Vol 10, No 4 (2018)

The catalytic properties of Amberlyst A-21 anion-exchange resin in the gas-phase disproportionation reaction of trichlorosilane (TCS) at temperatures (up to 423 K) critical for the resin are investigated for the first time. It is established using thermal desorprtion followed by pyrolysis that Amberlyst A-21 undergoes thermal destruction to form chloromethane and the spherical polymer matrix decomposes at above 423 K. In the temperature range of 333–423 K, the apparent activation energy of disproportionation of TCS with using Amberlyst A-21 is 37.12 kJ/mol and the reaction rate constant is 0.80 s⁻¹ (at 423 K). Three months of testing of the resin in disproportionation of TCS at 423 K demonstrates its stable catalytic activity.

It is shown that copolymers of polyethylene- and polypropyleneglycolmaleates (p-EGM and p‑PGM) with acrylic acid (AA) can be used as matrices for the preparation of effective metal-polymer complexes for hydrogenation of organic compounds. Electron microscope and dynamic scattering are used to determine the average nanoparticle size of 112 nm; the nanoparticles are spheres with a uniform distribution along the polymer’s cross section. The contents of nickel and cobalt in p-EGM/AA are 0.52 and 0.48 wt %, respectively, and 0.49 and 0.51 wt % in p-PGM/AA, respectively. It is found that raising the temperature from 25 to 40°C allows the rate of pyridine hydrogenation to be increased substantially as a result of catalyst activation and an increase in the number of catalyst active centers, due to the swelling of the polymer network and its transition from the tight globular to the expanded state. Raising the current’s strength from 1 to 3 A lowers the yield of piperidine, which does not allow the increase in the current density to be used to shorten the length of synthesis. It may be concluded that the experimental data allow a final product of hydrogenation with higher rates and yields to be obtained.

The physicochemical state of supported platinum and the surface of the support is studied for a number of industrial 0.5 wt % Pt/graphite (freshly prepared, after the synthesis of hydroxylamine sulfate via NO hydrogenation in sulfuric acid, and regenerated) by scanning electron microscopy (SEM), transmission electron microscopy(TEM), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and CO chemisorption. It is shown that platinum particles agglomerate in a catalyst during operation, and its regeneration results in finer dispersity of the supported metal. Despite the common opinion that a platinum surface is modified by sulfur during the synthesis or regeneration of such catalysts, no evidence of this is found via XPS. Data showing that the surface nitrogen-containing graphite groups formed during the preparation of a catalyst are responsible for the modification of the absorption properties of platinum particles with respect to CO are obtained for the first time. The latter seems to be one of the factors that influence the catalytic properties of platinum in NO hydrogenation.

The catalytic properties of the industrial “palladium on sibunit” catalyst (ICT-3-31, 0.5 wt % Pd) were studied in the reduction of menthone into menthol. Menthone was reduced both at 250 and 350°C using isopropanol as an H-donor under the conditions of the hydrogen transfer reaction (HTR). For comparison, a noncatalytic reaction was performed under the same conditions. At 350°C the conversion of menthone was the same (61–62%) in the presence of the catalyst and without it. In the reaction with the catalyst, the selectivity on the desired product menthol decreased considerably (from 98% down to 23%), and the amount of the by-products increased (from 2 up to 77% based on changed menthone). When the temperature of the catalytic reaction was lowered to 250°C, the reduction selectivity increased to 42%, but the conversion of menthone decreased to 10%. All the products of menthone conversion were identified and pathways of their formation suggested. At 250–350°C the carbon support sibunit catalyzed the dehydration of menthone, which hindered the satisfactory yields of the target alcohol. Other side reactions catalyzed by ICT-3-31 were dehydrogenation into p-menthenes and their further aromatization resulted in the formation of substituted benzenes—p-cymene and thymol. ICT-3-31 can be effectively used in HTR, if more reactive organic substrates are involved in the reaction below 200–250°C or stronger H-donors are applied.

