Svetlana A. Selishcheva

In this paper, high-loaded copper-containing catalysts synthesized by the different methods (sol–gel, fusion, coprecipitation) have been studied in furfural hydroconversion in a batch reactor at a hydrogen pressure of 5.0 MPa and a temperature of 100°C. The reduction temperatures and phase composition of the catalysts have been determined by physicochemical methods. It has been shown that the highest activity in the studied process is exhibited by a coprecipitated copper–alumina catalyst, which provides the production of furfuryl alcohol with a selectivity of 100% at 100–130°C; in addition, in the presence of this catalyst, 2-methylfuran can be synthesized with a yield of 65% at 200°C. The phase composition of the catalyst reduced at a selected temperature and the catalyst after reaction has been determined.

Highly loaded copper-containing catalysts synthesized by different methods (sol-gel, alloying and coprecipitation) were studied in hydroconversion of furfural in a batch reactor at a hydrogen pressure 5.0 MPA and temperature 100 °С. The reduction temperature and phase composition of the catalysts were determined using physicochemical methods. The highest activity in the process under consideration was observed for the coprecipitated copper-alumina catalyst, which at 100–130 °С allows obtaining furfuryl alcohol with 100 % selectivity; in addition, 2-methylfuran can be produced in the presence of this catalyst with the yield of 65 % at 200 °С. The phase composition of the catalyst reduced at a chosen temperature and the catalyst after the reaction was determined.

In this study, the high-loaded copper-containing catalysts modified with Fe and Al were successfully applied for the hydroconversion of furfural to furfuryl alcohol (FA) or 2-methylfuran (2-MF) in a batch reactor. The synthesized catalysts were studied using a set of characterization techniques to find the correlation between their activity and physicochemical properties. Fine Cu-containing particles distributed in an amorphous SiO₂ matrix, which has a high surface area, provide the conversion of furfural to FA or 2-MF under exposure to high pressure of hydrogen. The modification of the mono-copper catalyst with Fe and Al increases its activity and selectivity in the target process. The reaction temperature strongly affects the selectivity of the formed products. At a H₂ pressure of 5.0 MPa, the highest selectivity toward FA (98%) and 2-MF (76%) was achieved in the case of 35Cu13Fe1Al-SiO₂ at the temperature of 100 °C and 250 °C, respectively.

This paper describes the chemical engineering aspects for the preparation of highly active and stable nanocomposite photocatalysts based on N-doped TiO₂. The synthesis is performed using titanium oxysulfate as a low-cost inorganic precursor and ammonia as a precipitating agent, as well as a source of nitrogen. Mixing the reagents under a control of pH leads to an amorphous titanium oxide hydrate, which can be further successfully converted to nanocrystalline anatase TiO₂ through calcination in air at an increased temperature. The as-prepared N-doped TiO₂ provides the complete oxidation of volatile organic compounds both under UV and visible light, and the action spectrum of N-doped TiO₂ correlates to its absorption spectrum. The key role of paramagnetic nitrogen species in the absorption of visible light and in the visible-light-activity of N-doped TiO₂ is shown using the EPR technique. Surface modification of N-doped TiO₂ with copper species prevents its intense deactivation under highly powerful radiation and results in a nanocomposite photocatalyst with enhanced activity and stability. The photocatalysts prepared under different conditions are discussed regarding the effects of their characteristics on photocatalytic activity under UV and visible light.

The heightened interest in liquid organic hydrogen carriers encourages the development of catalysts suitable for multicycle use. To ensure high catalytic activity and selectivity, the structure–reactivity relationship must be extensively investigated. In this study, high-loaded Ni–Cu catalysts were considered for the dehydrogenation of methylcyclohexane. The highest conversion of 85% and toluene selectivity of 70% were achieved at 325 °C in a fixed-bed reactor using a catalyst with a Cu/Ni atomic ratio of 0.23. To shed light on the relationship between the structural features and catalytic performance, the catalysts were thoroughly studied using a wide range of advanced physicochemical tools. The activity and selectivity of the proposed catalysts are related to the uniformity of Cu distribution and its interaction with Ni via the formation of metallic solid solutions. The method of introduction of copper in the catalyst plays a crucial role in the effectiveness of the interaction between the two metals.

CuFe-containing catalysts with different copper oxide content were prepared by fusion of metal salts. The obtained catalyst showed high activity in the hydrogenation of furfural to furfuryl alcohol (FA) in the batch reactor in the presence of isopropanol as a solvent at a temperature of 100 °C and a hydrogen pressure of 6.0 MPa. The yield of FA and furfural conversion are 97% and 98%, respectively. In the solvent-free reaction in the flow-type reactor; the most active catalyst Cu₂₀Fe₆₆Al₁₄ leads to the 96% formation of FA with 100% conversion of furfural at liquid hourly space velocity (LHSV) = 1 h⁻¹; 160 °C and a hydrogen pressure of 5.0 MPa during 30 h. According to the X-ray diffraction (XRD) method, the active component of the spent and fresh Cu₂₀Fe₆₆Al₁₄ catalyst is the same and is represented by metallic copper and Fe₃O₄-type spinel. Using different methods, the formation of active sites was investigated.