Role of ReO_x Species in Ni-Re/Al₂O₃ Catalyst for Amination of Monoethanolamine

Abstract

The role of ReO x species in Ni-Re/Al 2 O 3 catalyst for amination of monoethanolamine (MEA) was investigated using a combination of experimental (Raman spectroscopy, in situ X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, scanning transmission electron microscopy−energydispersive X-ray spectroscopy line scan, and extended X-ray absorption fine structure) and theoretical (density functional theory (DFT)) methods. Characterization and simulation results indicate that rhenium oxide specie prefers to atomically disperse on the surface of NiO in calcined Ni-Re/Al 2 O 3 catalyst. After reduction, the surface of metallic Ni is decorated by ReO x with multiple valence states; meanwhile, a small amount of Ni−Re alloy was detected by extended X-ray absorption fine structure (EXAFS). DFT results indicate that different-valent ReO x species in Ni-Re/Al 2 O 3 catalyst have different functions during reaction. The high-valent ReO x (x ≥ 3) distributed on the Ni 0 particle surface play an important role in decreasing the surface energy of Ni 0 particle, thus stabilizing Ni 0 particles against sintering and increasing the lifetime of Ni-Re/Al 2 O 3 catalyst during amination reaction. The synergistic effect between Ni 0 and low-valent ReO x (x < 3) sites facilitates the abstraction of hydrogen in MEA and improves the activity of Ni-Re/Al 2 O 3 catalyst for MEA amination.

Efficient Hydrogenation of Xylose and Hemicellulosic Hydrolysate to Xylitol over Ni-Re Bimetallic Nanoparticle Catalyst

“…As shown, the two samples exhibited similar Ni 2p spectra. Besides a binding energy at approximately 862.5 eV assigned to the shake-up satellite of Ni 2p3/2, two peaks at approximately 853.0 and approximately 856.0 eV were observed, which were ascribed to Ni 0 and NiO species [38,44], respectively. Moreover, it was observed that the binding energy of Ni 0 species shifted from 853.5 eV for Ni/AC to a higher binding energy of 854.0 eV for Ni-Re/AC(n Ni :n Re = 1:1).…”

“…Nanomaterials 2020, 10, x FOR PEER REVIEW 8 of 14 Figure 5 presents the XPS spectra of the Re 4f region for Re/AC and Ni-Re/AC(n Ni :n Re = 1:1). For the two samples, five deconvoluted peaks appeared at 40.8, 41.9, 43.2, 45.0, and 45.8 eV, which were assigned to the 4f7/2 of Re 0 , Re 3+ , Re 4+ , Re 6+ , and Re 7+ species [38,44], respectively. Similar phenomena for Re 4f spectra were also found for other Ni-Re samples (See Figure S3 in the Supplementary Material).…”

Thermal Stability of Ru–Re NPs in H2 and O2 Atmosphere and Their Activity in VOCs Oxidation: Effect of Ru Precursor

“…Ayvali et al found that dissociation of CO at the metallic surface of small RuRe NPs was easier than with pure Ru and Re (as the result of a synergic effect) and therefore, high reactivity towards CO dissociation validates the use of bimetallic structures in the Fischer-Tropsch process [18]. The recently reported studies for Re-based bimetallic catalysts, for example for the Re-Ni/ Al 2 O 3 catalysts, indicate that Re promoter could effectively suppress the Ni 0 sintering process [19]. Also, for the bimetallic Co-Re particles supported on Al 2 O 3 superior sintering resistance was reported by Mom et al [20].…”

“…It is also possible that part of rhenium species is associated with the ruthenium phase, and there was an enrichment of ReO x species at the peripheral interface of the RuO 2 particles and the γ-Al 2 O 3 and additionally, some rhenium species may also exist as a thin film on top of the RuO 2 oxide particles. Ma et al[19] studied the role of ReO x species in the Ni-Re/Al 2 O 3 catalyst for amination reaction using a combination of various experimental and theoretical methods and found that rhenium oxide species prefer to atomically disperse on the surface of NiO in calcined Ni-Re/ Al 2 O 3 catalyst. Our XRD results clearly show that metal segregation in the bimetallic Ru-Re catalysts leads to RuO 2 agglomeration and transformation of the Re phase into a highly dispersed species.…”

Effects of Ni particle size on amination of monoethanolamine over Ni-Re/SiO2 catalysts

“…The catalytic performance of the Ni-Re/SiO2 catalysts for MEA amination was evaluated in a trickle-bed reactor. As described previously [21,22], about 3.6 ml (1.9 g) of oxide state catalysts were placed in the center of a stainless steel reaction tube, and the residual space was filled with silica sand. Before reaction, the catalyst was reduced in situ.…”