Conferences

Geus lectures

 

Lectures in the field of materials, spectroscopy and catalysis

2011- Prof. Robert Davis

2010- Prof. Charles Kappenstein

2010- Prof. Anders Holmen
2008- Prof. Freek Kapteijn
2007- Prof. Johannes Lercher
2006 - Prof. Hans Niemantsverdriet
2006 - Prof. Avelino Corma
2005 - Prof. John Geus

Scope
The group of Inorganic Chemistry and Catalysis organizes a series of lectures named after Prof. J.W. Geus, who founded the department in 1971. His research activities involved a.o. catalyst preparation, sulfur processes and carbon fibrils. He is (co-)author of around 300 scientific papers and (co-)inventor of approximately 90 patents.

Language
The language of the lectures will be English.

Venue
The venue of the lecture series will be the Utrecht University; this will usually be in the Went-building at the Sorbonnelaan 16 in Utrecht. 
At the specific announcement per lecture and at this website, you can find the room where the lecture will take place. 
Detailed information about how to find the building can be found at the website as well (please check 'contact/route'). 

More information and announcements
If you want more information, or if you want to subscribe for receiving the announcements for the Geus lectures automatically, please contact us by e-mail or by phone (030-2537400).

 

Next lecture will be given by

Thursday, June 30, 2011 at 4.00 p.m.

Prof. Robert J. Davis

(Department of Chemical Engineering, University of Virginia, Charlottesville, VA, USA)

Introduction Prof. Robert Davis

Robert Davis obtained his Ph.D. degree in Chemical Engineering from Stanford University in 1989. He subsequently worked as a postdoctoral research fellow in the Chemistry Department at the University of Namur in Belgium. He joined the faculty in Chemical Engineering at the University of Virginia in 1990 as an assistant professor, was promoted to associate professor in 1996, full professor in 2002, and Earnest Jackson Oglesby Professor in 2009. Professor Davis has also served as the Chair of Chemical Engineering at the University of Virginia since 2002. He has received the Emmett Award of the North American Catalysis Society, the NSF Young Investigator Award, the DuPont Young Professor Award, the Union Carbide Innovation Recognition Award, and the UVa Rodman Scholars Award for Excellence in Teaching. Professor Davis has co-authored more than 100 publications, 1 patent and 1 textbook, entitled “Fundamentals of Chemical Reaction Engineering”. He has delivered over 100 invited lectures at conferences, academic departments and industrial research groups, and has co-authored over 100 additional presentations at technical meetings. Professor Davis has served as President of the Southeastern Catalysis Society, Chair of the 2006 Gordon Research Conference on Catalysis, Chair of Catalysis Programming of the AIChE, Chair of a US government panel charged with worldwide assessment of Catalysis by Nanostructured Materials, Director of the Catalysis and Reaction Engineering Division of the AIChE, Director of the North American Catalysis Society, Co-chair of an International Catalysis Workshop in China, member of the Advisory Board of the International Conferences on Solid Acid and Base Catalysis, and member of the editorial boards of Journal of Catalysis, Applied Catalysis A and B, Journal of Molecular Catalysis A, ChemCatChem and ACS Catalysis.

 

Some Current Challenges in the Conversion of Biorenewable Molecules over Supported Metal Catalysts

The conversion of biorenewable feedstocks to fuels and chemicals is one approach to partially relieve our growing dependence on fossil fuels. However, there are many scientific and engineering challenges to overcome. In this work, the selective catalytic oxidation of the model polyol glycerol to glyceric acid has been investigated over supported Au catalysts in alkaline water solutions. The influences of solution pH, reactor configuration, gold particle size and addition of Pd were studied in detail. Although the smallest of Au nanoparticles revealed the highest turnover frequency, large Au particles and even bulk Au powder catalyzed the oxidation reaction at high pH. Results from isotopic labeling experiments with 18O showed direct participation of hydroxide from the solution instead of gaseous oxygen in the oxidation reaction, which accounts for the very strong influence of solution pH on the reaction rate and product selectivity as well as the production of peroxide during the reaction. These results are extended to the oxidation of hydroxymethylfurfural in basic solution.

The selective reduction of glycerol to propanediols was also studied over supported metals in aqueous solution. By directly comparing the reaction of glycerol to propylene glycol and ethylene glycol over Pt and Ru catalysts under identical conditions, we concluded that a C-C cleavage path exists on Ru that is not favored on Pt. Moreover, the higher rate of glycerol conversion and shift in product distribution with increasing solution pH indicated solution-phase reactions can be strongly coupled to metal-catalyzed reactions. Although supported Pt catalysts produced mainly 1,2-propanediol under the conditions of study, promotion of Pt by Re resulted in the formation of some 1,3-propanediol that was not observed with monometallic Pt catalysts. The influences of catalyst composition and solution pH on the reaction rate and product distribution during oxidation and reduction reactions will be discussed.

