Том 65, № 1 (2024)

It has been experimentally shown that N-heteroaryl-substituted α-diphenylphosphinoglycines N-(pyrazin-2-yl)-α-diphenylphosphinoglycine, N-(pyridin-2-yl)-α-diphenylphosphinoglycine and N-(pyrimidin-2-yl)-α-diphenylphosphinoglycine obtained by the reaction of three-component condensation of diphenylphosphine, the corresponding primary amine and glyoxylic acid monohydrate are capable in combination with Ni(COD)₂, where COD is cyclooctadiene-1,5, to form active forms of catalysts for selective homogeneous dimerization and trimerization of ethylene with the formation of butene-1 and hexene-1 as the main products. It has been established that the obtained organo-nickel catalytic systems provide a yield of short-chain (C₄–C₆) olefins at the level of 90% with a selectivity for linear α-olefins of 97%. The study of the influence of temperature on the process of homogeneous ethylene oligomerization using the obtained compounds made it possible to establish that the optimal temperature for ethylene oligomerization, providing the highest selectivity to butene-1 and hexene-1, is 80–105°C at the optimum pressure of ethylene is 20–35 atm. Under these conditions, the selectivity for butenes is 71.4–72.6% (selectivity for butene-1 – 69.3–71.1%), for hexenes 20.6–21.2% (selectivity for hexene-1 – 19.2–19.5%), and the optimal duration of the oligomerization process at a temperature 105°C is 1.5 h, which provides the rate of formation of butene-1 equal to 168.1 golig gNi⁻¹h⁻¹) and the rate of formation of hexene-1 – 47.3 golig gNi⁻¹h⁻¹).

A new catalytic system for reductive C(sp²)–C(sp³) cross-electrophile coupling of was designed: Ptᴵᴵ iodo complexes in acetone solution containing an excess of NaI catalyzes the coupling of methyl iodide with vinyl iodide to form propylene. In parallel, the product of C(sp²)–C(sp²) coupling, 1,3-butadiene, is released in minor amounts. The total yield of the products based on the consumed vinyl iodide is almost quantitative. Under conditions of a large excess of methyl iodide, kinetics of vinyl iodide uptake follows pseudo-first-order law. The cross-coupling proceeds in a sequence of steps: oxidative addition of CH₃I to Ptᴵᴵ iodo complexes to form methyl Pt^IV species – reduction of the latter with I^– into the corresponding Ptᴵᴵ derivative – oxidative addition of C₂H₃I to the last one – reductive elimination of propylene from the intermediate methyl vinyl Pt^IV complex.

The physicochemical and catalytic (CO₂ hydrogenation) characteristics of Mo-containing catalysts have been studied. Catalysts with an oxide content of Mo 8 and 15 wt% were prepared by impregnation with ammonium paramolybdate γ-Al₂O₃ followed by drying and calcining at 500°C. The introduction of Mo oxide reduces the pore volume of the support and increases their average size, which indicates the distribution of the deposited molybdenum oxide in the pores of the support. According to X-ray diffraction data, the calcined catalyst contains practically no crystalline MoO₃ phase. According to the Raman spectra, oxygen-containing formations are present on the catalyst surface, in which Mo atoms are tetrahedrally and octahedrally coordinated with respect to oxygen atoms. The impregnated MoO₃ oxide is partially reduced by hydrogen during linear heating starting from 320°C. Hydrogenation of CO₂ (gas of composition, vol.%: 30.7 CO₂, 68 H₂, rest. N₂, sample 0.5 g) was studied in the mode of linear heating up to 400°C. The main reaction is the reverse reaction of CO steam reforming. The contribution of the methanation reaction to CO₂ hydrogenation is small. An increase in temperature and pressure has a positive effect on CO₂ conversion. With an increase in pressure from 1 to 5 MPa, the CO content increases approximately twofold. In the hydrogenation of CO₂, γ-Al₂O₃, preheated in a flow of H₂ to 400°C, also exhibits noticeable activity, although significantly lower compared to Mo-containing catalysts. With increasing pressure, the activity of aluminium oxide and Mo-containing catalysts, increases.

In this work, using the method of X-ray photoelectron spectroscopy (XPS), a comparative study of the nature of the interaction of NO₂ at room temperature and a pressure of 10⁻⁵ mbar with two samples of highly oriented pyrolytic graphite (HOPG), on the surface of which rhodium was preliminarily deposited by vacuum deposition, was carried out. Before metal deposition, one of the HOPG samples was annealed in vacuum at 600°C, and the other was subjected to bombardment with argon ions, followed by exposure to air at room temperature for an hour in order to introduce strongly bound oxygen atoms into the surface composition. After deposition of rhodium on two samples of HOPG prepared, two model catalysts were obtained, designated as Rh/C and Rh/C(A)-O. It was found that the interaction of NO₂ with Rh/C led to the oxidation of graphite with the destruction of the surface layer. The Rh particles remained in the metallic state, but at the same time they were introduced into the near-surface layer of the carbon support. On the contrary, when the Rh/C(A)-O sample was treated with NO₂, the deposited rhodium was partially converted into RH₂O₃, while the graphite was oxidized to an insignificant degree and retained its original structure. The role of surface oxygen in the stabilization of graphite with respect to oxidation to NO₂ was discussed.