Evgeniya Frantsina

Thermodynamic stability of coke-generating compounds formed on the surface of platinum dehydrogenation catalysts in their oxidation with water

Results of thermodynamic analysis and mathematical simulation of the deactivation of a platinum dehydrogenation catalyst by coke-generating compounds are presented. An approach to increasing the catalyst on-stream time has been proposed, suggesting implementation of a procedure for calculating the optimal flow rate of water fed to the reactor to maintain the conditions of thermodynamic equilibrium of the coke formation reaction and oxidation of intermediate condensation products with water.

Developing a Method for Increasing the Service Life of a Higher Paraffin Dehydrogenation Catalyst, Based on the Nonstationary Kinetic Model of a Reactor

The service life of an industrial catalyst can be prolonged by improving the technological conditions of its operation. This allows us to maximally eliminate the catalyst deactivation factors. A specific feature of the catalytic dehydrogenation of hydrocarbons is its nonstationarity produced by the deactivation of catalysts. The results of modeling the industrial catalytic process of C9-C14 paraffin dehydrogenation—the key stage in the production of linear alkylbenzenes—is discussed in this paper. We consider (1) thermodynamic analysis of reactions by means of quantum chemistry, (2) estimation of the kinetic model’s parameters by solving the inverse kinetic problem, (3) selection of an equation that describes the coke deactivation of a catalyst, and (4) development of a method for increasing the service life of a dehydrogenation catalyst using a nonstationary model based on the quantitative consideration of the water added to a reactor within a temperature range of 470–490°C. The higher alkane dehydrogenation flowsheet proposed on the basis of these models allows us to predict the operation of a reactor in different water supply regimes. It is shown that the service life of a catalyst grows by 20–30% on the average, if water is fed by increasing portions.

Development of an intelligent system for controlling paraffin dehydrogenation catalyst operation in production of linear alkyl benzenes

In this article, we present the main results on the modeling of the industrial process of catalytic C9–C14n-paraffin dehydrogenation, which is one of the technological stages in the production of linear alkyl benzenes used for the synthesis of synthetic detergents. The application of the developed mathematical model for evaluating the influence of the raw material composition on the target product yield is considered. The calculation results on the optimal technological modes for different dehydrogenation Pt catalysts and also on the prediction their lifetime are given.

Determination of the Optimal Operation Mode of the Platinum Dehydrogenation Catalysts

The main results of thermodynamic analysis and mathematical simulation of the deactivation of a platinum dehydrogenation catalyst by coke-generating compounds are presented. Developed model allows calculating the optimal flow rate of water fed to the reactor to maintain the conditions of thermodynamic equilibrium of the coke formation reaction and oxidation of intermediate condensation products with water. A comparative evaluation of different raw cycles of platinum-dehydrogenation catalysts is presented and shown to cause reduced production of the desired product was the change the composition of the feedstock.

Intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by redistribution of hydrogen between the units

The dehydrogenation and dewaxing of hydrocarbons of middle-distillate fractions, which proceed in the hydrogen medium, are of great importance in the petrochemical and oil refining industries. They increase oil refining depth and allow producing gasoline, kerosene, and diesel fractions used in the production of hydrocarbon fuels, polymer materials, synthetic detergents, rubbers, etc. Herewith, in the process of dehydrogenation of hydrocarbons of middle distillate fractions (C9–C14) hydrogen is formed in the reactions between hydrocarbons, and the excess of hydrogen slows the target reaction of olefin formation and causes the shift of thermodynamic equilibrium to the initial substances. Meanwhile, in the process of hydrodewaxing of hydrocarbons of middle distillate fractions (C5–C27), conversely, hydrogen is a required reagent in the target reaction of hydrocracking of long-chain paraffins, which ensures required feedstock conversion for production of low-freezing diesel fuels. Therefore, in this study we suggest the approach of intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by means of redistribution of hydrogen between the two units on the base of the influence of hydrogen on the hydrocarbon transformations using mathematical models. In this study we found that with increasing the temperature from 470 °C to 490 °C and decreasing the hydrogen/feedstock molar ratio in the range of 8.5/1.0 to 6.0/1.0 in the dehydrogenation reactor, the production of olefins increased by 1.45–1.55%wt, which makes it possible to reduce hydrogen consumption by 25,000 Nm3/h. Involvement of this additionally available hydrogen in the amount from 10,000 to 50,000 Nm3/h in the dewaxing reactor allows increasing the depth of hydrocracking of long-chain paraffins of middle distillate fractions, and, consequently improving low-temperature properties of produced diesel fraction. In such a way cloud temperature and freezing temperature of produced diesel fraction decrease by 1–4 °C and 10–25 °C (at the temperature of 300 °C and 340 °C respectively). However, when the molar ratio hydrogen/hydrocarbons decreases from 8.5/1.0 to 6.0/1.0 the yield of side products in the dehydrogenation reactor increases: the yield of diolefins increases by 0.1–0.15%wt, the yield of coke increases by 0.07–0.18%wt depending on the feedstock composition, which is due to decrease in the content of hydrogen, which hydrogenates intermediate products of condensation (the coke of amorphous structure). This effect can be compensated by additional water supply in the dehydrogenation reactor, which oxidizes the intermediate products of condensation, preventing catalyst deactivation by coke. The calculations with the use of the model showed that at the supply of water by increasing portions simultaneously with temperature rise, the content of coke on the catalyst by the end of the production cycle comprises 1.25–1.56%wt depending on the feedstock composition, which is by 0.3–0.6%wt lower that in the regime without water supply.

