The kinetics of n-butane dehydrogenation to butadiene is studied with temperature (T) variation of 550–625°C, duration of dehydrogenation stage (t) of 5–30 min, and space velocity (V) of 4400–35 200 h−1 on industrial catalyst K-CrOx/γ-Al2O3 at a fraction of 56–94 μm. The catalyst is stabilized before studies. The granulated catalyst in a reduction–dehydrogenation–regeneration cycle at 593°C, and then as a fraction of 56–94 μm in dehydrogenation–regeneration cycle at 650°C. The maximum selectivity toward butadiene of 25 mol

The authors formulate a mathematical model of the non-stationary single-stage dehydrogenation of n-butane to butadiene in an adiabatic fixed-bed reactor for the first time, based on a kinetic model that describes the formation of coke and primary and secondary by-products on a K-CrOx/γ-Al2O3 catalyst. The model allows prediction of the yield of butadiene and other products depending on the activity of the catalyst, the composition of initial mixture, the period of the dehydrogenation cycle, and the degree of catalyst dilution with an inert material (including the non-uniform dilution of a catalyst with an inert material along the bed length). It also allows assessment of the temperature regime of the catalyst’s operation and the degree of its coking along the bed. It is shown that the model is adequate for describing the conversion of n-butane, the formation of butadiene and butylene, the accumulation of coke, and the loss of catalyst activity using test calculations of main technological parameters as an example.

The mathematical model of the adiabatic fixed-bed catalytic reactor for direct dehydrogenation of n-butane to butadiene operating under nonstationary conditions is formulated for the first time. The model includes kinetic equations that describe the formation of primary products, by-products, secondary products and coke on the K-CrOx /γ-Al2O3 catalyst [Cat. Ind. 2024. V. 24(1). P. xx–xx]. The model allows predicting the yield of butadiene and other products depending on the process parameters, such as the catalyst activity, the feed gas composition, the cycle time of the dehydrogenation period, the ratio of the catalyst to inert material (for both uniform and non-uniform dilution). The model allows calculating the temperature regime of the catalyst operation and the degree of its coking along the bed length. The adequacy of the model to the industrial process in the description of n-butane conversion, butadiene and butylene formation, coke accumulation and loss of catalyst activity is shown on the example of test calculations of the main process parameters.

The kinetics of dehydrogenation of n-butane to butadiene was studied on K-CrOx /γ-Al2O3 catalyst particles of 56–94 μm size by varying the temperature T = 550÷625 °C, the time of catalytic step TOS = 5÷30 min, and the space velocity GHSV = 4400÷35200 h–1. The catalyst was similar to the commercial one. Prior to the studies, the catalyst granules were stabilized during the reduction-dehydrogenation-regeneration cycle at 593 °C, then the catalyst particles milled to a size of 56–94 μm were stabilized during the dehydrogenation-regeneration cycle at 650 °C. The highest butadiene selectivity of ~25 mol.% was obtained at n-butane conversion of 26–30 % (GHSV = 35200 h–1) at T = 600 °C and TOS = 5 min, and the highest butadiene yield of ~10 mol.% was obtained when the conversion was increased to ~50 % (GHSV = 8800 h–1) under the same conditions. Increasing T to 625 °C, TOS to 30 min and decreasing GHSV to ~4400 h–1 resulted in an increase in by-product selectivity to ~50 mol.%. It was found that the observed activation energy of product formation rates decreases in the series: by-products > butylene > butadiene. A kinetic model is proposed that takes into account the formation of butadiene via butylene, the formation of by-products such as ethane/ethylene and methane/propylene in the butylene hydrocracking reactions, and the secondary conversion reactions of by-products. Inhibition of dehydrogenation reactions by components of the reaction mixture, coke formation and its effect on catalyst activity are also considered in the model. The adequacy of the kinetic model is confirmed by good agreement of the calculated results with the experimental data.

The paper is devoted to the study of the highly exothermal methanol to formaldehyde oxidation process at elevated methanol load in a slit-channel microstructured reactor with porous nickel catalytic plates containing fine particles of iron-molybdenum catalyst. A 3D non-isothermal mathematical model describing the coupled processes of heat and mass transfer in the channels and plates of the reactor has been developed. The model allows for convective and diffusion heat and mass transfer in the channels; the catalytic reactions and heat transfer by thermal conductivity throughout the plates; interphase transfer. For the first time, the model takes into account the diffusion of reagents in the catalytic plates.It has been experimentally shown that methanol conversion increases with increasing temperature, decreasing linear velocity and decreasing methanol inlet concentration. The formaldehyde selectivity under test conditions is 99.9-100 %. The temperature at the outlet of channels is almost the same as the temperature of the side surface of the reactor. The developed model is adequate to the process in the whole range of conditions investigated. It is theoretically shown that channels of the maximum possible width and height 0.28-0.6 mm are the most efficient in terms of formaldehyde yield. Increasing the channel height to 0.6 mm makes it possible to reduce catalyst load in the reactor almost without loss in formaldehyde yield compared to the minimum possible channel height.

