Vol 8, No 3 (2016)

Some features of the behavior of highly exothermic selective oxidation processes in a monolith microchannel reactor (MCR) are studied experimentally using the oxidation of methanol to formaldehyde on a Fe–Mo catalyst as an example. The process can be intensified considerably by intensively withdrawing heat from the reaction zone, operating at increased methanol concentrations of up to 12–12.5%, and using catalyst particles smaller than 0.25 mm to increase the useful product yield per unit of catalyst volume by 7–12 times, compared to multitubular reactors. The thermal operating mode of MCRs is close to the optimum theoretical regime for this class of processes, thereby making it easier to achieve high selectivity to formaldehyde. Due to the abovementioned reduction in the activity of Fe–Mo catalyst in MCRs, the prospects for using MCRs in this process must be estimated along with solving the problem of catalyst stability. The use of MCRs appears to be very promising and technologically sound when dealing with catalytic processes whose intensification is not accompanied by an appreciable reduction in activity.

The effect of the particle size of an IK-8-21 domestic titanium-magnesium catalyst on the properties of polypropylene (PP) produced during the polymerization of propylene in a liquid monomer is studied. Catalysts with particle sizes of 20 to 64 μm are shown to have high activity and identical sensitivity to hydrogen and allow PP to be obtained with a narrow distribution of particles over size, high isotacticity, and close values of crystallinity, melting temperature, and physicomechanical properties. A slight decrease in the activity and bulk density of PP powder is observed when the average size of catalyst particles is increased from 20 to 43 μm. A more notable reduction in the activity and bulk density of PP powder is observed for catalyst with particle sizes of 62 to 64 μm. IK-8-21 catalyst is not inferior to its foreign analogues with respect to the properties of the resulting PP.

The process of heavy crude oil steam cracking using semi-flow (with respect to water) and steadystate regimes at 425°C without catalyst is investigated. It is established that in the case of a semi-flow regime, water acts predominantly as a physical agent facilitating the distillation of hydrocarbon fractions and thus preventing their transformation into petroleum coke. A reduction in coke yield is observed for a steady-state regime in comparison to a semi-flow regime; the introduction of water results in enhanced conversion of the high-boiling fraction and an increased yield of light fractions in the composition of liquid products. Based on the obtained data, it is concluded that water plays a positive role during the conversion of heavy crude oil, and that the steam cracking process is promising for production of lighter synthetic and/or semi-synthetic oils.

New methods are developed for conducting adsorption–catalytic processes to remove volatile organic compounds (VOCs) from exhaust gases at industrial enterprises. New flowsheets are proposed for these processes, in particular a system with localized heating of a part of the catalyst bed to initiate the combustion of adsorbed VOCs, and a system separating a full adsorption–catalytic bed into parallel sections with nonsimultaneous regeneration. Studies combine pilot-scale experiments and mathematical modeling. The flowsheet, in which the initiating heater is located directly in the catalytic adsorbent bed considerably reduces (by at least two orders of magnitude) the energy expenditures on regeneration, both in terms of specific energy consumption for purifying a unit volume of exhaust gases and in terms of the power required for the heater. Separating the bed into several sections allows a severalfold reduction in the maximum concentrations of pollutants and the gas temperature at the outlet of the adsorption–catalytic system during its operation. The proposed methods are characterized by high efficiency of gas purification and low energy consumption, so they can be widely used in protecting the atmosphere against VOC emissions.

As an example of the liquid-phase hydrogenation of methyl-phenol ketone to 1-phenylethanol, variants of the construction of a pilot reactor are considered for performing long-term tests of heterogeneous catalysts of a fixed bed. Calculations for the reactor unit during hydrogenation on NTK-11 are presented as an example. It is shown that a cascade of three adiabatic reactors with a catalyst bed height of 4.5 m each is needed to ensure a residual reactant concentration below 1 wt %.

The effect of the hydrodynamic regime in the stirring of a copper carbonate–ammonia suspension containing an alumina–silica support on the chemical and phase composition of an active component (AC) precursor for a catalyst of cyclohexanol dehydrogenation to cyclohexanone is studied. By means of X-ray diffraction, differential thermal analysis, and adsorption, the precursor is found to precipitate in a developed turbulent regime, predominantly in the form of nanostructured hydroxocarbonate structures strongly bonded to the support. Some catalytic and textural properties of CAS-C (copper–alumina–silica for caprolactam) samples are studied with AC contents of 20 to 30 wt % (on a copper oxide basis). The laboratory technology is scaled up to industrial conditions. CAS-C samples and commercial H3-11 catalyst (BASF) are subjected to catalytic tests (in a flow-type reactor with a fixed catalyst bed 40 cm³ in volume at a temperature of 250°C and atmospheric pressure). The CAS-C catalyst is shown to be similar to the H3-11 catalyst in terms of selectivity, and to considerably surpass it in activity and thermal stability.

Cathode catalysts for a hydrogen–oxygen fuel cell (FC) with proton-conducting (acidic) and anion-conducting (alkaline) electrolytes are synthesized via the pyrolysis of nitrogen-containing iron and cobalt complexes on the surfaces of highly disperse carbon materials. The catalysts are characterized by X-ray photoelectron spectroscopy (XPS) and tested under model conditions on a thin-layer disk electrode and as a part of a membrane electrode assembly of hydrogen–oxygen FCs. The properties of the CoFe/C system formed via the pyrolysis of macroheterocyclic cobalt and iron compounds on carbon materials (XC-72 soot and multiwall nanotubes (MNTs)) are described for the first time. According to XPS data, the surface of the CoFe/C catalytic systems is enriched with carbon (95.5 at %) and contains nitrogen (2 at %), oxygen (2 at %), and metals (0.5 at %). According to the results from electrochemical measurements under model conditions, the CoFe/MNT catalytic systems approaches 60% Pt/C (HiSPEC9100) commercial platinum catalyst according to their activity in the oxygen reduction reaction in an alkaline medium (0.5 M KOH). The half-wave potentials are 0.85 and 0.88 V for CoFe/MNT and 60% Pt/C (HiSPEC9100) catalysts, respectively. The maximum specific powers of hydrogen–oxygen FCs with anion-conducting electrolytes are 210 mW/cm² (60% Pt/C (HiSPEC9100) based cathode) and 180 mW/cm² (CoFe/MNT based cathode). The characteristics of a membrane electrode assembly with a non-platinum cathode correspond to the best analogs described in the literature. The results of this work show the prospects for further studies on scaling this technology for the synthesis of the proposed non-platinum cathode catalysts and optimizing the architecture of the membrane electrode assembly of FCs based on them.

The effect of the mechanical activation of rice husk on the reactivity of its carbohydrates was studied. The activation was performed in a pilot-scale centrifugal roller mill. The mechanical treatment of the raw material led to an increase in its reactivity due to the increase in the specific surface area and amorphization of the crystalline regions of cellulose. The optimum process conditions of activation, leading to the preparation of a reactive product from rice husk, were determined: rotor frequency 1500 rpm, raw material feed rate 30 kg/h. The rice husk particles were ground to 45–50 μm under these conditions. These changes led to a sevenfold increase of the yield of low-molecular carbohydrates in the complete enzymatic hydrolysis of the material.