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Catalysis Lecture 1

INTRODUCTION TO CATALYSIS

drrabiulhussain
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Catalysis Lecture 1

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  1. Catalysis: An introduction Dr.Rabiul Hussain School of Material Science & Engineering Jimma Institute of Technolgy, Jimma University E-mail: rabiul786@gmail.com Ph.No. +251-0966882081 (Ethiopia) +91-9508832510 (India) 7/6/2020 DR.RABIUL HUSSAIN 1

  2. OUTLINES Introduction What is catalysis? History of Catalysis Types of Catalysis Characteristics of catalytic reactions Field of Applications

  3. What is Catalysis? • The term “catalysis” was introduced as early as 1836 by Berzelius in order to explain various decomposition and transformation reactions. He assumed that catalysts possess special powers that can influence the affinity of chemical substances. [Catalysis(Greek kata = wholly, lein = to loosen)]. A definition that is still valid today is due to Ostwald (1895): “a catalyst accelerates a chemical reaction without affecting the position of the equilibrium.” A catalyst is defined as a substance which alters the rate of a chemical reaction, itself remaining chemically unchanged at the end of the reaction. The process is called Catalysis. • •

  4. Catalysis • A catalyst which enhances the rate of a reaction is called a Positive catalyst and the process Positive catalysis or simply Catalysis. • A catalyst which retards the rate of a reaction is called a Negative catalyst and the process Negative catalysis. • Catalysis is the occurrence, study, and use of catalysts and catalytic processes

  5. Catalysis • Wilhelm Ostwald proposed its valid definition in terms of the concepts of chemical kinetics: “A catalyst is a substance which affects the rate of a chemical reaction without being part of its end products”. • In 1909, Ostwald was awarded the Nobel Prize in Chemistry contributions to catalysis. for his

  6. Early History of Catalysis • Neolithic age ( ~5000B.C.)  Biocatalytic fermentation in wine manufacture. • 500B.C. Soap manufacture (hydrolysis of animal fats with potash lye) • 1500A.C. Alchemists formed sulfuric acid by a mysterious catalytic process

  7. Early History of Catalysis • 1831 Pelegrine Phillips (a Bristol vinegar manufacturer) obtained the 1stknown patent in catalysis for the reaction SO2+ air ® SO3 (Pt sponge as catalyst)  The catalyst used now-a-day is V2O5/ SiO2 • 1835 J.J. Berzelius coined the word “ catalysis”Greek words “ cata” means “ down”“ lysis ” means “ split” or “ break”

  8. Early History of Catalysis • “ This new force, which is unknown until now, is common to both organic and inorganic nature. I do not believe that it is a force completely independent of electrochemical affinities; … It is more convenient to give this force a separate name. I would therefore call this the catalytic force. I would furthermore, call the decomposition of substances resulting from this force catalysis, just as the decomposition of substances resulting from chemical affinity is called analysis.” Berzelius

  9. Early History of Catalysis • 1909 Ostwald (German) received Nobel Prize for studies of reaction rate over catalysts. • 1912 Paul Sabatier (French) received Nobel Prize for studies of catalytic hydrogenation of organic compounds. https://www.nobelprize.org/prizes/chemistry/1909/ostwald/biographical/ https://www.nobelprize.org/prizes/chemistry/1912/sabatier/facts/ https://www.nobelprize.org/prizes/chemistry/1909/ostwald/lecture/ https://www.nobelprize.org/prizes/chemistry/1912/sabatier/lecture/

  10. Early History of Catalysis • 1915 Haber Process: N2+ 3H2 2 NH3(Fe catalyst) • 1919 Fritz Haber (German) received Nobel Prize <https://www.nobelprize.org/prizes/chemistry/1918/haber/lecture/>

  11. EARLY HISTORY OF CATALYSIS • 1880 Carl Groebe – Accidentally broke a thermometer while stirring a mixture of hot naphthalene and H2SO4 – phthalic anhydride & phthalic acid===dye chemistry • 1899 Arrhenius equation k = A exp( -Ea/RT) • 1903 Ostward process – 2NH3+ 7/2 O2 2NO2+ 3 H2O (Pt sponge as catalyst) RESULT=== HNO3industry

  12. Early History of Catalysis • 1920 Sabatier published the 1st book on catalysis • 1923 Methanol synthesis • 1930 Fischer-Tropsch Process: • 1932 Langmuir (USA) received Nobel Prize  For surface chemistry and Langmuir isotherm

  13. Early History of Catalysis • 1936 Modern era in catalysis – Catalytic cracking of petroleum (acid treated clays as catalyst) – BET surface area – Deuterium discovery isotope research • 1963 Ziegler (German) & Natta(Italian)received Nobel Prize for stereoregulated polymerization catalyst

  14. Early History of Catalysis The Nobel Prize in Chemistry 1963 was awarded jointly to Karl Ziegler and Giulio Natta "for their discoveries in the field of the chemistry and technology of high polymers."

