Polyaniline–13X zeolite composite‐supported platinum electrocatalysts for direct methanol fuel cell applications

We successfully synthesized 13X zeolite using a hydrothermal method. Then, composites of polyaniline (PANI) with 13X zeolite and PANI–13X with platinum were prepared by chemical oxidative polymerization and chemical reduction, respectively. Field emission scanning electron microscopy, X‐ray diffraction, Raman spectroscopy and Brunauer–Emmett–Teller techniques were used to characterize the PANI–Pt and PANI–Pt–13X composites. Further, the electrocatalytic activity towards methanol oxidation of the synthesized catalysts was explored using cyclic voltammetry in 1 mol L^?1 CH₃OH + 0.5 mol L^?1 H₂SO₄ solution. From the obtained results, PANI–Pt–13X shows superior performance compared to PANI–Pt towards methanol oxidation and electrical conductivity. Hence, the 13X zeolite‐incorporated PANI–Pt composite could be an efficient catalyst for direct methanol fuel cell applications. © 2019 Society of Chemical Industry     

Development of technology for the production of microspherical alumina support for the alkane dehydrogenation catalyst: III. The effect of the phase composition of microspherical supports on their thermal stability

This publication continues a series of our reports on the optimization of preparation conditions for obtaining a thermally stable support for the alkane dehydrogenation catalyst. The phase composition effect on the stability, particle size distribution, structure, texture, and mechanical properties of supports heated to 1100°C is reported. Microspherical alumina supports obtained by successive thermal and hydrothermal treatments of gibbsite are compared to commercial supports obtained by the thermochemical activation (TCA) of gibbsite. The dimensions of the support granules decrease upon heating because of shrinkage, which is governed by the phase composition of the granules and by the packing of their constituent boehmite and alumina crystallites. Three temperature intervals can be distinguished in the shrinkage of the granules. In region I (<600°C), there is intensive shrinkage via the diffusion glide of crystallites, the mechanical strength of the granules remaining invariable. In region II (600–900°C), the polymorphic transformations of alumina accompanied by sintering via surface diffusion do not affect the dimensions and strength of the granules. In region III (>900–1000°C), shrinkage takes place via coalescent sintering. For commercial manufacturing of microspherical alkane dehydrogenation catalysts and for ensuring their stability at 550–900°C, it is recommended to use alumina supports containing the minimum possible amount of χ-Al₂O₃. As the single-phase boehmite support obtained by our technology is heated to 1100°C, its granules shrink by no more than 14.4% and show an attrition resistance of 89% or above. The support based on the gibbsite TCA products, which contains 14–23 wt % χ-Al₂O₃, is characterized by 3–5% greater granule shrinkage and 6–12% lower mechanical strength.     

Morphological and structural features of polyacrylonitrile fibres spun by the dry-wet method

Conclusions -- A technological regime for the preparation of polyacrylonitrile fibres from binary and ternary copolymers has been chosen; these differ from known specimens in having a more uniform cross-sectional structure and a smoother elementary filament surface.-- A considerable difference in crystalline structure of fibres from binary and ternary copolymers which have been spun into a dimethyl sulfoxide—water bath has been shown.-- Fibres from the binary or ternary copolymer which have been spun into a precipitation bath having a large dimethyl sulfoxide content in water are characterized by a lower degree of swelling.-- Shrinkage of fibres from the binary copolymer in the temperature range 200–220°C is twice as small as the shrinkage of fibres from the ternary copolymer.Deceased.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 19–22, May–June, 1991.     

Pilot tests of the microspherical aluminochromium KDI-M catalyst for <Emphasis Type="Italic">iso</Emphasis>-butane dehydrogenation

Results from pilot tests of microspherical aluminochromium KDI-M catalyst mixed with IM-2201 in a large-scale unit (Nizhnekamskneftekhim) for iso-butane dehydrogenation are discussed. Compared to KDI catalyst, its modified analogue KDI-M is more active and selective; the optimized grain-size composition and mechanical strength ensures higher yields of iso-butylene and longer nonstop operation (up to 400 days) of the reactor unit.     

Two-electron exchange between impurity centers of tin in PbS<Subscript><Emphasis Type="Italic">z</Emphasis></Subscript>Se<Subscript>1–<Emphasis Type="Italic">z</Emphasis></Subscript> solid solutions

Using emission Mössbauer spectroscopy on ^119mmSn(^119mSn) and ¹¹⁹Sb(¹¹⁹mSn) isotopes, the electron exchange process between neutral and doubly ionized U ^– tin centers is studied in partially compensated PbS _z Se_1–z solid solutions. The activation energy of this process for compositions with z ≈ 1 is comparable to the deposition depth of the tin energy levels in the band gap of PbS (~0.11(1) eV, and for compositions with z ≈ 1, it is comparable with the correlation energy of donor U ^– tin centers in PbSe (~0.05(1) eV). For all compositions of solid solutions, the exchange is realized by the simultaneous transfer of two electrons with the use of the delocalized states of the valence band.     

Genesis of the structure and the phase and elemental compositions of an aluminum oxide catalyst in the isomerization process of n-butylenes

An investigation of the changes in the characteristics of the porous structure, phase, and elemental compositions of catalyst samples for the isomerization of n-butylenes using a set of physicochemical methods has been conducted. In has been established that under hydrothermal conditions of the isomerization process, aluminum oxide recrystallization takes place, resulting in a decrease of its specific surface value and a displacement of the maximum of the distribution of pore diameters to the region of greater values. A porous structure transformation scheme has been suggested while operating the isomerization catalyst for n-butylenes. It has been supposed that the partial phase change of γ-Al₂O₃ into δ-Al₂O₃ occurring under industrial conditions of the isomerization of n-butylenes is caused by an accumulation of metal compound admixtures supplied with the feed flow.     

Creation of a sharp cube texture in ribbon substrates of Cu–40% Ni–<Emphasis Type="Italic">M</Emphasis> (<Emphasis Type="Italic">M</Emphasis> = Fe,Cr, V) ternary alloys for high-temperature second generation superconductors

The structure and the process of texture formation in ribbons made of Cu–Ni–M (M = Fe, Cr, V) ternary alloys have been studied upon cold rolling deformation to a degree of ~99% and subsequent recrystallization annealing. The possibility of obtaining a perfect cube texture in a thin ribbon made of copper–nickel-based ternary alloys with additives of iron, chromium, and vanadium has been shown, which opens the prospects of the use of these alloys as substrates in the technology of production of tapes of high-temperature second-generation superconductors. Optimal annealing regimes have been determined, which make it possible to obtain a perfect biaxial texture close to single-crystalline one with the content of cube-oriented grains {001}〈100〉±10° more than 99% on the surface of the textured ribbon.