Isao Takahara

Promoting effects of CO2 on dehydrogenation of propane over a SiO2-supported Cr2O3 catalyst

Abstract The effects of carbon dioxide on the dehydrogenation of C 3 H 8 to produce C 3 H 6 were investigated over several Cr 2 O 3 catalysts supported on Al 2 O 3 , active carbon and SiO 2 . Carbon dioxide exerted promoting effects only on SiO 2 -supported Cr 2 O 3 catalysts. The promoting effects of carbon dioxide over a Cr 2 O 3 /SiO 2 catalyst were to enhance the yield of C 3 H 6 and to suppress the catalyst deactivation.

Production of olefins from ethanol by Fe-supported zeolite catalysts

Ethanol conversion to C3+ olefins over Fe/H-ZSM-5 catalysts was investigated. Fe is a non-toxic and cheap metal. C3+ olefins are useful not only as fuels but also chemicals. Fe catalysts are fully effective even in the presence of water in EtOH. Therefore, there is no need to remove water from water-containing ethanol, such as bio-ethanol. The initial selectivity of C3+ olefins was not affected by the kind of Fe source and calcination temperature significantly, except in the case of iron phosphate used as the iron source, which showed low C3+ olefins selectivity. In general, the selectivity of C3+ olefins was slightly decreased with time-on-stream. As causes of catalytic deactivation, carbon deposition on the catalyst and framework collapse of the zeolite support can be considered. However, in the cases of Fe2(SO4)3- and FeCl3-derived catalysts, calcined at 700 °C, the decrease in C3+ olefins selectivity could be suppressed. In general, selectivity of aromatics was decreased and selectivity of ethylene was increased with time-on-stream. Used catalyst can be regenerated by air treatment at 500 °C, but the degree of regeneration was dependent on the kind of iron starting materials and the calcination temperature. An FeCl3-based catalyst, calcined at 700 °C, and catalysts calcined at 900 °C (irrespective of iron source) can be almost completely regenerated, while Fe(NO3)3- or Fe2(SO4)3-based catalyst, calcined at 700 °C, cannot be completely regenerated by this treatment.

Dehydrogenation of Ethylbenzene to Styrene in the Presence of CO2 over Calcined Hydrotalcite-Like Compounds as Catalysts

Calcined hydrotalcite-like compounds were effective catalysts for the dehydrogenation of ethylbenzene in the presence of CO2 as an oxidant. X-ray diffraction patterns suggested that the catalyst components are distributed uniformly. The activity (areal rate) of Fe(1)/Al(2)/Zn(6) oxide catalyst (molar ratios in parentheses) was the highest among the catalysts tested.

Development of high performance Raney Cu-based catalysts for methanol synthesis from CO2 and H2

Catalytic hydrogenation of CO2 into methanol has been investigated over Raney Cu-based catalysts. The Raney catalysts leached in NaOH/ZnO solutions showed high activities and selectivities for methanol synthesis. The deposition of Zn on the surface of Cu particles increased the surface area and the specific activity of Raney Cu-M. Raney Cu-Zr developed was significantly more active than a ommercial catalyst.

Effects of Pretreatments of Cu/ZnO-Based Catalysts on Their Activities for the Water–Gas Shift Reaction

The effects of the pretreatments of Cu/ZnO-based catalysts prepared by a coprecipitation method on their activities for the water–gas shift reaction at 523K were investigated. The activity of a Cu/ZnO/ZrO2/Al2O3 catalyst for the water–gas shift reaction was less affected by calcination at temperatures ranging from 673-973K and by H2 treatment at 573 or 723K than that of a Cu/ZnO/Al2O3 catalyst. The catalyst activity could be correlated mainly to the Cu surface area of the catalyst.

Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions

The specific activity of Cu-based catalyst supported on Al2O3, ZrO2 or SiO2 for methanol synthesis and reverse water–gas shift reactions was improved by the addition of ZnO to the catalyst. On the other hand, the specific activity of the supported Cu-based catalyst for methanol steam reforming and water–gas shift reactions was not improved by the addition of ZnO to the catalyst.

Effects of Pre-Treatment of a Silica-Supported Gallium Oxide Catalyst with H2 on Its Catalytic Performance for Dehydrogenation of Propane

The pre-treatment of a silica-supported gallium oxide catalyst with H2 at 823 K increased the yield of aromatics and the selectivity to aromatics in the dehydrogenation of propane over the catalyst at 823 K. Gallium oxide in the catalyst was partially reduced with H2 at 823 K. NH3 desorption and DRIFTS studies on the gallium oxide catalyst suggest that the dehydrogenation of propane over a silica-supported gallium oxide catalyst would proceed in the following way: (1) the dehydrogenation of propane to produce propene would occur on Ga sites including Gaδ+–H sites and (2) the aromatization of propene to aromatics on Ga–O–H acid sites.

Hydrogen production by conversion of methane over nickel-supported USY-type zeolite catalysts

Hydrogen production by conversion of methane over Ni-supported zeolite catalysts was investigated, and Ni-supported USY-type zeolite (Si/Al2 = 14.0, 360) was found to have longer catalytic lifetime than Ni-supported silica (Cab-O-Sil) catalyst, which had been reported to have the longest catalytic lifetime for this reaction.

Production of Olefins and Propylene from Ethanol by Zr-Modified H-ZSM-5 Zeolite Catalysts

Ethanol conversion to C3+ olefins, especially propylene, using Zr-modified H-ZSM-5 catalysts was investigated. Zr-modification to H-ZSM-5 zeolite could improve the initial yield of C3+ olefins and propylene and could reduce the initial yield of ethylene. In general, catalysts exhibiting the higher initial yield of propylene showed the steeper decrease in propylene yield as the reaction proceeded. However, Zr-modification to H-ZSM-5 could depress the decrease in propylene yield for aqueous ethanol. As cause of catalytic deactivation, carbon deposition on catalyst and framework collapse of zeolite support can be considered. The addition of water to Zr-modified H-ZSM-5 catalyst could depress carbon deposition in some degree, and, as a result, the decrease in propylene yield could be depressed.

Dehydrogenation and Isomerization of n-Butane or Isobutane Over Cr Catalysts Supported on Zeolites

Dehydrogenation and isomerization of n-butane or isobutane into isobutene over Cr catalysts supported on zeolites were investigated. We found that Cr catalyst supported on H-SSZ-35-type zeolite, having one-dimensional cage-type channel structure, was very effective for this reaction and the yield of isobutene was 5.44% from n-butane and 9.57% from isobutane. In this reaction, it is suggested that dehydrogenation of butanes is accelerated by Cr2O3 loading, and solid acidity of the zeolite support favors isomerization.