Kh. Kh. Gilmanov

Diffusion model of the dehydrogenation of isoamylenes into isoprene in a fixed iron-potassium catalyst bed

A mathematical model is suggested for the dehydrogenation of isoamylenes into isoprene in a fixed bed of industrial, self-regenerating, iron-potassium catalysts (KDOM and ZhKD). The model takes into account the size and shape of catalyst granules, the rate constants and activation energies of the forward (dehydrogenation) and reverses (hydrogenation) reactions, those of cracking and catalyst self-regeneration reactions, and the buildup of leachable and nonleachable coke. The mathematical model adequately describes the physical and chemical processes occurring in the dehydrogenation of isoamylenes in industrial reactors at different amounts of iron-potassium catalyst and varied reactor operation parameters (feed flow rate, degree of dilution of the feedstock with water vapor, temperature and pressure at the reactor inlet. It provides means to optimize the technological parameters of the industrial process.

Influence of hydrothermal treatment conditions on the structure and catalytic activity of alumina during the skeletal isomerization of n-butenes

In order to obtain an efficient alumina catalyst for skeleton isomerization of n-butenes with a high catalytic activity, we study the influence of hydrothermal treatment (HTT) of alumina systems at 150–200°C on the parameters of the crystalline and pore structure, and acid-base properties of industrial γ-Al2O3. It is shown that the HTT of aluminum hydroxide increases the sizes of microcrystallites and reduces the alumina’s specific surface area and the number of acid-base centers. This reduces the activity in the reaction of skeletal isomerization of n-butenes. HTT of the two-phase alumina-aluminum hydroxide system produces smaller crystallites of γ-Al2O3 and raises the acidity of the alumina obtained after calcination at 550°C; as a result, the catalytic activity increases. This method can be used to enhance the activity of industrial samples of alumina in the reaction of skeletal isomerization of n-butenes.

Dehydrogenation of methylbutenes to isoprene: Mathematical analysis of technology upgrade options. Part I

The mathematical modelling of conventional metylbutene dehydrogenation technology (performed in an adiabatic reactor) and of three versions of this process conducted in a pseudo-isothermal mode is performed to select a variant of modernization that is optimal in terms of energy efficiency. These variants are (1) a single-reactor design with a fractional supply of steam to the upper and middle zones of the catalyst bed; (2) a design with two reactors in series and intermediate heating of the contact gas in an interstage superheater; and (3) a design with two reactors in series and the adding of an overheated gas into the interreactor space. It is shown that each of the new designs can significantly increase the effectiveness of the process, compared to the conventional technology. A comparative analysis is performed of the dependences of the selectivity and yield of isoprene formation on the amount of heat energy Q supplied in the experimental designs. It is concluded that at long times of contact, the greatest increase in the isoprene yield (5.5%) and selectivity (5.6%) is obtained with design (2), especially when Q > 8.5 × 106 J/kg.

Polymerization of propylene in liquid monomer using state-of-the-art high-performance titanium-magnesium catalysts

A comparative study of propylene polymerization in liquid monomer is performed under laboratory conditions using the IK-8-21 Ti-Mg catalyst designed at the Boreskov Institute of Catalysis and imported industrial catalysts (conditionally labeled TMC-1, -2, and -3). The activity and stereospecificity of the catalysts are estimated along with properties of the resulting polypropylene (granular composition and physicomechanical characteristics). It is shown that the IK-8-21 catalyst is not inferior to imported counterparts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on IK-8-21 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene synthesized on the domestic IK-8-21 catalyst are similar to those for polypropylene prepared with the imported TMK-1 catalyst.

Pilot tests of a new domestic ZhKD catalyst for the dehydrogenation of isoamilenes into isoprene

At the Synthetic Rubber Plant of OAO Nizhnekamskneftekhim, the dehydrogenation of isoamilenes into isoprene is currently performed on KDOM-08 catalysts with an insufficiently high yield of isoprene throughout the period of its industrial operation. More stable and highly active catalysts must be used to make the process more efficient. Under Russian Federation Government Decree No. 218, ZhKD-1 and ZhKD-2 iron-potassium catalysts have been developed by improving their formulas and optimizing their phase composition through selecting the proper ratio of initial compounds. To evaluate the possibility of transitioning to the new domestically-produced iron-potassium catalysts, we have performed pilot tests of the ZhKD-1 and ZhKD-2 catalysts in the dehydrogenation of methylbutenes into isoprene in adiabatic flow fixed-bed reactors at the Synthetic Rubber Plant of OAO Nizhnekamskneftekhim. The KDOM-08 catalyst used in the amount of 25 t in reactor 1 of the first system is taken as a base for comparison. The ZhKD-1 and ZhKD-2 catalysts are loaded into parallel reactors 7 and 8 of the fourth system. The KDOM-08 catalyst is shown to operate more efficiently under industrial conditions at loads of 1.0–2.0 t/h for 1000–3000 h, after which its performance characteristics deteriorate due to its gradual deactivation. The ZhKD-1 and ZhKD-2 catalysts are substantially superior to their industrial analogues in isoprene yield. It has been found that the ZhKD-2 catalysts operate more efficiently at even longer runs (4000–5000 h) and feedstock flow rates of 1.0–2.0 t/h, and the ZhKD-1 catalysts exhibits better activity (30–33 %) and selectivity (87–92 %) at higher loads of 2.3–3.0 t/h for up to 5000 h. From our analysis of the catalysts’ operation over the last 1000 h, it follows that at the same process temperatures (619°C) and feedstock loads (2.5 t/h), the ZhKD-1 and ZhKD-2 catalysts operate at a lower steam dilution coefficient (6.1 t/t) than the KDOM-08 catalyst (6.8 t/t). The rebuilding of reactors 7 and 8 allows the loaded catalyst mass to be reduced from 25 to 17 t, thereby almost doubling the daily output of isoprene per ton of catalyst. It is obvious that higher activity and selectivity along with smaller loads makes the use of the ZhKD-1 and ZhKD-2 catalysts economically profitable.