Raising the efficiency of higher alkanes dehydrogenation process

Recent development of the consumer market is actively stimulating the advances in industry, including petrochemicals. Particularly, active development of the production of synthetic detergents and linear alkylbenzenes (LAB), demand growth of 6% per year. High demand for LAB (which is the raw material for different detergents) is caused primarily by the fact that the synthetic detergents made from these substances are characterized by the balance between the products environmental quality, washing power and the price. The biodegradability of detergent is directly connected to the composition of its surface-active part. This is why there is great need to increase the productivity of existing industrial plants for LAB, as well as to increase the depth of crude oil refining with reduced losses of heat and power at each stage of production. In this case improving the technological process is closely related to the quality of the equipment and the efficiency of the catalyst used. In the course of work the formalized reaction network of process was built, and the kinetic and mathematical models were developed. Kinetic and mathematical models were designed to implement in the computer modeling system, based on the formalized reaction network of process. A possible method of Pt-catalyst recovery has been offered for higher alkanes dehydrogenation process.

Comparative analysis of catalyst operation in the process of higher paraffins dehydrogenation at different technological modes using mathematical model

Abstract This paper presents the results of comparative analysis of three run cycles of platinum catalyst for higher paraffins C9–C14 dehydrogenation process, performed using mathematical model. The results of model calculations were compared with the experimental data obtained at the industrial unit. It was established that deactivation of the platinum dehydrogenation catalyst is influenced by the technological modes of its operation, such as temperature, pressure, hydrogen/feedstock molar ratio and water supply. In the process of higher paraffins dehydrogenation, the phenomenon of platinum catalyst self-regeneration is observed. This occurs due to the action of feedstock components, in particular water and hydrogen involved in oxidation and hydrogenation of intermediate condensation products (coke structures). Model calculations showed that with a decrease in the hydrogen/feedstock molar ratio and simultaneous increase in water supply, depending on the temperature and composition of feedstock, it is possible to slow down deactivation process and increase the catalyst service life. This fact was experimentally confirmed at industrial unit.

Research of diesel fuels dewaxing process via mathematical model

The aim of the work is to carry out the research of diesel fuels dewaxing process. The study is based on fundamental mathematical model of the process, which takes into account poisoning of the metal centers and acid sites due to coking. Formed mathematical model was implemented for monitoring calculation with the aim of improving the efficiency of dewaxing catalyst loaded to the industrial reactor. Three operational modes were recorded for dewaxing unit. Optimization calculation of temperature at summer mode revealed that temperature in the dewaxing reactor could be decreased to 325°C without fuel quality loss.

An integrated criterion of efficiency for Pt catalysts in the dehydrogenation of higher n-paraffins

The deactivation of catalysts by coke-forming structures in the dehydrogenation of higher n-paraffins is discussed. The patterns of coke formation on a catalyst subject to process conditions are presented. A mathematical model of the process is described to show its adequacy. A calculation algorithm for the optimum mode of operation of a dehydrogenation catalyst is constructed, and the calculation results are given. Dehydrogenation catalysts of different brands are compared with respect to several parameters (coke formation on catalysts, the yield of the reaction by-product, and the dynamics of temperature rise in the reactor). The model can be used to estimate the efficiencies of catalysts in a cycle and to compare them.