The catalytic performance of iron-based nanodispersions in Fischer–Tropsch synthesis in two different slurry reactor types, specifically a continuous stirred-tank reactor (CSTR) and a slurry bubble column reactor (SBCR), was comparatively investigated. It was found that, at equal process temperatures, the CO conversion in the SBCR using a gas disperser with four equally spaced 1-mm holes was lower than that in the CSTR. However, this observation is inconsistent with other reports in the literature. Replacing this disperser with a plate with a single centered 2-mm hole enhanced the CO conversion up to values close to those obtained in the CSTR. The reaction rate constants were calculated for the different reactor types.

The homogeneous acetic acid synthesis-type Ru–Co–Li/N-methylpyrrolidone catalyst for CO and H2 transformations has been studied at moderately high pressures. For 1CO:2H2, low acetic acid selectivity has been observed, along with remarkable methyl acetate selectivity, the absence of aldehydes and ethyl acetate and sharp deviations from the Anderson-Schultz-Flory distribution for both alcaohols and long-chain hydrocarbons. For 1CO:1H2 and slightly elevated pressure, acetic acid selectivity slightly increased, notable ethyl acetate formation was detected, and both long-chain hydrocarbons and alcohols disappeared. Hypotheses are discussed about the direct parallel formation of all observed product groups (hydrocarbons, alcohols, esters, and acetic acid) and hydrocarbon chain growth limitations according to the formed Ru–Co cluster size in the presence of the aforementioned catalytic system.

The equilibrium parameters of steam isobutanol reforming were calculated. These include the H 2 yield, selectivity with respect to carbon-containing gases, and feed conversion. The calculated data, on the whole, agree with the published data and experimental values of the isobutanol conversion and yield of isobutyraldehyde and higher alkanes on Ni–Co catalysts supported on biochars prepared by hydrothermal carbonization of cellulose. On the other hand, the calculated yields of H 2 , СО, and СН 4 disagree with the experimental data, which suggests that the equilibrium in the experiments on the steam isobutanol reforming on this catalyst is not attained. Feeding a homogeneous mixture of water, isobutanol, and ethanol into the reactor at 700°С allows the Н 2 yield to be increased from 58 to 66% and the water conversion, from 58 to 76% compared to the steam reforming of isobutanol without ethanol. The addition of ethanol allows the coking to be significantly reduced and the H 2 and СО yield higher than 90% at 900°С to be reached.

The results of calculations of thermodynamic equilibria published over the last 15 years and experimental data for the catalytic steam reforming of ethanol, propanol, and n- and isobutyl alcohols were analyzed. When the conversion of the initial alcohol and yield of H-2 approach equilibrium values, the selectivity to CO, CO2, and methane can both approach the equilibrium values and appreciably differ from them depending on the catalyst and reaction conditions. This illustrates a complicated character of the kinetic control of reforming reactions and demonstrates a possibility of generating either hydrogen, or synthesis-gas enriched in hydrogen.

Cu-Co-containing cellulose-based carbon composite materials (Cu-Co/Cel) were formed by a matrix isolation method. Using X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared-Fourier spectroscopy (IR-Fourier spectroscopy), and non-isothermal research methods, the physicochemical properties of the composites were established. The catalysts are nanosized particles distributed in a carbon matrix, containing fragments of a system of conjugated bonds (C=C-C=C) of various lengths. Cu-Co/Cel catalysts are active in the synthesis of alcohols from CO and H-2, demonstrating high CO conversion (68%) and specific activity (17 mol CO g(Me)(-1) s(-1)). Differences in the mechanism of alcohol formation from CO and H-2 on cellulose-based composites and an oxide support (comparison catalyst) were shown by analyzing the distribution of synthesis products.

Published data on noncatalytic pyrolysis of natural gas in molten metals are analyzed. The most illustrative results obtained in the past two decades are described. The use of molten metals as reaction medium allows solving the problem of coking of pyrolysis reactors owing to the flotation of the carbon formed to the molten metal surface. The use of liquid metal bubbling reactors allowing the process to be performed at temperatures of up to 1200°С is considered. The maximal conversion was 78% at 1175°С and feeding rate of 50 mL min–1. The major factors favoring more complete conversion of natural gas in the processes under consideration are elevated temperature, decreased gas bubble size due to the use of bubbling systems of various types, and longer residence time of the gas in the heat carrier due to an increase in the reactor length or to use of various types of packing.

The gas-liquid ejector functioning mechanisms that may be involved in three-phase Fischer-Tropsch suspension synthesis using nano-scale catalyst particles are studied for the first time. It is shown for a model bubble device representing a pilot reactor of the referred synthesis process that it is possible for the ejector to perform simultaneously the functions of both the gas disperser of the column and of the device that ensures forced circulation of the liquid medium in the whole device loop. Supersonic gas ejection condition is achieved and its effect on the bubbling pattern is determined.

