The effect of catalyst preparation on catalytic activity: IV. The design of Ni/Al2O3 catalysts prepared by incipient wetness

Heterogeneous hydrogenation catalysts

“…There are other factors, too. Thus, according to Huang and Schwarz, 49,107 with the same metal dispersity, the selectivity of CO hydrogenation depends on the acid-base properties of supports. This dependence can be determined, for example, by the intermediate interaction of the surface complexes CH x OH bound through an oxygen atom to acidic Lewis centres (L) at the metal ± support interface According to this scheme, the selectivity of formation of higher hydrocarbons should depend on the strength of CO molecule bonding (q CO ) and the energy of acid ± base interaction.…”

Methods for Preparation of Catalytic Materials

“…For reagents, such as Ni(NC>3)2, an increase in solution concentration results in lower solution pH which influences the dissolution of the support.227 Such effects were found when preparation variables (Ni content, impregnant pH) were examined in relation to the catalytic performance of Ni/Al203 prepared by incipient wetness. 228 Changes in metal concentration dramatically affected the dispersion of Ni. In this system, the metal dispersion and the partitioning between surface Ni and Ni incorporated in the support depended also on the crystallinity of the support, a factor which determines its dissolution properties.229 On the other hand, the dispersion of RU/AI2O3 prepared by incipient wetness was relatively unaffected by increases in weight loading because the ruthenium salt affords a better buffering of the (acidic) impregnation solution.…”

Enhancement of Residue Hydroprocessing Catalysts by Doping with Alkali Metals

“…Changes in the acidity of the support surface by means other than alkali doping have been observed to alter the dispersion of the active transition metals; for example, Lewis et al found that dispersion of Ni and Ni−Mo increased with increasing acidity when P was added to the alumina prior to deposition of the transition metals. Huang and Schwartz also found that decreasing the pH of the solution during deposition of the transition metals resulted in higher dispersion. On the basis of X-ray photoelectron spectroscopy, Boorman et al .…”