Hydrotalcite-derived Co-containing mixed metal oxide catalysts for methanol incineration

Abstract

The Co-Mg-Al mixed metal oxides were prepared by calcination of co-precipitated hydrotalcite-like precursors at various temperatures (600-800°C), characterised with respect to chemical (AAS) and phase (XRD) composition, textural parameters (BET), form and aggregation of cobalt species (UV-vis-DRS) and their redox properties (H 2 -TPR, cyclic voltammetry). Moreover, the process of thermal decomposition of hydrotalcite-like materials to mixed metal oxide systems was studied by thermogravimetric method combined with the analysis of gaseous decomposition products by mass spectrometry. Calcined hydrotalcite-like materials were tested as catalysts for methanol incineration. Catalytic performance of the oxides depended on cobalt content, Mg/Al ratio and calcination temperature. The catalysts with lower cobalt content, higher Mg/Al ratio and calcined at lower temperatures (600 or 700°C) were less effective in the process of methanol incineration. In a series of the studied catalysts, the best results, with respect to high catalytic activity and selectivity to CO 2 , were obtained for the mixed oxide with Co:Mg:Al molar ratio of 10:57:33 calcined at 800°C. High activity of this catalyst was likely connected with the presence of a Co-Mg-Al spinel-type phases, containing easy reducible Co 3? cations, formed during high-temperature treatment of the hydrotalcite-like precursor.

Cu-Mg-Fe-O-(Ce) Complex Oxides as Catalysts of Selective Catalytic Oxidation of Ammonia to Dinitrogen (NH3-SCO)

“…Characteristic diffraction lines occurring at approximately 21,35,41,43,50,63,67,74,78,85 and 88 °2θ were ascribed to spinel-like phases labelled as: (Cu,Mg)Fe2O3 (ICDD PDF-2 card No 01-076-9731). As expected [14,18,33], high temperature of calcination (800 °C) favors the formation of complex oxide structures; therefore, these patterns were observed for each sample irrespective of the copper loading. Apart from the complex spinel phases, characteristic diffraction lines for simple oxides like periclase (MgO) and tenorite (CuO) were also found.…”

“…Higher temperatures of calcination promote the formation of more thermally stable species and reorganization of the already existing structures into more complex ones. In the case of samples modified by Ce (800-Cu-Mg-Fe-O-Ce), the XRD patterns exhibit additional characteristic diffraction lines at positions 33,38,45,55,66,70 and 82 • 2θ related to CeO 2 phase (ICDD PDF-2 card No 01-080-5548). The lines characteristic for individual oxide species are at the same positions irrespective of the copper amount or Ce intercalation, which means that all samples are characterized by a similar cell parameter of individual phases a = 0.84 nm for MgFe 2 O 4 , a = 0.42 nm for MgO, a = 0.47 nm, b = 0.34 nm, c = 0.51 nm for CuO and a = 0.51 nm for CeO 2 oxide.…”

Thermal stability changing caused by chromium (iii) in the carbonated magnesium-aluminum hydrotalcite

“…Then, at immediately higher temperatures, the lamellae dehydroxylation begins to occur, which largely depends on the individual thermal stability of the metal hydroxides present in the material (Puttaswamy e Kamath, 1997) This stage can extend up to over 400 ºC, depending on the composition, and can accelerate the last stage of decomposition, which is interlayer decarbonation. Depending on the composition, hydrotalcite structures not yet decarbonated can be regenerated by hot rehydration, since the anchoring of the carbonate anion gives structural memory to hydrotalcite (Basag et al, 2017;Rhee e Kang, 2002).…”

Hydrogen Production Performances via Steam Reforming over Hydrotalcite Derived Catalyst: A Sustainable Energy Production Review

“…Different factors are strongly related to the catalytic performance of HT derived materials. The performance of HT derived catalyst mostly depends on its preparation procedure [14] [15] [16] [17] [18], pore size [19], total surface area [20] [21] [22], modification [23] [24] [25] [26], types of metal constituents [18] [27] [28], composition [1] [29] [30] [31], promoters [32] [33] [34] [35], operating temperature [36]. Different metallic oxides prepared by HT precursors have shown super catalytic performance during fuel processing [5] [6] [14] [28] [36] [37] [38] [39] [40].…”

“…This redesign can be done by being adjusted the M i and M ii metal ions as well as their ratio [41] [43] [44] [45] [46] [47]. Basąg et al, [18] reported that the performance of HT derived catalyst obtained at higher temperatures. In the last decades, a number of efforts have been taken where the focuses on highly stable and active catalysts.…”