G. A. Bukhtiyarova

Hydrodeoxygenation of methyl palmitate over sulfided Mo/Al2O3, CoMo/Al2O3 and NiMo/Al2O3 catalysts

The catalytic properties of sulfided Mo/Al2O3, CoMo/Al2O3 and NiMo/Al2O3 catalysts in the hydrodeoxygenation of methyl palmitate as a model compound for triglyceride feedstock were studied at 300 °C and 3.5 MPa in the batch reactor using n-tetradecane, m-xylene and hydrotreated straight-run gas oil (HT-SRGO). The comparison of catalysts performance in n-tetradecane allowed us to see that the sulfided Mo/Al2O3, CoMo/Al2O3 and NiMo/Al2O3 catalysts revealed the same rate of the methyl palmitate conversion but the rate of the intermediate oxygenates conversion decreased in order: CoMoS/Al2O3 > NiMoS/Al2O3 > MoS2/Al2O3. A mixture of linear saturated and unsaturated C15 and C16 hydrocarbons was produced when the oxygenates were fully consumed. The main products obtained over the Mo/Al2O3 and CoMo/Al2O3 catalysts were C16 hydrocarbons (C16/C15 – 16.1 and 2.79, respectively); however, C15 hydrocarbons were preferentially formed over the NiMo/Al2O3 catalyst (C16/C15 – 0.65), highlighting the different contributions of the hydrodeoxygenation (HDO) and decarboxylation/decarbonylation (DeCOx) pathways during the hydroconversion of methyl palmitate over these catalysts. Investigating the solvents influence on the activity of the CoMo/Al2O3 and NiMo/Al2O3 catalysts in the methyl palmitate HDO revealed that the reaction rate was decreased in the following order: n-tetradecane > HT-SRGO > m-xylene. The aromatic compounds did not retard the methyl palmitate transformation, but inhibited the conversion of the intermediate oxygenates. Decreased C16/C15 ratios were observed over both catalysts when m-xylene was used as the reaction medium instead of n-tetradecane.

Formation conditions of a magnetically ordered phase ɛ-Fe2O3. A FMR in situ study

The ferromagnetic resonance (FMR) method in situ is used to study the initial stages of the formation of ɛ iron oxide nanoparticles deposited on silica gel at temperatures up to 600°C. It is shown that at high-temperature treatment of starting samples obtained by impregnation with an iron(II) sulfate solution, supermagnetic ɛ-Fe2O3/SiO2 nanoparticles form with a narrow size distribution. An analysis of the FMR data in comparison with the data of other methods enables the formulation of the formation conditions for systems of deposited ɛ-Fe2O3 nanoparticles without other polymorph impurities.

Hydrocracking of vacuum gas oil in the presence of supported nickel-tungsten catalysts

The supports containing 70% Al2O3 and 30% β zeolite (AZ-1 and AZ-2), which differed in mixing procedures, and the Ni-W/AZ-1 and Ni-W/AZ-2 catalysts were characterized using an adsorption technique, high-resolution electron microscopy, IR spectroscopy, and X-ray photoelectron spectroscopy and tested in the hydrocracking reaction of vacuum gas oil (VGO). It was found that the supports differed in texture characteristics and surface Lewis acidity at the same composition and similar concentrations of Brønsted acid sites. The formation of Ni-W-S sulfide species on the surfaces of both of the supports occurred in different manners: multilayer Ni-W-S sulfide species were formed on AZ-1 (Ssp = 220 m2/g), whereas single-layer species were mainly formed on AZ-2 (Ssp = 380 m2/g). It was found that catalysts containing multilayer Ni-W-S sulfide species, which were characterized by a higher degree of sulfidation, provided a higher yield of diesel fuel upon the hydrocracking of VGO, whereas catalysts containing single-layer Ni-W-S sulfide species were more active in the reactions of VGO hydrodesulfurization and hydrodenitration.

Catalytic processes and catalysts for production of elemental sulfur from sulfur-containing gases

The modern technologies for production of elemental sulfur are considered. It is demonstrated that along with the further wide application of the conventional Claus process with conventional alumina catalyst in the observable future some new trends which may significantly influence the technological picture of recovered sulfur manufacturing may be formulated: active development of Claus tail gas cleanup processes with the stress on replacement of subdewpoint Sulfreen-type processes by processes of hydrogen sulfide selective oxidation by oxygen; development of novel highly-efficient technologies for hydrogen sulfide decomposition to sulfur and hydrogen; application of new catalysts forms, first of all — at microfiber supports for Claus and H2S oxidation processes; wider application of titania and vanadia catalysts at the newly constructed Claus units; development of technologies and catalysts for direct purification of H2S-containing gases and for catalytic reduction of SO2 for sulfur recovery from smelter gases. All these prospective routes are actively developed by Russian science and some of them are completely based on domestic developments in this area.

