Shu-ichi Niwa

Selective hydrogenation of oleic acid to 9-octadecen-1-ol: Catalyst preparation and optimum reaction conditions

A new catalyst, ruthenium-tin-alumina is found to selectively hydrogenate oleic acid to 9-octadecen-1-ol (oleyl + elaidyl alcohol) at low pressure with high yield. Catalyst preparation methods, catalyst raw materials and activation conditions have a significant effect on the activity of the catalyst. The optimum atomic ratio of ruthenium to tin is about 1:2. Catalyst prepared by an improved sol-gel method shows higher activity and selectivity than catalysts prepared by impregnation and coprecipitation methods. Chloride is found to have a negative effect on catalytic activity. The best catalyst is prepared from chloride-free ruthenium and tin raw materials. Under the optimum reaction conditions of 250°C and 5.6 MPa, the selectivities for 9-octadecen-1-ol and total alcohol (9-octadecen-1-ol + stearyl alcohol) formation are 80.9% and 97%, respectively, at a conversion of 81.3%.

Thermal behaviour of alumina from aluminium alkoxide reacted with complexing agent

Several aluminas were synthesized from aluminium isopropoxide using some organic complexing agents as solvents. The difference in the properties, especially specific surface area, of the aluminas obtained was investigated. The thermal behaviour of the aluminas depended on the complexing abilities of the solvents used. The transmission electron microscopic studies confirmed that size and shape of the gel particles were controlled by the complexing agents.

Influence of solid-state transformation time on the nucleation and growth of silicalite 1 prepared from layered silicate

The nucleation and crystal growth of silicalite 1 precursors synthesized by solid-state transformation were studied using X-ray diffraction, thermal analysis, IR spectroscopy,29Si and 13C NMR and electron microscopy. Silicalite 1 was obtained after 16 h at 130 °C in a closed glass ampoule. Comparison with hydrothermal synthesis showed that the characterization of the precursors presents some similarities, however, nucleation and crystal growth were much shorter for solid-state transformation. 29Si NMR showed that nucleation started during the first stage (cation exchange) for solid-state transformation, but only during the second stage for solid-state transformation. It was also observed that the major changes occurred during the beginning of crystal growth for solid-state transformation but during nucleation for hydrothermal synthesis. The results were explained by the fact that the starting materials were completely different: single layered silicate for solid-state transformation and colloidal silica for hydrothermal synthesis.

Effect of the type of preparation on the properties of titania/silicas

Abstract Titania/silicas were prepared by four methods: (i) complexing-agent assisted sol—gel, (ii) coprecipitation, (iii) hydrogel kneading and (iv) xerogel kneading. The properties of these titania/silicas were investigated by thermal gravimetry and differential thermal analysis (TG-DTA) X-ray powder diffraction, solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), ammonia temperature programmed desorption (TPD) and nitrogen adsorption. Of the four methods, the complexing-agent assisted sol—gel method gave the most homogeneous titania/silicas. Their TiOSi bond formation, acidities, and specific surface areas depended on completing agents used in the preparations and the Ti/Si ratios of raw materials. In contrast, the kneading titania/silicas were heterogeneous and their properties did not depend on the Ti/Si ratio. The dependence of properties of coprecipitated titania/silicas on their Ti/Si ratio were intermediate between those of complexing-agent assisted sol—gel and kneading.

Effect of preparation methods on properties of alumina/titanias

Alumina/titanias have been prepared by three methods: complexing-agent-assisted sol–gel; coprecipitation; and hydrogel kneading. The relationship between the preparation methods and the properties of the alumina/titanias was investigated by thermal gravimetry and differential thermal analysis (TG–DTA), X-ray powder diffraction, laser Raman spectroscopy, solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR), ammonia temperature-programmed desorption (TPD) and nitrogen adsorption. Of the three preparation methods, the complexing-agent-assisted sol–gel method gave the most homogeneous alumina/titanias, and their acidities and specific surface areas depended on complexing agents used in the preparation and the Ti:Al ratios of the raw materials. In contrast, kneading alumina/titanias were relatively heterogeneous and their properties did not depend on the Ti:Al ratio. Regarding the dependences of properties of alumina/titanias on the Ti:Al ratio, coprecipitation alumina/titanias are intermediate between complexing-agent-assisted sol–gel and kneading ones.

