Catalytic Reaction Engineering Catalysis and Catalytic Reactors Textbook: Elements of Chemical Reaction Engineering, 4th Edition CHE 404 Catalytic Reaction Engineering Chapter 10 Catalysis and Catalytic Reactors PART 1

What is Catalyst? Definition 화학공정 (촉매) What is Catalyst? Definition Definition A catalyst is a substance which increases the thermodynamically feasible reaction rate while remaining unaltered at the end of the reaction; A substance which alters the speed of a chemical reaction by its presence although not being consumed significantly Catalysis: an act of catalyst (Berzelius, 1936) The word catalysis comes from two Greek words. cata - ‘down’ lysein - ‘split or break’ to denote the breaking down of the normal forces which inhibit the reaction of molecules. Rxn: A + B  P (Adsorption) (Surface reaction) (Desorption) What is Catalysis? Chemical Engineering, Dong-A University 2

Action of Catalysts: Energy Diagram 화학공정 (촉매) Action of Catalysts: Energy Diagram -rA = kCAn, k = k0e(-Ea/RT) -Ea ↓  - rA ↑ ΔG0 A catalyst changes only the rate of a reaction but cannot change the equilibrium. ΔG0 The initial and final states are the same by both un-catalyzed and catalyzed process,  The overall free Gibbs energy, ΔG0 is therefore identical,  All the thermodynamic parameters, including the equilibrium constant Keq = exp (- ΔG0 /RT) were not affected and catalysts only permit to attain the equilibrium more quickly. Chemical Engineering, Dong-A University 3

화학공정 (촉매) Action of Catalysts The use of catalyst DOES NOT vary G & Keq values of the reaction concerned.  Whether a reaction can proceed or not and to what extent a reaction can proceed is solely determined by the reaction thermodynamics, which is governed by the values of G & Keq, NOT by the presence of catalysts.  In other word, the reaction thermodynamics provide the driving force for a rxn; the presence of catalysts changes the way how driving force acts on that process. e.g CH4(g) + CO2(g) = 2CO(g) + 2H2(g) G°373=151 kJ/mol (100 °C) G°973 =-16 kJ/mol (700 °C)  - At 100°C, G°373=151 kJ/mol > 0. There is no thermodynamic driving force, the reaction won’t proceed with or without a catalyst  - At 700°C, G°373= -16 kJ/mol < 0. The thermodynamic driving force is there. However, simply putting CH4 and CO2 together in a reactor does not mean they will react. Without a proper catalyst heating the mixture in reactor results no conversion of CH4 and CO2 at all. When Pt/ZrO2 or Ni/Al2O3 is present in the reactor at the same temperature, equilibrium conversion can be achieved (<100%). Chemical Engineering, Dong-A University 4

Steps in Catalytic Reactions 화학공정 (촉매) Steps in Catalytic Reactions A  P Not limiting if small cat. particle high fluid velocity Limiting steps ! Step-4 >75% Chemical Engineering, Dong-A University 5

Energy Diagram during Reaction Step in the overall reaction Energy level of the system Er (catalytic) Er (thermal)  Hr Reactant Product Adsorption Reaction Desorption A catalyst changes only the rate of a reaction but cannot change the equilibrium. CHE 404 Chemical Reaction Engineering Chapter 10

화학공정 (촉매) History of Catalysis 1835 - New word "katalysis", breaking down or loosening, was introduced by J. J. Berzelius Major breakthrough in industrial catalysis 1908 - Synthesis of ammonia from nitrogen and hydrogen gases using osmium as catalyst, by Frith Harber 1913 - The ammonia synthesis was commercialized at BASF as the Harber-Bosch process. Mittasch at BASF developed iron catalysts. 1928 - The synthesis of methanol from CO and H2 over ZnO-Cr2O3. The cracking of heavier petroleum fractions to gasoline using acid-activated clay. 1932 - The alkylation of isobutane to C3-C4 olefins in the presence of AlCl3, leading to branched C7-C8 HCs for high quality gasoline by Ipatieff et al, and commercial process of UOP, USA. 1938 - Fischer-Tropsch synthesis of HCs from CO and H2 over iron catalyst. Chemical Engineering, Dong-A University 7

Industrial Application of Heterogeneous Catalysis 화학공정 (촉매) Industrial Application of Heterogeneous Catalysis Quantum developments in industrial application of heterogeneous catalysis ENERGY & CLEAN TECH Fuel Cell xTL(CTL, GTL, BTL ) CO2 Conversion Batteries (Li-Air) Photosynthesis Electrocatalysis etc Chemical Engineering, Dong-A University 8

Organization of Catalysts 화학공정 (촉매) Organization of Catalysts Main focus Chemical Engineering, Dong-A University 9

Solid Catalysts: what they contain? 화학공정 (촉매) Solid Catalysts: what they contain? Chemical Engineering, Dong-A University 10

Principles and concepts in heterogeneous catalysis 화학공정 (촉매) Principles and concepts in heterogeneous catalysis  Sabatier’s Principle Proposes the existence of an unstable intermediate compound formed between the catalyst surface and at least one of the reactants This intermediate (surface formate) must be stable enough to be formed in sufficient quantities and labile enough to decompose to yield the final product. The measure of stability of the intermediates ~ heat of formation Hf Au isn’t good catalyst because it doesn’t form strong enough attachments, W ins’t a good catalyst because it adsorbs too strongly.  A max rate is observed at intermediate Hf over Pt or Ir catalyst. Chemical Engineering, Dong-A University 11

Possible another reaction: Porous Catalysts Typical example: Zeolite (SEM image of zeolite) (TEM image of Pd-Pt/Beta) Possible another reaction: Ethane cyclization CHE 404 Chemical Reaction Engineering Chapter 10

Shape Selectivities in Zeolites CHE 404 Chemical Reaction Engineering Chapter 10

Catalytic functions for hydrocarbon processing What do we want to do with hydrocarbons? 1) something with C-H : metals 2) something with C-C : acids 3) something with C-H & C-C : both metals & acids 14 CHE 404 Chemical Reaction Engineering Chapter 10

R&D in Catalysis: Multi-discipline approach 화학공정 (촉매) R&D in Catalysis: Multi-discipline approach Chemical Engineering, Dong-A University 15