Behavior of Coprecipitated NiAl₂O₄/Al₂O₃ Catalysts for Low-Temperature Methane Steam Reforming

Abstract

The suitability of the nickel aluminate phase as an effective precursor for producing highly active and stable Ni/ alumina catalysts was investigated in the steam reforming of methane with a H 2 O/CH 4 ratio of 3 in the 450−650°C temperature range. Particularly, the effect of the preparation route, including dissolution followed by crystallization, coimpregnation, and coprecipitation, for obtaining either bulk or alumina-supported samples was analyzed. A special attention was paid to correlating the characteristics of the calcined catalytic precursors with a Ni content varying between 17 and 33 wt %, namely, textural properties, composition, nature, and relative abundance of the existing nickel phases (NiAl 2 O 4 and NiO), as well as reducibility, with the Ni crystallite size, dispersion, and metallic surface area obtained after a severe high-temperature reduction step (850°C). A high intrinsic activity was found for the coprecipitated catalysts. This route was also effective for increasing the available metallic surface area. The best reforming performance (with a methane conversion of 78−80% and yield of hydrogen close to 1.63 at 650°C and 38 400 cm 3 CH 4 g −1 h −1 ) was achieved by a reduced alumina-supported (17 wt % Ni)NiAl 2 O 4 catalyst and the bulk NiAl 2 O 4 catalysts prepared by coprecipitation.

Combined steam and CO2 reforming of CH4 using coke oven gas on nickel-based catalyst: Effects of organic acids to nickel dispersion and activity

“…The previously reported activation energies were also summarized in Table 3 reforming reactions and catalysts [9,17,[38][39][40][41][42][43][44][45][46][47], and the present results on the Ni/Al 2 O 3 (OA) were well matched with those activation energies by showing the them around 72.9-246.0 kJ/mol. To derive the kinetic parameters, the elementary reactions such as CDR, RWGS, SRM1, and SRM2 as listed below, where active sites for these four reactions are assumed as the same sites, were considered based on the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanisms according to our previous work [41].…”

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

“…Pure NiO presents intense signals at 380, 420, and 720 nm which illustrate the Ni 2+ (Oh) in the cubic (rock-salt) NiO lattice [44]. Ni/Al.550, on the other hand, shows a doublet signal at 600-650 nm which is related to the Ni 2+ (Td) species in the nickel aluminate spinel lattice [44,45]. Besides, small absorption bands at 380 nm can be assigned to Ni 2+ (Oh) in the NiAl2O4 spinel [46].…”

MgO/NiAl2O4 as a new formulation of reforming catalysts: Tuning the surface properties for the enhanced partial oxidation of methane

“…As aforementioned this might be explained by a strong interaction of NiO with Mg species resulting from a surface density close to that corresponding to a theoretical surface monolayer. [5,23,32]. However, as reported in Table 3, the XPS peak positions seemed to depend on the MgO content.…”

“…For example, the MgO(5)-NiAl catalyst showed the lowest Ni 2p 3/2 peak binding energy (855.2 eV). This shift was explained by an enrichment of the near surface of MgO(5)-NiAl sample with NiO [5,23]. Moreover, as revealed by the FWHM data reported in Table 3, the MgO(5)-NiAl sample showed the broadest Ni 2p 3/2 peak (3.7 eV), thus suggesting a larger heterogeneity in nickel environments.…”