Features of various Fe-containing nanosized slurry Fischer-Tropsch catalysts, obtained in situ by thermolysis, were investigated experimentally (catalytic tests, XRD, hermomagnetometric methods) and theoretically (DFT ab initio calculations, regression analysis). XRD patterns of the samples reveal the presence of preferentially single Fe7C3, Fe5C2 and Fe2C. A quantitative correlation was found between the values of the most important hydrocarbon group selectivity at 260 degrees C and the residual magnetization of the spent samples, regardless of promoter nature and amount. The Fe7C3 model clusters, according to the DFT results, prefer to be in high-spin states and substantiate the preference of associative coordinated CO. Because the CO associative sorption is unfavourable for chain growth on Fe Fischer-Tropsch catalysts and the carbides have Curie points <260 degrees C, the presence of nanosized paramagnetic carbide particles has been suggested to cause the abovementioned correlation. (C) 2019 Elsevier Inc. All rights reserved.

Kinetic models are developed for the molecular-mass distribution of the products of hydrogenolysis of mixed long-chain n -alkanes experimentally studied in the three-phase slurry reactor over nanosized cobalt-containing Fischer–Tropsch catalysts. The models are based on different hypotheses pertaining to the ratios of probabilities for the cleavage of C–C bonds as a function of their position in n -alkane chains with allowance made for the occurrence of secondary transformations of products and the vapor-liquid equilibrium in the mixture of n -alkanes in a hydrogen medium. It is demonstrated that the experimentally observed features of this distribution cannot be described in terms of the known theories of C–C bond cleavage in the hydrogenolysis of long-chain alkanes (terminal methane splitting and uniform or normal distribution of product composition). The hypothesis of a regular increase in the probability of C–C bond cleavage on going from the center of the carbon chain to its ends is advanced. Calculations performed using combinations of the distribution following this hypothesis and the normal distribution make it possible to solve the problems mentioned above.

The experimental data on the hydrogenolysis of long-chain alkanes over suspended cobalt Fischer–Tropsch catalysts are presented which demonstrate the specific character of the molecular-mass distribution of its products (the combination of excess methane, local minimum at С 3 –С 7 carbon chain lengths, and local maximum at С 12 –С 16 carbon chain lengths). These results provide the experimental verification for the model of the mentioned distribution previously advanced by the authors which includes the hypothesis that the probability of С–С bond cleavage in an alkane molecule increases from the chain center to its ends. These distribution features are observed in the conversion of both alkanes of the suspension medium and individual n -alkanes ( n -С 16 Н 34 ) at different temperatures for in situ synthesized nanosized catalysts and commercial oxide samples and for n -С 16 Н 34 after distillation of the hydrocarbon medium of the preliminarily suspended nanosized catalyst.

Effect of mode parameters, such as the feed gas flow rate, its content of dimethyl ether, and content of a catalyst in the suspension, on the main parameters of the dimethyl ether conversion into light C 2 –C 4 olefins in a three-phase system (slurry reactor) in the presence of a catalytic suspension based on a nanosize zeolite Mg–MFI dispersed in silicone oil was examined. The values of the parameters, at which the conversion of dimethyl ether occurs in the steady state mode under favorable hydrodynamic conditions at a relative chemical stability of the dispersion medium and its minimum mechanical entrainment from the reactor, were found. Irrespective of the dimethyl ether concentration in the operating gas, the reaction was shown to occur with conversion of up to ~80% at selectivity of ~50%, and ethylene is the main reaction product (up to 30 wt %).

Bubbling in the liquid phase simulating the reaction medium consisting of molten paraffin and iron-containing nanosized catalyst was studied. An aerator (disperser) for a model bubbling installation with the design and process parameters maximally similar to those of an intended slurry reactor with nanosized iron-containing catalytic suspension for performing Fischer–Tropsch synthesis was chosen.

Fischer–Tropsch synthesis in the presence of nanosized cobalt-containing catalysts suspended in a mixture of long-chain alkanes has been studied. It has been found that the molecular-mass distribution of the products differs substantially from the typical Anderson–Schulz–Flory distribution. The most evident cause of this phenomenon is the intense hydrogenolysis of long-chain alkanes of the liquid medium which occurs during catalyst activation; this process may proceed to a sufficient extent during Fischer–Tropsch synthesis. The molecular-mass distribution of hydrogenolysis products shows a number of specific features that differ appreciably from those for both classical hydrogenolysis (cracking) in the presence of zeolites and terminal methanolysis, which is frequently observed in the presence of group VIII metals. Problems encountered during the construction of models for the observed distribution are discussed.