ChemMechanismsLect4ME525SP2011

ChemMechanismsLect4ME525SP2011 - ME 525: Combustion Lecture...

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ME 525: Combustion Lecture 4: Elementary Reactions and hemical Mechanisms Chemical Mechanisms Prof. Robert P. Lucht Room 87, Mechanical Engineering Building School of Mechanical Engineering Purdue University West Lafayette, Indiana ucht@purdue edu Lucht@purdue.edu 765-494-5623 (Phone) anuary 0 2011 School of Mechanical Engineering, Purdue University January 20, 2011
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Lecture Topics The hydrogen/bromine reaction mechanism. The Zeldovich mechanism. Unimolecular reactions. School of Mechanical Engineering, Purdue University
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H 2 -Br 2 Reaction Mechanism The global reaction is given by 22 2 H Br HBr overall reaction  Bodenstein and Lind found that the rate of this reaction was given by 1/2 H B r H B         exp 2 2 exp 2 1/ kH dH r dt B r B r  School of Mechanical Engineering, Purdue University
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H 2 -Br 2 Reaction Mechanism his result can be explained by the following mechanism: This result can be explained by the following mechanism: 2 1 2 chain -initiating step k MB r B r M   2 2 2 3 chain -propagating step chain -propagating step k B rH H B r H k H Br HBr Br  2 4 chain -propagating step hain termination step k HH B r H B r k r Br M Br M 2 5 chain - termination step Br   School of Mechanical Engineering, Purdue University
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Chain initiation step: Why is the first reaction the chain- H 2 -Br 2 Reaction Mechanism initiation reaction rather than H 2 dissociation? Br 2 bond energy is 46 kcal/gmol (193 kJ/gmol) and H 2 bond energy is 04 kcal/gmol (435 kJ/gmol) 104 kcal/gmol (435 kJ/gmol). 2 1 2 chain -initiating step k MB r B r M   Chain propagating steps : very fast, low activation energy reactions (0-40 kJ/gmol). One radical consumed, one radical roduced branching ratio of one produced, branching ratio of one.
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This note was uploaded on 12/27/2011 for the course ME 525 taught by Professor Lucth during the Fall '11 term at Purdue University-West Lafayette.

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ChemMechanismsLect4ME525SP2011 - ME 525: Combustion Lecture...

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