E. Yu. Gerasimov

Catalytic properties of CoMo/Al2O3 sulfide catalysts in the hydrorefining of straight-run diesel fraction mixed with rapeseed oil

CoMo/Al2O3 sulfide catalysts varying in preparation method and Co/Mo ratio have been tested in the hydrorefining of a mixture of straight-run diesel fraction and rapeseed oil in a flow reactor at a temperature of 340–360°C, a hydrogen pressure of 4.0–7.0 MPa, and a liquid hourly space velocity of 1–2 h−1. A comparison between catalysts prepared using citric acid (CoMo/Al2O3-1.5) and both citric and orthophosphoric acids (CoMoP/Al2O3-1.5) as promoters, with Co/Mo = 0.3 and 0.5, has demonstrated that the most active catalyst in hydrodesulfurization and hydrodenitrogenation is the phosphorus-containing Co/Mo ≈ 0.5 sample. The addition of rapeseed oil to straight-run diesel fraction lowers the hydrodesulfurization and hydrodenitrogenation activities of the CoMo sulfide catalysts, irrespective of the method by which they were prepared. The fatty acid triglyceride conversion selectivity of these catalysts depends on the Co/Mo ratio and on reaction conditions: decreasing the Co/Mo ratio from 0.46 to 0.26, lowering the reaction temperature, and raising the hydrogen pressure and hydrogen-to-feedstock ratio increase the C18/C17 hydrocarbon ratio in the hydrogenated product. The addition of rapeseed oil improves the quality of the product; however, for attaining the preset residual sulfur level in this case, the process needs to be conducted at a higher temperature than the hydrorefining of straight-run diesel fraction containing no admixture.

Synthesis of homogeneous La1 − xCaxMnO3 solid solutions by the Pechini method and their activity in methane oxidation

Homogeneous La1 − xCaxMnO3 solid solutions have been synthesized by the Pechini method (using polymer-solid compositions). Their microstructure, stability at high temperatures, and catalytic activity in methane oxidation are reported. A continuous series of solid solutions stable in air up to 1100°C forms in the system, and the particle surface is enriched with calcium. A distinctive microstructural feature of the particles is their microporosity. The catalytic activity of all calcium-containing samples (except for x = 0.7) below 700°C is lower than that of lanthanum manganite and decreases under the action of the reaction medium, which can be due to the decrease in the amount of weakly bound oxygen on the surface because of the enrichment of the surface with calcium and the formation of strongly bound surface carbonates. The higher activity and stability of the La0.3Ca0.7MnO3 sample (calcined at 1100°C) above 500°C can be due to the formation of nanosized areas with an Mn3O4 structures on the perovskite particle surface in the reaction medium.

Synthesis of NiW/Al2O3 hydrotreating catalysts from ammonium paratungstate using chelating agents

Procedures are suggested for preparing NiW/Al2O3 catalysts using ammonium paratungstate as a tungsten source and citric acid and D(+)-sorbitol as chelating agents. The catalysts prepared using the suggested reagents are characterized by increased dispersity of the sulfide component compared to the NiW/Al2O3 catalyst prepared by the traditional procedure using ammonium metatungstate and nickel(II) nitrate. In transformations of dibenzothiophene, quinoline, and naphthalene, the NiW/Al2O3 catalysts prepared using ammonium paratungstate and citric acid or D(+)-sorbitol considerably surpass in the activity the NiW/Al2O3 catalyst prepared by the traditional procedure.

A new catalyst for the deep hydrotreatment of vacuum gas oil, a catalytic cracking feedstock

A new CoNiMo/Al2O3 deep vacuum gas oil hydrotreatment catalyst designed for the production of catalytic cracking feedstocks containing 200–500 ppm of sulfur is developed. The method for its preparation includes the following stages: the preparation of a support with specified textural, strength, and granulometric characteristics; the synthesis of bimetallic (Co-Mo and Ni-Mo) complex compounds in solution; and their deposition and drying. The new sample is compared to current domestic and imported industrial analogs according to their physicochemical (texture, morphology, active phase structure) and catalytic characteristics and analyzed. It is shown that the catalyst allows hydrotreatment at temperatures 5–20°C lower and target fraction yields 4–13% higher than all the reference samples. The high activity of the new catalyst is due to the formation of one-layer trimetallic Co(Ni)MoS phase particles at the stage of its sulfidation. The catalyst preparation technique is ready for industrial use (OOO Sintez, Barnaul, 1000 t/yr), and the principal technological regimes of the hydrotreatment of vacuum gas oil on the developed catalyst are determined.

Effect of the reaction medium on the structure of the La1 − xCaxMnO3 (x = 0–1) solid solutions prepared by the pechini method

AbstractThe phase composition and microstructure of La1 − xCaxMnO3 (x = 0–1) materials prepared by the Pechini method from polymer-salt stocks were studied after testing these materials in methane oxidation. According to X-ray diffraction data, the reaction medium causes no significant changes in the samples, while high-resolution transmission electron microscopy indicates that the x > 0.3 samples are unstable. Under the action of the reaction medium, the perovskite structure of these samples undergoes partial decomposition accompanied by the formation of planar defects having a lower manganese content. The number and degree of segregation of these defects increase with increasing calcium content. The calcium oxide and manganese oxide phases as segregated nanoparticles are observed on the particle surface. These changes are caused by the decrease in the oxygen content of the manganites under the action of the reaction medium

Influence of the size and charge of nonstoichiometric silver sulfide nanoparticles on their interaction with blood cells

(T,P_{O_2 } )

Synthesis and characterization of Sibunit-supported Pd–Ga, Pd–Zn, and Pd–Ag catalysts for liquid-phase acetylene hydrogenation

, by the formation of vacancies, and by the variation of the charge of the manganese cations, as well as by the charge ordering tendency of the manganese cations. Therefore, the observed changes in catalytic activity under the action of the reaction medium for x > 0.3 can be due to perovskite decomposition accompanied by the formation of planar defects, the release of the manganese oxide and calcium oxide phases, and their subsequent sintering.

PtPd-nanoparticles supported by new carbon materials

Silver sulfide nanoparticles have been synthesized through chemical deposition from aqueous solutions of silver nitrate and sodium sulfide in the presence of sodium citrate as a complexing agent and stabilizer. The nanoparticles have a Ag2S core with a monoclinic crystal structure, covered with a carbon-containing citrate shell. Varying initial reactant concentrations, we can obtain core/shell nanoparticles with a tailored Ag2S core size and carbon-containing shell thickness.