TKP2 Heterogen katalyse VK

Heterogeneous Catalysis Advanced Course

• Purpose: Specialization in Heterogeneous Catalysis• Goal: Prepare the students to

– Learn more about (heterogeneous) catalysis– Understand and assess reported experimental work– Plan and interpret own experiments– Provide training in reporting

• Involving– Knowledge of theory, and theoretical limitations– Knowledge of practical methods – Training in presentation (written and oral)

• Expected effort:– 3,75 STP, i.e. approx. 1/8 semester, or 120 hours– < 10 hours lectures– Main part: Own studies, work with projects (vide infra) and preparation for exam

• Assessment: Oral examination + excercise (written + oral part)

Seminars/topics/dates• Topic 1: Introduction Wed Sep 10 13:15 -(K24)

• Topic 2: Materials Wed Sep 10 13:15 -(K24)

• Topic 3: Characterization Wed Sep. 17 14:15- (K5-323)

• Topic 4: Kinetics Tue Sep. 23 13:15- (K5-323)

• Topic 5: Activity measurements Wed Sep. 24 14:15- …(K24)

• Topic 6: Deactivation Wed Sep. 24 14:15- …(K24)

Heterogeneous catalysis

• Different disciplines or points of view:– Kinetics (Reaction engineering)

– Materials and synthesis (Inorganic chemistry)

– Characterization (and detailed understanding, mechanism) (Instrumental analysis, surface science)

• Catalysis can (must!) be studied at several levels:– Microscopic (atomic level)

– Mesoscopic (nano-micrometer level)

– Macroscopic (reactor -process level)

Common fundament: • General chemistry, inorganic chemistry• Chemical Reaction Engineering and earlier

subjects (including ”Prosessteknikk” (Intr. Chem.Eng.) and Physical Chemistry):– Mass- and energy balances, kinetics, reactor design– In particular Chem. Reaction Engineering (Textbook:

Scott Fogler) Chap. 10: catalysis, definitions, rate, rate limiting step (rds)

• Reaction kinetics and catalysis– Emphasis on heterogeneous catalysis

Basics

• Definition: – A catalyst increases the rate of a (desired) chemical

reaction without being consumed in the reaction– Does not influence the equilibrium

• Terms– Activity, selectivity, life-time– Classification according to type of material

• Reaction rate – Defined for different units (based on catalyst volume,

weight, total area, specific area, turnover)– global, local rate (intrinsic rate)

Continued...

• Mechanisms– Elementary steps– Rate determining reaction step (rds) – PSSA

• Adsorption amd desorption– Physical adsorption, chemisorption – Lennard Jones-diagram, heat of adsorption, activation

energy– isotherms (Langmuir, etc.)

• Chemisorption and determination of dispersion of supported metal catalysts

Continued further...

• Catalytic mechanisms

– Adsorption, desorption rate determining• E.g. NH3-synthesis (adsorption, applying the Temkin isotherm)

– Surface reaction is rds• Power rate law, LH, LHHW• Bimolecular reactions (LH, Eley-Rideal, Mars - van Krevelen)

– Temperature dependancy, activation energy, heat of adsorption

• Mass transport– diffusion (bulk, Knudsen)

– diffusion and reaction, effectiveness factor, Thiele modulus

– particle external mass transfer limitations

– all those above linked to kinetics

Still continuing….

• Catalyst deactivation– Different deactivation mechanisms

• Catalyst materials– metals, oxides, zeolites…

• Activity-selectivity-lifetime measurements (”catalyst testing”)– Laboratory reactors

Some of these topics were given only a brief treatment previously and are also included here

Teaching and curriculum • Contents summarized in lectures/seminars :

– Materials– Characterization– Kinetics– Transport/testing– Deactivation

• Curriculum literature– Slides, textbooks, papers etc.

• Individual excercise – Each student gets a journal article on catalysis to study carefully– 2 parts to the excercise:

1. Write an essay discussing the fundamental theory and practice of catalysis in the article. See next slide for points to be included.

2. Present the content of the article in a scientific presentation (for the rest of the group)– pretend to be the author of the paper!

– Both parts will count towards the mark in the course (30% of the module)

• Read the article carefully and write a report (essay) describing carefully – including the key theory (equations and assumptions) and practical issues (how are the experiments done), covering:– Which chemical reaction is studied, the background (why is it interesting),

thermodynamics (heat of reaction, equlibrium) – Type of catalyst (material, form)– If catalyst materials are prepared: Preparation and material issues– Characterization

• surface area and porosity• structure and morphology• Dispersion

– How are the activity measurements done (reactor, experimental plan), calculations, how is deactivation handled etc.

– If necessary (e.g. something unclear) gather further information from the references in the paper or other sources.

• Sometimes experimental details are given in earlier papers by the same authors.

– Do not focus on the scientific findings!!

Essay

Presentation

• Prepare and perform an oral presentation of the article you have been given– Pretend you are the scientist (PI) behind the work– Give a scientific presentation

• Background • Methods• Theory• Results and discussion• Conclusions

– Be prepared to answer questions about the methods used in the paper

Suggested dates and deadlines

• Hand in essay: Monday November 3• Seminar(s) with presentations:

– Tuesday November 18 13:15 … (K5-201) – Wednesday November 19 13:15… (K5-201)

• Exam: Dec. 3