Catalysis in Industry最新文献

The synthesis of esters by the alkoxycarbonylation of unsaturated substrates of plant origin opens up the possibility of switching to alternative raw materials and provides a solution to a number of problems facing the chemical industry: resource saving, waste minimization, and increasing the environmental safety and efficiency of the processes being implemented. However, to date, only the production of methyl methacrylate, which includes ethylene methoxycarbonylation as one of the stages, has been implemented in industry. The aim of this review is to systematize and analyze the data published since 2010 in the field of ester synthesis by the alkoxycarbonylation of plant substrates under mild conditions. It has been found that, over the indicated period, the alkoxycarbonylation of pentenoic and undecenoic acids, oleic, linoleic, and erucic acids or their esters, and terpene compounds—citronellic acid and β-myrcene—has been implemented. It has been shown that high yields of linear products and selectivities for them under mild conditions have been provided mostly by using homogeneous palladium–diphosphine catalysts. The results of these studies open up broad prospects for the implementation of processes that are new for industry, namely, the alkoxycarbonylation of substrates of plant origin for synthesizing chemical products of high priority, primarily polymers.

Experience in the industrial use of the technology of synthetic hydrocarbons at the Novocherkassk Plant of Synthetic Products (NPSP) (Novocherkassk, Rostov region) has been summarized. More than 200 types of commercial products for general consumption were produced at NPSP. The article presents information on the production of syngas from natural gas, on the synthesis of hydrocarbons, and process catalysts.

The results of using capillary chromatographic columns with different stationary phases were compared to determine the purity of isopropanol obtained by hydrogenation of acetone. The study was performed with columns based on 2-nitroterephthalic acid-modified polyethylene glycol 20М (PEG20М/FFAP), poly(1-trimethylsilyl-1-propyne) (PTMSP032), and trifluoropropyl (25%) methyl silicone elastomer (SKTFT 50Х). The measurement times, asymmetry factors (A_s) of mixture components, and resolutions (R_s) of the acetone/isopropanol and isopropanol/internal standard pairs of compounds were compared; as a result, the PEG20М/FFAP capillary column was chosen. A technique for measuring the mass fractions of acetone and isopropanol using the internal standard method in the gas phase has been developed. n-Butanol was used as an internal standard. The detection limit was 1.45 for acetone, 1.43 for isopropanol, and 1.28 × 10^–12 g/s for n-butanol. The relative standard deviation (repeability factor) did not exceed 4.3% at a confidence level Р = 0.95.

Two samples of TiO₂/Cr₂O₃ composites are synthesized in the form of spherical grains via the stagewise thermal treatment of ion-exchange resins preliminarily saturated with chromium Cr³⁺ cations and dichromate ({text{C}}{{{text{r}}}_{{text{2}}}}{text{O}}_{7}^{{2 - }}) anions, and then coated with a film-forming titania-based solution. Calcination temperature regimes are set on the basis of a thermal analysis and determined by the type of ion-exchange resin selected as a template. The synthesized composites are generally composed of the α-Cr₂O₃ phase, and the content of the TiO₂ phase is less than 4%. The composites replicate the spherical shape of grains for the initial ion-exchange resins with sizes of 370 to 660 µm. The grains of the sample based on kaolinite adsorbing Cr³⁺ ions have a porous structure with bulbs and cavities. The anion-exchange resin-based sample grains have kinks and cracks over their surfaces due to a nonuniform distribution of adsorbed ({text{C}}{{{text{r}}}_{{text{2}}}}{text{O}}_{7}^{{2 - }}) anions in the initial anion-exchange resin. The composites exhibit catalytic activity in the deep p-xylene oxidation reaction. The cation-exchange resin-based sample is more active, due apparently to the smaller accessible titania surfaces in the anion-exchange resin-based sample as a result of the formation of a solid Ti³⁺ solution in α-Cr₂O₃.

The concepts of the effect of the adsorption of the reaction medium components on the selective hydrogenation of acetylene to ethylene under the action of supported palladium catalysts have been discussed. The role of interstitial solid solutions of carbon and hydrogen in palladium, which are formed upon contact of the catalyst with the reaction medium, in the occurrence of mass transfer processes between the surface and the subsurface layer of the active component has been shown. The ratio of activation barriers to ethylene desorption/adsorption processes, which determines the acetylene hydrogenation selectivity, can vary depending on the structure of palladium nanoparticles and the electronic state of Pd. In addition, changes in the electronic state affect the energy of the activated desorption of ethylene from palladium particles, and their structural features determine the energy of the activated adsorption and subsequent hydrogenation of ethylene to ethane.

