Camila Gomes Flores

Potassic zeolites from Brazilian coal ash for use as a fertilizer in agriculture

Brazilian coal has an ash content ranging from 30 to 50% by weight. Consequently, its use in coal-fired thermoelectric for power production generates a lot of waste. The construction sector is the largest consumer of coal ash, but it cannot absorb the entire amount generated. Thus, other applications for coal ash should be studied in aim to optimize the use of this industrial waste. This research had as focus to synthesize potassic zeolite from of the coal ash into on potassium fertilizer for the grown wheat plant. In this work, it was used a subbituminous coal from Mina do Leão (RS, Brazil) presenting 48.7% ash content on a dry basis. Concerning the synthesis of potassic zeolite, it was adopted the conventional method of hydrothermal treatment with potassium hydroxide. A schedule of experiments was conducted in order to define the optimum condition of zeolite synthesis that was then used an alkaline solution of 5M KOH with a reaction time of 24h at 150°C. According to this procedure, it was obtained a zeolite with a single crystalline phase, identified through X-ray diffraction as Merlinoite. Subsequently, it was performed a set of tests using potassic zeolite asa fertilizer for plants in a greenhouse. The synthesized potassic zeolite showed a good potential for its use as fertilizer in agriculture.

Direct Production of Iso-Paraffins from Syngas over Hierarchical Cobalt-ZSM-5 Nanocomposites Synthetized by using Carbon Nanotubes as Sacrificial Templates

This paper focuses on the effect of synthesis conditions on the structure of cobalt‐ZSM‐5 zeolites and the localization, dispersion, and reducibility of cobalt species and their catalytic performance in Fischer–Tropsch synthesis. The zeolite catalysts were prepared by using carbon nanotubes as sacrificial templates. Addition of pristine carbon nanotubes resulted only in a slight increase in the zeolite mesoporosity, whereas the presence of carbon nanotubes impregnated with cobalt drastically modified the zeolite morphology and texture. The zeolite mesoporous volume increased by 3–4 times. The catalysts prepared by using cobalt‐impregnated carbon nanotubes as templates showed 5–8 times higher Fischer–Tropsch reaction rates normalized by reducible cobalt compared with the catalysts prepared by conventional impregnation. Higher selectivity to isomerized branched hydrocarbons on these zeolites was attributed to the enhanced diffusion favoring removal of isomerized products and avoiding their cracking.

Influence of impregnation and ion exchange sequence on metal localization, acidity and catalytic performance of cobalt BEA zeolite catalysts in Fischer-Tropsch synthesis

Cobalt distribution between the external surface and micropores and acidity of the large pore BEA zeolite were controlled by choosing the sequence of impregnation and ion exchange procedures. Higher concentration of ion exchangeable cobalt was observed in the catalyst prepared by ion‐exchange of the zeolite proton form. The presence of Na+ instead of H+ ions in the exchange positions of zeolite favored deposition of cobalt on the external surface. The acid sites in the zeolite micropores can be then restored by subsequent ion exchange of sodium with ammonium nitrate and calcination. The catalytic performance of the cobalt zeolite catalysts prepared using different impregnation and ion exchange procedures was tested in the Fischer‐Tropsch synthesis. Higher reaction rates were observed over the catalysts, which did not contain cobalt ions in the cation sites of the zeolite. Lower methane selectivity, higher selectivity to long chain hydrocarbons and high fraction of isomerized products are observed when cobalt species are located on the zeolite outer surface and acid sites inside the BEA zeolite micropores.