ВЛИЯНИЕ ТИПА ЦЕОЛИТА КАК КОМПОНЕНТА КОМПОЗИТНОГО КОБАЛЬТОВОГО КАТАЛИЗАТОРА НА СОСТАВ ПРОДУКТОВ СИНТЕЗА ФИШЕРА–ТРОПША

The dependence of zeolite type in a composite catalyst, namely structural features, presence of alkali metal cation and total acidity, on the composition of Fischer-Tropsch product has been shown in the article. Highly dispersed skeleton cobalt (Raney cobalt) was used as active metal. It was found that the presence of zeolite in Hform in the composition of the catalyst results in the formation of a larger number of unsaturated and branched hydrocarbons. The cobalt composite catalyst based on HBeta zeolite is more active and more productive in the synthesis of C<sup>5+</sup> hydrocarbons from CO and H<sub>2</sub> than the catalyst based on KA zeolite. Assumptions of the role of zeolite acid sites in secondary transformations of hydrocarbons produced from CO and H<sub>2</sub> on skeleton cobalt were done.В статье исследована зависимость состава продуктов синтеза Фишера–Тропша от типа цеолита в составе композитного катализатора. При анализе результатов учтены струк-турные особенности, наличие катиона щелочного металла, общая кислотность. В качестве активного металла использовали мелкодисперсный скелетный кобальт. Установлено, что в присутствии цеолита в Н-форме образуется большее количество ненасыщенных и разветвленных углеводородов. Кобальтовый композитный катализатор на основе цеолита HBeta активнее и производительнее в синтезе углеводородов С5+ из СО и Н2, чем катализатор на основе цеолита КА. Сделаны предположения о роли кислотных центров цеолита во вторичных превращениях угле-водородов, образовавшихся из СО и Н2 на скелетном кобальте

The influence of zeolite type in composite cobalt catalyst on the Fischer–Tropsch synthesis product composition

The dependence of zeolite type in a composite catalyst, namely structural features, presence of alkali metal cation and total acidity, on the composition of Fischer-Tropsch product has been shown in the article. Highly dispersed skeleton cobalt (Raney cobalt) was used as active metal. It was found that the presence of zeolite in Hform in the composition of the catalyst results in the formation of a larger number of unsaturated and branched hydrocarbons. The cobalt composite catalyst based on HBeta zeolite is more active and more productive in the synthesis of C<sup>5+</sup> hydrocarbons from CO and H<sub>2</sub> than the catalyst based on KA zeolite. Assumptions of the role of zeolite acid sites in secondary transformations of hydrocarbons produced from CO and H<sub>2</sub> on skeleton cobalt were done

The Importance of Water for Purification of Longer Carbon Nanotubes for Nanocomposite Applications

Ultralong carbon nanotubes (UCNTs) are in high demand for nanocomposites applications due to their magnificent physical and chemical properties. UCNTs are synthesized by the catalytic chemical vapor deposition (CCVD) method and, before use as fillers in nanocomposites, should be purified of residual catalyst and non-CNT particles without significant destruction or scissoring of the UCNT. This study investigates the role of water vapor for purification of UCNTs from iron catalyst particles and the importance of water assistance in this process is confirmed. It was shown that wet air treatment of products of UCNTs CCVD synthesis under mild conditions can be used to sufficiently decrease residual iron catalyst content without significant carbon losses in comparison to the results obtained with dry air, while the residual iron content was shown to significantly influence the subsequent oxidation of different forms of carbons, including UCNTs. The increasing of D/G ratio of Raman spectra after wet air treatment of products of UCNTs CCVD synthesis makes it possible to conclude that iron catalyst particles transform into iron oxides and hydroxides that caused inner structural strains and destruction of carbon shells, improving removal of the catalyst particles by subsequent acid treatment. UCNTs purification with water assistance can be used to develop economically and ecologically friendly methods for obtaining fillers for nanocomposites of different applications

Competitive Formation Zones in Carbon Nanotube Float-Catalysis Synthesis: Growth in Length vs. Growth Suppression

Catalytic synthesis of carbon nanotubes (CNT) produces numerous various byproducts such as soot, graphite platelets, catalyst nanoparticles, etc. Identification of the byproduct formation mechanisms would help develop routes to more selective synthesis of better carbon-based materials. This work reports on the identification of the formation zone and conditions for rather unusual closed multishell carbon nanocapsules in a reactor for float-catalysis synthesis of longer CNT. Structural investigation of the formed nanocapsule material along with computational fluid dynamics (CFD) simulations of the reactor suggested a nanocapsule formation mechanism, in which CNT embryos are suppressed in growth by the in-reactor turbulence. By means of TEM and FFT investigation, it is found that differently oriented single crystals of γ–Fe2O3, which do not have clear connections with each other, determine a spherical surface. The carbon atoms that seep through these joints do not form crystalline graphite layers. The resulting additional product in the form of graphene-coated (γ–Fe/Fe3C)/γ–Fe2O3 nanoparticles can be a lightweight and effective microwave absorber