Total oxidation of methanol low temperatures on (Cu, Mn)-Mg-Al mixed metal oxides derived from hydrotalcites

A series of (Cu, Mn)-Mg-Al hydrotalcite-like layered double hydroxides (HTs) was synthesized by a co-precipitation method.The incorporation of Mn into the Mg-Al and Cu-Mg- Al HTs structure was investigated by employing powder X-ray diffraction. Calcination of the precursors resulted in destruc- tion of the layered structure and led to low-crystalline MgO. Ob- tained mixed metal oxides were tested as catalysts for the process of total oxidation of methanol.The catalytic performance of the Cu-containing samples was better comparing to the Mn-based catalysts and decreased in the following order: Cu-Mg-Al > Cu- Mn-Mg-Al > Mn-Mg-Al > Mg-Al. Quantitative total oxidation of methanol was achieved at 325 C with Cu-Mg-Al mixed oxides

MCM-41-type mesoporous silicas modified with alumina in the role of catalysts for methanol to dimethyl ether dehydration

MCM-41-type mesoporous silicas were modified with alumina by the impregnation, co-condensation, and template ion-exchange (TIE) methods. The obtained materials were characterized with respect to their chemical composition (ICP-OES), textural parameters (low-temperature N2 sorption), structure (XRD), and surface acidity (NH3-TPD) and tested as catalysts of methanol to dimethyl ether (DME) dehydration in a flow microreactor system. The catalytic performance of the studied materials was analyzed with respect to their porous structure, as well as their density and the strength of their acid sites. It was shown that the performance of the studied catalysts depends on the contribution of the surface exposed aluminum species, as well as their aggregation. For the most active catalyst, the study of its catalytic stability under rection conditions was performed. It was shown that the catalyst can be effectively regenerated by the incineration of carbon deposits under air flow at 550 °C for 1 h

Thermal transformation of polyacrylonitrile deposited on SBA-15 type silica : effect on adsorption capacity of methyl-ethyl ketone vapor

Thermogravimetry, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the studying of ther- mally induced structural changes of polyacrylonitrile (PAN) deposited on the surface of SBA-15 type meso- porous silica. Polymer was introduced onto the support by the precipitation polymerization of acrylonitrile in aqueous suspension of SBA-15. Low temperature transformation (to 723 K) of the deposited PAN was analyzed. It was found that at about 523 K, exothermic cyclization of polymer chains to the so-called ladder form of PAN occurred. However, the total cyclization of PAN required higher carbonization temperatures, at which gradual dehydroge- nation followed by graphitization was initiated. XPS revealed that the cyclic form of PAN and a relatively large amount of carbonyl species, formed during the carboniza- tion of the PAN/SBA-15 composite at 623 K, were responsible for the high sorption capacity in the methyl– ethyl ketone (MEK) vapor elimination. The efficiency in the MEK adsorption was also influenced by the content of PAN-derived carbon deposited on the SBA-15 surfac

An influence of thermal treatment conditions of hydrotalcite-like materials on their catalytic activity in the process of N2ON_2O decomposition

Hydrotalcite-like materials containing apart from magnesium and aluminum also copper, cobalt, nickel, and iron were prepared by a co-precipitation method. Thermal transformations of hydrotalcite-like materials were studied by thermal analysis methods as well as XRD, UV-vis-DRS, and XPS measurements of the samples calcined at various temperatures (600, 700, and 800 {\textdegree}C). Calcined hydrotalcites, especially those containing cobalt and copper, were found to be active and selective catalysts of N2O decomposition. It was shown that an increase in the calcination temperature significantly activated the Co-containing catalysts. Promotion of the samples with potassium resulted in activation of the hydrotalcite-based catalysts

Thermal transformations of Cu–Mg (Zn)–Al(Fe) hydrotalcite-like materials into metal oxide systems and their catalytic activity in selective oxidation of ammonia to dinitrogen

Layered double hydroxides (LDHs) containing Mg^{2+}, Cu^{2+} or Zn^{2+} cations in the Me^{II} positions and Al^{3+} and Fe^{3+} in the Me^{III} positions were synthesized by co- precipitation method. Detailed studies of thermal trans- formation of obtained LDHs into metal oxide systems were performed using high temperature X-ray diffraction in oxidising and reducing atmosphere, thermogravimetry coupled with mass spectrometry and temperature-pro- grammed reduction. The LDH samples calcined at 600 and 900 °C were tested in the role of catalysts for selective oxidation of ammonia into nitrogen and water vapour. It was shown that all copper congaing samples presented high catalytic activity and additionally, for the Cu–Mg–Al and Cu–Mg–Fe hydrotalcite samples calcined at 600 °C rela- tively high stability and selectivity to dinitrogen was obtained. An increase in calcination temperature to 900 °C resulted in a decrease of their catalytic activity, possibly due to formation of well-crystallised metal oxide phase which are less catalytically active in the process of selective oxidation of ammonia

Hydrotalcite derived (Cu, Mn)-Mg-Al metal oxide systems doped with palladium as catalysts for low-temperature methanol incineration

Hydrotalcite derived (Cu, Mn)–Mg–Al mixed metal oxides, synthesized by coprecipitation method, were found to be effective catalysts for methanol incineration. Copper and/or manganese oxides deposited on commercial γ-Al2O3 and MgO were used as the reference catalysts. Cu–Mg–Al–O mixed oxide system was found to be the most active catalysts in a series of the hydrotalcite originated metal oxides and supported samples. On the other hand, copper deposited on Al2O3 and MgO supports were significantly less active than the hydrotalcite derived catalysts. Activity of the catalysts was improved by deposition of small amount of palladium (0.5 wt.%). Temperature-programmed surface reaction method (CH3OH-TPSR) and in situ Fourier-transform infrared spectroscopy (FT-IR) were employed to study the species formed on the catalyst surface during the process of methanol oxidation