Promotion Effects of Copper and Lanthanum Oxides on Nickel/Gamma-Alumina Catalyst in the Hydrotreating of Crude 2-Ethylhexanol

Abstract

Nickel/gamma-alumina (Ni/γ-Al 2 O 3 ) catalysts promoted with Cu and La were prepared by the impregnation method and characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). XRD and HRTEM indicated that the addition of La and Cu was helpful to decrease the size of active particles and increase the dispersion of Ni species. TPR showed that Cu can effectively decrease the reduction temperatures of its own and Ni oxides, whereas La can change the proportion of various Ni species and increase the content of easily reducible Ni species. XPS and UV-vis DRS indicated that electron shift occurred on the Ni-based sample modified by Cu and enhanced remarkably by adding La. These findings suggest that Cu and La species induce both structural and electronic promotion effects, resulting in smaller particle size and weaker interaction between active components and the support, higher dispersions, and reducibility of active phases, ultimately enhancing the crude 2-ethylhexanol hydrotreating catalytic performance.

An Alumina-Supported Ni-La-Based Catalyst for Producing Synthetic Natural Gas

“…T species are more difficult to reduce than Ni 2+ OC ones [23,27], while the latter coincides with experimental observations from studies dealing with the promotion effects of La on Ni-based catalysts [26]. The H2-TPR profile of P_LaNi/Al (Figure 3) revealed the presence of three reduction bands within two major reduction zones at temperatures across the range of 290-750 °C.…”

“…The small shoulder at 695 °C was assigned to the reduction of Ni 2+ species, either tetrahedrally coordinated (i.e., Ni ) in the crystalline structure of the support as per previous reports [22,27], or in La-Ni-Al containing species derived from the strong interaction between La and Ni ions [26]. The former interpretation stems from the widely accepted perception that Ni species are more difficult to reduce than Ni ones [23,27], while the latter coincides with experimental observations from studies dealing with the promotion effects of La on Ni-based catalysts [26]. Additional H2-TPR analyses of Ni/Al (12.5 wt %) and La/Al (6.4 wt %) were conducted to assist with interpretation of the P_LaNi/Al profile ( Figure 3).…”

“…The peak at 583 • C was ascribed to octahedrally coordinated Ni 2+ species (i.e., Ni 2+ OC ) embedded in the crystalline structure of the γ-Al 2 O 3 support [24,27,28], which concurs with the formation of surface Ni-Al spinels. The small shoulder at 695 • C was assigned to the reduction of Ni 2+ species, either tetrahedrally coordinated (i.e., Ni 2+ T ) in the crystalline structure of the support as per previous reports [22,27], or in La-Ni-Al containing species derived from the strong interaction between La and Ni ions [26]. The former interpretation stems from the widely accepted perception that Ni…”

“…The H2-TPR profile of P_LaNi/Al (Figure 3) revealed the presence of three reduction bands within two major reduction zones at temperatures across the range of 290-750 °C. The lowtemperature zone between 290 and 425 °C contained a symmetrical band centred at 320 °C attributed to the reduction of amorphous NiO on the catalyst surface [22,[25][26][27] since no nitrates from the SCS were expected to remain after calcination at 500 °C [28]. The peak at 583 °C was ascribed to octahedrally coordinated Ni 2+ species (i.e., Ni ) embedded in the crystalline structure of the γ-Al2O3 support [24,27,28], which concurs with the formation of surface Ni-Al spinels.…”

“…The lowtemperature zone between 290 and 425 °C contained a symmetrical band centred at 320 °C attributed to the reduction of amorphous NiO on the catalyst surface [22,[25][26][27] since no nitrates from the SCS were expected to remain after calcination at 500 °C [28]. The peak at 583 °C was ascribed to octahedrally coordinated Ni 2+ species (i.e., Ni ) embedded in the crystalline structure of the γ-Al2O3 support [24,27,28], which concurs with the formation of surface Ni-Al spinels. The small shoulder at 695 °C was assigned to the reduction of Ni 2+ species, either tetrahedrally coordinated (i.e., Ni ) in the crystalline structure of the support as per previous reports [22,27], or in La-Ni-Al containing species derived from the strong interaction between La and Ni ions [26].…”