Kaoru Takeishi

Dimethyl ether and catalyst development for production from syngas

Dimethyl ether (DME) is manufactured from syngas using an indirect DME-synthesis method (two-step process), that consists of a methanol synthesis and dehydration process. The price of DME for this method depends on the methanol price; therefore, an economical process should be developed. A direct DME-synthesis method (one-step process) has been developed and the catalysts consist of methanol-synthesis catalysts and methanol-dehydration catalysts. Syngas, the raw material for DME, is produced from natural gas, coal and biomass for example. Currently, DME can be produced from biomass, so DME is in the spotlight as a potential biofuel. We have developed new catalysts and the Cu–Zn/Al2O3 catalysts prepared using the sol–gel methods, which are very effective for direct DME synthesis. Even if the raw gas is contaminated with oxygen, DME is effectively produced over these sol–gel catalysts. We hope that these catalysts will be widely used for economical DME synthesis from biomass, helping to solve environmental problems.

COMPARISON OF CARBON DIOXIDE AND CARBON MONOXIDE WITH RESPECT TO HYDROGENATION ON RANEY RUTHENIUM CATALYSTS

Abstract On Raney ruthenium catalysts pretreated with a mixed gas of water vapor and helium, the rate of hydrogenation of CO 2 was higher by three orders of magnitude than that of the hydrogenation of CO. However, the former reaction gives methane almost exclusively, while the latter reaction can give methanol. Since supported ruthenium catalysts usually catalyze both hydrogenations of CO and CO 2 with almost the same rate, Raney ruthenium catalysts were shown to be uniquely active for hydrogenation of CO 2 under the conditions studied here. The weight-based activity of methane production from CO 2 and hydrogen is much higher than that of the supported catalysts at 353–413 K and under 80 kPa. Methanol was also produced from CO 2 on Raney ruthenium catalysts, though the selectivity was negligibly lower than that from CO. With the mixtures of CO, CO 2 , and H 2 at 353 K and under 80 kPa, CO was preferentially hydrogenated, unless composition of CO was very small. Reaction mechanisms of COCO 2 hydrogenation are proposed.

Study of Raney ruthenium catalyst for methanol synthesis

Ruthenium (Ru) catalysts are known to dissociate the CO bond easily and to be effective for methanation or Fischer-Tropsch synthesis. However, several Ru systems yield oxygen-containing compounds. The reasons for these oxygenate synthesis activities have not been well discussed. Raney Ru catalysts have also been found active for methanol synthesis from CO and H{sub 2}. Methanol can be synthesized at a temperature as low as 353 K on Raney Ru. Fine particles of raney Ru powder catalyst can be suspended in a solution for the low-temperature methanol synthesis process in which a reduced Ni complex catalyst is supposed to be used. A new methanol process under low temperature and low pressure could save much of the energy required for the process, and new catalysts including Raney Ru should be studied in detail. The point of interest in the case of Raney Ru is why methanol is produced selectively, although Ru powder gives hydrocarbon exclusively. Here, the authors tried to identify the surface state of raney Ru that is related to methanol selectivity.