The paper investigates the basics for increasing the productivity of gas-phase catalytic oxidation processes effected in multi-tubular reactors due to their operation at more concentrated feedstock. Obviously, an increase in initial concentration of the oxidizable reagent seems very attractive, but it is associated with the need to modify the process parameters and/or technological chart in order to achieve the required performance figures. This often entails excessive formation of by-products and therefore overheating of the catalyst bed due to increased heat generation. The cumulative effect of many factors can prevent attaining an acceptably high conversion of feedstock and the yield of target products within a reasonable size of a multi-tubular reactor. The problems we studied are quite typical for highly exothermic catalytic oxidation processes, but are not widely discussed in the literature. On the example of nicotinic acid (NA) synthesis in multi-tubular reactor, we investigated the advantages of the process with elevated feed load (beta-picoline), in comparison with the conventional conditions. On the basis of comprehensive process simulation supported by the experimental evidence, for the first time we have shown how the process should be operated to achieve a significant progress in the reactor performance and the target product yield. Our theoretical study showed that the rise in the initial beta-picoline concentration from similar to 0.8 to similar to 3% accompanied by a relevant adjusting of the process parameters leads to a dramatic 1.5-2-fold gain in the specific productivity of catalyst; this could greatly improve the reactor capacity. Optionally, a given production capacity of multi-tubular reactor may be ensured by similar to 2 times less number of tubes. Thus, the synthesis of NA at elevated initial feed of beta-picoline shall be significantly enhanced in comparison with the conventional process. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The study deals with the synthesis of nitrous oxide via selective oxidation of ammonia in a microreactor (MCR), which is a metal disk with cylindrical channels filled with the manganese-bismuth oxide catalyst. The proposed 3D mathematical model of MCR takes into account axial and radial heat and mass transfer, catalytic reactions and related changes of the reaction mixture volume, heat exchange between the disk and channels, and thermal conductivity of the disk. Parameters providing the maximum output of nitrous oxide were determined with allowance for restrictions on the temperature in MCR channels. The highest efficiency of the nitrous oxide synthesis is achieved at a temperature of the outer edge of reactor 370 °С and an inlet concentration of ammonia 20 vol.%. The output per unit catalyst volume in MCR is approximately 1.5 times higher as compared to a tubular reactor; the maximum temperature corresponds to the optimal one, which provides the best selectivity of the process with respect to nitrous oxide.

In order to simulate strongly exothermic catalytic reactions in multichannel microreactors (MCMR), a new three-dimensional (3D) model is proposed. MCMR fabricated as brass disks 10 mm thick, with 250, or 500 parallel 1 mm channels are the subjects of experimental testing and modeling in the catalytic oxidation of methanol to formaldehyde. The 3D model incorporates two interconnected computational domains with the heat exchange between them, namely, the catalyst-filled channels and the metal disc. Axial effective conductivity and diffusivity in the channels, and intrinsic thermal conductivity of the metal disk are taken into account; the temperature of metal disk Tme is assumed variable. The new approach enabled to explore the influence of parameters on the process performance in various channels across the disk, which led to a correct prediction of the target product yield and of the critical temperature Tmax in the channels. Otherwise, the predicted yields and Tmax values would be overestimated or underestimated. The change in Tme as a result of the reaction heat generation dominates other factors that affect the establishment of Tmax. A generalized diagram provides permissible ranges for performing a strongly exothermic process in MCMR under constraints on the thermal stability of the catalyst, and relates the reaction heat generation to the appropriate intrinsic metal heat conductivity. The good agreement between simulated and observed results validates the approach and demonstrates the ability of the model to predict temperature, conversion and yield in each specific channel. Current study stimulates further use of the model for design and practical application of MCMR.

