Method for analyzing HR-TEM micrographs to propose and/or describe structures and their interaction in crystalline materials.

A general and versatile method for the analysis and processing of HR-TEM data useful for several applications is presented. The first utility is to identify the structures seen in the micrographs; also can be extended to propose the interaction of structure dynamics between various phases; and also it can be hybridized with the chemical method to make a proposal of new structure and/or phase. The general method consisted of four steps: 1) micrograph pretreatment, 2) measurement of planar distances, 3) structure identification, and 4) structure corroboration. Crystallographic planes were immediately identified by comparing the interplanar distances. Next, crystallographic data were collected from the Crystal Structures Database (ICSD) and introduced into Diamond software to visualize the planes in each structure. In addition, from the zone axis point of view it must show the planes aligned, similar as is observed in the HR-TEM micrograph.•It was possible establish the growth mechanism of the different structures by identifying how is the structural interaction between the different oxides and sulfide phases.•Method was successful applied to propose a new TiCoMoS sulfide phase through HR-TEM results.•The method can also be extended to other areas where structural studies with HR-TEM are viable, such as biology, electronics, among others.

Methanol Synthesis from CO2: A Review of the Latest Developments in Heterogeneous Catalysis.

Technological approaches which enable the effective utilization of CO2 for manufacturing value-added chemicals and fuels can help to solve environmental problems derived from large CO2 emissions associated with the use of fossil fuels. One of the most interesting products that can be synthesized from CO2 is methanol, since it is an industrial commodity used in several chemical products and also an efficient transportation fuel. In this review, we highlight the recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to methanol. The main efforts focused on the improvement of conventional Cu/ZnO based catalysts and the development of new catalytic systems targeting the specific needs for CO2 to methanol reactions (unfavourable thermodynamics, production of high amount of water and high methanol selectivity under high or full CO2 conversion). Major studies on the development of active and selective catalysts based on thermodynamics, mechanisms, nano-synthesis and catalyst design (active phase, promoters, supports, etc.) are highlighted in this review. Finally, a summary concerning future perspectives on the research and development of efficient heterogeneous catalysts for methanol synthesis from CO2 will be presented.

Data on TGA of precursors and SEM of reduced Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis.

The modification of Cu-Zn catalysts with low amount of Al and Ga (Al+Ga = 3%) was investigated and data corresponding to its influence on the decomposition of the calcined precursors and on the nanomorphology and surface concentration of reduced catalysts were presented in this contribution. The data presented here are supplementary material of the catalysts presented in the research article "Structure and activity of Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis" published in Catalysis Today [1].

Highly active Cu/ZnO-Al catalyst for methanol synthesis: effect of aging on its structure and activity.

The influence of aging of precipitates on the physical and catalytic properties of a copper/zinc oxide-aluminium (Cu/ZnO-Al) catalyst with an optimized composition (low Al concentration, Cu/Zn/Al = 68/29/3) prepared using co-precipitation has been investigated in detail. The change in the structure of precipitates with aging (from amorphous zincian georgeite to crystalline zincian malachite) strongly influences the micro- and nano-structure (Cu and ZnO crystallite size, exposed copper surface area, Cu-ZnO interactions and stability of ZnO) of the final Cu/ZnO-Al catalysts obtained after calcination and reduction of the precipitates. The results of catalytic activity in methanol synthesis from syngas show the higher intrinsic activity of the catalysts derived from aged zincian malachite precipitates as consequence of the increase in the exposed copper surface area and the Cu-ZnO contacts. The stability of catalysts under the reaction conditions was also improved in the catalysts derived from precipitates aged after crystallization of malachite. The catalyst derived from the precipitate removed close to the point of crystallization of malachite shows very poor activity in the methanol synthesis as consequence of its segregated large Cu crystallites in low contact with ZnO derived from the absence of carbonate retention after calcination of the precipitate and the presence of sodium species after conventional washing which favour the strong sintering and crystallization of Cu during reduction.

Removal of PAH compounds from liquid fuels by Pd catalysts.

Palladium catalysts supported on gamma-alumina (AN, AS), amorphous silica-alumina (ASA), and beta-zeolite (betaZ) were prepared with the aim to reduce the content of polycyclic aromatic hydrocarbons (PAHs) in diesel fuels. The removal of PAH compounds was evaluated with a model feed (toluene, naphthalene, and dibenzothiophene)that approached the composition of diesel fuel. The catalysts were characterized by N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, transmission electron microscopy, temperature-programmed reduction/temperature-programmed oxidation, Fourier transform (FT) IR of absorbed CO, and diffuse reflectance FT spectroscopy of adsorbed NH3. When palladium was supported on ASA instead of AN or betaZ, the intrinsic activity improved considerably. Such behavior is discussed in terms of larger Brønsted acidity and the degree of reduction of the Pd species on Pd/ASA. For the 2.2 Pd/betaZ catalyst, interaction of the Pd clusters with zeolite protons led to formation of Pddelta+ species, which are not active in the hydrogenation of aromatics. All catalysts were resistant to poisoning by S compounds.