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1-5 In a plant with an annual production capacity of 1500 t of styrene via the dehydrogenation of ethylbenzene, the amount of steam added is 2.6 kg of steam per kg of styrene, and the conversion rate of ethylbenzene at an inlet temperature of 650°C is 44.4%. The styrene yield was 40%, with the remaining by-products being benzene at 3%, toluene at 5%, and coke at 2%. The device operates 300 days per year. The purity of the raw material ethylbenzene is 98% (by mass), with the remainder being toluene. Then the total amount of gas produced after the reaction is ( ). A. 8.62 kg B. 8.35 kg C. 8.53 kg D. 7.676 kg. How to solve this problem? The question mentions that the remaining by-products are 3% benzene, 5% toluene, and 2% coke – what is used as the basis for these percentages?
Chemical reaction equations: C6H5C2H5→C6H5CH＝CH2+H2 106 104 2; C6H5C2H5+H2→C6H5CH3+CH4 106 2 92 16; C6H5C2H5→C6H6+C2H4 106 78 28; C6H5C2H5→7C+3H2+CH4 106 7×12 3×2 16
C. The answer is correct. Chemical reaction equations:
C6H5C2H5 → C6H5CH=CH2 + H2 106 104 2
C6H5C2H5 + H2 → C6H5CH3 + CH4 106 2 92 16
C6H5C2H5 → C6H6 + C2H4 106 78 28
C6H5C2H5 → 7C + 3H2 + CH4 106 7×12 3×2 16
(1) The production rate of styrene per hour is… The amount of ethylbenzene required per hour is: The amount of ethylbenzene that is converted per hour is 530×0.444 = 235.32 kg/h = 2.22 kmol/h. The amount of unreacted ethylbenzene is 530 – 235.3 = 294.7 kg/h. The amount of steam required per hour is 530×2.6 = 1378 kg. The amount of industrial raw material, ethylbenzene, required per hour is… The amount of toluene required per hour is 10.8 kg.
(2) Quantities of various components in the products:
Styrene: 208.3 kg
Toluene:
Benzene: 2.22×0.03×78 = 5.23 kg
Coke: 2.22×0.02×7×12 = 3.72 kg
Ethylbenzene: 294.7 kg
Ethylene (gas): 2.22×0.03×28 = 1.86 kg
Methane (gas): (2.22×0.05 + 2.22×0.02)×16 = 2.49 kg
Hydrogen (gas): (2 + 2.22×0.02×3 – 2.22×0.02)×2 = 4.177 kg
The total amount of gas is 1.86 + 2.49 + 4.177 = 8.53 kg.
A. The answer is incorrect. B. The answer is incorrect. C. The answer is incorrect. All 3 answers result from incomplete calculation during the computation process; not all of the generated gas was taken into account. A. One option is missing: hydrogen reacts with ethylbenzene to produce toluene and methane; therefore, the answer is 8.62 kg. B. The answer is obtained by calculating, in the reaction where ethylbenzene breaks down into carbon, hydrogen, and methane, as 2.22×0.02. The total amount of hydrogen is (2 + 2.22×0.02 – 2.22×0.02)×2 = 4.0 kg, and the total mass of gases is 8.35 kg. D. The calculation for the amount of methane gas is incorrect.
C6H5C2H5 → C6H5CH=CH2 + H2 106 104 2
C6H5C2H5 + H2 → C6H5CH3 + CH4 106 2 92 16
C6H5C2H5 → C6H6 + C2H4 106 78 28
C6H5C2H5 → 7C + 3H2 + CH4 106 7×12 3×2 16
(1) The production rate of styrene per hour is… The amount of ethylbenzene required per hour is: The amount of ethylbenzene that is converted per hour is 530×0.444 = 235.32 kg/h = 2.22 kmol/h. The amount of unreacted ethylbenzene is 530 – 235.3 = 294.7 kg/h. The amount of steam required per hour is 530×2.6 = 1378 kg. The amount of industrial raw material, ethylbenzene, required per hour is… The amount of toluene required per hour is 10.8 kg.
(2) Quantities of various components in the products:
Styrene: 208.3 kg
Toluene:
Benzene: 2.22×0.03×78 = 5.23 kg
Coke: 2.22×0.02×7×12 = 3.72 kg
Ethylbenzene: 294.7 kg
Ethylene (gas): 2.22×0.03×28 = 1.86 kg
Methane (gas): (2.22×0.05 + 2.22×0.02)×16 = 2.49 kg
Hydrogen (gas): (2 + 2.22×0.02×3 – 2.22×0.02)×2 = 4.177 kg
The total amount of gas is 1.86 + 2.49 + 4.177 = 8.53 kg.
A. The answer is incorrect. B. The answer is incorrect. C. The answer is incorrect. All 3 answers result from incomplete calculation during the computation process; not all of the generated gas was taken into account. A. One option is missing: hydrogen reacts with ethylbenzene to produce toluene and methane; therefore, the answer is 8.62 kg. B. The answer is obtained by calculating, in the reaction where ethylbenzene breaks down into carbon, hydrogen, and methane, as 2.22×0.02. The total amount of hydrogen is (2 + 2.22×0.02 – 2.22×0.02)×2 = 4.0 kg, and the total mass of gases is 8.35 kg. D. The calculation for the amount of methane gas is incorrect.
The answers to some questions are incorrect; when calculating the weight of hydrogen, 2.22*0.05 should be subtracted, as the yield of toluene in the second reaction is 5%. Calculated in this way, there is no correct answer; please have those with similar expertise verify it.
How was 530 calculated? Solve.
I think the yields should be 3% for benzene, 5% for toluene, and 2% for coke, because the first part mentions that the yield of styrene is 40%, while the answer given in Tiantai University’s exercise set is calculated based on selectivity; I believe that answer is incorrect.
I think the same way; after looking at the solution process, it seems that 3%, 5%, and 2% are based on the amount of ethylbenzene that participates in the reaction
I think the same way; after looking at the solution process, it seems that 3%, 5%, and 2% are based on the amount of ethylbenzene that participates in the reaction
Following the solution approach for Tian Da*’s problem, the mass at the inlet and outlet is not conserved; proceed with the calculation