Synergistic effects of CeO₂-supported bimetallic Ni–Cu, Co–Cu, and Ni–Fe catalysts on steam reforming of ethanol

Abstract

The synergistic effects of CeO 2 -supported bimetallic NiCu, CoCu, and NiFe catalysts on the reduction properties, crystal structure, and catalytic performance during steam reforming of ethanol were investigated. Both metals in the bimetallic catalysts were reduced at lower temperatures than were the metals in the associated monometallic catalysts, and they formed alloy crystallites. It was confirmed from activity tests of the monometallic catalysts that Ni and Co were relatively active components and that Cu and Fe were less active. The combination of Ni and Co with Cu (NiCu/CeO 2 and CoCu/CeO 2 ) resulted in increases in H 2 and CO 2 yields and inhibition of carbon deposition during reactions at 673 K. On the other hand, the incorporation of Ni with Fe (NiFe/CeO 2 ) showed a lower activity than did Ni/CeO 2 at 673 K but exhibited a higher H 2 yield and higher resistance to carbon deposition at 873 K, in which case NiFe alloys were formed. These results indicate the advantages of alloying a catalytically active metal with a less active metal during steam reforming of ethanol.

セリア担持ニッケル–銅触媒の還元挙動とエタノール水蒸気改質における触媒性能に及ぼす触媒組成の効果

“…We also demonstrated that the addition of relatively inactive Cu to Ni/CeO2 and Co/CeO2, each at metal loadings of 5 wt%, resulted in enhancement of the H2 yield and resistance to carbon deposition at 673 K 30) . In this study, we report the effects of the Ni : Cu ratio and metal loading on the reduction behavior of bimetallic Ni _ Cu catalysts supported using pure CeO2 and their catalytic performance for SRE.…”

“…Figure 7 shows the TG profiles of the catalysts employed for SRE at 673 K and 873 K for 9 h. The total quantities of the carbon deposits estimated from the weight losses are summarized in Table 1. The weight losses due to carbon combustion were classified into two groups: a small weight loss at 490-530 K and a relatively large weight loss at ≥ 600 K. As described previously 29), 30) , the former is related to carbon deposits chiefly on Cu, and the latter is attributed to fibrous carbon deposits on Ni. At a reaction temperature of 673 K, Ni10 produced a relatively large quantity of carbon, which was reduced by more than half by replacing only 2 wt% of the Ni with Cu (Ni8Cu2).…”

Statistical Approach on Ethanol Reforming

“…In addition to the influence of Ni on the breakdown of C–C bonds, Ni has characteristics that favor methane reform, or methane consumption, as well as temperature increase. , The influence of these factors, Ni and temperature, on methane reforming was clearly observed in the regression model adjusted for the CH 4 flow, so that both Ni and the interaction between it and temperature favored CH 4 consumption (region F of Scheme ).…”

“…Moreover, Ni favors a greater conversion of CH 4 and CO, 6 as it facilitates the breakdown of the C−C bond 7,8 and does not suffer CO poisoning. 6 However, in spite of these advantages, Ni favors the formation of coke, 9,10 and to avoid coke deactivation, some studies indicate the coparticipation of Cu in the presence of Ni as responsible for the decrease of coke and CH 4 . 8,9 Among the supports studied for the steam or oxidative reforming of ethanol, the support that presents high mobility of oxygen atoms and hydroxyls is CeO 2 .…”

“…6 However, in spite of these advantages, Ni favors the formation of coke, 9,10 and to avoid coke deactivation, some studies indicate the coparticipation of Cu in the presence of Ni as responsible for the decrease of coke and CH 4 . 8,9 Among the supports studied for the steam or oxidative reforming of ethanol, the support that presents high mobility of oxygen atoms and hydroxyls is CeO 2 . 11 The mobility of oxygen or hydroxyls is important, because it governs the stability of the catalyst activity and the conversion of CO and methyl groups to CO 2 .…”