Effect of Synthesis Method on Properties of Layered Double Hydroxides Containing Ni(III)

Unstable oxidation state +3 of nickel can be stabilized in the structure of layered double hydroxides, the resulting crystallinity and properties being dependent on the synthesis method. Three different wet chemical methods (co-precipitation at variable pH, co-precipitation followed by hydrothermal treatment, co-precipitation with microwave treatment) were used to synthesize Mg/Ni–Al layered double hydroxides containing triply charged nickel cations. Lattice parameters of the samples synthesized by various methods were found to differ from each other by about 1.5%. The most crystallized sample was obtained by hydrothermal synthesis. The oxidation state of nickel in the LDH samples was confirmed by XPS. TEM mapping gave evidence of the uniform distribution of nickel in all the samples. The LDHs’ reduction with hydrogen and thermal transformations of the phase composition and morphology of LDHs were studied in detail. The properties of the samples synthesized by the different methods were shown to be quite similar.

Decarboxylation of p-Coumaric Acid during Pyrolysis on the Nanoceria Surface

Temperature-programmed desorption mass spectrometry (TPD MS) was used to study the pyrolysis of p-coumaric acid (pCmA) on the nanoceria surface. The interaction of pCmA with the CeO2 surface was investigated by FT-IR spectroscopy. The obtained data indicated the formation on the nanoceria surface of bidentate carboxylate complexes with chelate (Δν = 62 cm−1) and bridge structure (Δν = 146 cm−1). The thermal decomposition of pCmA over nanoceria occurred in several stages, mainly by decarboxylation. The main decomposition product is 4-vinylphenol (m/z 120). The obtained data can be useful for studying the mechanisms of catalytic thermal transformations of lignin-containing raw materials using catalysts containing cerium oxide and the development of effective technologies for the isolation of pCmA from lignin.

INFLUENCE OF VANADIUM OXIDE ADDITIVE ON THERMAL TRANSFORMATIONS OF CERAMIC MASS

A comparative study of thermal transformations of ceramic mass (CM) based on α-Al2O3 modified with vanadium oxide additives introduced into CM by wet mixing and by deposition on the surface of the CM particles using molecular layering nanotechnology was carried out. The structural and chemical transformations of the obtained compositions were characterized by differential thermal analysis under linear heating conditions at a rate of 10°С/min, in the temperature range from room temperature to 1000°C. Changes in the phase composition, specific surface area of the compositions, and the state of the modifying additive before and after heating were studied using x-ray diffraction, low-temperature nitrogen adsorption, and ultraviolet–visible diffuse reflectance spectroscopy

Catalytic pyrolysis of lignin-cellulose biomass and its model phenolic components on the nanosized oxides surface

Lignocellulose is currently considered as a potential renewable source of a wide range of valuable chemicals, including aromatics. Catalytic pyrolysis is the promising method for the conversion of biomass raw materials. The development of renewable biomass pyrolysis technologies requires fundamental research on catalytic thermal transformations of lignocellulosic raw materials. Therefore, in this work, the methods of IR spectroscopy, temperature programmed desorption mass spectrometry (TPD MS) and thermogravimetric analysis were used to investigate the catalytic thermal transformations of rapeseed meal (RM) and ferulic acid (FA) as a model phenol-containing component of such raw material on the surface of nanosized oxides CeO2, SiO2 TiO2/SiO2, Al2O3/SiO2 and CeO2/SiO2. The most effective catalyst in the conversion of biomass to ketones was a nanocomposite CeO2/SiO2 with the highest content of nanoparticles of CeO2 (24%). According to the data of FTIR spectroscopic studies, the interaction of FA with the CeO2 surface occurs with the participation of phenol and carboxyl groups. The main products of thermal decomposition of FA on the surface of CeO2 are 3-methoxy-4-vinylphenol, guaiacol, coumaric acid and hydroxybenzene. Condensed aromatics (naphthalene, alkylnaphthalenes) were registered in small quantities.