Kh. Kh. Gil’manov

Transformation of the phase structure of an iron oxide catalyst for dehydrogenation of methyl butenes under industrial exploitation conditions

X-ray phase, differential-thermal, and elemental analyses were used to study the transformation of the phase structure of an iron oxide catalyst for dehydrogenation of methyl butenes after exploitation.

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.

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.

The influence of physicomechanical characteristics of microspherical supporters and dehydrogenation catalysts on their abrasive activity in fluidized bed conditions

In industrial lower paraffin dehydrogenation reactor units with a microspherical chromoalumina catalyst fluidized bed, abrasive wear of internal equipment surfaces proceeds by the fatigue and plastic deformation mechanism, and the wear direction coincides with the catalyst motion trajectory. The wear degree is defined by wearing material and granule physicomechanical properties, which have been taken into account along with hydrodynamic conditions for the formation of fluidized bed to suggest a mathematical model, describing the influence of physicomechanical, structural characteristics and sizes of granule on the abrasive ability of industrial microspherical paraffin dehydrogenation catalysts and aluminum oxide supporters. The most significant factors have been revealed: salient item density on the granule surface, abrasion resistance, microhardness, and sphericity degree. The developed mathematical model permits to predict the abrasive activity of granules under their operation, to estimate the internal reactor surface wear time necessary to attain the critical thickness, and to choose optimal methods for the synthesis of catalysts and supporters with minimal abrasive activities.

Effects of cracking and coke formation on the selectivity of iron oxide catalysts in the dehydrogenation of methylbutenes to isoprene

The contributions of cracking and coke formation reactions to a decrease in the selectivity of domestic and imported catalysts for the dehydrogenation of methylbutenes (isopentanes and isoamylenes) into isoprene have been determined. It has been found that hydrothermal treatment in industrial reactors favorably affected an increase in the catalytic characteristics of a domestic iron oxide catalyst for dehydrogenation. The conditions for catalyst activation have been optimized with respect to the temperature and duration of hydrothermal treatment.

Effect of heat-treatment conditions on the formation of polyferrite phases from an iron-oxide-based dehydrogenation catalyst

The formation of polyferrites from an iron-oxide-based catalyst under various heat-treatment conditions has been studied by thermal analysis and x-ray diffraction. Promoters are shown to influence the aggregation of secondary particles and the recrystallization temperature of the ferric oxide. Mechanisms are proposed for potassium polyferrite formation at high and low heating rates. The effect of heat-treatment temperature on the potassium ferrite and iron oxide contents of the catalyst is analyzed.

Effect of the paste molding pressure on the mechanical strength of an iron oxide catalyst in the dehydrogenation of methylbutenes

The effect of the paste molding pressure on the physicomechanical and texture characteristics of catalysts was studied. An indirect criterion is suggested to evaluate the molding pressure in industrial extruders, whose optimal value ensures good physicomechanical properties of the catalysts and kinetic control over the catalyzed reaction. The results obtained were verified in paste molding on various industrial extruders, and this enabled the optimal choice of the molding equipment.

Effect of the paste molding pressure on the activity of iron oxide catalyst in dehydrogenation of methylbutenes

The effect of the paste molding pressure on the activity of an iron oxide catalyst in dehydrogenation of methylbutenes was studied. The study involved detailed analysis of the pore structure of the samples by mercury porosimetry and determination of the mode of the catalytic process (kinetic or diffusion control). The range of pore sizes in which dehydrogenation reactions occur was determined.

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 (<600°C), there is intensive shrinkage via the diffusion glide of crystallites, the mechanical strength of the granules remaining invariable. In region II (600–900°C), the polymorphic transformations of alumina accompanied by sintering via surface diffusion do not affect the dimensions and strength of the granules. In region III (>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-Al2O3. 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.

Problems and perspectives of the development of innovative technologies in OAO Nizhnekamskneftekhim

This paper discusses prospects for the innovative development in the OAO Nizhnekamskneftekhim corporation. Only the innovative technologies are identified from the entire variety of research and development activities of last years, and their development and industrial implementation is analyzed in a number of examples. The key participants of the innovative technologies market are briefly noted, and Russian academic institutions (Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences) in the research and development and in the development and implementation of their own new catalysts take more active involvement. Some successful aspects of the integration of the university research and science-technical services of the corporation are exemplified by the cooperation of Kazan (Volga) Federal University and the Nizhnekamskneftekhim corporation. The problems of innovative development in other universities and the effectiveness of Russian state policy in the development of the innovative economy are briefly reviewed.