  15. History of Catalysis WORK: Often, chemical reactions are speeded up by surfaces, as in the case when gaseous molecules come in contact with a metal surface. During the 1960s Gerhard Ertl developed a number of methods for studying surface chemical reactions. Among other things, he made use of techniques for producing a very pure vacuum, which had been developed within the semiconductor industry. Gerhard Ertl was able to map out details of a process of great importance in the production of artificial fertilizer: the Haber-Bosch process in which nitrogen in the air is converted to ammonia via an iron catalyst.

  16. History of Catalysis

  17. History of Catalysis

  18. History of Industrial Catalysis continued

  19. History of industrial Catalysis

  20. Characteristic of Catalytic Reactions The following features or characteristics are common to most of the catalysts. 1) A catalyst remains unchanged in mass and chemical composition at the end of the reaction. • A small quantity of catalyst is generally needed to produce almost unlimited reaction. For example, one ten-millionth of its mass of finely divided platinum is all that is needed to catalyze the decomposition of hydrogen peroxide. On the other hand, there are catalysts which need to be present in relatively large amount to be effective. Thus in Friedel-Crafts reaction, anhydrous aluminium chloride functions as a catalyst effectively when present to the extent of 30 per cent of the mass of benzene.

  21. Characteristic of Catalytic Reactions • 3) A catalyst is more effective when finely divided. In heterogeneous catalysis, the solid catalyst is more effective when in a state of fine subdivision than it is used in bulk. (4) A catalyst is specific in its action: While a particular catalyst works for one reaction, it will not necessarily work for another reaction. Different catalysts, moreover, can bring about completely different reactions for the same substance. For example, ethanol (C2H5OH) gives ethene (C2H4) when passed over hot aluminium oxide, but with hot copper it gives ethanal (CH3CHO). •

  22. Characteristic of Catalytic Reactions • (5) A catalyst cannot, in general, initiate a reaction: In most cases a catalyst speeds up a reaction already in progress and does not initiate (or start) the reaction. But there are certain reactions where the reactants do not combine for very long period(perhaps years). For example, a mixture of hydrogen and oxygen, which remains unchanged almost in definitely at room temperature, can be brought to reaction by the catalyst platinum black in a few seconds. According to this view, the reacting molecules (in the absence of catalyst) do not possess minimum kinetic energies for successful collisions. The molecules rebound from collision without reacting at all. Thus it is now considered that the catalyst can initiate a reaction.

  23. Characteristic of Catalytic Reactions • (6) A catalyst does not affect the final position of equilibrium, although it shortens the time required to establish the equilibrium. It implies that in a reversible reaction the catalyst accelerates the forward and the reverse reactions equally. Thus the ratio of the rates of two opposing reactions i.e., the equilibrium constant, remains unchanged.

  24. Characteristic of Catalytic Reactions • (7) Change of temperature alters the rate of a catalytic reaction as it would do for the same reaction without a catalyst. Some catalysts are, however, physically altered by a rise in temperature and hence their catalytic activity may be decreased. This is particularly true with colloidal solutions like that of platinum, since a rise in the temperature may cause their coagulation. In such a case the rate of reaction increases up to a certain point and then gradually decreases. The rate of reaction is maximum at a particular temperature called the optimum temperature.

  25. Types of Catalysis • The numerous catalysts known today can be classified according to various criteria: structure, composition, area of application, or state of aggregation.

  26. Classification of Catalysts Main two classes: 1. Homogeneous catalysis 2. Heterogeneous Catalysis • Also, there is a third types of catalysis known as Enzyme catalysis which is largely of biological interest.

  27. Homogeneous Catalysis • In homogeneous catalysis, the catalyst is in the same phase as the reactants and is evenly distributed throughout. This type of catalysis can occur in gas phase or the liquid (solution) phase. Examples of Homogeneous Catalysis in Gas Phase:

  28. Homogeneous Catalysis

  29. Heterogeneous Catalysis • The catalysis in which the catalyst is in a different physical phase from the reactants is termed Heterogeneous catalysis. • The most important of such reactions are those in which the reactants are in the gas phase while the catalyst is a solid. The process is also called Contact catalysis since the reaction occurs by contact of reactants with the catalyst surface. • In contact catalysis, usually the catalyst is a finely divided metal or a gauze. This form of catalysis has great industrial importance.

  30. Heterogeneous Catalysis

  31. Heterogeneous Catalysis

  32. Application of Catalysis • Four major sectors of the world economy; petroleum and energy production, chemicals and polymer production, food industry and pollution control, involve catalytic processes.

  33. Application of Catalysis • Catalysts are used to produce fuels such as gasoline, diesel, heating oil, fuel oil etc. Production of plastics, synthetic rubbers, fabrics, cosmetics etc. involve catalytic processes. Automobile emission catalysts are used to reduce emissions of CO, NOx and hydrocarbons from mobile vehicles. The pharmaceutical industry uses catalysts for production of drugs that are used to save lives and improve the health of people. Catalysts are also widely used in food processing. More than 90 % of industrial processes actually use catalysts in one form or the other. • • • •

  34. Application of Catalysis

  35. Pollution Control and Catalysis

  36. Application to Catalysis

  37. 7/6/2020 DR. RABIUL HUSSAIN : 966882081 39

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