Thermodynamics and Rate Processes. D.Kunzru Dept. of Chemical Engineering I.I.T.Kanpur

Transcription

1 Thermodynamics and Rate Processes D.Kunzru Dept. of Chemical Engineering I.I.T.Kanpur

2 Importance of Chemical Reaction Engineering chemical reactor is usually the heart of any process traditional applications: petroleum refining, petrochemicals, pharmaceuticals, environmental pollution. emerging areas : microelectronics, advanced materials, biotechnology, energy from renewable resources, sustainable development, catalytic distillation. thorough understanding of the multiscale phenomena involved is required to design any reactor.

3 Objectives of a Comprehensive Course(s) on CRE After taking these courses a student should be able to : analyze and model an operating reactor design a new reactor troubleshoot develop the reaction kinetics for a new reaction ( most industrial processes involve heterogeneous reactions and proper understanding of kinetics, heat transfer, mass transfer and hydrodynamics is essential)

4 Suggested Topics Homogeneous Reactors Introduction: definition of rate of reaction; types of reactors; industrial reactions and reactors. Basic concepts in chemical kinetics: reaction rate constant; reaction order; elementary and nonelementary reactions. Determination of reaction kinetics from a mechanism: pseudosteady state hypothesis ;rate-controlling step; chain reactions; enzyme reactions. Experimental determination of reaction kinetics: different types of laboratory reactors; collection and analysis of rate data; differential and integral method of analysis.

5 Homogeneous Reactors (contd.) Isothermal reactor design for single reactions :batch reactor; semi-batch reactor; CSTR; plug flow reactor; multiple reactor systems. Design for multiple reactions in isothermal reactors: mass balances; selectivity and yield; parallel,series and complex reactions; best operating conditions for multiple reactions. Nonisothermal reactors: energy balances for batch, CSTR and plug flow reactors; adiabatic and nonadiabatic reactors; multiple reactors with interstage cooling; multiple steady states in a CSTR. Analysis of non-ideal reactors :RTD; zero-parameter models ( segregated flow and maximum mixedness models) one-parameter models(tank-in-series model and dispersion model);applications to scaleup and troubleshooting.

6 Heterogeneous Reactors Introduction: importance of solid catalysts ; physical adsorption, chemisorption. Rate equations for solid catalyzed reactions: LH models; redox kinetics; Eley Rideal model; quantitative interpretation of rate data. External mass and heat transfer effects: fundamentals; effect on observed rates; mass transfer-limited reactions in packed beds and on metallic surfaces.

7 Heterogeneous Reactors (contd.) Reaction and diffusion in porous catalysts: effective diffusivity; internal effectiveness factors ;Weisz criteria;falsified kinetics; experimental determination of effectiveness factors. Nonisothermal effectiveness factors: role of heat transfer Global rate of reaction Design of fixed bed reactors: simultaneous solution of mass, energy and momentum balance equations.

8 Heterogeneous Reactors (contd.) Catalyst deactivation: types of deactivation; determination of deactivation kinetics; operating policies for deactivating catalysts. Gas-liquid noncatalytic reactions: introduction; review of physical mass transfer; different regimes of mass transfer with chemical reaction; global rates of reaction for different regimes ; design of different types of gas-liquid reactors. Multiphase reactors: Types of multiphase reactors and their applications; determination of global rates for multiphase reactions; experimental methods for evaluation of parameters; design of mechanically-agitated slurry reactors, bubble column reactors and trickle bed reactors.

9 Some Suggested Experiments Determination of homogeneous kinetics in a batch reactor Determination of homogeneous kinetics in a CSTR Determination of homogeneous kinetics in a PFR Determination of heterogeneous kinetics in a packed bed ( ion exchange resin catalyst) RTD of a continuous stirred reactor RTD of a packed bed reactor

10 Suggested Books Fogler, H.S., Elements of Chemical Reaction Engineering, Prentice-Hall, 4 th edition. Smith, J.M., Chemical Engineering Kinetics, McGraw-Hill, International Student Edition (3 rd edition). Levenspiel,O., Chemical Reaction Engineering, 3 rd edition, Wiley-Eastern Ltd.

11 Objectives of a Course on Thermodynamics central to the practice of any branch of engineering. applications in work, energy and equilibrium problems: energy balances needed in many areas ; phase equilibria is the basis for most separation and purification processes after such a course, the students should understand phase diagram of pure and multicomponent systems, the condition of equilibrium, equation of state and importance of thermodynamic variables and their applications.

12 Suggested Topics Laws of Thermodynamics: introduction; work; heat; energy ; review of First Law for closed and open systems; properties of ideal gas and real fluids. Reversibility and Entropy: reversibility; the second law of thermodynamics;carnot engine; entropy change for closed and open systems. Application of Thermodynamics to Flow Processes: turbines; compressors; flow of compressible fluids.

13 Suggested Topics ( contd.) Fundamental Equations: calculus of thermodynamics; Euler s theorem for homogeneous functions; Legendre s transformations; derivatives in terms of measurable properties. Thermodynamic Properties of Pure Fluids: equations of state; ideal gas heat capacities; fundamental equations from experimental data, fugacity and corresponding states. Equilibria and Stability: equilibrium criteria; stability criteria; Maxwell construction; binodals ; Gibbs Phase Rule; Clapeyron equation and vapor pressure correlations.

14 Suggested Topics (contd.) Thermodynamic Properties of Mixtures: mixing function; partial molar quantities; Gibbs-Duhem relation for mixtures; partial molar quantities from experimental data; ideal gas mixtures and fugacities; ideal mixtures and activities; excess functions; excess Gibbs free energy models; infinite dilution properties and Henry s Law. Phase Equilibria of Mixtures: VLE; LLE; VLLE; osmotic pressure and osmotic coefficients; boiling point elevation and freezing point depression. Chemical Reaction Equilibria: the standard Gibbs free energy change and equilibrium constant;equilibrium conversion for a single reaction; temperature and pressure effects on equilibrium conversion; heterogeneous reactions,;multiple chemical reactions.

15 Suggested topics (contd.) Introduction to Molecular Thermodynamics: microscopic origin of entropy and elementary statistical mechanics.

16 Suggested Experiments Determination of heat of combustion Vapor-liquid equilibrium Liquid-liquid equilibrium boiling point elevation

17 Suggested Books J.M.Smith, H.C.Van Ness and M.M.Abbott; Introduction to Chemical Engineering Thermodynamics, McGraw-Hill, Singapore (1996) S.I.Sandler, Chemical Engineering Thermodynamics, Wiley, N.Y (1999) Y.V.C. Rao, Chemical Engineering Thermodynamics, Universities Press (India) Ltd., Hyderabad (2001) References for elementary statistical thermodynamics A. Z. Panagiotopoulos, Essential Thermodynamics (Chapter 3), Drios Press, Princeton (2011). K. A. Dil and S. Bromberg,Molecular driving forces: statistical thermodynamics in chemistry and biology, Garland Science (2002).

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