(Comprehensive Problem on multiple reactions with heat effects) Styrene can be produced fr...

(Comprehensive Problem on multiple reactions with heat effects) Styrene can be produced from ethylbenzene by the following reaction:

ethylbenzene ↔ styrene + H2 (1)

However, several irreversible side reactions also occur:

ethylbenzene → benzene + ethylene (2)

ethylbenzene + H2 → toluene 4- methane (3)

[J. Snyder and B. Subramaniam, Chem. Eng. Sci., 49, 5585 (1994)]. Ethylbenzene is fed at a rate of 0.00344 kmol/s to a 10.0-m3 PFR (PBR) along with inert steam at a total pressure of 2.4 atm. The steam/ethylbenzene molar ratio is initially [i.e., parts (a) to (c)] 14.5:1 but can be varied. Given the following data, find the exiting molar flow rates of styrene, benzene, and toluene along with 5’si/bt for the following inlet temperatures when the reactor is operated adiabatically.

(a) T0 = 800 K

(b) T0 = 930 K

(c) T0 = 1100 K

(d) Find the ideal inlet temperature for the production of styrene for a steam/ethylbenzene ratio of 58:1. (Hint: Plot the molar flow rate of styrene versus T0. Explain why your curve looks the way it does.)

(e) Find the ideal steam/ethylbenzene ratio for the production of styrene at 900 K. [Hint: See part (d).J

(f) It is proposed to add a counter current heat exchanger with Ua = 100 kJ/m3/min/K where Ta is virtually constant at 1000 K. For an entering steam to ethylbenzene ratio of 20, what would you suggest as an entering temperature? Plot the molar flow rates and .S’sv/bt .

(g) What do you believe to be the points of this problem?

(h) Ask another question or suggest another calculation that can be made for this problem.

Additional information:

The kinetic rate laws for the formation of styrene (St), benzene (B), and toluene (T), respectively, are as follows. (EB = ethylbenzene)

The temperature T is in Kelvin and P¡ is in atm.