Location
The lecture will start at 4.00 p.m. in room DDW 1.30 in the David de Wied building, Universteitsweg 99 in Utrecht.

 

 

 

Friday, November 19, 2010 at 4.00 p.m.

Prof. C. Kappenstein

(LACCO, Laboratory of Catalysis, CNRS, University of Poitiers, France)

Introduction Prof. Charles Kappenstein

Prof. Charles Kappenstein was born in Lorraine, France in 1946. After a primary school teacher study in Metz, he left this career and started chemistry study at the University of Strasbourg (France). After his graduation, he got a position as assistant professor at the University of Reims in 1968 in the field of coordination and solid state chemistry. He obtained his Ph.D. in 1977 on the coordination chemistry of copper(I) with cyanide ligands in solution and solid state. Then in 1978, he was postdoc at the TU, Munich by Prof. E.O. Fischer, in the field of organometallic chemistry of carbenes and carbines.

In 1981, he moved to the University of Poitiers as associate professor, and spent a sabbatical semester in 1985 by Prof. H. Knözinger, at the LMU, Munich to start his work in catalysis. He was appointed as full professor in 1992 and distinguished professor in 2007. He is emeritus professor since September 2010.

After starting on the preparation and characterization of supported metallic catalysts, he moved in 1994 in the applications of catalysis to propulsion, focusing in the synthesis, development and control of catalyst for the decomposition of propellants. His work was supported by numerous contracts with French Space Agency (CNES), European Space Agency (ESA), European Community (FP7 project GRASP), and French and foreign companies. More recently, he proposed with success the use of different types of structured supports to replace the traditional alumina pellets.

He published more than 160 publications and was full or co-supervisor for 37 Ph.D. theses.

He was awarded the coordination chemistry price by the Société Chimique de France in 1981 and Professeur d'Honneur of the University Cuza, Iasi (Romania) in 2003; he received the Bronze Medal of the University Safarik, Kosice (Slovakia) in 2004.

He developed cooperation with several countries to improve international relationships between students and teachers: Hungary, Romania, Slovakia, Korea, China, India, Egypt, Algeria, Morocco, USA, Kuweit.

 

Catalysis and Propulsion

The use of catalysis in the field of propulsion began just before WWII in Germany with the catalytic decomposition of hydrogen peroxide H2O2 through liquid injection of permanganate salts: He-176 plane; V1 catapult; V2 turbo-pump gas generator. Hydrogen peroxide was also used for torpedo and submarine propulsion with diesel oil. After WWII, the UK Black Knight rocket program associated kerosene with H2O2 (bipropellant propulsion system) and silver screen catalyst bed.

During the late fifties, the start of the space programs lead to the development of monopropellant propulsion system, using pure hydrazine and Ir/Al2O3 catalysts, to control orbit and orientation of launched satellites.

But in the late nineties, the toxicity of hydrazine associated with environmental concerns promoted the search for less toxic monopropellants. The most currently studied substitutes are energetic aqueous ionic mixtures containing an oxidizer and a fuel in water. The proposed oxidizers are HAN (hydroxylammonium nitrate [NH3OH][NO3]) or ADN (ammonium dinitramide [NH4][N(NO2)2]). Different fuels are associated with these oxidizers: molecular fuels (glycine, glycerol, urea, methanol, etc.) or ionic fuels. The challenge is to develop a catalyst active at low temperatures and resistant at the high temperatures of the product gases.

Other hydrazine substitutes have also been proposed: highly concentrated hydrogen peroxide (90-98 wt-%) and nitrous oxide N2O(g), with the challenge to find an active catalyst, able to survive at 1600°C.

Current objectives, prospective applications, and corresponding challenges are:

  • Hybrid engines: the hot oxygen formed during the decomposition of a liquid oxidizer burn a solid fuel.

  • Hypergolic bipropellants: the direct mixture of an oxidizer (like H2O2) and a liquid fuel (like kerosene) can be made hypergolic (i.e. spontaneous ignition), by adding an adequate catalyst to the fuel.

  • Air breathing high speed scramjet or pulse detonating engines (PDE): the catalytic transformation of the current fuels can increase the detonability of the air-hydrocarbon mixtures.

  • Catalytic ignition of cryogenic H2-O2 mixtures.

  • Catalyst as burn rate modifier for solid propulsion.

Location
The lecture will start at 4.00 p.m. in room BBL201 in the Buys Ballot Laboratory, Princetonplein 5 in Utrecht.
 

 

Wednesday, February 10, 2010 at 4.00 p.m.

Prof. Anders Holmen

(NTNU, Trondheim)

 

Introduction Prof. Anders Holmen

Anders Holmen is professor of Chemical Engineering at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway.

