The effect of solution variables on metal weight loading during catalyst preparation

Heterogeneous hydrogenation catalysts

“…Stronger metal ± support bonding is predominant in catalysts with low Ni content. 105 Low pH values facilitate isomorphic substitution of Ni in the octahedral lattice of Al 2 O 3 , which favours the predominant existence of this metal in the NiAl 2 O 4 form. Only this structure was revealed in the 0.8% Ni/ Al 2 O 3 specimen.…”

“…The concentration of electrolyte, ionic strength, and pH of impregnation solution influence not only the content of Ni in the catalyst, but also the amount of active nickel precursors and hence the physicochemical properties and the hydrogenation activity of the catalysts formed. 103,105 The procedure for the preparation of Ni/Al 2 O 3 catalysts affects their structure, activity, and selectivity, e.g., in the hydrogenation of CO. 47, 49, 103 ± 108 Temperature-programmed desorption (TPD) of H 2 and its interaction with CO allowed us to obtain data on the accessibility of surface Ni centres to H 2 and CO at various conditions of preparation of low-percentage catalysts. Surprisingly, the variation of Ni content from 0.8 mass % to 8.3 mass % proved to have little effect on the adsorption of H 2 and the active nickel surface calculated from the results obtained (Table 3).…”

“…According to Kester and Falconer, 48 the two CO peaks correspond to two types of active centres of different composition on the surface of the Ni catalyst. The low-temperature peak is supposed 48,105 to correspond to NiO, while the high-temperature peak corresponds to NiAl 2 O 4 . Stronger metal ± support bonding is predominant in catalysts with low Ni content.…”

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].…”

Preparation of γ-Al2O3 porous nanosolid/fluorescein fluorescent nanocomposites by a simple method

“…In particular, ␥-Al 2 O 3 has received wide attention, with established use as a sorbent, catalyst and catalyst support [1][2][3][4][5][6][7][8], etc. On the other hand, a large amount of dangling bonds and vacancies on the surface of nanoparticles makes it possible for the preparation of nanocomposite materials with excellent properties by surface reaction [9].…”