Structural Transformation of Cu–Mg–Al Mixed Oxide Catalysts Derived from Hydrotalcites During Shift Reaction

Abstract

Cu-Mg-Al mixed oxide catalysts were prepared from calcination of hydrotalcite-like compounds. XRD patterns showed formation of CuO and MgO phases, where aluminum oxides are well dispersed. The Cu-MgAl catalysts exhibited high stability during 40 h with time on stream for the shift reaction at 250°C, which can be related to the major presence of metallic copper, confirmed by in situ XRD reaction measurements, and no change of the mean crystallite size, suggesting high resistance to sintering. DRIFTS results confirmed the major presence of metallic Cu particles at the catalyst surface but also an insignificant amount of cationic copper species.

Ultraviolet–Visible Spectroscopy and Temperature-Programmed Techniques as Tools for Structural Characterization of Cu in CuMgAlOxMixed Metal Oxides

“…One of the key parameters in the synthesis of [M 2+ 1– x M 3+ x (OH) 2 ] x + (A n – ) x / n layered double hydroxides is the trivalent metal relative content, x = M 3+ /(M 2+ + M 3+ ), which can take a wide range of values depending on the nature of the metals. For MgAlCO 3 LDH, values of x have been reported between 0.1 and 0.5 (9 < M 2+ /M 3+ < 1), , while reported x values for CuMgAl LDHs range from approximately 0.15 to 0.5 (5 < M 2+ /M 3+ < 1), − ,,− which becomes narrower with increasing Cu content and M 2+ /M 3+ ratio (Figure ). XRD diffractograms of the prepared CuMgAlCO 3 LDHs suggest, however, that pure LDH phases are obtained over a more limited range.…”

“…2,4,5 Other catalysts related to CuO/ZnO/Al 2 O 3 include CuO/ MgO/Al 2 O 3 mixed metal oxides (MMOs), which share similar synthesis protocols and catalytic properties for a number of reactions, including phenol alkylation with methanol, 9 ethanol coupling, 10 cinnamaldehyde hydrogenation, 11 methane combustion, 12 glycerol hydrogenolysis, 13 ethanol steam reforming, 14 and the water gas shift reaction. 15 The application of CuO/MgO/Al 2 O 3 mixed oxides for multiple reactions highlights their importance as versatile, easy to prepare, and inexpensive catalysts.…”

A Review on Catalysts Development for Steam Reforming of Biodiesel Derived Glycerol; Promoters and Supports

“…In this regard, it was believed that the Ni-Mg-Al mixed oxides derivate from hydrotalcite had presented a proper catalytic performance in various catalytic processes such as dry and steam reforming of methane [97][98][99][100] and ethanol [101][102][103][104]. Furthermore, the Cu-Mg-Al hydrotalcite type catalysts also showed superior catalytic activity in the water-gas shift (WGS) reaction [105]. The bimetallic of Ni and Cu catalyst has been initially studied for the SR of ethanol with decreased coke deposition [106][107][108], however even though it was expected that this configuration could be efficiently applied for the SR of glycerol, but Manfro et al [109] investigated the Ni-Cu hydrotalcite based catalysts with 20 wt% of nickel oxide and 0, 5, and 10 wt% of copper oxide.…”

Tailored products of dealloying as-sintered Al–Cu alloys in sodium hydroxide solutions

“…When the temperature exceeds 500 C, the amount of Al 2 Cu increases with the enhanced diffusion rate and a reversible eutectic reaction (Al + Al 2 Cu 4 L) occurs when the temperature is about 540 C. Various phases are obtained when their compositions are changed as detected. 85 Cu 15 suggests a poorly-crystallized crystal face 40,41. This is also true for the (402) face which corresponds to 2q ¼ 73 46.…”