The paper proposes a method for synthesizing a heterogeneous catalyst that contains single Pd sites on γ-Al 2 O 3 surface. This method involves preliminary heterogenization of a Pd complex with a hydroxyquinone (e.g., alizarin) on the γ-Al 2 O 3 surface, followed by hydrogenolysis of the Pd–alizarin bond, reduction of Pd(II) into Pd(0), and removal of alizarin. The catalyst was examined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and tested in propane oxidation into key petrochemicals. During the test, the catalyst exhibited high activity (242 mol of the product per g-at Pd per hour).

The paper proposes a method for synthesizing a heterogeneous catalyst that contains single Pd sites on γ-Al2O3 surface. This method involves preliminary heterogenization of a Pd complex with a hydroxyquinone (e.g., alizarin) on the γ-Al2O3 surface, followed by hydrogenolysis of the Pd–alizarin bond, reduction of Pd(II) into Pd(0), and removal of alizarin. The catalyst was examined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and tested in propane oxidation into key petrochemicals. During the test, the catalyst exhibited high activity (242 mol of the product per g-at Pd per hour).

This study investigated the effects of ionol (2,6-di- tert -butyl-4-methylphenol) and CCl 4 as inhibitors of radical reactions in propane oxidation with oxygen in the presence of co-reductants. These compounds inhibit the activity of a Pd/C–FeSO 4 –H 2 catalytic system. Homogeneous catalytic systems based on Pd or Rh compounds, cocatalysts, and co-reductants promote molecular mechanisms for the reaction. The only exception is a Pd(α,α-bipy)Cl 2 –FeSO 4 –CO system, in which both ionol and CCl 4 act as inhibitors.

Heterogenized catalysts were prepared by the immobilization of the homogeneous catalytic systems containing the rhodium complexes, copper compounds, and perfluoroorganic acids onto porous carriers. The activity of the catalysts was studied in the processes of CO oxidation and co-oxidation of CO and propane. The state of the catalyst components was determined and the possibility of their interaction was evaluated by X-ray spectroscopy (XANES and EXAFS) and electrospray mass spectrometry (ESI-MS). The oxidation of CO on the RhCl3-CuCl2-C3F7COOH/γ-Al2O3 catalyst in a flow reactor at 70–80 °C and atmospheric pressure occurs in an oscillating mode. The co-oxidation of propane and CO at 80–95 °C and a pressure of 1.0–1.5 MPa is basically possible but occurs with a low yield of propane oxygenates.

Variation of the nature of the components of the catalytic systems comprising a catalyst [Pd/C, Pd(α,α-bipy)Cl2, RhCl3] and a cocatalyst (FeSO4, CuSO4), as well as a coreductant (H2, CO), allows exerting some control over the selectivity of the process of propane oxidation with oxygen. In particular, the yield of carbonyl compounds such as acetone and propanal in the presence of the Pd/C–FeSO4–H2catalytic system reached 90%, and that of propyl esters in the presence of RhCl3–CuSO4–CO catalytic system was 64.5%. These differences are supposedly attributable to the changes in the process mechanism depending on the composition of the catalytic systems.

The effect of copper compounds and phosphorus–molybdenum–vanadium heteropoly acids (HPAs) H5PMo10V2O40 and H7PMo8V4O40 used as cocatalysts in the cooxidation of propane and CO in the presence of rhodium, palladium, and platinum compounds in an aqueous AcOH medium has been studied. It has been shown that these HPAs are fairly effective; however, in catalyst systems with rhodium and palladium compounds, these HPAs are inferior to Cu(I,II). The inner-sphere and outer-sphere reaction mechanisms have been studied as the most probable oxidation mechanisms; the contribution of each of the mechanisms to the overall process has been determined.

The best examples of catalysts and catalytic systems for the oxidative functionalization of alkanes and mechanisms of their action are considered. The prospects for industrial application of homogeneous catalysis in the synthesis of key petrochemical products, diff erent oxygenated organic compounds based on natural and associated petroleum gases, are outlined. Special attention is given to transformations of methane.

