Catalysts

This paper presents the synthesis and characterization of anionic rhodium(I) complexes obtained by the reaction of a homogeneous Wilkinson catalyst or a rhodium cyclooctadiene dimer with ionic liquids as precursors. All newly produced complexes were characterized spectroscopically (NMR, ESI-MS, FT-IR) and their thermal stability was examined (TGA, melting point). Moreover, their catalytic activity was determined in the hydrosilylation of octene or allyl glycidyl ether with 1,1,1,3,3,5-heptamethyltrisiloxane and in the hydroboration reaction of styrene with pinacolborane (HBpin). All catalysts used were insoluble in the reactants, which allowed for their isolation and repeated use. Their activity was compared in subsequent 10 (hydrosilylation) or 5 (hydroboration) catalytic cycles. The obtained results allowed the selection of the most effective catalytic systems, which can be a real alternative to traditional homogeneous catalysts, offering greater ease of recovery and reuse.

Hydrogenases are key enzymes in microbial energy metabolism, catalyzing the reversible conversion between molecular hydrogen and protons. Among them, [NiFe]-hydrogenases are particularly attractive for biocatalytic applications due to the oxygen tolerance of several members of this class and their ability to couple hydrogen oxidation with redox cofactor regeneration. In this study, a recombinant soluble [NiFe]-hydrogenase from Cupriavidus necator H16 was successfully expressed in Escherichia coli BL21 (DE3), purified, and characterised with a focus on its applicability for NAD⁺ regeneration. Unlike previous studies that primarily used native C. necator extracts or complex maturation systems, this work provides the first quantitative demonstration that an aerobically purified recombinant soluble [NiFe]-hydrogenase expressed in E. coli can function effectively as an NAD⁺ regeneration catalyst and operate within multi-enzymatic cascade reactions under application-relevant conditions. The crude recombinant enzyme displayed a volumetric activity of 0.273 ± 0.024 U/mL and a specific activity of 0.018 ± 0.002 U/mg_cells in the hydrogen oxidation assay, while purification yielded a specific activity of 0.114 ± 0.001 U/mg with an overall recovery of 79.2%. The enzyme exhibited an optimal temperature of 35 °C and a pH optimum of 7.00. Thermal stability analysis revealed rapid deactivation at 40 °C (k_d = 0.4186 ± 0.0788 h⁻¹, t_1/2 ≈ 1.7 h) and substantially slower deactivation at 4 °C (k_d = 0.1141 ± 0.0139 h⁻¹, t_1/2 ≈ 6.1 h). Batch NADH oxidation experiments confirmed efficient cofactor turnover and high specificity towards NADH over NADPH. Finally, integration of the hydrogenase into a one-pot two-enzyme glucose oxidation system demonstrated its capacity for in situ NAD⁺ regeneration, although the reaction stopped after approximately 5 min due to acidification from gluconic acid formation, highlighting pH control as a key requirement for future process optimization.

The paper studied the effect of high-voltage short-pulse electrohydraulic discharge (HVSPED) on the processes of catalytic cracking of oil sludge in order to increase the yield of light hydrocarbon fractions. A set of laboratory experiments was carried out varying the key parameters of HVSPED—discharge voltage, capacitance of capacitor banks and processing time. As a catalyst, the developed nanocomposite catalyst bentonite was used, with nickel packed. The optimal electrophysical parameters of oil sludge treatment by HVSPED were determined, providing the maximum yield of gasoline and kerosene fractions. The effectiveness of HVSPED treatment of oil sludge in the presence of a catalyst was confirmed by DTA–thermogravimetric analysis and chromatographic-mass spectral analysis of the light and middle fractions of the hydrogenate. The proposed approach made it possible to enhance the resource and energy efficiency of oil sludge processing using HVSPED, demonstrating high potential for further industrial application