CO2 reforming of methane over Ni-Ru supported catalysts: On the nature of active sites by operando DRIFTS study

Abstract

The present paper addresses the nature of the active sites of a bimetallic Ni-Ru supported catalyst on the dry reforming of methane (DRM). The structural characterization by XRD and Raman spectroscopy, along with the reducibility study (TPR-H2) of the samples, evidenced the existence of a strong Ni-Ru interaction in the bimetallic system. We have assumed that Ru atoms block the most reactive Ni sites (step-edge sites) leaving less reactive centers for methane activation (terraces). In this way, operando DRIFTS measurements revealed that Ru decreases the catalytic activity but favors the carbon gasification and prevents the CO dissociation.

High‐Performance Bimetallic Catalysts for Low‐Temperature Carbon Dioxide Reforming of Methane

“…Several pretreatment conditions were studied, which included calcined (C), calcination-reduction (CR), and direct reduction (DR). The Ru x Ni y Mg 1-x-y O catalysts prepared via DR pretreatment method demonstrated In contrast to previously reported results, Á lvarez et al [14] showed that monometallic Ni/MgAl (CH 4 conversion = 55 %, CO 2 conversion = 70 %) presented the highest catalytic activity, followed by Ni-Ru/MgAl (CH 4 conversion = 30 %, CO 2 conversion = 40 %) and Ru/MgAl (CH 4 conversion = 5 %, CO 2 conversion = 10 %). The lower catalytic activity in the bimetallic Ni-Ru catalyst could be caused by the altering in the electronic structure of Ni metal by Ru metal which covered the step-edge sites of Ni particles, which consequently forbade the more dominant Ni step-edge sites and shifted to less sensitive Ni terrace sites for methane activation.…”

Ru and Ni—Privileged Metal Combination for Environmental Nanocatalysis

“…In Table 2, we have compiled the examples of preparation and application of Ru/Ni systems. wet impregnation, calcination dry reforming of methane [83] 15 wt.% Ni-0.5 wt.% Ru/MgO/Al 2 O 3 wet impregnation, calcination dry reforming of methane [84] 14 wt.% Ni-1 wt.% Ru/CeO 2 -Al 2 O 3 co-precipitation, wet impregnation, calcination hydrogen production via steam reforming of simulated bio-oil [10] 10 wt.% Ni-1 wt.% Ru/C incipient-wetness impregnation, calcination hydrogenolysis of lignin [11] Ni-Ru (various loading)/C chemical reduction, galvanic replacement, calcination catalic hydrogenation [85,86] 1 wt.% Ni-0.3 wt.% Ru/ZnSe: CGSe flux-assisted method, precipitation photocatalytic hydrogen evolution [87]…”

“…They can also easily get deactivated at high temperatures by sintering and/or coke deposition and are particularly susceptible to sulfur poisoning, e.g., from H 2 S [80,91,97]. There are several solutions that can improve the performance and life span of this type of catalyst, for instance, using a support [83,91,[98][99][100], catalytic promoters [91,99,100], coupling with other non-noble elements into alloys or spinel structures [100,101], or composing bimetallics with noble metals [10,53,[74][75][76]84]. Ruthenium is one of the most used noble metals for this purpose.…”

“…However, in this way we can also reduce the performance by decreasing the interaction between Ni and the spinel as in Ru-Ni/MgAl 2 O 4 [83]. In turn, it is suggested that Ru atoms probably block the most reactive Ni sites (step-edge sites) in an Ni-Ru/MgAl catalyst, leaving fewer reactive centers for methane activation (terraces), which favors carbon gasification and prevents CO dissociation [84]. Furthermore, the H 2 :CO ratio in the RM is shifted to lower values for ruthenium-nickel catalysts in compared to catalysts that contain only nickel particles [98].…”

Carbon Dioxide Reforming of Methane over Ni Supported SiO2: Influence of the Preparation Method on the Resulting Structural Properties and Catalytic Activity

“…One method is to change the acidity and alkalinity of the catalyst carriers, such as MgO [11,12], Al 2 O 3 [12][13][14], CaO [15][16][17], and CeO 2 [18][19][20]. The second method is to dope a small amount of a noble metal such as Rh or a transition metal such as Co into a Ni-based catalyst to prepare a bimetallic catalyst [21][22][23]. The third is to choose different catalyst preparation methods, such as the preparation of Ni-based catalysts with core-shell structures [24][25][26][27][28][29][30], the preparation of Ni-based catalysts by plasma technology [10,31,32], and other methods [33,34].…”