He worked as a research scientist and later as a group leader of the Petrochemistry and Catalysis Group at SINTEF Applied Chemistry before joining the Faculty of Chemical Technology, Norwegian Institute of Technology (NTH), in 1981. He has been a visiting scientist at Norsk Hydro, Norway and Stanford University, USA and a visiting professor at the Institute de Recherché sur la Catalyse in Villeurbanne, France, the University of Bologna, Italy and the Research Centre of Statoil, Norway. He has been the main supervisor for more than 45 Ph.D. students. He received Statoil’s Forskerpris in 1994 and will receive the Award For Excellence in Natural Gas Conversion in 2010.

His main area of research is heterogeneous catalysis in oil refining, petrochemistry and in particular gas conversion in areas such as pyrolysis, dehydrogenation and Fischer-Tropsch synthesis.

 

Performance of supported Co catalysts for Fischer-Tropsch synthesis

Fischer-Tropsch synthesis aims at converting syngas into high quality diesel. The syngas may be produced from different C-containing feedstocks i.e. natural gas, oil, coal or biomass. Cobalt is considered the most favourable catalyst for the synthesis of long-chain hydrocarbons from natural gas-based syngas due to its high activity and selectivity to long chain hydrocarbons and relatively slow deactivation.

Cobalt site-time yields have usually been considered independent of both cobalt dispersion and the nature of the support. However, it has been shown recently (in Utrecht) that for Co supported on carbon nanotubes, a positive correlation exists between the Co particle size and the site-time yield for Co particles provided that the particles are less than 6-7 nm. For Co supported on Al2O3 the results are not so unambiguous and for small Co particles supported on Al2O3 the extent of reduction is relatively low.

Experimental evidence shows that the C5+ selectivity depends on the particle size, on the support material and of course on the reaction conditions. It is known that the addition of steam to the feed results in an increased C5+ selectivity. The use of promoters has also an influence on the C5+ selectivity and Re gives in most cases an increase in the selectivity of C5+.

Co catalysts deactivate during use and several mechanisms have been proposed including sintering, carbon formation and possibly Co oxidation. The rate of deactivation also depends on the Co dispersion and on the nature of the support material. For slurry type reactors the mechanical strength of the catalyst particle is also very important.

The effect of the Co dispersion and the support on the performance of Fischer-Tropsch synthesis catalysts is still far from being well established and different theories and approaches will be discussed in the lecture.
 

Location
The lecture will start at 4.00 p.m. in room N020 in the Went-building, Sorbonnelaan 16 in Utrecht.
After the lecture, drinks are being served.

 

Friday, November 21 at 4.00 p.m.

Prof. Freek Kapteijn

(TU Delft)

Introduction Prof. Freek Kapteijn

Freek Kapteijn (TU Delft) graduated in 1974 at the university of Amsterdam in Chemistry and Mathematics. His Ph.D. on the metathesis of alkenes was received at the same university. As postdoc he focused on Coal Science and Heterogeneous Catalysis. In 1987 he received a tenure position at the University of Amsterdam and he moved to Delft University of Technology in 1993. In 1999 he was nominated ‘Anthonie van Leeuwenhoek’ professor in Delft and he leads per 2008 the section of Catalysis Engineering.

Prof. Kapteijn spent several periods abroad among which in Nancy, France (Villermaux, ENSIC) and Zürich, Switzerland (Prins, ETH), and is guest professor at Zehjiang Normal University, China.
He is co-author of over 300 publications and (co)-promotor of over 30 Ph.D. students.
The current interests of Prof. Kapteijn include the synthesis and application of structured catalysts (zeolites, monoliths, catalytic membranes) in multiphase and multifunctional conversion processes, adsorption and diffusion in zeolites, MOFs and their membranes, and transient kinetics.
The related specific applications of heterogeneous catalysis cover selective hydrogenation and oxidation, hydroisomerization, N2O decomposition, Fischer-Tropsch synthesis, MTO and fine chemicals production.

Structured catalysts or structure in catalysis?

Catalytic conversions are the heart of many industrial processes and of activities that improve directly or indirectly our living environment. The catalyst applied is the essential element in these operations, and is usually the result of intensive R&D effort to an optimal selectivity, activity and stability. This development, however, does not end with the catalytic material, which is in essence a primary condition; the mode of application in a reactor and process is at least as important.

