Chromatographic effect during the preparation of γ-Al2O3 supported Cu−Mn catalysts

Abstract

A strong chromatographic effect has been established during copper-manganese formate impregnation ofy-A1203. The samples obtained have been characterized by adsorption, IR, X-ray and magnetochemistry methods.

Surface and Texture Characterization of Alumina-Supported Manganese Oxide Catalysts and Their Formate Precursors

“…The metal formates are known to decompose without melting in crystallized water, thus resulting in the formation of oxide phases of high dispersity. The impregnation procedure of ␥-Al 2 O 3 with mixed manganese-copper formate solutions was discussed elsewhere and a strong chromatographic effect was observed (6). Our investigations show that the catalysts prepared from formates are promising in relation to NO conversion with ammonia (7).…”

“…The formation of mixed aquo-formate manganese complexes in the solutions additionally to the simple aquo manganese complexes is also expected, especially in the case of the saturated solution because of the strong affinity of the formate ions to the metal ions (indeed the crystal structure of solid Mn(HCOO) 2 ⅐ 2H 2 O is built up by Mn(HCOO) 6 and Mn(HCOO) 2 (H 2 O) 4 structural elements). Furthermore, the deposition of the hydrated formate ions and neutralization between the free formic acid and the basic alumina OH groups also occur.…”

A Chromatographic Effect Observed during Deposition of Cu–Mn Precursors on Active Carbon

“…In practice the adsorption of one of the components on the active support sites hinders the adsorption of the other component. This effect is observed with alumina on which Cu-Co or Ni-Mn ion pairs (4,5) have been deposited and with active carbon where Cu-Co deposition (6) has been performed. In papers (3,5) it has been shown how this effect might be avoided.…”

“…In this case the adsorbed amount of Cu (C s ) rises from 1.39 wt% for a single-component sample (1.0 Cu/AC) to 1.50 wt% for a two-component sample (1.0Cu1.0Mn/AC). In this respect active carbon greatly differs from alumina where the two metals are adsorbed on the same adsorption sites and in two-component solutions the presence of copper ions sharply reduces the adsorption capacity of alumina with respect to the other ion in the impregnating solution (4).…”

“…When two-component precursors are deposited, a definite ratio between the two metals in the active phase should be maintained. We have shown in several publications (3)(4)(5)(6) that during the formation of two-component supported catalysts as a result of impregnation, the so-called chromatographic effect is observed. It consists of prevailing adsorption of one of the components, which leads to a change in component ratio of the supported active phase as compared to that in the impregnating solution.…”