Deactivation of Alumina Supported Catalysts Due to Spinel Formation

Abstract

An important cause of deactivation of alumina supported transition metal (oxide) catalysts is a solid state reaction between the active component and the support. We therefore studied the hightemperature behavior of Me layers (Me = Co, Ni, Cu and Fe) on polycrystalline α-A12O3 and γ- Al2O3 substrates. The samples were first oxidized at moderate temperatures and then annealed at high temperatures (up to 1000 °C) in O2, N2, or N2/O2 mixtures. The interfacial reaction to MeA12O4 was assessed using Rutherford Backscattering Spectrometry and X-ray diffraction. The reaction rate strongly depends on the transition metal element Me: Fe < Ni < Co < Cu. Low oxygen pressures favour spinel formation. γ-A12O3 shows a much higher reactivity towards the MeOx overlayers than α-Al2O3.

Hydrogen Yield from Low Temperature Steam Reforming of Ethanol

“…The results (see Figure 12) agree with those in Figure 11. Bolt et al (1994) reported that an important cause of deactivation of alumina supported transition metal (oxide) catalysts was a solid state reaction between the active component copper and the support alumina that forms CuAl 2 O 4 . This observation also could not be considered in this case as the presence of CuAl 2 O 4 spinel was observed in the fresh catalysts after calcining at 700ºC.…”

Effects of K2O–Li2O doping on surface and catalytic properties of Fe2O3/Cr2O3 system

“…The ionizing radiations might also increase the number of active components by splitting them into small-sized particles besides modifying their acidic properties [12,13]. The doping with certain foreign oxides such as Li 2 O, K 2 O or ZnO hinders the metal oxide-support interactions thus increasing the stability of catalytically active constituents [16][17][18][19][20][21][22][23]. This treatment induced significant changes in the physicochemical characteristics of the treated solids such as the electrical, magnetic, textural and acidity features of the resulting solid catalysts.…”

Phase Diagram of the Quaternary Al(NO3)3-Cu(NO3)2-Zn(NO3)2-H2O System

“…[9] The principal function of these materials called catalyst stabilizers is to prevent or to inhibit metal-support interaction. [10] Therefore, the knowledge of the phase diagram of metallic salts is very important, as it can provide the basis for elaborating igneous mixed oxides in a wide range.…”