Solid-phase synthesis of aluminum–molybdenum (Al–Mo) and aluminum–nickel–molybdenum (Al–Ni–Mo) model composites as part of propylene metathesis catalysts has been conducted under mechanical activation. The structure of Al–Mo and Al–Ni–Mo model composites has been studied by X-ray diffraction analysis, high-resolution transmission electron microscopy, infrared spectroscopy, and diffuse reflectance electron spectroscopy (DRES). The DRES method has shown the presence of isolated monomeric and oligomeric molybdate compounds in the Al–Ni–Mo model composites. Granular metathesis catalysts have been synthesized by molding the Al–Mo and Al–Ni–Mo model composites with aluminum hydroxide and subsequent calcining. It has been shown that the highest activity in the propylene metathesis reaction is exhibited by an aluminum–molybdenum catalyst containing 2.6 wt % Ni, 13.0 wt % Mo, and 32.7 wt % Al. At a process temperature of 200°C, a pressure of 0.1 MPa, and a propylene feed space velocity of 1 h^–1, in the presence of this catalyst, the propylene conversion achieves 33.7%; this fact makes this catalyst promising for practical applications. At the same time, the weight fraction of ethylene and butenes in the reaction product composition is 17.5 and 71.3%, respectively.

Data on the ways of controlling the molecular structure of polyethylene (PE) synthesized over the supported catalysts containing Fe(II) bis(imino)pyridyl (LFeCl₂) and Ni(II) bis(imine) (*LNiBr₂) complexes immobilized on a silica gel modified with aluminum oxide (SiO₂(Al)) are presented. Linear polyethylene with different molecular masses and a controllable molecular weight distribution (MWD) is synthesized by varying the conditions of polymerization on LFeCl₂/SiO₂(Al) catalysts. Ethylene homopolymerization over *LNiBr₂/SiO₂(Al) catalysts results in branched polyethylene with molecular mass and thermophysical characteristics close to that of low density polyethylene synthesized by ethylene copolymerization with α-olefins over supported metallocene and Ziegler type catalysts. A way for designing supported bicomponent catalysts containing LFeCl₂ and *LNiBr₂ complexes immobilized on an SiO₂(Al) support for the targeted synthesis of polyethylene with a required molecular structure is proposed. Examples are given for the synthesis of linear polyethylene with a bimodal MWD on a bicomponent supported catalyst containing two different LFeCl₂ complexes, the synthesis of polyethylene with a controllable distribution of branches on a bicomponent catalyst prepared via the immobilization of LFeCl₂ and *LNiBr₂ complexes on a SiO₂(Al) support, and the modification of a chromium oxide catalyst with LFeCl₂ complex for controlling the molecular mass and branch distributions in synthesized polyethylene are given.

Silica gels are porous materials that are commonly used both in industry and in everyday life. Russian manufacturers produce spherical and powdered silica gels; however, a number of fields of application of silica gels are entirely dependent on import. Therefore, it is necessary to develop silica gel production technologies, the introduction of which would make it possible to replace imported silica gels. Methods for improving the properties of spherical silica gels and new solutions for the production of SiO₂, in particular, silica gel powders and silica gels with an ordered pore structure, are described. It is proposed that they should be produced using cheap feedstocks, in particular, the aluminum industry waste Si-stoff and the cheap natural material diatomite. It is shown that control of the silica precipitation and structure formation parameters provides the formation of silica gels with a wide range of pore structure characteristics, which makes it possible to use them in various fields.

The isomerization of heptane and hexane and their mixtures in the presence of Pt/WO₃–ZrO₂ catalysts with a tungsten oxide content of 10–35 wt % has been studied. It has been shown that the best parameters of the isomerization of a mixture of C₆–C₇ alkanes are achieved in the presence of catalysts containing 15–20 wt % WO₃. According to temperature-programmed desorption of ammonia, this range of tungsten oxide content is characterized by an increase in the number of acid sites, which, according to IR spectroscopy of adsorbed CO molecules, occurs mostly due to an increase in the number of Brønsted acid sites.