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.

Influence of the heat treatment conditions on the activity of the CoMo/Al2O3 catalyst for deep hydrodesulfurization of diesel fractions

The effect of the heat treatment temperature on the sulfidation and activity of CoMo/Al2O3 catalysts designed for deep hydrodesulfurization of diesel fuel was studied. The catalysts were prepared using citric acid as a chelating ligand. The organic ligands present in the samples heat-treated at 110 and 220°C retard the decomposition of dimethyl disulfide and the formation of the sulfide phase but make the catalyst more active than the samples calcined at higher temperatures.

Complexes forming from ammonium paramolybdate, orthophosphoric acid, cobalt or nickel nitrate, and carbamide in solution and their use in the preparation of diesel fuel hydrodesulfurization catalysts

It is demonstrated by 14N, 17O, 31P, and 95Mo NMR spectroscopy that the heteropolyanion [P2Mo5O23]6− forms in impregnating solutions containing orthophosphoric acid, ammonium paramolybdate, cobalt or nickel nitrate, and carbamide. The anion forms labile complexes with Co2+ or Ni2+ cations by coordinating to them through terminal oxygen atoms of the MoO6 octahedra and outer oxygen atoms of the PO4 groups. The catalysts prepared by supporting these complexes on Al2O3 are highly active in diesel fuel hydrodesulfurization. They compare well with the best foreign analogues and are superior to most of the Russian commercial hydrodesulfurization catalysts.

Preparation of supported iron-containing catalysts from a FeSo4 solution: The effect of the support

The iron compounds resulting from the impregnation of the most common supports—alumina and silica gel-with an aqueous FeSO4 · 7H2O solution and subsequent heat treatment in air are identified by thermal analysis and Mössbauer spectroscopy. The state of the active component of the iron-containing catalysts depends strongly on the nature of the support.

HKUST-1 silica aerogel composites: novel materials for the separation of saturated and unsaturated hydrocarbons by conventional liquid chromatography

HKUST-1 silica aerogel composite (HKUST-1@SiO2) has been studied as a stationary phase for the efficient separation of unsaturated hydrocarbons from saturated aliphatics by conventional liquid chromotography (LC). HKUST-1@SiO2 has been prepared via an advanced sol–gel method and subsequent drying in supercritical CO2 to minimize the deterioration of the individual properties of the MOF and silica aerogel structures and tune its properties to be acceptable for flow mode. The synthesized composite was characterized by X-ray diffraction, FT-IR spectroscopy, XPS, scanning electron microscopy with EDAX mapping and low-temperature nitrogen adsorption. According to these data, the composite represents physically dispersed domains of HKUST-1 in the silica aerogel network. It was shown that the HKUST-1@SiO2 composite can be used as a highly efficient stationary phase for conventional liquid chromatographic separation of cyclohexene or benzene from cyclohexane. This is the first time a MOF composite has been used for the separation of organic molecules by LC, demonstrating new vistas for the application of these materials in the flow mode.

The use of X-ray absorption spectroscopy for developing new-generation Co-Mo catalysts of hydrotreating of diesel fuel

The immediate problem facing the Russian petroleum refining industry is to turn to the production of gasoline complying with European standards [1]. Nowadays, only 12 of the 27 large Russian oil refinery plants have mastered the production of low-sulfur diesel fuel containing less than 0.05% sulfur [2]. Almost all diesel fuel that meets Euro 2, Euro 3, and Euro 4 standards is produced with the use of foreign catalysts since domestic catalysts do not have the required activity level. In this context, Russian industry should proceed as soon as possible to produce new-generation heterogeneous catalysts in which all surface compounds are active centers of hydrorefining reactions. According to the basic principles of the preparation of such catalysts expounded in [3], active center precursors—bimetallic Co‐Mo compounds—should be obtained when preparing an impregnating solution and the structure of these compounds should remain unaltered during the genesis of catalysts. The existence of such a structure in an oxide precursor of hydrorefining catalysts will ensure the formation of highly active disperse sulfide particles during the sulfiding step. To purposefully use this approach, the state and structure of catalyst active component precursors should be thoroughly monitored at all stages of their preparation. The most suitable for this purpose is X-ray absorption spectroscopy, which makes it possible to identify the structure of compounds synthesized in solution and on the support surface during catalyst preparation [4]. In this paper, we report the results of the EXAFS and XANES study of the structure of bimetallic oxide precursors of the active phases of hydrorefining Co‐Mo catalysts. A bimetallic compound and allied catalyst were synthesized from the ammonium salt of the tetranuclear anion [Mo 4 (e 6 c 5 O 7 ) 2 O 11 ] 4– . Solutions and cata