液相苯与稀乙烯变相催化分离生成乙苯的化学平衡、物料平衡和热量平衡计算

Calculation of Chemical, Material, and Heat Equilibrium for Ethylbenzene Synthesis through Alkylation of Dilute Ethylene with Liquid Benzene via Catalytic Phase Exchange Method

提出了液相苯和稀乙烯变相催化分离制乙苯的反应示意图,对该烷基化反应部分的化学平衡、物料平衡和热量平衡进行了计算.在温度185℃,压力2·0MPa,乙烯1mol/h,氮4mol/h,新鲜苯3mol/h的条件下,烷基化反应后的绝热温升为175·6℃.计算的温升、乙烯转化率和乙苯选择性结果与实验结果基本相符.从反应段上部补充的35℃的新鲜苯与反应段流出的202·6℃气体进行热交换后,体系温度达到185·9℃,稍高于反应温度(185℃).但从反应段下部进入的35℃的稀乙烯与反应段流出的202·6℃的液体混合进行热交换时,由于稀乙烯使液体产物汽化,导致体系温度大幅度降低,平衡时体系温度仅为153·5℃,远低于所要求的反应温度.计算结果表明,需给体系提供91·5kJ的热,或者将稀乙烯加热至523℃,混合后体系平衡温度才能达到185℃.

The chemical, material, and heat equilibrium of ethylbenzene.synthesis through alkylation of dilute ethylene with benzene via catalysis and a gas phase-liquid phase exchange method was analyzed and calculated. The isothermal temperature increase is 175.6 ℃ under the conditions of 1 mol/h ethylene, 4 mol/h N2, 3 mol/ h benzene, 185 ℃, and 2.0 MPa. The calculation values of temperature increase, ethylene conversion, and ethylbenzene selectivity are in agreement with the experimental results. In the upper section of the reactor, after the heat exchange of fresh benzene of 35 ℃ with the out gas mixture of 202.6 ℃ from the reaction section, the equilibrium temperature of the system is 185.9 ℃ , which is 0.9 ℃ higher than the reaction temperature. However, in the bottom section of the reactor, when dilute ethylene of 35 ℃ mixes with the liquid products of 202.6 ℃ , the equilibrium temperature is only 153.5 ℃. This is because dilute ethylene needs a lot of heat energy to make the products from the liquid phase to the gas phase. Only when the dilute ethylene temperature is increased to 523 ℃ or 91.5 kJ heat energy is added, the equilibrium temperature can reach 185 ℃.