Biogas as renewable raw material for syngas production by tri-reforming process over NiCeO2 catalysts: Optimal operative condition and effect of nickel content

Hydrogen-rich gas production by steam reforming of n-dodecane

“…The principal role of ceria was connected with the ability to increase the adsorption of steam by its vacant oxygen and to transfer oxygen to the supported metallic site, keeping the surface relatively free of carbon. This self-decoking capability of ceria-based catalysts, due to the gasification reaction by oxygen species from the lattice, was previously studied and discussed by other authors [52][53][54][55] and also in our previous papers [34,36,40,56,57]. In addition, partial incorporation of Pt ions into the ceria matrix to form Pt-Ce solid solution (as revealed from XRD and TPR analysis) enhanced oxygen mobility by increasing CeO 2 structural defects.…”

Copper as promoter of the NiO–CeO 2 catalyst in the preferential CO oxidation

“…According to Saw et al [12], the improved catalytic performance of Cu-modified NiO-CeO 2 systems might be attributed to the formation of Ni-Cu alloys. Conversely, other studies [8,9,26] suggest that the enhanced activity in CO oxidation and CO 2 selectivity is due to synergistic effect between well-dispersed copper species and surface oxygen vacancies generated via insertion of Ni species in ceria structure. As seen, the precise chemical nature of the resulting interaction between Ni and Cu species in catalytic processes is still an open question in the literature and it is not well understood.…”

“…The results revealed a decrease in the lattice parameter from 5.413 Å in pure ceria to 5.407 Å in both NiCeO and CuNiCeO systems, suggesting that part of the Ni species has been inserted into the ceria structure. In principle, the cell contraction observed could be assigned to the smaller size of Ni 2+ ions (0.72 Å) when compared with Ce 4+ ions (0.97 Å), which in turn would imply in the formation of a Ce 1−x Ni x O 2 solid solution [26] On the other hand, Cu added a posteriori and remaining Ni (which have not been incorporated) are believed to form segregated phases CuO and NiO, respectively, as evidenced by our XRD patterns. Moreover, no significant changes in the mean crystallite size were observed ( Table 2).…”

“…Interestingly, two overlapping reduction peaks centered at lower temperatures (245 and 280 • C) were also observed. The first peak at 245 • C can be attributed to the reduction of O 2 molecules possibly adsorbed on surface oxygen (O) vacancies [26,34]; as discussed in Section 3.1, the incorporation of Ni species into the ceria lattice usually generates O vacancies that can easily adsorb O 2 molecules, which in turn can be easily reduced by H 2 at lower temperatures. The second peak located at 280 • C corresponds to the reduction of Ni species present into the CeO 2 lattice [26].…”

Analysis of Syngas Production from Biogas via the Tri-Reforming Process

“…In the study of Vita et al [21], tri-reforming simulated biogas over a Ni/ceria based catalysts was carried out and the H 2 O/CH 4 and O 2 /CH 4 molar ratios, reaction temperature, and nickel content effects on the catalyst's performance were studied. They found that the H 2 /CO ratio could be flexibly adjusted using added amounts of oxygen and steam in order to meet the requirements of downstream processes.…”