Babayev R.K., Tamili N.T.
STUDY OF THE DEHYDROGENATION PROCESS OF HIGHER NORMAL PARAFFINIC HYDROCARBONS FOR COMPUTER MODELING *
Аннотация:
the oxidative dehydrogenation of n-paraffin hydrocarbons represents a promising approach for producing linear olefins. Conducting the dehydrogenation of higher n-paraffins in the presence of oxygen helps eliminate the nonstationary and cyclic nature of traditional processes. The current focus on this method stems from the necessity to develop higher olefin production utilizing readily available raw materials. This article examines the kinetic patterns of the oxidative dehydrogenation process for higher n-paraffinic hydrocarbons. The resulting kinetic model was analyzed computationally across a broad range of parameters, providing insights into how the primary parameters (Ci) and process characteristics evolve with contact time (τ).
Ключевые слова:
dehydrogenation, paraffins, catalyst, olefins, kinetics, n-decane, non-stationarity, atmospheric oxygen, water vapor, model
DOI 10.24412/2712-8849-2025-384-430-436
The dehydrogenation of higher normal paraffins in the presence of oxygen represents a promising approach for producing higher olefinic hydrocarbons. These hydrocarbons find significant application in the production of surfactants used in anionic synthetic detergents (alkylbenzene sulfonates) with biodegradability exceeding 90%. Due to their high reactivity, higher olefinic hydrocarbons are extensively utilized in various sectors of the economy, including as active components in synthetic detergents, oil additives, and corrosion inhibitors [1].Dehydrogenation in the presence of oxygen eliminates the non-stationary and cyclic nature of conventional processes. Current research focuses on this method to establish the production of higher olefins based on readily available raw materials. Presently, surfactant production primarily relies on alkylbenzenes synthesized by alkylating benzene with chlorinated paraffins or kerosene. This process releases hydrogen chloride and chlorine into the environment, causing ecological harm. Utilizing olefinic hydrocarbons derived from paraffin dehydrogenation in surfactant production enables the creation of an environmentally sustainable process.Kinetic studies of the reaction were conducted in a laboratory-scale reactor under gradient-free conditions at temperatures ranging from 813–853 K. The initial molar concentrations of n-decane and oxygen were varied within the ranges of (2.537–5.075) × 10⁻⁴ mol/L and (0.374–1.869) × 10⁻⁴ mol/L, respectively, with contact times not exceeding 0.12 s. The catalyst employed was a nickel-antimony-vanadium oxide system modified with lithium oxide, supported on Al₂O₃. The specific surface area of the catalyst, determined via low-temperature nitrogen adsorption and calculated using the BET method, was 80–100 m²/g with a bulk density of 0.873 g/cm³ and tablet sizes of 2–3 mm.Gas analysis for CO₂ and low-molecular-weight hydrocarbons (C₁–C₆) was performed using an LHM-80M chromatograph equipped with a 6 m column. The same instrument, using a 3 m column filled with NaX zeolite, was used to determine H₂, CO, O₂, and CH₄. Paraffinic and olefinic hydrocarbons were analyzed with a Tsvet-100 chromatograph, and aromatic hydrocarbons from the dehydrogenation process were characterized using a chromatograph-mass spectrometer.The study investigated the effects of varying concentrations of reactants, target products, and by-products on the reaction rates, paraffin hydrocarbon conversion, and oxygen consumption. It was found that increasing the paraffin hydrocarbon concentration from 2.148 × 10⁻⁴ to 3.745 × 10⁻⁴ mol/L enhanced the formation rates of both target and by-products. Concurrently, the oxygen concentration decreased significantly, attributed to rapid consumption at the catalyst beds inlet. The maximum oxygen consumption rate was observed at a paraffin concentration of 3.745 × 10⁻⁴ mol/L, with nearly complete oxygen conversion within the catalyst volume.The influence of the target product (decene) concentration on its formation rate was examined within a range of 0 to 0.7159 × 10 mol/L at a constant contact time of 0.04 s, maintaining fixed oxygen and paraffin concentrations. Increased olefin concentrations in the feedstock led to higher CO₂ formation rates, indicating partial combustion of olefinic hydrocarbons in the oxygen flow.Introducing CO₂ into the reaction products reduced the hydrocarbon combustion rate within the catalyst, freeing oxygen for coke deposit removal from the catalyst surface. This redistribution increased the catalysts active surface area. Changes in hydrogen concentration in the feedstock had minimal impact on paraffin hydrocarbon conversion rates or product formation. However, oxygen consumption during coke burning reduced the target products formation rate. A decline in olefin hydrocarbon production corresponded to decreased aromatic hydrocarbon formation.Raising oxygen concentration in the catalyst bed reduced coke deposition, enhancing hydrocarbon cleavage rates. The presence of paraffinic and olefinic hydrocarbons, CO₂, H₂, and oxygen in the reaction mixture did not inhibit the formation rates of olefinic hydrocarbons.The experiments revealed the reactions rate-limiting stage under the studied conditions. Tests varying catalyst grain diameters (1.5–3 mm) and mixture flow velocities (0.13–0.53 m/s) showed consistent results under identical conditions, confirming negligible influence of external and internal diffusion on the reaction rate.Based on the obtained kinetic data, a set of independent reaction pathways was identified for further optimization:
Номер журнала Вестник науки №3 (84) том 2
Ссылка для цитирования:
Babayev R.K., Tamili N.T. STUDY OF THE DEHYDROGENATION PROCESS OF HIGHER NORMAL PARAFFINIC HYDROCARBONS FOR COMPUTER MODELING // Вестник науки №3 (84) том 2. С. 430 - 436. 2025 г. ISSN 2712-8849 // Электронный ресурс: https://www.вестник-науки.рф/article/21807 (дата обращения: 16.12.2025 г.)
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