Effect of the catalyst structure on the catalytic activity in dehydrogenation of 2-methyl butane

Calorimetry, thermogravimetry, X-ray diffraction analysis, and low-temperature adsorption of nitrogen were used to study the structure of bimetallic Pt-Sn catalysts on zinc-alumina spinel supports. The effect of the porous structure of the catalyst samples synthesized on their catalytic activity in dehydrogenation of 2-methyl butane was analyzed. © Pleiades Publishing, Ltd., 2010

Isoprene manufacturing process on a new bimetallic (platinum-tin) catalyst

The influence of the reaction conditions on the characteristics of the one-step process of the dehydrogenation of 2-methylbutane or 2-methybutenes to isoprene in the presence of a new bimetallic (Pt-Sn) catalyst was studied. It was shown that this catalyst supported on a material with an optimal structure holds promise for use in the industrial-scale process for the manufacturing of isoprene via one-step dehydrogenation. © 2010 Pleiades Publishing, Ltd

Influence of the phase composition of the support on the catalytic activity of bimetallic catalysts

The influence of the nanocrystalline structure of an aluminum-zinc spinel support on the catalytic activity of bimetallic Pt-Sn catalysts in dehydrogenation of 2-methylbutane was studied. The formation of the spinel structure in solid-phase reactions of aluminum and zinc oxides was examined. © 2010 Pleiades Publishing, Ltd

Development of technology for the production of microspherical alumina support for the alkane dehydrogenation catalyst: III. the effect of the phase composition of microspherical supports on their thermal stability

This publication continues a series of our reports on the optimization of preparation conditions for obtaining a thermally stable support for the alkane dehydrogenation catalyst. The phase composition effect on the stability, particle size distribution, structure, texture, and mechanical properties of supports heated to 1100°C is reported. Microspherical alumina supports obtained by successive thermal and hydrothermal treatments of gibbsite are compared to commercial supports obtained by the thermochemical activation (TCA) of gibbsite. The dimensions of the support granules decrease upon heating because of shrinkage, which is governed by the phase composition of the granules and by the packing of their constituent boehmite and alumina crystallites. Three temperature intervals can be distinguished in the shrinkage of the granules. In region I (900-1000°C), shrinkage takes place via coalescent sintering. For commercial manufacturing of microspherical alkane dehydrogenation catalysts and for ensuring their stability at 550-900°C, it is recommended to use alumina supports containing the minimum possible amount of χ-Al2O 3. As the single-phase boehmite support obtained by our technology is heated to 1100°C, its granules shrink by no more than 14.4% and show an attrition resistance of 89% or above. The support based on the gibbsite TCA products, which contains 14-23 wt % χ-Al2O3, is characterized by 3-5% greater granule shrinkage and 6-12% lower mechanical strength. © 2011 Pleiades Publishing, Ltd

Effect of the granulometric composition of microspherical catalyst on the product yield for the dehydrogenation of iso-butane

The effect of the granulometric composition of microspherical KDI alumina-chromia catalysts on variation of the height and density of a fluidized bed was analyzed during pilot industrial testing at the OAO Nizhnekamskneftekhim iso-butane dehydrogenation plant. It was ascertained that one of the factors determining the acceleration of the cracking reactions was a rise in temperature to 600-610°C in the upper part of the reactor at the level of grid no. 10 due to the reduction of the upper boundary of the fluidized bed as a result of carryover from the reactor-regenerator system of catalyst particles smaller than 20 microns. The formation of a stable fluidized bed on the upper grid of the reactor depends on the content of 20-40 μm particles within the circulating catalyst. In order to compensate for the carryover of the catalyst, it is recommended that the mixture of catalysts accumulated in the first and second electrofilter fields be loaded into the system as well. This load consists of ~25 wt % of the fraction with particle sizes of 20-40 μm and is as good the initial KDI in terms of catalytic parameters, ensuring stabilization of the fluidized bed height at a level of 52%, lowering of the temperature at the tenth grid of the reactor to 568°C, reduction of the yield of cracking products to 4.0 wt %, a 3% increase in the average daily output of iso-butylene, and a 7% decrease in the consumption of iso-butane. Recovery of the irrevocable carryout of the catalyst from the system and the formation of a stable fluidized bed were achieved by alternating the additional loading of the catalysts from the first and second fields of the electrofilter and the initial KDI with optimized fraction composition at a 4 : 1 ratio. © Pleiades Publishing, Ltd., 2011

Engineering problems in the operation of microspherical chromium oxide/alumina catalysts for the dehydrogenation of paraffins

