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MATHEMATICAL MODEL OF THE EFFICIENCY OF THE CATALYST IN THE SYNTHESIS OF VINYL ACETATE
Firdavsiy Buronov
Senior teacher, Karshi engineering-economics institute, Uzbekistan, Karshi E-mail: _ [email protected]
Farhod Salohiddinov
Senior teacher, Karshi engineering-economics institute, Uzbekistan, Karshi E-mail: [email protected]
МАТЕМАТИЧЕСКАЯ МОДЕЛЬ ЭФФЕКТИВНОСТИ КАТАЛИЗАТОРА В СИНТЕЗЕ ВИНИЛАТЦЕТАТА
Буронов Фирдавсий Эшбуриевич
преподаватель,
Каршинского инженерно-экономического института, Республика Узбекистан, г. Карши
Салохиддинов Фарход Абдираззокович
ст. преподаватель, Каршинский инженерно-экономический институт, Республика Узбекистан, г. Карши
АННОТАЦИЯ
Изучены кинетические законы и кинетика и механизм реакции этилена в паровой фазе. Установлено, что общая скорость реакции пропорциональна размеру неинформированных и модифицированных активных центров палладия (а не кластеров). Доказано, что избыточное количество модификатора (как ацетат калия, так и мис) может снижать эффективность катализатора и блокировать активные центры.
ABSTRACT
The kinetic laws and kinetics and mechanism of the vapor phase reaction of ethylene have been studied differently. It was found that the total rate of the reaction was proportional to the amount of unmodified and modified active centers of palladium (not clusters). Excess amounts of the modifier (both potassium acetate and copper) have been shown to block active sites by reducing catalyst efficiency.
Ключевые слова: этилен, кислород, уксусная кислота, винилацетат, кинетическое уравнение, механизм.
Keywords: ethylene, oxygen, acetic acid, vinyl acetate, kinetic equation, mechanism
Production of vinyl acetate in heterogeneous catalysts began in Germany in the late 1930s, a method that has not lost its relevance today: the reaction is carried out in a catalytic system of zinc acetate in a temperature range of 160-240 ^ and a carrier Zn(OA)2 (activated carbon) at a pressure close to
atmospheric pressure, is carried out [1-2-3]. To reduce the yield of ethylidendiacetate, the reaction is carried out in excess acetylene (ratio of acetylene to acetic acid = 410: 1) and the process is carried out either in tubular reactors, or in fake dilute layer reactors of the catalyst.
The volumetric load is 100-500 h-1, the conversion of acetic acid is about 50%, the yield of vinyl acetate is 4080 kg/m3 per hour. Due to the accumulation of polymer and resin on the zinc acetate catalyst, it loses its activity over time, forcing the process temperature to gradually increase from 160-180 ^ to 220-240 ^ [4-5-6-7].
Mathematical model of catalyst efficiency.
In order to create a general mathematical model showing the dependence of the efficiency of the catalyst on its composition, we present the experimental dependencies in Table 1[8-9-10].
Bibliographic description: Buronov F., Salohiddinov F. Mathematical model of the efficiency of the catalyst in the synthesis of vinyl acetate // Universum: технические науки : электрон. научн. журн. 2021. 5(86). URL: https://7universum.com/ru/tech/archive/item/11845
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Table 1
Conditions for conducting a series of experiments and the mathematical models obtained in them
Test Series Number Number of components in catalyst (%) W (vinyl acetate), mol/hr W (CO2), mol/hr
Pd CH3COOK Cu
I 0,3-3,0 0 0 (0,35-[Pd])/(1+0,05[Pd]4) (0,08-[Pd])/(1+0,065[Pd]3)
II 0,2 2,0-20,0 0 (0,1-(1+ [CH3COOK]))/( 1,0+0,013 *[CH3COOK]2) 0,04+0,0043-[CH3COOK]
III 0,15 5 0,053,0 0,24+047 [au] 1+1,75 [au] 0,075+0,018-[ Au]
The total rate of reaction is proportional to the amount of unmodified and modified active centers of palladium (not clusters). Excess amounts of the modifier (both potassium acetate and copper) block the active sites, reducing the efficiency of the catalyst. The physical meaning of the partial mathematical models obtained here consists of fractional-linear functions. The difference in the equations of the rates of formation of vinyl acetate and CO2 indicates that these reactions occur at different active sites of the catalyst.
