Showing papers by "Atsushi Takahashi published in 2010"
TL;DR: In this article, a phosphorus-modified ZSM-5 zeolites were used to transform ethanol to propylene and the selectivity of propylene formation depended strongly on the phosphorus content in the zeolite; the highest propylene yield (32%) was observed over H-ZSM-1(80) modified with phosphorus at a P/Al molar ratio of 0.5.
Abstract: In this work, phosphorus-modified ZSM-5 zeolites were used to transform ethanol to propylene. The selectivity of propylene formation depended strongly on the phosphorus content in the zeolites; the highest propylene yield (32%) was observed over H-ZSM-5(80) modified with phosphorus at a P/Al molar ratio of 0.5. The enhancement of propylene selectivity with increasing phosphorus content was attributed to reduction of strong acid sites on the H-ZSM-5. Modification of the zeolite with phosphorous also improved the material's catalytic stability.
123 citations
TL;DR: In this paper, the catalytic performance of protonated ZSM-5 type zeolites containing alkaline earth metals was investigated in the conversion of ethanol to light olefins, especially propylene (C3H6).
Abstract: Protonated ZSM-5 type zeolites containing alkaline earth metals (M-HZSM-5, M: alkaline earth metal) were prepared under various synthesis conditions and their catalytic performance in the conversion of ethanol to light olefins, especially propylene (C3H6), were investigated in detail. The C3H6 yield and the catalytic stability were strongly dependent on M/Al and SiO2/Al2O3 ratios as well as on the reaction conditions. Among M-HZSM-5 zeolites, the Sr-HZSM-5 zeolite having a SiO2/Al2O3 ratio of 184 and a Sr/Al ratio of 0.1 exhibited the highest C3H6 yield of ca. 32 C-% and a high catalytic stability at the reaction condition of 500 °C and W/F value of 0.03 gcat/ml/min.
80 citations
TL;DR: In this paper, the Pt/ZrO 2 /SiO 2 mixed oxides with different ratios (2:1 to 4:1) were prepared by a deposition-precipitation method from zirconium hydroxide and colloidal silica and used as supports for platinum nano particles.
Abstract: ZrO 2 /SiO 2 mixed oxides with different ratios (2:1 to 4:1) were prepared by a deposition–precipitation method from zirconium hydroxide and colloidal silica and used as supports for platinum nano-particles. The synthesized catalysts along with Pt/ZrO 2 reference materials were tested for CH 4 reforming with CO 2 at a high temperature of 1073 K and at high space velocity. Very high reforming activity was observed for the Pt/ZrO 2 /SiO 2 (4:1) sample among all the prepared catalysts. The effect of zirconia to silica ratio on the physico-chemical properties that determine the catalytic activity has been investigated characterizing all the catalysts after calcination, reduction as well as after reaction with several techniques. From X-ray diffraction patterns, BET and H 2 chemisorption measurements, X-ray photoelectron and FTIR spectra, the better catalytic properties of the Pt/ZrO 2 /SiO 2 (4:1) sample have been explained by higher Pt dispersion due to the absence of remaining free silica and the presence of amorphous ZrSiO 4 in higher amount. Additionally, a better thermal stability of the prepared ZrO 2 /SiO 2 supports compared to ZrO 2 was evidenced after ageing at 1073 K for 16 h in particular for the ratio 4:1. It also underlines the interest of the preparation method.
49 citations
TL;DR: In this article, MFI-type zeolite catalysts with various Si/Al2 ratios (73, 97, 128, 176, 207) were prepared by hydrothermal synthesis under atmospheric pressure.
Abstract: Industrial demand for propylene is increasing. Alternative sources of propylene other than petroleum are of wide interest. The catalytic transformation of bioethanol is a promising avenue for the production of propylene. However, the reaction mechanism and the nature of active sites on the catalyst remained unclear. In this work, MFI-type zeolite catalysts with various Si/Al2 ratios (73, 97, 128, 176, 207) were prepared by hydrothermal synthesis under atmospheric pressure. We characterized these MFI catalysts by BET surface area measurements, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, temperature programmed desorption of ammonia, and 27Al MAS NMR to understand the effect of the Si/Al2 ratio. The ethanol conversion reaction was systematically investigated using these catalysts according to the contact time and reaction temperature. The conversion of ethanol yielded similar product distributions over these catalysts at different contact times, indicating that the product distribution has no relationship with the Si/Al2 ratio. Also, the propylene production rates per acidic site of these catalysts were similar. These results strongly imply that the acidic sites of the different MFI-type zeolite catalysts have the same nature, as well as the same reactivity. The catalytic activity was proportional to the number of acidic sites.
46 citations
Patent•
04 Nov 2010
TL;DR: In this paper, a method for manufacturing gold nano clusters of smaller than 2 nm in an average cluster size and using them as catalysts for an oxidation reaction and a hydrogenation reaction was proposed.
Abstract: PROBLEM TO BE SOLVED: To establish a method for manufacturing gold nano clusters of smaller than 2 nm in an average cluster size and to provide gold nano clusters usable as catalysts for an oxidation reaction and a hydrogenation reaction, etc. of which high selectivity is required. SOLUTION: The gold nano clusters of equal to or smaller than 2 nm in an average cluster size can be prepared by using an arc plasma vapor deposition method, which are carried on the surface of metal oxide comprising titania, alumina, silica, zirconia or ceria, or these composite oxides. The composite of the obtained gold nano clusters and the metal oxides can be used as the catalyst of oxidation reaction or hydrogenation reaction. COPYRIGHT: (C)2011,JPO&INPIT
5 citations