The influence of nickel loading on reducibility of NiO/Al₂O₃ catalysts synthesized by sol-gel method

Abstract

Abstract:The sol-gel method was used to synthesize nickel-alumina catalysts with various nickel loadings. Chemical and physical properties of support and supported nickel were characterized by TGA, DTA, EDX, SEM, BET, XRD and TPR techniques. Calcination temperature (500 • C) was determined by performing thermogravimetric analysis (TGA) and differential thermal analysis (DTA) on the samples. Energy dispersive X-ray (EDX) was used to determine the actual content of nickel on alumina. N 2 adsorption test revealed that the specific surface area varied between 550 and 223 m 2 /g for pure alumina and 30%Ni/Al, respectively. X-ray diffraction (XRD) patterns showed no peaks due to NiO species and NiO species were well dispersed on the support by formation of NiAl 2 O 4 phase. Temperature-programmed reduction (TPR) indicated that the nickel species mainly presented in NiAl 2 O 4 phase and small amount of NiO. In the 20 percent nickel loading, the surface NiAl 2 O 4 phase, which is between NiO and bulk NiAl 2 O 4 phases in terms reducibility, was formed considering as a successful result.

Co-Production of Ethanol and 1,2-Propanediol via Glycerol Hydrogenolysis Using Ni/Ce–Mg Catalysts: Effects of Catalyst Preparation and Reaction Conditions

“…The major peaks observed were at 400 °C for the catalyst prepared by IM and calcined at 550 °C, and at 400 °C, 357 °C, and 465 °C, for the DP-prepared catalysts calcined at 550 °C, 350 °C, and 650 °C, respectively. These peaks are likely from the reduction of bulk NiO, while the different peak temperatures are attributed to the interaction strength between NiO and CeO2 support [38][39][40]. The change in preparation method did not alter the peak temperature positions noticeably, suggesting that there was no change in the interaction between the active metal and the support.…”

“…The change in preparation method did not alter the peak temperature positions noticeably, suggesting that there was no change in the interaction between the active metal and the support. Raising the calcination temperature on the DP-prepared catalysts shifted the major peaks to higher temperatures, suggesting that the alterations of support properties and strengthening of the Ni-support interaction occurred [38][39][40], as observed in Ni catalysts by others [27,28]. A distinct minor peak in the vicinity of 213 • C was observed with the catalyst prepared by DP and calcined at 350 • C, which could be from the reduction of NiO, which had no or minimal interaction with the support [27].…”

“…The reducibility, or change in oxidation state, of the NiO species and metal-support interaction was studied through H2-TPR experiments (Figure 2) [38]. The catalysts were the ones of 25 wt % Ni/Ce-Mg (9:1 mol/mol) prepared by IM and DP and calcined at 350 °C, 550 °C, and 650 °C.…”

“…The reducibility, or change in oxidation state, of the NiO species and metal-support interaction was studied through H 2 -TPR experiments (Figure 2) [38]. The catalysts were the ones of 25 wt % Ni/Ce-Mg (9:1 mol/mol) prepared by IM and DP and calcined at 350 • C, 550 • C, and 650 • C. The major peaks observed were at 400 • C for the catalyst prepared by IM and calcined at 550 • C, and at 400 • C, 357 • C, and 465 • C, for the DP-prepared catalysts calcined at 550 • C, 350 • C, and 650 • C, respectively.…”

Precious Metals Supported on Alumina and Their Application for Catalytic Aqueous Phase Reforming of Glycerol

“…Weight loss of up to 10% between 90 and 185°C can be attributed to the removal of physically adsorbed water and organics, for example hydrated aluminium hydroxide, which can possibly formed. For metal impregnated over γ-Al 2 O 3 samples, the weight loss at temperature range of 200 to 500°C were observed relating to the decomposition of chemically and strongly bound water molecules and organic groups, such as metal nitrate which entrapped in the pores support [15]. The total weight loss of the supported metal samples was more than the total weight loss of the support, as expected.…”