Slides kinetics

8/13/2019 Slides kinetics

1/14

Introductionbrief history

Early work of L F Wihelmy1850 on sucrose inversion

F W Ostwaldthirty years later next major move

A G Harcourt and W.Essen invoked procedures similar

to those used today (1834-1919)

Order of reactions

Treated first order and second order reactions

Macroscopic and microscopic kinetics studied

Systems in thermal equilibrium, Boltzman distribution


2/14

A BRIEF HISTORY OF CHEMICAL KINETICS

(AND OF CRE)

(Ref.: "The World of Physical Chemistry," by K. J. Laidler, Oxford

Univ. Press, 1993)1850: Wilhelmy (Germany) studied the rate of inversion of sucrose(hydrolysis into D-(+)-glucose and D-(-)-fructose in the presence of an

acid) and found it to be proportional to the concentrations of both thesugar and the acid.1864: Guldberg and Waage (Norway) formulated their "law of massaction," according to which the reaction "forces" are proportional to the

product of the concentrations of the reactants:K=[R]r[S]s/([A]a[B]b)where a, b, r and s are the stoichiometric coefficients in the chemicalequation A+B=R+S. So the rate of the forward reaction is proportional to[A]a[B]band that of the reverse reaction is proportional to {R]r[S]s.


3/14

History of Kinetics1865: Harcourt and Esson (UK) analyzed the reactions between H2O2and HIand between KMnO4and (COOH)2. They wrote the corresponding differential

equations, integrated them and determined the concentration vs. timerelationships. They also proposed an equation for the temperaturedependence of the reaction rate, k = A TC.1884: van't Hoff (The Netherlands) published his "Studies of ChemicalDynamics" (tudes de dynamique chimique), in which he generalized and

further developed the work of Wilhelmy, Harcourt and Esson. In particular, heintroduced the differential method of analysis. He also analyzed thetemperature dependence of the equilibrium constant (now called the "van'tHoff equation") and of forward and reverse reaction rates.1887: Ostwald (Germany; Latvia) introduces the terms "reaction order" and"half-life" in his "Lehrbuch der allgemeinen Chemie."1889: Arrhenius (Sweden) further analyzed the temperature dependence ofreaction rate, k = A exp(-B/T), and gave it an "energy barrier" interpretation;this is now called the "Arrhenius equation.

http://www.ems.psu.edu/~radovic/KineticsHistory.html


4/14

Scope of Chemical kineticsField Description

Biology Physiological processes

Chemical Engineering Reactor Design

Electrochemistry Electrode processes

Geology Flow processes

Inorganic Chemistry Reaction mechanismsMechanical Engineering Physical metallurgy, dislocation mobility

Metallurgical Eng. & Materials Science Kinetics in solids-diffusion, nucleationgrowth, migration, growth of phases, PVD,CVD

Organic Chemistry Reaction mechanismPhysics Viscosity, diffusion, nuclear processes

Pharmacology Drug action


5/14

Chemical kinetics- What is involved?

Study of rate and mechanisms by which onespecies is converted into another

Rates considered on specific basis per unit

volume of reaction mixture for a homogenousreaction or per unit mass of catalyst for aheterogeneous reaction

Mechanism is the sequence of individualevents whose overall result produce theobserved reaction


6/14

Kinetics of Processes- why do this course?

Enable design of equipment used for carrying out

processes for materials synthesis/transformations

What type and size of equipment is essential to

accomplish a desired extent of a materials process? Operating conditions, provisions for exchange of energy

constitute the process design

Cost analysis, choice of construction materials,

instrumentation and control define the process


7/14

Chemical synthesis in microreactors has the greatest impact for

processes requiring precisely-controlled or challenging operatingconditions (difficult compounds, energetic intermediates, or high

pressures and temperatures) and for on-demand, on-site production.

(Jensen Group)

From a simple reaction between molecules to the economical design of a chemicalreactor, kinetics and catalysts are the key.


8/14

Few steel blast furnaces and steel mills


9/14

Kinetics of Processes - How do we do this?

Combine chemical rates with physical processesby writing conservation equations

Express physical processes i.e rates of energytransfer and of mass transfer from one chemical

species to another Terms for converting one chemical species

through intrinsic rate for that conversion step

Body of knowledge about variables that affectthis intrinsic rate and equations which correlatesuch data is the kinetics of process


10/14


11/14

Kinetics of Processes - How do we do this?

Conservation equations depend on the type ofreactor and not the reactions

Terms of mass and energy transfer are the samefor a reactor

Ideal reactors are CSTR, plug flow, packed bed

Correlations obviate the need for experiments

Intrinsic rates must be obtained from expriments

From a beaker to a plantscaling up


12/14

MM 305: Kinetics of Processes-AdminCredit structure L T P C 2 1 0 6

Class tests 1+1 (before and after midsem) 20Dates- Thu. 30 Jan and 20 Mar. (tentative)Submissions at the end of every tutorial class 10Mid sem Feb. 17-22 - 20End sem Apr. 18-1 May- 50

Total Marks : (10+5+20+5+10+50) 100(No re-exam requests will be entertained)

Total contact hours : 41 (from the calendar)Tutorials: 11 (generally scheduled on Thursdays)

Problem solving is important: ideally two students to a group. To berandomised.

TAs: Aditya Kulkarni, 09d11012:Yash Sheth, 09d11024:Sheshank Kumar, 09d11028:Vaibhav Jain, 09d11031:Ranjeet Singh Banthiya, 09d11025


13/14

1. Thermodynamics vs kinetics; Homogeneous vs heterogeneous reactions.

Chemical reaction kinetics: order of reactions, Arrhenius equation. Ratetheories.2. Homogenous reactions. Ideal batch reactors, continuous stirred tank

reactors, plug flow reactors. Residence time & RTD. Mixing. Design ofreactors for homogenous Reactions.

3. Heterogeneous Reactions - Elements of mass transfer, diffusion in fluids,mass transport equation, mass transfer coeff. Mass transfer in porousmaterials, ordinary & Knudsen diffusion, pore size distribution. Adsorption :Physical vs Chemical, Adsorption isotherms, BET method. Surface reactions& their Kinetics.

4. Fluid-fluid reactors with homogeneous& heterogeneous reactions. Fluid-

solid contactors / reactors: packed bed, fluidized bed. Heat transfercontrolled reactions.

5. Examples from materials processing: CVD/PVD reactors, thin film deposition,.Combustion, oxidation/reduction, drying, calcinations, precipitation etc.

Course content


14/14

Texts/References1. K.J. Laidler, Chemical Kinetics, 3rdEd., Harper and Row, New

York, 1987.2. O. Levenspiel, Chemical Reaction Engineering, 3rdEd., John

Wiley, New York, 1999.3. H.S. Fogler, Elements of Chemical Reaction Engineering,

3rdEd., Prentice Hall of India, New Delhi, 1999.4. A.W. Adamson and A.P. Gast, Physical Chemistry of Surfaces,6thEd., Wiley-Interscience, 1997.

5. George Roberts, Chemical reactions and chemical reactors,John Wiley & Sons, 2009.

6. Lanny D. Schmidt, The engineering of chemical reactions,Oxford, 2005

7. Stoichiometry and thermodynamics of metallurgicalprocesses, Y.K.Rao 1985

Slides kinetics

Documents

Transcript of Slides kinetics