The effect of catalyst preparation on catalytic activity

X-ray diffraction study of the hydrogen reduction of NiO/α-Al2O3 steam reforming catalysts

“…Bartholomew and Farrauto explained these effects in terms of the chemistry of preparation, pretreatment and reduction conditions [31]. Later, based on a comprehensive study of preparation parameters, Schwarz and coworkers [32][33][34][35][36][37][38][39][40][41][42] advanced the theory that Al 3+ ions dissolve during impregnation at low pH and subsequently incorporate into crystallized NiO precursors [40]. Clause et al, however, demonstrated that NiO lattice parameters in coprecipitated hydrotalcite-type precursors remain unchanged and Ni-doped alumina phases exist on the surface of NiO, thereby imparting greater stability against sintering and resulting in lower reducibility [43].…”

From Al2O3-supported Ni(II)-ethylenediamine Complexes to CO Hydrogenation Catalysts: Importance of the Hydrogen Post-treatment Evidenced by XPS

“…Despite its non negligible content in ionic nickel and the former oxidation of metal particles upon exposure to air, H 2 -post-treated Nien 2 appears to challenge catalysts prepared without organic ligands in terms of metallic surface area exposed. In comparison, catalysts mentioned in the literature containing 6-9 Ni wt% and prepared from nickel nitrate exhibit metallic surface areas comprised between 2 and 9 m 2 g cat -1 [5,[15][16][17][18]. Preliminary catalytic results show that systems prepared by decomposition of Ni(II)-en complexes are able to catalyze carbon monoxide hydrogenation and open the way to a more complete kinetic investigation.…”

“…From the H 2 -desorption experiment, the fraction of metallic nickel exposed (FME) is evaluated to be 34% with respect to the total amount of Ni on the catalyst (assuming a stoichiometry of adsorption H/Ni 0 = 1 [5,9]), a value higher than those given by Bartholomew et al [15] for a 9 Ni wt% catalyst reduced at 75% (FME = 19%), or by Huang and Schwarz for 6-8 Ni wt% catalysts prepared by reduction of nickel nitrate and also characterized by hydrogen thermodesorption (FME B 11%) [16,17]. The application of the equation linking dispersion D and the average particles diameter Ø (D (%) = 97.1/Ø (nm) [9]) leads to a value of Ø comprised between 2 and 3 nm; the small size accounts for the high sensitivity of the catalysts to exposure to air.…”

Spray-Dried Ni Catalysts with Tailored Properties for CO2 Methanation

“…During the drying in the tube furnace, the evaporation of the solvent in the droplets initiated a self-assembly process leading to spherical dry particles formed by several small single nanoparticles. In this study, BB formed by two different supports, SiO 2 with two different primary particle sizes (8 and 20 nm), here named as BB (8) and BB (20) and Al 2 O 3 with a primary particle size of 50 nm (BB(Al 2 O 3 )), using two different nickel loadings of 10 and 20 wt% were produced. The nickel loading in the BB can easily be adjusted by adding different nickel nitrate amounts to the prepared suspension before the spray-drying process.…”

“…Most of the catalysts are produced by impregnation methods of the different support materials [19][20][21][22], co-precipitation [23], so-gel [16], and flame synthesis [24,25]. The first three of these methods are usually batch processes and require various time-consuming steps.…”