A homogeneous catalytic system containing palladium( ii ) halides, diphenyl- m -sulfo-phenylphosphine (or palladium halide complexes with diphenyl- m -sulfophenylphosphine) and hydrohalic acid was developed and studied in the liquid-phase water gas shift reaction. The system based on palladium bromide and hydrobromic acid in aqueous acetic acid (20–40 vol.%) showed the highest activity. The dependences of the initial reaction rate on the concentrations of reagents and catalyst components were studied, a mechanism for the process was proposed, and a kinetic model was developed and found to agree well with experimental results.

Heterogeneous rhodium–copper chloride catalysts for gas-phase oxidation processes were prepared via the cold impregnation of γ-Al2O3 with aqueous RhCl3 and CuCl2 solutions. Heptafluorobutyric or pentafluorobenzoic acids were additionally deposited onto these catalysts to simulate the action of homogeneous rhodium–copper chloride catalytic systems in the coupled alkane–carbon monoxide oxidation reaction. The catalysts were studied in the reactions of carbon monoxide oxidation and coupled propane–CO oxidation with dioxygen by diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) and electron paramagnetic resonance (EPR). The obtained data indicate the probable transfer of electrons between rhodium and copper compounds.

Catalytic systems RhCl3–KI–NaCl and RhCl3–Cu(OAcf)2–NaCl in aqueous perfluorinated carboxylic acids (CF3COOH, C3F7COOH) are effective in coupled oxidation of alkanes and carbon monoxide with dioxygen. In their presence, predominant is the outer-sphere oxidation of alkanes into respective esters (alcohols) with involvement of peroxo rhodium species as an oxidant (mechanism A). The process occurs partially by the inner-sphere mechanism B involving Rh–alkyl intermediates. Mechanism B is supported by (a) formation of alkyl chlorides, (b) synthesis of acetic acid in conversion of methane, and (c) positional selectivity in oxidation of propane.

Immobilization of rhodium (palladium)-copper-chloride catalytic systems in ionic liquids as high-boiling-point solvents affects the distribution of propane oxidation products: the acetone yield increases and the yield of alcohols decreases. Propane is oxidized to acetone, bypassing the isopropanol formation step. Methane is oxidized under more severe conditions than propane, giving methyl trifluoroacetate as the main product. Mechanisms of action of the catalytic systems based on rhodium and palladium are close to each other and likely include oxo or peroxo complexes as intermediates.

Иммобилизация родий (палладий)–медь–хлоридных каталитических систем в ионных жидкостях (ИЖ) как высококипящих растворителях, влияет на распределение продуктов окисления пропана: увеличивается выход ацетона и снижается выход спиртов. Пропан окисляется в ацетон, минуя стадию образования изопропанола. Метан, окисляясь в более жестких условиях, чем пропан, дает основной продукт метилтрифторацетат. Механизмы действия каталитических систем на основе родия и палладия близки и, по-видимому, включают оксо- или пероксокомплексы в качестве интермедиатов.

The oxidative decarbonylation of acetic and propionic acids with the formation of the corresponding alcohol and alkyl carboxylate is observed in the RhIII/CuI,II/Cl− catalytic system in the presence of O2 and CO. The decarbonylation of propionic acid in a deuterated solvent results in the substitution of hydrogen atoms by deuterium in the alkyl part of the products to form CH2DCOOD (CHD2COOH) and CHD2COOD (CD3COOH). The subsequent decarbonylation of deuterated acetic acids affords the corresponding deuteromethanols detected as esters with propionic and deuteroacetic acids. The substitution of the hydrogen atom by deuterium in the alkyl part of molecules of the products of oxidative decarbonylation of propionic acid, when the reaction is carried out in a deuterated solvent, indicates that propionic acid behaves as saturated hydrocarbon and blocks the oxidation of poorly soluble methane. Unlike propionic acid, acetic acid enters only the oxidative decarbonylation reaction and does not block methane oxidation.