The possibility of preparing a mixture of 1,3-dialkylimidazole salts from commercially available reagents via multicomponent condensation is considered. The main factors affecting the yield of the target product, and the experimental data needed for scaling up the process, are discussed. It is shown that the prepared mixtures are close in some key properties (e.g., viscosity at different temperatures, heat capacity) to the pure salts. The possibility of using the prepared salts as solvents for catalytic hydrodechlorination and catalyst components for the alkylation of aromatic compounds is demonstrated.

The catalytic hydrogenation of nitrobenzene (NB) is an important technological stage in the production of aniline (AN). The catalytic behavior of hypercrosslinked polystyrene based ruthenium catalyst 3%Ru/MN270 in the three-phase hydrogenation of NB to AN is considered in this work. The following parameters are varied: 0.12 to 0.24 mol/L of NB; 1.11 × 10⁻⁴ to 11.12 × 10⁻⁴ mol/L of catalyst; temperatures of 160 to 190°C; and partial hydrogen pressures of 0.113 to 1.013 MPa. The optimum process parameters are determined to ensure 98% selectivity toward aniline with 97% conversion of nitrobenzene.

Results are presented from studying the steam cracking of heavy oil at a temperature of 425°C and a pressure of 2.0 MPa over dispersed iron and molybdenum based catalysts in a slurry reactor. The catalysts are synthesized through the decomposition of water-soluble precursors of metal salts in situ. The yield of upgraded oil (the sum of liquid products) is found to grow with steam cracking, in comparison to thermal cracking (80 and 77%, respectively). The use of dispersed monometallic (iron- or molybdenum-containing) catalysts and a bimetallic catalyst for the catalytic steam cracking (CSC) of heavy oil increases the yield of SOPs. In addition, the yield of light fractions (Т_b < 350°C) in the CSC process is found to grow in comparison to steam and thermal cracking, and the viscosity and density of products falls, relative to the initial feedstock.

The oxidation of diesel fuel was studied using the vibrofluidized and fluidized beds of disperse river sand in the presence of iron-containing microspheres isolated from the fly ash of coal boiler stations: ferrospheres and cenospheres activated with iron oxide. The results were compared with the available data on the oxidation of diesel fuel using the microspheres of commercial catalysts for complete oxidation of organic compounds. In the presence of ferrospheres and cenospheres with deposited iron oxide at 500–600°C, deeper oxidation of diesel fuel was observed than in the vibrofluidized bed of an inert material (river sand). The most complete oxidation (84.3%) was observed with ferrospheres at 700°C. The ferrospheres used in the oxidation of diesel fuel in the fluidized bed of the inert material showed lower activity under these conditions than the commercial catalysts based on СuСr₂О₄/А1₂О₃ and disperse Fe₂O₃. Nevertheless, higher oxidation rate, 97.8%, can be achieved in the presence of ferrospheres by arranging flare combustion of diesel fuel above the bed. In this case, the flame length decreases by half compared with that above the bed of the inert material. This, as well as the decreased CO content and unburnt carbon in combustion products, indicate the catalytic activity of ferrospheres fed to the flame.

The conventional way of producing microcrystalline cellulose (MCC) from wood raw materials is multistage; it is based on integrating the environmentally hazardous processes of pulping and bleaching of cellulose and the acid hydrolysis of the amorphous phase of cellulose. This work describes an improved single-stage catalytic method for the production of MCC from softwood and hardwood that is based on the peroxide delignification of wood in an acetic acid–water medium under mild conditions (100°C, atmospheric pressure) in the presence of an environmentally safe TiO₂ solid catalyst. The processes of MCC production via the peroxide catalytic delignification of various wood species are optimized experimentally and mathematically. The following optimum modes for the production of MCC with a yield of 36.3–42.0 wt % of absolutely dry wood, a residual lignin content of ≤1.0 wt %, and a hemicellulose content of ≤ 6.0 wt % are determined: For aspen: 5 wt % H₂O₂, 25 wt % CH₃COOH, and a liquid/wood ratio of 10. For birch: 5 wt % H₂O₂, 25 wt % CH₃COOH, and a liquid/wood ratio of 15. For silver fir: 6 wt % H₂O₂, 30 wt % CH₃COOH, and a liquid/wood ratio of 15. For larch: 6 wt % H₂O₂, 30 wt % CH₃COOH, and a liquid/wood ratio of 15.