卷 11, 编号 3 (2019)

Different ways of preparing 2,3,5-trimethyl-1,4-benzoquinone (TMQ), a key intermediate in the synthesis of vitamin E, via the catalytic oxidation of 2,3,6-trimethylphenol (TMP) are considered. It is shown that aqueous solutions of Mo–V phosphoric heteropolyacids (HPAs) are promising catalysts for the oxidation of TMP with oxygen. Different technological options are analyzed for using HPAs in this reaction: the one-stage homogeneous acetic acid oxidation of TMP and a biphasic two-step procedure. The efficiency of a biphasic version that ensures high (up to 99.5%) selectivity for TMQ and high catalyst productivity in the target reaction (≈600–800 g TMQ \({\text{L}}_{{{\text{cat}}}}^{{ - 1}}\) h⁻¹) is proved.

A study is made of the effect of the composition of the active component of copper-doped nickel catalysts on their activity and selectivity in the hydrodeoxygenation (HDO) of model compounds of vegetable oils (esters) to remove oxygen atoms from them with the formation of alkanes. It is shown that the Ni/Al₂O₃ and Ni–Cu/Al₂O₃ catalysts are active in this process. With them, the hydrodeoxygenation of methyl ester of hexadecanoic acid mixed with ethyl ester of decanoic acid results in the formation of С₆−С₁₆ alkanes and oxygen-containing products, while methane and ethane can be found in the gas phase. When the Ni : Cu ratio in the catalysts is lowered, the conversion of esters and the capability of these catalysts for C–C bond hydrogenolysis are reduced. This means the introduction of copper can promote retention of the carbon skeleton of alkanes obtained as a result of hydrodeoxygenation, along with the amount of methane. According to X-ray diffraction data, introducing copper into the Ni/Al₂O₃ catalyst results in the formation of Ni_1 – xCu_x solid solutions. According to X-ray photoelectron spectroscopy data, lowering the content of copper in the Ni–Cu/Al₂O₃ catalyst raises the Ni : Cu ratio on a sample’s surface.

Cu- and Fe-containing catalysts are studied in the reaction of selective hydrogenation of furfural to furfuryl alcohol (FA). The catalysts are prepared by alloying the respective metal nitrates and reduced before the reaction directly in the reactor at 250°C. The process is conducted in a batch reactor at 150°C and 6.0 MPa of hydrogen pressure. It is shown that the most active catalyst is Cu₂₀Fe₆₆Al₁₄, the furfural conversion and selectivity toward FA in the presence of which are 96 and 97 mol %, respectively. Inside a continuous-flow reactor in the presence of this catalyst, 100% furfural conversion can be attained at a selectivity toward FA of up to 95 mol % at 160°C and 5 MPa of hydrogen pressure. The resulting catalyst remains active for 30 h of continuous operation. The high activity of the copper–iron catalyst is likely due to the presence of stabilized finely divided copper particles in it.

Changes in the structural, textural, and acidic properties of Mg–HZSM-5/Al₂O₃ catalyst subjected to pretreatment (thermal and hydrothermal) of varying temperatures and durations are studied. The catalysts are characterized by XRF, XRD, ²⁷Al solid-state NMR spectroscopy, nitrogen adsorption, DRIFT spectroscopy, and ammonia TPD. The catalytic activity of the samples in converting dimethyl ether (DME) to lower olefins is studied. It is shown that the initial catalytic activity of an Mg-containing zeolite catalyst is determined by the total acidity of the surface and does not depend on the initial acid site strength distribution, while the stability of the catalyst depends on its morphological properties.

The behavior of a two-phase flow inside the inlet pipeline of a catalytic reactor is investigated. In addition to the classical approach using familiar flow diagrams, means of computational fluid dynamics are used for three-dimensional modeling of the spatial distribution of phases in the pipeline during operation. Results show a nonuniform distribution of the liquid phase over the over the pipeline outlet cross section surface, plus a mass flow of the liquid phase that is not stable over time. The maximum peak flow rates exceed the average values by ~300%. Compared to data from flow diagrams, CFD modeling shows that a change in the gas flow in the investigated range does not alter the nature of a two-phase flow, but an increase in the gas flow reduces the irregularity of the distribution of the liquid phase over the pipeline outlet cross section. Data on the behavior of a flow are needed to design catalytic reactor structures that ensure the uniform distribution of a two-phase flow to the catalyst bed for, e.g., hydrotreating reactors in the oil refining industry.

The main fields of application of immobilized enzymes from the class of oxidoreductases and prospects for their use in technological processes were analyzed. The structure of the most important enzymes from the class of oxidoreductases and the mechanisms of their catalytic action were described. The main factors affecting the activity of enzymes, methods for their immobilization, and examples of effective use in technological processes were given. The main trends in the development of this field were analyzed.