Properties of Sol-Gel Derived Ru/Cu/Si02 Catalysts and Role of Water in the Selective Hydrogenation of Benzene to Cyclohexene with the Catalysts

Abstract Ru/Cu/SiO 2 catalysts were prepared using sol-gel and impregnation methods, and activated with hydrogen before and after calcination. The four types of the catalysts obtained were characterized by TEM, XRD, XPS, and adsorption of hydrogen, benzene, cyclohexene and water. From the results, it was found that the catalysts which have fine metal particles and low adsorptive abilities for hydrogen and cyclohexene, for example, lwt%Ru/O. lwt%Cu/SiO 2 prepared by sol-gel method and activated before Calcination, are suitable for the production of cyclohexene. It was also concluded that the roles of water in the partial hydrogenation of benzene with the Ru/Cu/SiO 2 catalyst are to expel and isolate cyclohexene from the catalyst surface.

Materials chemistry communications. New preparation method for highly siliceous zeolite films

Highly siliceous zeolite films of silicalite and ZSM-5 were prepared by a new preparation method using cellulose moulding.

Catalytic activity of a zeolite disc synthesized through solid-state reactions

Abstract ZSM-5 zeolite in a disc-shaped form was synthesized by a new method in which reactions occurred in the solid state. The proton form of the zeolite was prepared by ion exchange of the sodium ions of the disc-shaped pellet in hydrochloric acid solution. The catalyst prepared was characterized by SEM, thermogravimetry, nitrogen adsorption and ammonia TPD. High p -xylene selectivity was observed for the new disc-shaped ZSM-5 zeolite catalyst in the alkylation of toluene with methanol. This catalytic feature was attributed to the inherent character of the zeolite, since its structure consisted of inter-grown individual HZSM-5 crystals forming secondary mesopores which promote the high gas permeability of the zeolite disc.

Hydrogenation of 9-octadecenoic acid by Ru-Sn-Al2O3 catalysts : effects of catalyst preparation method

Evaluation of the method of preparation and the sequence of metal incorporation onto the catalyst showed that they had profound effects on the catalytic behavior of Ru−Sn−Al2O3 catalysts used in the selective hydrogenation of oleic acid to 9-octadecen-1-ol. When Ru was loaded first onto the support and then followed by Sn, the catalyst had lower activity but greater ability to preserve the unsaturated bond. On the other hand, when the sequence of loading was reversed, the behavior of the catalyst changed correspondingly, i.e., the catalyst showed higher activity but poorer ability to protect the unsaturated bond. The metal particles incorporatedvia the sol-gel method were finely and evenly distributed on the support. As such, they were more readily shielded by the second metal particles that were subsequently incorporatedvia the impregnation process. When both metals were loadedvia the sol-gel process, the best result was obtained with superior performance in activity, as well as selectivity in the preservation of double bond.

Preparation and Properties of the Catalysts by A Chemical Mixing Procedure

Various solid catalysts were prepared by a chemical mixing technique, composed of four steps (complexing, gelation, drying and activation) and characterized by the preparation of a homogeneous solution containing catalyst precursors and the uniform coagulation of the solution through hydrolysis. The mixed-oxides prepared by the technique were expected to be more homogeneous than those prepared by kneading and coprecipitation methods. The chemically mixed ruthenium catalysts were much more effective for the partial hydrogenation of benzene to cyclohexene without any assistance from poisons. Furthermore, the chemically mixed alumina-silicas showed much higher activities for the conversion of methanol to hydrocarbons than the kneaded alumina-silica.