Vol 10, No 2 (2018)

The properties of catalytic systems based on iron oxide and inorganic matrices of oil-bearing rocks (basalt, clay, sandstone) in the decomposition of ammonium nitrate, oxidation of methane, and hydrocracking of asphaltenes were studied. The catalytic systems were iron oxide (hematite with a particle size of D = 11.0–20 nm, preparation temperature 453–473 K) fixed on matrices during co-hydrolysis of carbamide and iron chloride under hydrothermal conditions at temperatures of T = 433–473 K and pressures of 0.6–1.6 MPa. The iron oxide catalysts based on basalt and clay were most active in deep oxidation of methane (at 773 K, \({X_{C{H_4}}}\) = 83% and 72.9%, respectively); the Fe₂O₃/basalt and Fe₂O₃/sandstone systems were more active in the decomposition of ammonium nitrate. In hydrocracking of asphaltenes to maltenes, the catalyst activity decreased in the series Fe₂O₃/basalt > Fe₂O₃/clay > Fe₂O₃/sandstone, the iron oxide catalysts on clay being most selective. The obtained experimental data confirm that natural materials (oil-bearing rocks: basalt, clay, and sandstone) may be used for the development of catalytic systems for reactions in oil beds and of advanced technologies for increasing the oil recovery.

The kinetics of the direct synthesis of dimethyl ether (DME) from synthesis gas (21.8 vol % CO, 5.2 vol % CO₂, 5.3 vol % N₂, and 67.7 vol % H₂) is studied under laboratory flow reactors in a pressure range of 0.2–5 MPa in the presence of a bifunctional catalyst. The bifunctional catalyst is synthesized by pelletizing a mixture of appropriate fractions of the following milled commercial components: a Megamax 507 methanol catalyst and γ-alumina with a graphite additive. Data on the activation of the bifunctional catalyst are consistent with the TPR data for the original Megamax 507 sample, suggesting that the synthesis conditions for the bifunctional catalyst do not affect the state of copper oxide. At temperatures of up to 280°C, a space velocity of about 4000–10000 L/(kg_cat h), and a pressure of 3–5 MPa, the productivity with respect to oxygenates (DME and methanol) grows linearly along with the load. An increase in load results in a limiting value that can be used to determine the maximum oxygenate productivity of the catalyst as a function of temperature and pressure. A set of experimental data on the effect of space velocity, temperature, and pressure on the composition of the converted gas and the DME/methanol ratio is derived.

Methodological aspects of the screening of granular chromia–alumina dehydrogenation catalysts are discussed, along with ways of estimating their lifetime by treating catalysts in a steam–air medium. The efficiency of using small reactors (with diameters of less than four effective granule sizes) to compare the catalytic activities of catalysts at the screening stage is demonstrated by the example of Mg- and Zr-promoted chromia–alumina catalysts.

Prospects for conversion of refinery gas to high-octane components of motor fuel were discussed. The feedstock of the Russian petrochemical complex can be expanded by introducing light hydrocarbons— nonmarketable refinery waste products—in the production of ecologically safe high-octane components of gasoline based on tert-butanol and isopropanol. A series of articles in the field of related applied research and experimental developments were announced.

An experimental study is performed of a circulating fluidized bed of two types of finely dispersed Geldart A particles with different bulk densities. The first type of particles have bulk density ρ_b = 1200 kg/m³, while the bulk density of the second type of particles is ρ_b = 1300 kg/m³. The studies are performed on a test bench 0.7 m in diameter and 5.75 m tall at room temperature with air used as the fluidizing gas. The velocity of fluidization ranges from 0.1 to 0.75 m/s. The bed is sectioned along its height with a set of horizontal diffuser grids. The results from measuring the fluctuations, the average drops in pressure, and the pressure distribution along the height of the fluidized bed are used to estimate the effect produced by the density of particles on its operational regimes. Velocity of transition U_c, determined from the mean-square deviations of pressure drop fluctuations, is 0.40 m/s for lighter particles and 0.35 m/s for heavier particles. Velocity of transition U_c determined from the power of the energy spectrum of pressure fluctuations Е is 0.45 and 0.40 m/s for lighter and heavier particles, respectively. The results from pressure measurements along the bed height show a linear drop with increasing bed height, and this drop is faster for heavier particles than for lighter particles.