Модернизация промышленной технологической схемы дегидрирования метилбутенов в изопрен. Сообщение 2. Анализ результатов опытно-промышленной апробации и промышленная реализация модернизированной схемы

Pilot testing of the technology for dehydrogenation of methylbutenes to isoprene was achieved using a two-reactor system with additional overheated steam fed to the inter-reactor space. A pilot setup with two adiabatic reactors was used at the total ZhKD-3 catalyst loading 60,0 dm 3 , 565–620 °C, contact time 0,18–0,25 s, feed to steam mass ratio C 5 H 10 1,0 : (6,0÷30,0) and extra pressure 0,6–0,8 kg/cm 2 . Dependence of the isoprene concentration in the contact gas on the heat energy supplied by the feed and steam was determined under the traditional process conditions and in the pseudoisothermic mode, the latter was achieved by feeding additional overheated steam to the inter-reactor space. 10–12 % increase in the isoprene yield was demonstrated in the improved process. The industrial process conditions were determined on the basis of the results obtained. The improved process was tested at a Nizhnekamsk plant using a setup for dehydrogenation of methylbutenes in a reactor with the catalyst loaded in two beds with 9 t of the catalyst in each. Regularities established during pilot testing were, in general, proved true, while the selectivity was lower because of some design drawbacks to be eliminated. Reliability of the mathematical model was proved by comparing experimental and calculated data.

Pilot tests of the microspherical aluminochromium KDI-M catalyst for iso-butane dehydrogenation

Results from pilot tests of microspherical aluminochromium KDI-M catalyst mixed with IM-2201 in a large-scale unit (Nizhnekamskneftekhim) for iso-butane dehydrogenation are discussed. Compared to KDI catalyst, its modified analogue KDI-M is more active and selective; the optimized grain-size composition and mechanical strength ensures higher yields of iso-butylene and longer nonstop operation (up to 400 days) of the reactor unit.

Upgrading the industrial process flowsheet for the dehydration of methylbutenes to isoprene. II: Analysis of plant test results and industrial implementation of the upgraded design

Pilot tests of technology for the dehydration of methylbutenes to isoprene are performed in a tworeactor system with an additional supply of an overheated gas into the interreactor space. The tests are performed on a pilot plant with two adiabatic reactors. The total volume of the catalyst charge is 60 dm3, the temperatures are 565–620°С, the contact time is 0.18–0.25 s, the raw material is diluted with steam in a weight ratio of С5Н10: Н2О = 1.0: (6.0–30.0), and the excess pressure is 0.6–0.7 kgf/cm2. The dependence of the isoprene concentration in the contact gas on the heat energy supplied by the raw material and steam is determined under conventional conditions of the process and in a pseudo-isothermal mode via an additional supply of overheated gas into the interreactor space. It is shown that the isoprene yield is increased by 10–12% by using the upgraded mode. The conditions for conducting the industrial process are determined based on the obtained results. After upgrading the design, tests are performed at the synthetic rubber factory of PAO Nizhnekamskneftekhim on a plant for the dehydrogenation of methylbutenes in the reactor with a doublelayer catalyst bed (nine tons per layer). The patterns established during the pilot tests generally prove to be true, but the selectivity of the process is reduced due to a number of design flaws. Corrective measures are outlined. Comparison of the experimental results and the calculated values confirm the accuracy of the mathematical model.

Study of factors affecting the erosive wear of equipment for dehydrogenation units in fluidized beds of microspherical chromia-alumina catalysts under industrial operating conditions

The main problems associated with the operation of microspherical treating-type chromia-alumina catalysts with increased strength during isoparaffin dehydrogenation are discussed. The erosive wear of the walls of overflow pipelines when using a mixture of treating-type KDI and conventional IM-2201S catalysts and ways of solving the problem are emphasized. It is found that the main reason for an increase in erosive wear is the greater momentum of catalyst particles due to a higher mean particle size and gas transport rate; upon transitioning from IM-2201S to a mixture of IM-2201S and KDM (70 : 30), the mean particle size of the equilibrium catalyst grows from 68 to 74 μm. The optimum size range of a high-strength catalytic system in which the activity does not increase over time is calculated with a lower rate of transport gas injection while keeping the number of particles 20–40 μm in size at 20–30 wt %. Pilot batch production of high-strength catalyst in the optimum size range is recommended in order to shift units for the industrial dehydrogenation of isobutane to the use of treating-type KDI catalyst without the addition of IM-2201S.

Investigating the mechanism of the effect of cerium additives on the properties of the iron-potassium system-the active component of dehydrogenation catalysts of hydrocarbons Report 2

The properties of the Fe2O3-K2O and Fe2O3-K2O-CeO2 model systems with weight ratios of 80 : 20 and 50 : 20: 30, respectively, are studied by means of thermal, magnetic, X-ray and dispersion analysis, and low-temperature nitrogen adsorption. It is found that the successive formation of mono- and polyferrite phase occurs during the interaction of iron oxide and potassium carbonate. It is proposed that the activity of the iron-potassium catalyst is proportional to the content of the surface monoferrite phase. It is found that introducing cerium into the iron-potassium system leads to a redistribution of potassium mono- and polyferrites in the ferrite phase, raising the proportion of monoferrite. Introducing cerium therefore promotes the activity of the catalyst system. The results from this study will be used to develop new iron-potassium catalysts with high catalytic activity in the dehydrogenation of isoamylenes into isoprene.