well with increasing crystallite size of the product. The crystallite size of the product was in turn controlled by the glycol used, and increased in the following order (carbon number of glycol): 2 < 3 < 6 ≪ 4. The honeycomb-like texture was preserved even after calcination. Because of the well-developed honeycomb-like texture, the alumina derived from the product obtained by the treatment of aluminium isopropoxide in 1,4-butanediol had quite large pore diameters (70 and 700 nm) and a large pore volume (2.4cm3g−1) with a sufficient surface area (184 m2g−1).

Formation of niobium double oxides by the glycothermal method

Abstract Thermal reaction of niobium alkoxide in organic media at 300°C yielded amorphous niobia, which maintained a surface area above 130 m2/g after calcination at 500°C. Niobium double oxides (LiNbO3, Zr6Nb2O17, CaNb2O6, CrNbO4, FeNbO4, ZnNb2O6 and R3NbO7 (R; rare earth)) were directly obtained by the reaction of niobium alkoxide with the corresponding metal alkoxide, acetate or acetylacetonate in 1,4-butanediol at 300°C. In some cases, amorphous product was obtained; however, double oxides (SrNb2O6, Co4Nb2O9, etc.) crystallized from the products at low temperatures.

Reactions of rare earth acetate hydrates in glycols at high temperatures

The reaction of rare earth acetate hydrate in ethylene glycol at 300°C yielded two novel crystalline products, one from La-Gd and the other from Tb-Lu and Y. IR and NMR spectra of these products suggested the presence of both acetate groups and ethylene glycol moieties, and it was concluded that these products are ethylene glycol complexes of rare earth acetate (hydroxide) oxide. On the other hand, the reaction of rare earth acetate hydrate in other glycols such as 1,3-propanediol and 1,4-butanediol yielded rare earth diacetate hydroxide, two morphs of rare earth acetate oxide and rare earth acetate dihydroxide, depending on the ionic size of rare earth element, but the glycol complexes were not formed. In all cases, acetate groups of rare earth acetate were not completely eliminated from the coordination sites of the rare earth element by the reaction in glycols but the reaction in ethylene glycol could liberate the acetate groups more easily than other glycols because of high coordination ability of ethylene glycol.

Solvothermal synthesis of large surface area zirconia

The reaction of zirconium n-propoxide in glycol at 300°C yielded microcrystalline tetragonal zirconia (ZrO2). The crystallite size of the product depended on the carbon number of the glycol and increased in the following order (carbon number of glycol): 2<6<4, which suggested that the heterolytic cleavage of O-C bond of gylcoxide formed by transesterification is the prime factor for the formation of the product. In toluene, zirconium isopropoxide also gave tetragonal zirconia at 300°C, and zirconium tert-butoxide decomposed at 200°C yielding amorphous zirconia, while zirconium n-propoxide was stable at 300°C. These results suggest that the reaction in toluene depends on the structure of the alkyl group of the alkoxides. Thus-obtained tetragonal zirconias maintained large surface areas (90–160 m2/g) even after calcination at 500°C.