Katsutoshi Nagaoka

Influence of the reduction temperature on catalytic activity of Co/TiO2 (anatase-type) for high pressure dry reforming of methane

Abstract 0.5xa0wt.% Co/TiO 2 was prepared by incipient wetness impregnation with Co(NO 3 ) 2 ·6H 2 O and TiO 2 , which contains only anatase as crystal structure. The influence of reduction temperature (973–1223xa0K) on the catalytic activity of the 0.5xa0wt.% Co/TiO 2 was investigated for the CH 4 /CO 2 reaction under 2.0xa0MPa mainly at a space velocity (SV) of 6000xa0mlxa0g −1 xa0h −1 . Co/TiO 2 reduced below 1123xa0K lost its activity completely at the beginning of the reaction. The results of TPO revealed that large amounts of coke (≧2.9xa0wt.% carbon for 24xa0h) were deposited on the catalysts during the CH 4 /CO 2 reaction. On the other hand, Co/TiO 2 reduced at and above 1123xa0K kept relatively stable activity for 24xa0h and did not show significant amounts of deposited coke (≦0.25xa0wt.% carbon). The natures causing different catalytic behavior among the catalysts were discussed with the results of TEM, XRD, and TPR. In addition, slow deactivation of the Co/TiO 2 reduced at 1123xa0K, probably due to the oxidation of the metallic cobalt, was inhibited by the addition of small amount of ruthenium (Ru/Co=0.05) and it was found that the strong resistance to the coking of the Co/TiO 2 reduced at 1123xa0K was retained after the addition of ruthenium.

Titania supported ruthenium as a coking-resistant catalyst for high pressure dry reforming of methane

Abstract Support (SiO2, Al2O3, MgO, and TiO2) effects on catalytic behavior of Ru catalysts for the CH4/CO2 reforming were investigated under 2 (industrial condition) and 0.1 MPa at 1023 K. The order of the catalytic activity of the four catalysts investigated was dependent on the reaction pressure. High coking rate was observed at high pressure. 2 wt % Ru / TiO 2 , showing a low coking extent, is a promising candidate for industrial use.

Activation mechanism of methane-derived coke (CHx) by CO2 during dry reforming of methane – comparison for Pt/Al2O3 and Pt/ZrO2

The reaction of methane-derived coke (CHx: intermediate of the reforming reaction and also a source of coke deposition) with CO2 was studied on supported Pt catalysts in relation with CO2 reforming of methane. Temperature-programmed hydrogenation (TPH) was performed to investigate the reactivity of coke deposition after the catalyst was exposed to CH4/He at 1070 K. Coke on Pt/Al2O3 could be hydrogenated around 873 K, while for Pt/ZrO2 this was above 1073 K. The results indicate that the reactivity of coke with hydrogen was higher on Pt/Al2O3 than on Pt/ZrO2, which was different from the reactivity of coke towards CO2. Thus, the reactivity of CO2 was studied and compared on these catalysts by several technics. The amount of CO evolution was measured during CO2 flow at 1070 and 875 K. Rate and amount of converted CO2 were higher on Pt/ZrO2 than on Pt/Al2O3. Pt/ZrO2 was proven to react with CO2 to produce CO and active oxygen (CO2→CO+O) (probably on its oxygen defect site) more easily than Pt/Al2O3.

Influence of the phase composition of titania on catalytic behavior of Co/TiO2 for the dry reforming of methane

The phase transfer of TiO2 from anatase to rutile for a 10 wt% Co/TiO2 catalyst during the reduction causes serious disappearance of activity at 0.1 MPa during CH4/CO2 reforming, whereas the transfer for 0.5 wt% Co/TiO2 brings about relatively stable activity at 2 MPa.

Active site generation by water for the activation of methane over non-reducible oxide catalysts: A study of MgO system

MgO was proposed to form an active structure [vacancy + O - ] above 973K. The temperature dependency of H 2 desorption, XPS, and 18 O 2 isotopic exchange results supported the model and on such an active site, the oxidative coupling of methane (OCM) can be initiated. It was proposed that adsorbed (and absorbed) water was responsible for the active site generation. The addition of water promoted C 2 production during the OCM and the water isotope effect on C 2 production could also be observed.

Mechanism of carbon deposit/removal in methane dry reforming on supported metal catalysts

The greater resistance to coke deposition for Pt/ZrO2 compared to Pt/Al2O3 in the CH4/CO2 reaction has been attributed to the higher reactivity of coke with CO2 on Pt/ZrO2 [1]. Hence, in this communication, the reaction of coke derived from methane (CHx: which is an intermediated in the reforming reaction and also a source of coke deposition) with CO2 was studied on Pt/Al2O3 and Pt/ZrO2 at 1070 K. The reactivity of coke itself on Pt, as measured by its reaction with H2, was higher on Pt/Al2O3 than on Pt/ZrO2. However, the reactivity of coke toward CO2 was lower. Hence, the difference between the two catalysts cannot be attributed to the difference in the reactivity of coke itself. Next, the ability of the active site to activate CO2 (probably oxygen defect sites on the support), as shown by CO evolution measurement in CO2 stream, was higher on Pt/ZrO2 than on Pt/Al2O3. Therefore, the high reactivity of coke toward CO2 on Pt/ZrO2 is attributed not to the intrinsic reactivity of coke itself but to the high activity of CO2 at oxygen defect sites of ZrO2 that are in the vicinity of Pt particles.