Relationship between the crystal structure, conductive and catalytic properties of perovskites Bi4Fe2xV2−2xO11−δ

The relationship between the crystal structure of bismuth vanadates Bi4Fe2xV2−2xO11−δ, where V5+ ions are partially replaced by Fe3+ cations, and their conductive properties and catalytic activities in conversions of isobutanol was established. A correlation between concentration of Fe ions, activation energy of dehydrogenation, and conductance activation energy was revealed. © 201

Understanding the electron-accepting sites on the surface of cage zirconium phosphates of nasicon type doped with cobalt, nickel and copper ions

This paper looks at the synthesis of new type of catalysts — solid electrolytes with cation-type sodium ion conductivity that fall within the NASICON family. The paper also examines their surface adsorption properties. Complex sodium zirconium phosphates doped with ions of 3d metals — i. e. cobalt (II), nickel (II) and copper (II), were synthesized by sol gel method. Sodium ions are substituted with doping ions in the cationic part of the structure. Detailed analysis of the physico-chemical properties of the synthesized structures has been carried out that involved X-ray diffraction analysis, scanning electron-ion spectroscopy, scanning microscopy and thermal desorption of nitrogen. It was found that the composition and structural parameters of the synthesized phosphates conform with the literature. The study looked at the surface electron-accepting properties of the sodium zirconium phosphates of the following composition: Na(1 – 2х) MхZr2(PO4)3 withх = 0.125 and 0.25, whereM2+M — Co2+, Ni2+, Cu2+. The study procedure involved spectrophotometric method based on adsorption of pyridine and spectrokinetic method based on the indicator test showing how fast the blue aniline colour forms from the adsorbed paraphenylenediamine. Several acid sites have been identified on the surface and in the micropores of the phosphates. It was established that the nature and number of such sites are governed by the nature and amount of the introduced doping ions. It is shown that the colour generation rate tends to increase in the row Ni ~ Co < Cu, which has a qualitative correlation with the growth of ion radii. It is demonstrated that the ions of 3dd metals introduced in the NASICON structure enable to control the acidic properties of their surface and obtain catalysts with predefined properties. This research was funded by the Russian Foundation for Basic Research under the Project No. 18-33-20101. This publication was prepared with support from the Programme “5-100” implemented by Peoples’ Friendship University of Russia. © 2019, "Ore and Metals" Publishing house. All rights reserved

Effect of Crystal Structure on the Catalytic Properties of Bi4Zr2xV2−2xO11−δ Perovskites in the Decomposition of Isobutanol

Abstract: The effect crystal structure has on the catalytic properties of complex zirconium-containing bismuth vanadates Bi4Zr2xV2–2xO11–δ in the decomposition of isobutanol is studied. Complex oxides are obtained by means of solid-state synthesis and studied via IR spectroscopy, X-ray powder diffraction, and XPS. The catalytic activity of Bi4Zr2xV2−2xO11−δ perovskite in the dehydrogenation of isobutanol grows along with the content of zirconium(ΙV) ions and phase changes α → β → γ, with the highly conductive γ-phase being the one most active. It is found that an increase in the dehydrogenating activity of the samples is associated with a drop in the activation energy of the reaction and a change in the state of the solid solution’s current carriers. © 2020, Pleiades Publishing, Ltd

Relationship between the crystal structure, conductive and catalytic properties of perovskites Bi₄Fe_2xV_2−2xO_11−δ

The relationship between the crystal structure of bismuth vanadates Bi4Fe2xV2−2xO11−δ, where V5+ ions are partially replaced by Fe3+ cations, and their conductive properties and catalytic activities in conversions of isobutanol was established. A correlation between concentration of Fe ions, activation energy of dehydrogenation, and conductance activation energy was revealed

NASICON Catalysts with Composition Na(Cs)1 – 2xMxZr2(PO4)3 for Transformations of Aliphatic Alcohols

Abstract: The activity of solid electrolytes from the family of Na(Cs)–Mx–Zr phosphates (NZP and CZP) with dopant ions M+2 = Co+2 and Ni+2 synthesized by the sol–gel method is studied in the gas-phase transformations of isopropanol and isobutanol. It is found that the amount of M+2 and its nature, as well as the direction of a change in the catalyst temperature (heating or cooling in the range of 473−693 K), affects the activity of M-NZP and M-CZP. In the transformation of isopropanol, hysteresis of the acetone yield, counter-clockwise (type I) for Co-NZP and clockwise (type II) for Ni-NZP, is observed in the heating–cooling cycles. An increase in the activity of Co-NZP in the cooling mode (type I) is related to a rise in the apparent activation energy of alcohol dehydrogenation under conditions of the formation of new catalytically active sites in the form of a Co+2−Zr+4 → Co+3−Zr+3 ion pair with the oxidized form of M and the reduced form of Zr. Type I hysteresis of the total alcohol conversion is observed in the transformations of isobutanol to olefin and aldehyde over Co(Ni)-CZP. The hysteresis is associated with a decrease in the activation energy of alcohol dehydrogenation. The main reaction over the Co(Ni)-CZP catalysts is the dehydration of alcohol with an increase in the activation energy of the reaction upon cooling, for example, by 53 kJ/mol for Ni0.25-CZP. © 2020, Pleiades Publishing, Ltd