1 Lecture 12 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.

2 Today’s lecture Multiple Reactions Selectivety and YieldSeries Reactions Complex Reactions

3 4 Types of Multiple ReactionsSeries: A → B → C Parallel: A → D, A → U Independent: A → B, C → D Complex: A + B →C + D, A + C → E With multiple reactors, either molar flow or number of moles must be used (no conversion!)

4 Selectivity and Yield There are two types of selectivity and yield: Instantaneous and Overall. Instantaneous Overall Selectivity Yield

5 Selectivity and Yield Example: Desired Product: Undesired Product:To maximize the selectivity of D with respect to U run at high concentration of A and use PFR.

6 Gas Phase Multiple Reactions

7 Multiple Reactions Chapter 8A) Mole Balance of Each Species Flow Batch

8 Multiple Reactions Chapter 8A) Rates: a) Rate law for each reaction b) Net Rates c) Relative Rates

9 Multiple Reactions Chapter 8Stoichiometry: Example: A → B → C (1) A → B k1 (2) B → C k2

10 Multiple Reactions Chapter 81) Mole Balance: V=V0 (constant batch)

11 Multiple Reactions Chapter 8Laws Net rates 2) Rates: Relative rates

12 Batch Series Reactionsexample: A → B → C (1) A → B (2) B → C t topt Ci A B C 1) Mole balances:

13 Batch Series Reactions2) Rates: Laws: Relative:

14 Batch Series Reactions3) Combine: Species A: Species B:

15 Batch Series ReactionsUsing the integrating factor, at t = 0, CB=0

16 Batch Series ReactionsWhen should you stop the batch series reaction to obtain the maximum amount of B? Let’s see. t topt Ci A B C

17 Example: CSTR Series Reactions ABCwhat is the optimal ? 1) Mole Balance:

18 Example: CSTR Series Reactions ABC2) Rates: Laws: Net: Relative:

19 Example: CSTR Series Reactions ABC3) Combine:

20 Example: CSTR Series Reactions ABCFind maximum concentration of B

21

22 Net Rate of Reaction for species AFor N reactions, the net rate of formation of species A is: For a given reaction i: (i) aiA+biB ciC+diD:

23 Example A: Liquid Phase PFRComplex Reactions Example A: Liquid Phase PFR NOTE: The specific reaction rate k1A is defined with respect to species A. The complex liquid phase reactions follow elementary rate laws NOTE: The specific reaction rate k2C is defined with respect to species C.

24 Example A: Liquid Phase PFRThe reaction takes place in a PFR. The feed is equal molar in A and B and FA0=200 mol/min and the volumetric flow rate is 100 dm3/min. The reaction volume is 50 dm3 and the rate constants are: Plot FA, FB, FC, FD and SC/D as a function of V.

25 Example A: Liquid Phase PFRMole Balances:

26 Example A: Liquid Phase PFRNet Rates: (5) (6) (7) (8) Rate Laws: (9) (10)

27 Example A: Liquid Phase PFRRelative Rates: Reaction 1 (11) (12) Reaction 2 (13) (14)

28 Example A: Liquid Phase PFRSelectivity If one were to write SC/D=FC/FD in the Polymath program, Polymath would not execute because at V=0, FC=0 resulting in an undefined volume (infinity) at V=0. To get around this problem we start the calculation 10-4 dm3 from the reactor entrance where FD will not be zero and use the following IF statement. (15)

29 Example A: Liquid Phase PFRStoichiometry: (16) (17) (18) (19) Parameters: (20) (21) (22)

30 End of Lecture 12

31 Supplementary Material - Blood Coagulation

32

33 Notations

34 Notations

35 Mole Balance

36 Mole Balance

37 Mole Balance

38 Result

39 Blood Coagulation Many metabolic reactions involve a large number of sequential reactions, such as those that occur in the coagulation of blood. Cut → Blood → Clotting Figure A. Normal Clot Coagulation of blood (picture courtesy of: Mebs, Venomous and Poisonous Animals, Medpharm, Stugart 2002, Page 305)

40 Schematic of Blood Coagulation

41 Cut A + B C D E F Clot