The aim of this work is to develop a new hydroisomerization catalyst based on molybdenum carbides that is resistant to the influence of sulfur compounds and applicable for the synthesis of low-pour-point diesel fuels that are similar in parameters to the fuel synthesized using platinum-containing catalysts. In the first part of the work, supports with different porous structures and acidities (Beta, ZSM-5, ZSM-12, and SAPO-31) are synthesized and studied. In the second part of the work, bifunctional catalysts prepared by modifying these supports with nanosized molybdenum carbides are studied. All samples contain the same amount of Mo₂C (10% in terms of the equivalent amount of MoO₃). The catalysts are tested using a model isomerization reaction of n-decane. The catalyst based on silicoaluminophosphate ATO (SAPO-31) proves to be the most effective one. In order to optimize its composition, larger batches of samples with different Mo₂C contents (5, 7 and 10% in terms of the equivalent amount of MoO₃) are prepared. The catalytic properties are studied using the hydroisomerization of actual diesel fractions. The optimum content of Mo₂C (7 wt %) in the bifunctional catalyst is determined.

Traditional processes of acid-catalyzed hydrolysis of wood are ineffective due to the low quality of formed glucose solutions contaminated with impurities that inhibit fermentation of glucose to ethanol. This problem grows during the hydrolysis of birch wood containing large amounts of hemicellulose. This work proposes producing quality glucose solutions using sulfuric acid (H₂SO₄, 80%) catalyzed hydrolysis at 25°C the cellulosic products formed during the catalytic peroxide delignification of birch wood. It is established that the composition of cellulosic products strongly affects the contents of glucose, xylose, and impurities inhibiting the enzymatic synthesis of bioethanol: furfural, 5-hydroxymethyl furfural, and levulinic acid. High yields (80.4–83.5 wt %) of glucose are achieved using cellulosic products produced by integrating the processes of sulfuric acid hydrolysis of hemicelluloses from birch wood and peroxide delignification of prehydrolyzed wood in the presence of catalysts: 2% H₂SO₄ and 1% TiO₂. Concentration of inhibitors of enzymatic processes in these hydrolyzates is below the allowable limits. Hydrolyzates with maximum glucose content (86.4–88.5 wt %) and minimum concentration of inhibiting impurities produced by acid hydrolysis of cellulosic products treated with an 18% solution of NaOH. Gas chromatography, HPLC, and chromato-mass spectrometry are used to analyze the composition of hydrolyzates. Cellulosic products are examined by SEM, XRD, and chemical analysis.

The liquid phase hydrogenation of biomass derived (–)-carvone into industrially valuable dihydrocarvone was studied over monometallic Au catalysts supported on alumina, titania and zirconia, as well as on the mesoporous carbon support Sibunit in methanol as a solvent (100°C, hydrogen pressure 9 bar). It was shown that among the three types of functional groups present in carvone, which can be hydrogenated, namely C=O, conjugated and isolated C=C groups, hydrogenation of the latter was predominant. The catalytic activity was found to depend on the catalyst support type. Under comparative reaction conditions, the carvone conversion increased in the following sequence: Au/C ≪Au/ZrO₂ < Au/Al₂O₃ ≪Au/TiO₂. A higher activity of Au catalysts over metal oxides as compared to Au/C can be caused by the presence of acid sites as well as oxygen vacancies in their structure allowing strong adsorption of carvone through its carbonyl moiety. All catalysts supported on oxides showed similar selectivity towards trans- and cis-dihydrocarvone with the ratio between isomers (trans-/cis-isomer) being about 1.8, while this value for Au/C was close to 3.9, which can be related to a much lower carvone conversion in the latter case.

Hydrogen-generating solid-state NaBH₄ composite are promising systems for storing and transporting hydrogen intended for use in low-temperature proton-exchange membrane fuel cells. Catalysts are introduced into the composites to ensure the generation of hydrogen at ambient temperatures. In this work, the effect of the synthesis conditions for cobalt catalyst on the gas generation rate is analyzed. It is found that the efficiency of hydrogen generation depends on the nature of the cobalt salt and pH of the aqueous solution of the salt in which the active component precursor is reduced under the action of sodium borohydride because these factors determine the composition, degree of dispersion, and magnetic behavior of the cobalt systems. It is found that the highest rate of gas generation—505 cm³/min per gram of the composite with a hydrogen content of 8.4 wt %—is observed for a sample reduced with sodium borohydride in a hydrochloric acid solution of cobalt chloride with a pH of 1.3. The results can be used to develop effective inexpensive cobalt catalysts for the production of hydrogen from pelletized solid-state NaBH₄ composite.