Lecture 10 Chemical Reaction Engineering CRE is the

Lecture 10 Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place.

Today’s lecture �Definition of Selectivety �Instantaneous SD/U = r. D/r. U �Overall = FD/FU �Semibatch Reactors 2

Selectivity in Multiple Reactions Selectivity Instantane SD/U = r. D/r. U ous Overall ŜD/U = FD/FU 3 Keep CA high and CB low. Yield

Semibatch reactors �Semi Batch reactors can be very effective in maximizing selectivity in liquid phase reactions. �The reactant that starts in the reactor is always the limiting reactant. 4

Semibatch reactors A+B→C+D B, v 0 A Initial V Liquid level and volume increase 5

Semibatch reactors Mass Balance: 6

Semibatch 1) Mole balances: Species A: in – out + gen = acc 7

Semibatch 1) Mole balances: Species B: 8

Semibatch 9

Semibatch 2) Rate Law: 3) Stoichiometry: 10 4) Parameters:

Semibatch Example B, v 0 CO 2 example: A + B → C + D + CO 2 1 a) Mole balances: 11 A

Semibatch Example 1 b) Mass balances: 2) Rate Law: 12

Semibatch Example 3) Stoich: 4) Parameters: 13

Polymath Screenshots: 14

Semi Batch Reactors Three Forms of the Mole Balance applied to Semi Batch Reactors: 1. Molar Basis 2. Concentrati on Basis 3. Conversion 15

Consider the following elementary reaction: A+B C+D -r. A=k. CACB The combined Mole Balance, Rate Law, and Stoichiometry may be written in terms of number of moles, conversion, and/or concentration: Conversion 16 Concentration No. of Moles

Polymath Equations: 17

Equilibrium Conversion in Semibatch Reactors with Reversible Reactions Consider the following reaction: A+B C+D Everything is the same as for the irreversible case, except for the rate law: 18

Equilibrium Conversion in Semibatch Reactors with Reversible Reactions Where: At equilibrium, 19 Xe changes with time. then

End of Lecture 10 20