We analyze the effects of fluidized bed height, circulation ratio, and pressure drop in a reactor on the operational efficiency of a dehydrogenation unit in order to determine the reasons for a decrease in iso-butylene yield and catalyst circulation ratio, leading to an increase in the concentration of by-products at the iso-butane dehydrogenation plant of OAO Nizhnekamskneftekhim, where a mixture of catalysts with different physicomechanical characteristics (abrasion resistance, bulk density, fractional composition) is used to increase the iso-olefin yield. It is revealed that the main reason for the decrease in the olefin yield is the accelerated drop in pressure in the reactor due to a reduction in the free area of the waste-heat boiler tubes and scrubber grids as a result of the formation of hard-to-remove solid sediments consisting of potassium silicate and components of less durable IM-2201 catalysts (e.g., alumina and chromium oxide) on their walls. The sediment accumulation rate is proportional to the IM-2201 catalyst abrasiveness, which increases after a highly durable impregnated catalyst is added. To prevent an undesirable increase in the pressure, it is forbidden to combine catalysts with different physicochemical characteristics, obtained by the technologies of spray drying and support impregnation. In order to use the more durable impregnated chromium oxide/alumina catalysts separately and provide the required fluidized bed height of no less than 45.0% of the total reactor height, it is necessary to improve their aerodynamic properties, and to optimize their fractional composition in particular. The equilibrium catalyst formed during operation and circulating directly in the reactor/regenerator circuit must contain up to 30 wt % of <40-μm granules in order to guarantee the required height and to form a stable fluidized bed with no splashing at a constant level on the device's upper grid, with less entrainment of fine granules and optimum circulation. © 2010 Pleiades Publishing, Ltd

Selecting the conditions of molding iron oxide catalysts for dehydrogenation

The effect of the conditions for molding iron oxide catalysts for dehydrogenation of isoamylenes to isoprene on their operation characteristics was studied. The investigation of laboratory samples allowed us to determine the optimum molding pressure (200-250 MPa) under which high mechanical strength (strength factor KG = 33.4-37.3 N/mm), the stability of the kinetic characteristics in the dehydrogenation reaction, and the formation of 15-50 nm pores, ensuring the occurrence of the process in the kinetic region, were attained. we propose using the extrudate density as an indirect criterion for estimating the molding pressure under industrial conditions of extrusion. It was shown that in order to develop high strength properties (KG ~ 29.1 N/mm) of the catalysts upon their production under industrial conditions and to ensure the occurrence of the reaction in the kinetic region, the extrudate density must be 2.40-2.46 g/cm3. The obtained results were verified via paste molding on various industrial extruders, thereby enabling us to recommend the type of molding extrusion equipment. © Pleiades Publishing, Ltd., 2011

Recurrence time in chronic posttraumatic osteomyelitis of the tibia

Chronic posttraumatic osteomyelitis is a difficult-to-cure disease of the musculoskeletal system. The relationship between the course of the disease and the presence of type 2 diabetes mellitus has been revealed. It is necessary to predict the time of remission after initial diagnosis in this concomitant pathology. The paper includes data on the rehabilitation outcome of 57 patients with Ciery-Mader 3A (group 1) and 3B (group 2) osteomyelitis. Type 2 diabetes mellitus was a factor of systemic deficiency in wound healing in group 2. Clinical, radiological, and descriptive statistics methods were used. In patients with chronic osteomyelitis and concomitant type 2 diabetes mellitus, the risk of recurrence of purulent inflammatory process in the first year of follow-up increased by 20%. In the absence of systemic compromising factors, purulent process recurrence became more likely in the longterm follow-up periods up to 5 yearsХронический посттравматический остеомиелит является трудноизлечимым заболеваний опорно-двигательной системы. Выявлена взаимосвязь между течением заболевания и наличием сахарного диабета 2 типа. Необходимо прогнозирование сроков ремиссии после первичной постановки диагноза при данной сопутствующей патологии. В работу включены данные по исходу реабилитации 57 пациентов с остеомиелитом 3А (1 группа) и 3B (2 группа) по Ciery-Mader. Фактором системного дефицита заживления ран во второй группе являлся сахарный диабет 2 типа. Применены клинический, рентгенологический и методы описательной статистики. При наличии у пациентов хронического остеомиелита и сопутствующего сахарного диабета 2 типа риски рецидива гнойно-воспалительного процесса в первый год наблюдения возрастали на 20%. В отсутствии системных компрометирующих факторов рецидив гнойного процесса становился более вероятным в отдаленные периоды наблюдения до 5 ле

Effect of the catalyst structure on the catalytic activity in dehydrogenation of 2-methyl butane

Calorimetry, thermogravimetry, X-ray diffraction analysis, and low-temperature adsorption of nitrogen were used to study the structure of bimetallic Pt-Sn catalysts on zinc-alumina spinel supports. The effect of the porous structure of the catalyst samples synthesized on their catalytic activity in dehydrogenation of 2-methyl butane was analyzed. © Pleiades Publishing, Ltd., 2010

Isoprene manufacturing process on a new bimetallic (platinum-tin) catalyst

The influence of the reaction conditions on the characteristics of the one-step process of the dehydrogenation of 2-methylbutane or 2-methybutenes to isoprene in the presence of a new bimetallic (Pt-Sn) catalyst was studied. It was shown that this catalyst supported on a material with an optimal structure holds promise for use in the industrial-scale process for the manufacturing of isoprene via one-step dehydrogenation. © 2010 Pleiades Publishing, Ltd