1. Fig. 2 Conversion Equations.
Design of Ethylbenzene Production in a Packed Bed Reactor Jaycelyn Jefferson, Ajibola Olojo, Justin Schuetzeberg   Prairie View A&M University 100 University Dr, Prairie View, Texas 77446, United States
Abstract
The objective of this project was to design a reactor that would produce one-fifth of the total United States ethylbenzene production using a vapor phase reaction. Ethylbenzene, a highly flammable organic compound, is one of the most produced compounds in industry. The colorless liquid is mostly used in the petrochemical industry as an intermediate in the production of styrene. The gas phase ethylation of benzene was used to produce the required 6.3 billion kg ethylbenzene/year. The reactor design achieved the highest selectivity of the complex reaction mechanism. Zeolite catalysts were used because the catalysts were more efficient than other alternatives, less harmful to the environment, and more economically feasible. Design constraints included operating conditions of temperatures between 440°C to 450°C and pressures ranging from 1400kPa to 1800kPa.
A 330 cubic-meter packed bed reactor was used for production. Simulations of the reactor operation were conducted using ASPEN Plus software. The successful completion of the project proved the mass production of ethylbenzene is possible when the proper safety measures are taken, the reaction mechanism is feasible, and the proper reactor is used.
Introduction
Formation of the desired product ethylbenzene occurs by alkylation of a benzene ring. Benzene will react with ethylene in the presence of a solid ZSM-5 catalyst in the vapor phase. This is achieved using a packed bed reactor with initial conditions set to a pressure, and temperature of 1800kPa and K respectively. The reaction forming the desired product is part of a complex system of reactions. Two side reactions occur concurrently with the desired reaction, producing diethylbenzene, and three ethylbenzene.
The three reactions that combine to comprise the overall reaction mechanism consist of six molecules. ET, BZ, EB, DEB, TEB. They stand for ethylene, benzene, ethylbenzene, m-diethylbenzene, and 1,3,5-triethylbenzene respectively. To form the desired product as mentioned, ET+BZEB, two undesired reactions occur. The first produces the undesired m-diethylbenzene, ET+EBDEB, and the second forms the undesirable three 1,3,5-triethylbenzene, ET+DEBTEB.
2. Discussion
Polymath was utilized to find reactor volume based on the mole balances, and rates of reactions. Using an initial feed of kmol ethylene/hr, 2000 kmol benzene/hr, and 1000 kmol ethylbenzene/hr, it is recommended that a reactor of volume 330 m3 be used to carry out the reaction to completion.
Aspen was used to simulate the large scale production of ethylbenzene with an initial feed of kmol ethylene/hr, 2000 kmol benzene/hr, and 1000kmol ethylbenzene/hr inside of a 330 cubic meter packed bed reactor. The peng-robinson equation of state package was selected as our basis of calculation. At a design temperature and pressure of K and 1800kPa, the two side reactions do not occur. The selectivity of ethylbenzene is equal to kmol/hr which equates to kg ethylbenzne/yr. This means that 1 reactor will be sufficient for producing 1/5 of the kg ethylbenzene produced in the USA every year. According to Aspen, 14% of the ethylene feed is converted to ethylbenzene and 70% of the limiting reactant, benzene, is converted into ethylbenzene.
3. Conclusion
In conclusion, the gas phase alkylation of benzene, coupled with the necessary parameters, led to the desired amount of ethylbenzene. The highest selectivity is 1 because the side reactions never actually occur, according to Aspen. The yield is YEB = ( k1ETCETCBZ)/( - k1ETCETCBZ). A packed bed reactor was used because it operates well with the vapor phase. It also has a high conversion per unit mass and a low operating cost. The volume of the reactor is 330 cubic meters. The use of Zeolite catalysts proved to be beneficial, not only because they are less harmful to the environment, but also because they are economically viable and efficient. The optimum conversion is 70% of benzene.  The mass production of ethylbenzene is possible when the proper safety measures are taken, the reaction mechanism is feasible, and the proper reactor is used.
Fig. 2 Conversion Equations.
Fig. 1 PBR in ASPEN
Fig. 3 Stream summaries
Proceedings of the 2018 ASEE Gulf-Southwest Section Annual Conference The University of Texas at Austin
April 4-6, 2018