Taking into account the above considerations, we have the following functional dependencies:
Wea=[Pd] • (C1+C2 [CH3COOK]+C3 [Cu] )/( I+C4 [Pd] 4+C 5[CH3COOK]2+C6[Cu])
WCO2 = [Pd]-(Ci +C2 [CH3COOK]+C3'[Cu])/(1+C4 [Pd]4)
The numerical values of the coefficients C1-C6 and CT-C4' were obtained by comparing the data of the equations with the partial model of the reaction rates obtained earlier and using a number of regression methods. Thus, the generalized mathematical models of catalyst activity, which are defined as the rates of reactions for the formation of vinyl acetate and CO2, are as follows:
Wba = ([Pd]-(0,35 + 0,38[CH3COOK] + 4,2[Cu]))/((1 + 0,05(1 + 80[Pd]4 + 0,01[CH3COOK]2 + 1,1[Cu])))
Wco2 = ([Pd]-(0,09 + 0,0244[CH3COOK] + 0,1[Cu]))/((1 + 0,07(1 + 20[Pd]4)))
Among all the experiments, the rates of the formation of vinyl acetate and the values calculated by mathematical models are well matched.
The correlation between the experimental and calculated values for the rates of carbon dioxide formation is two parallel straight lines - for a series of experiments on the effect of [Cu] (curve 1 to the right of Fig. 1). and [Pd] for a series of experiments on the effect of quantity (curve 2 to the right of Fig. 1). The significant increase in the experimental values of the Wco2 velocities for a series of reactions to study the effects of copper is explained by the use of the above-mentioned reason - the use of catalyst samples prepared in violation of the technology. Thus, the velocities of Wco2 differ from those calculated from the experimental values by a constant magnitude, indicating that additional reactions of eth-ylene combustion occur in the holder rather than in the active palladium centers. The latter value used mathematical models to optimize the catalyst composition in order to find the most efficient samples.[11-12-13]
Figure 1. Correlation between experimental and calculated values of reaction rates
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Using mathematical models of the dependence of catalyst activity on the components stored in it (Pd, CH3COOK and Cu), we determined their optimal composition to achieve both high rates and selectivity of vinylacetate formation: 0.4% Rd + 4% Cu + 7% CH3COOK / VKTs. [3-4-5-7]
Effect of steam-gas mixture volume rate on vinyl acetate yield. BGA volumetric velocity range: 2000 to 10000 h-1 in the middle zone of the reactor at a temperature of 165°C, a pressure of 4 atm, a ratio of
ethylene to acetic acid 4: 1 and an oxygen content of 7%. The results of the experiments are presented in Table 2.
The dependence of the reagent conversion on the time the reaction mass remains in the reactor is linear, indicating that the reaction rate is constant during this time due to the insignificant value of the reagent conversion. This is confirmed by maintaining the linearity of the time dependence of vinyl acetate output and CO2 formation. [11-12]
Table 2.
The effect of the volumetric velocity of a vapor-gas mixture on the yield of vinyl acetate
Reaction time, Eat vinyl acetate, Education CO2 Selectivity and conversion
hour gr mol gr mol (CH3COOH) (C2H4)
Volumetric speed nrC=2000 hour-1
8 280 3,26 31,17 0,708 0,902 (26,5) (7,36)
16 568 6,61 63,19 1,436
24 872 10,14 96,95 2,203
32 1152 13,39 128,02 2,909
40 1416 16,46 157,37 3,576
48 1672 19,44 185,86 4,224
Volumetric speed nrC=4000 hour -1
8 299,2 3,48 32,52 0,739 0,904(12,04) (3,33)
16 619,2 7,20 67,28 1,529
24 923,2 10,73 100,27 2,279
32 1211,2 14,08 131,58 2,991
40 1504,2 17,53 163,82 3,723
48 1795,2 20,87 195,03 4,433
Volumetric speed nrC=6000 hour -1
8 304 3,53 22,66 0,515 0,932(8,76) (2,35)
16 624 7,20 46,23 1,051
24 936 10,88 69,86 1,588
32 1232 14,33 92,007 2,091
40 1520 17,67 113,45 2,578
48 1816 21,12 135,61 3,082
Volumetric speed nrC=7500 hour -1
8 328 3,81 21,41 0,486 0,94 (7,07) (1,88)
16 672 7,81 43,87 0,997
24 1000 11,63 65,33 1,485
32 1312 15,26 85,72 1,980
40 1632 18,98 106,62 2,423
48 1960 22,79 128,01 2,909
Conclusion
The process of obtaining ethylene by catalytic oxidation in the vapor phase to obtain vinyl acetate was studied in detail in a catalyst of the order 0.4% Rd + 4% Cu + 7% CH3COOK / VKTs. The overall rate of the reaction was found to be proportional to the amount of unmodified and modified active centers of palladium (not clusters). Excessive amounts of the modifier (both
potassium acetate and copper) have been shown to reduce the efficiency of the catalyst and block the active sites. The study selected the following optimal conditions for the reaction: in the middle zone of the reactor at a temperature of 165° volumetric speed -2000 h - 1, 4 atm, the ratio of ethylene to acetic acid is 4: 1 and the oxygen content is 7%. A mechanism for the formation of vinyl acetate from ethylene and acetic acid in the presence of a palladium catalyst has been proposed.
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