The reasons for the formation of nitrous oxide (a greenhouse gas with CO2-equivalent equal to 310) at modern plants manufacturing weak nitric acid are analyzed. The amount of annual N2O emission depending on the operating conditions of the ammonia converter and on the method of the removal of nitrogen oxides NOx is estimated. A technological scheme of simultaneous low-temperature removal of NOx and N2O from exhaust tail gases is proposed, in which V/Al catalyst for the selective catalytic reduction (SCR) of NOx with ammonia and Cs/Co3O4 catalyst for N2O decomposition are used. Mathematical modeling of a 2-layer catalytic reactor is carried out; the charges of both SCR catalyst and N2O decomposition catalyst are determined, which ensures compliance with environmental emission standards for all nitrogen oxides.

Catalytic hydrogenation of the plant oils includes a filtration stage in which the solid catalyst must be separated from its suspension in the melted hydrogenation products. For effective separation of the catalyst, a proper selection of the filter cloth and filtration conditions is necessary. The subject of this study is filtration of finely dispersed carbon material Sibunit through a porous woven filtering cloth in circulation mode. Sibunit is the carrier for Pd catalysts that are regarded as prospective for hydrogenation of vegetable oils; the carbon-based catalysts can be reused and can therefore be more economical than conventional nickel catalysts. To reliably predict the efficiency and duration of filtration of the catalyst suspended in the hydrogenated products, the mathematical model of the filtration process must adequately describe the complex physical phenomena that occur during the process. In the article, a one-dimensional mathematical model was developed, which took into account the main physical phenomena of the filtration process, such as percolation of the particles through a porous filter, accumulation of the particles along the filter pores, and a gradual cake growth. Woven fabric contains two types of pores: the pores between the threads and the pores between the fibers. Model assumes that polydisperse particles can both penetrate through the filter cloth and accumulate inside the tissue and on its outer surface. It is assumed that the hydraulic resistance of the cake increases due to the growth of its height only, and the hydraulic resistance of the filter cloth increases due to particles trapped in the pores. Numerical analysis of the model was carried out in the range of parameters typical for industrial conditions. It has been found that the process efficiency, which was defined as the minimum time required filtering a certain amount of hydrogenated oil to the maximum degree of catalyst purification, depends mainly on the time taken to form a cake layer of sufficient height. Higher efficiency of the filtration process is favored by the higher filter porosity, the greater thread diameter, and the smaller pore size between the fibers. In contrast to the thin pores formed by the fibers, the large pores between threads allow more particles to pass through the filter; therefore, for practical use it is necessary to adjust the filter cloth porous structure with the particles size distribution. The model was verified by comparing the predicted results with experimental data.

Palladium-containing catalyst based on binder-free granular sulfated zirconium oxide for n-butane isomerization has been investigated. It has been found that Pd content of 0.2–1.0 wt % slightly influences textural characteristics and other physicochemical properties of bifunctional catalysts; however, it determines their activity and selectivity in the reaction studied, with the optimal palladium content being 0.5 wt %. Parameters of the isomerization process have been studied depending on the composition of industrial n-butane fractions. It has been shown that impurities of isobutane, propane, neopentane, isopentane and pentane in an amount of no more than 2% do not exert a effect on isobutane production; nonetheless, the conversion of n-butane and selectivity for isobutane both increase when more pure n-butane fractions are used. It has been found that the process for isobutane production by isomerization of the n-butane fraction under the optimal conditions at H2 /n-C4 = 0.1 and 140–150°C makes it possible to obtain a high isobutane yield (up to 52 wt %) and avoid the undue formation of С1–С3 alkanes.

The process of dehydrating ethanol to ethylene by varying geometrical dimensions of a ring-shaped alumina catalyst is studied using a mathematical 2D model of a multitubular reactor. The set of ring sizes determines equivalent grain size Req, on which catalyst’s effectiveness factor η depends in turn. A procedure is proposed for assigning grains with different geometric dimensions to four structural groups, depending on the technique used to synthesize samples with the same equivalent size Req. Based on this approach, a system of criteria is developed for selecting catalyst grains with the best characteristics for given conditions. The geometric sizes of grains and other parameters that ensure the highest ethylene yield at the lowest values of the pressure drop and the residence time are determined.

