Mössbauer study of nanodimensional nickel ferrite-mechanochemical synthesis and catalytic properties

Iron-nickel spinel oxide NiFe2O4 nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron-nickel oxides are investigated by X-ray diffraction and Mössbauer spectroscopy. Their catalytic behavior in methanol decomposition to CO and methane is tested. An influence of the preparation method on the reduction and catalytic properties of iron-nickel samples is established

Studies on CuCe0.75Zr0.25Ox preparation using bacterial cellulose and its application in toluene complete oxidation

A series of CuCe0.75Zr0.25Ox catalysts (CCZ) were synthesized based on the environmental‐friendly bacterial cellulose (BC) by using the sol‐gel method. The corresponding synthesis mechanism, physicochemical properties of the catalysts and catalytic performances for toluene oxidation were comprehensively studied. In the presence of BC without sugar, the CCZ−A synthesized by ethanol‐gel exhibits better catalytic activity than the CCZ−W synthesized by water‐gel, which may be due to the different roles of BC in different solvents. However, it is worth noting that the graft copolymerization between BC and active metal (Ce4+, Cu2+) is the same process in both water‐gel and ethanol‐gel. The activity of CCZ‐SW synthesized by water‐gel using BC with sugar is obviously higher than that of CCZ−W and CCZ−A. The temperature of complete degradation of toluene over CCZ‐SW is 205 °C, which is 35 °C lower than that of CCZ−W. The results from BET, Raman and H2‐TPR indicate that the larger the specific surface area, the more oxygen vacancies and better low‐temperature reducibility, that are mainly responsible for the excellent activity of CCZ‐SW. The existence of sugar in BC could hinder the agglomeration of active metal particles during the calcination process. Combined with the results of in situ DRIFT, the adsorbed toluene on the catalyst surface is oxidized into alkoxide, aldehydic and carboxylic acid species as intermediates before the complete oxidation into CO2 and H2O.

Acidic sites in beta zeolites in dependence of the preparation methods

WOS: 000221001400013Beta zeolites synthesized by different methods are compared in their structure peculiarities and acidic properties by nitrogen physisorption, IR-KBr. pyridine sorption-desorption and thermoprogrammed desorption of ammonia. It is found that mesopores could be obtained in beta zeolites with the change of the activation procedure. Methanol conversion to dimethyl ether and hydrocarbons is used as a test reaction for understanding of the acid center function. (C) 2004 Elsevier B.V. All rights reserved

Optimization of the preparation procedure of cobalt modified silicas as catalysts in methanol decomposition

Novel modified “chemisorption–hydrolysis” technique and conventional “incipient wetness impregnation” procedure were compared for loading of cobalt species on mesoporous silica supports. Effect of cobalt amount, pH of the precursor solution, duration of the “chemisorption” procedure and pre-treatment medium, as well as topological characteristics of the mesoporous silica support were investigated. The state of the loaded cobalt species was studied by XRD, FTIR, FTIR of adsorbed pyridine, UV–vis, XPS and TPR methods and their catalytic properties were elucidated in methanol decomposition to hydrogen and carbon monoxide. The “incipient wetness impregnation” technique facilitates the formation of finely dispersed spinel cobalt oxide species. Their catalytic activity could be significantly increased by hydrogen pretreatment, but the effect is more pronounced when mesoporous silica with ordered pseudo 1D pore structure (SBA-15) is used as a support. The modified “chemisorption–hydrolysis” procedure facilitates the formation of strongly interacting with the support cobalt species, which are stable under the reduction conditions. Their properties could be regulated during the modification procedure, by varying the cobalt content and pH of the impregnated solution as well as by the duration of the “chemisorption” procedure

Non-critical raw material catalysts for oxygen reduction reaction: valorization of biomass waste

Poster presented at the HYCELTEC 2019 conference, VII Symposium on Hydrogen, Fuel Cells and Advanced Batteries, 1-3 july 2019, Barcelona (Spain).Peer reviewe

Activated carbons from waste biomass and low rank coals as catalyst supports for hydrogen production by methanol decomposition

Activated carbons with different textural and chemical surface characteristics were synthesized from waste biomass and low rank coals, and furthermore used as a host matrix for cobalt species, varying the preparation and modification methods. The obtained activated carbons and modified samples were characterized by complex of various physicochemical methods, such as: low temperature physisorption of nitrogen, XRD, EPR, XPS, UV–Vis and TPR with hydrogen. Boehm method was applied for qualitative and quantitative determination of oxygen-containing groups on the carbon surface before and after cobalt deposition. The catalytic properties of cobalt modifications were tested in methanol decomposition. The dominant effect of activated carbon texture over the surface chemistry on the state and catalytic behavior of cobalt species was discussed.Financial support from Bulgarian Academy of Sciences and Bulgarian Ministry of Education (Projects DFNI-Е01/7/2012 and DFNI-E02/2/2014) is gratefully acknowledged.Peer reviewe

Mössbauer study of nanodimensional nickel ferrite-mechanochemical synthesis and catalytic properties

International audienceIron-nickel spinel oxide NiFe2O4 nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron-nickel oxides are investigated by X-ray diffraction and Mössbauer spectroscopy. Their catalytic behavior in methanol decomposition to CO and methane is tested. An influence of the preparation method on the reduction and catalytic properties of iron-nickel samples is established

Effect of the rehydration on the acidity and catalytic activity of SAPO molecular sieves

International audienc