New results of endothermic dehydration of undiluted ethanol on alumina catalyst in pilot wall-heated tubular reactor are presented. Activity and physicochemical characteristics of the proprietary acid-modified alumina (AMA) prepared by gibbsite flash calcination in TSEFLAR (TM) reactor were compared to the properties of commercially available alumina samples prepared by precipitation (CS1) or flash calcination of gibbsite in a flue gas (CS2). The samples differed in phase composition, which corresponds to gamma-Al2O3 in CS1, mixed gamma- and chi-Al2O3 in AMA and CS2; sodium content and concentration of Lewis acid sites (LAS) were different as well. Acid modification resulted in AMA catalyst with improved acidic properties and catalytic activity higher than that of CS2, despite the lower sodium content in the latter. Ethanol-to-ethylene dehydration in the wall-heated tubular reactor proceeded at the catalyst bed temperatures mainly below 385 degrees C, where AMA catalyst is the most active due to the highest content of strong LAS. The heat-agent temperature favors yield of ethylene rather than that of by-products. Higher linear velocity and porosity contribute to a flatter axial temperature profile in the bed; a higher average integral temperature gives a quantitative estimate. This ensures higher ethylene yield with a lower ethanol consumption even at a reduced heat-agent temperature. On the ring-shaped AMA catalyst, the greater ethylene yield, catalyst productivity and sharply reduced hydraulic resistance are reached compared to CS2 cylinders. For the first time we showed that use of AMA ring-shaped catalyst in wall-heated tubular reactor in contrast to the SynDol alumina based catalyst in adiabatic reactor can improve the catalyst productivity by 5-8 times and WHSV by 5-12 times.

The present work is focused on the intensification of catalytic ethanol-to-ethylene dehydration process in multitubular reactor by applying the ring-shaped particles of the optimal geometric sizes instead of conventional granules. A new simulating approach allowed us to select the optimal sizes of rings under wide variation of their height h, inner d and outer diameter D. Reducing the pellets size h x d x D from 6 x 2.3 x 6 to 3 x 4.4 x 6 mm leads to an increase in the effectiveness factor from 0.46 to 0.76, thus enhancing catalyst activity due to less intraparticle diffusion. The impact of various factors on the total enhancement of ethylene productivity over ring-shaped catalysts was examined. The mechanical crushing strength of ring-shaped alumina catalysts and hydraulic resistance of the catalyst bed were tested experimentally. Increase in the effectiveness factor eta plays the major role, while heat and mass transfer parameters contribute less than 8%. Among other aspects, the process intensification (PI) pursues the goals of enhancing the process capacity, or downsizing the reactor. Our study revealed that at a fixed ethanol conversion, PI due to the optimal geometries may be expressed either as 2.1-fold increase in the reactor capacity, or as respective reduction in the tubes quantity. Both options may result in a significant improvement of the process performance. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The indicators of ethanol to ethylene catalytic dehydration process on trilobe- and ring-shaped samples of an alumina catalyst were compared at the fixed parameters: thermal agent temperature and catalyst load. Experiments were performed in a flow-through reactor of a laboratory setup and in a tubular reactor of a pilot installation. The use of the less active ring-shaped catalyst ensures higher values of ethanol conversion, ethylene yield, and catalyst performance and significantly lower hydraulic resistance, compared to the more active trilobe-shaped catalyst. This is caused by lower intensity of the heat absorption on the less active catalyst and, correspondingly, to the higher temperature in the ring bed due to higher bed porosity.

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.

Complete cycle of ethylene production from oat hulls as widespread agricultural waste was studied on a pilot scale. The cycle involved mechano-chemical, biotechnological and catalytic units. The oat hulls were pretreated with a 2%(w/w) sodium hydroxide solution in a setup consisting of a rotary-pulsating apparatus and a 100-L vessel to produce a pulp containing 90.3% of hydrolyzables. Simultaneous saccharification and fermentation of oat hull pulp with delayed inoculation (dSSF) into ethanol using commercial enzymes CelloLux-A and BrewZyme-BGX and non-GMO yeast Saccharomyces cerevisiae was carried out in 63-L reactor. At a solid loading of 33.3 g/L, the yield of reducing sugars was 97.9% on overall hydrolyzables basis. The ethanol yield during dSSF at a solid loading of 60 g/L was as high as 95 g ethanol/kg oat hulls. The produced raw-ethanol sample contained low impurities of methanol, propanol and alkali metals. The rectified ethanol samples were used for dehydration to ethylene with the overall production index as high as 38–51 g ethylene/kg oats hulls. A negative impact of the propanol and alkali metals impurities in the rectified ethanol on conversion and selectivity to ethylene were observed. Being purified from organic impurities, ethanol was dehydrated with higher conversion and selectivity to ethylene. When the ethanol samples that contain less than 0.02 g/L organic and no sodium impurities were used in ethanol dehydration process, the yield of ethylene was as high as 56 g ethylene/kg oats hulls. In this work, 12 kg of oat hulls was converted to 1.21 kg 94%(w/w) ethanol, which was then converted to 0.62 kg 99.5% ethylene; this is the first experimental study devoted to the production of ethylene from oat hulls on a pilot scale.