Random packed beds and slurry reactors are most commonly used but structured reactors provide a good alternative. Why would one use structured reactors?
Precision and intensification in catalytic processes are the basis for process improvement. It does not make sense to develop the best possible catalyst and to use it in a poorly performing reactor: a good catalyst deserves a good reactor and vice versa. All physical and chemical processes should be tuned to an optimal performance. This concert cannot be achieved in random packed beds due to an intrinsic coupling of the various processes.
In structured reactors kinetics, transport phenomena and hydrodynamics are decoupled, and the extra degrees of freedom allow an independent optimization of the individual rate processes. This structuring covers the whole length scale from the reactor size down to that of the active site, leading to a hierarchical organization. This approach not only pays off in practical applications but also in research activities.

The lecture will focus on examples of structuring in multiphase and multifunctional catalytic reaction systems. These include on the reactor level the monolith applied to heterogeneous and enzymatic catalysis, the monolithic stirrer, heat transport in various catalytic structures, the zeolite membrane reactor and the capillary reactor. On the catalyst level results with porous crystalline materials as zeolites and MOFs are presented for photo-catalysis and basic reactions.
Synthesis plays an essential role in all these activities, and the direct and indirect influence of John Geus in these developments will be highlighted.

Location
The lecture will start at 4.00 p.m. in room N017 in the Went-building, Sorbonnelaan 16 in Utrecht.
After the lecture, drinks are being served.

 

Tuesday, November 27 at 4.00 p.m.

Prof. Johannes Lercher

(Technischen Universität München)

Introduction Prof. Johannes A. Lercher

Johannes Lercher is professor at the Department of Chemistry at the TU München. His research is focussed on fundamental and applied aspects of alkane activation and functionalization, design of amine synthesis routes, molecular sieve based sorption and catalysis and in situ characterization of catalytic processes.

In 1981, Johannes Lercher obtained his doctoral degree at the TU Wien, under supervision of Heinrich Noller. In 1982, he had a lectureship at Yale University with Gary Haller and John Fenn.
From 1983 to 1993, he was appointed lecturer and Associate Professor at TU Vienna. In 1993, he started his professorship at the Department of Chemical Technology at the University of Twente. In 1998, he moved back to Germany and became professor at the Department of Chemistry at the TU München. At this university, he also was Dean of the Department of Chemistry from 2000 to 2003 and became senator from 2003 to 2007.

Prof. Lercher is author of over 330 papers and 10 patents. He is chairman of the Bavarian section of the German Society for Coal Gas and Oil, editor of Journal of Catalysis and member of the board of several catalysis journals. Before, he was President of the International Zeolite Association.
Prof. Lercher had an UOP Invitational lecture and received several awards, including the Award of Austrian Board of Trade and Industry, the Christian Doppler Award, the Shell – Center of Excellence Award, the PE-Award from the Indian Institute of Chemical Engineers.

Lecture: Catalytic conversion of alkanes by bifunctional catalysis

The catalyzed activation and selective conversion of light alkanes from methane to butane are the key routes to utilize a broader basis of fossil carbon resources. Activation is possible through acid base as well as redox chemistry. Carbenium ions are the key intermediates in the acid-base route and hydride transfer reaction the key single process that controls the overall performance of catalysts. At a monofunctional site, the generation of the carbocation requires such a high energy input that it occurs only at drastic reaction temperatures. Bifunctional sites, in contrast, able to polarize C-H bonds are the key to lower reaction barriers. Such active sites require special steric arrangements and it appears critical that soft Lewis acid sites are part of such a site.

It will be shown that complex catalysts and closely coupled reaction steps are needed to activate alkanes at mild temperatures. This will be discussed using isomerization and cleavage of alkanes, alkylation, and oxidative functionalization of methane. Only the subtle control of the functions and the catalytic elementary steps leads to active and stable catalysts. New catalytic materials and new potential process routes may be developed using the rigorous understanding of sorption and elementary steps as guiding principle.

Location
The lecture will start at 4.00 p.m. in room N017 in the Went-building, Sorbonnelaan 16 in Utrecht.
After the lecture, drinks are being served.

 

November 24, 2006 at 4.00 p.m.

Prof. Hans Niemantsverdriet



Prof. J.W. Niemantsverdriet 
Hans Niemantsverdriet is professor of Physical Chemistry of Surfaces and Dean of the Department of Chemical Engineering and Chemistry at the Eindhoven University of Technology.

He graduated from the Free University in Amsterdam in 1978 and obtained his Ph.D. from the Delft University of Technology in 1983. In 1984 he moved to Eindhoven on a NWO-Huygens Fellowship for 5 years, during which he also stayed at the University of München and the Fritz-Haber-Institute at Berlin. In 1989 he was appointed senior lecturer and in 1999 full professor at Eindhoven. Hans Niemantsverdriet is the recipient of the C. and C. Huygens Award of the Netherlands Organization of Scientific Research (1984) and of the Pionier Award of the same organization (1989), which enabled him to build up a surface science laboratory. He is author of over 200 publications and three books, Spectroscopy in Catalysis (VCH, 1993; 2nd edition Wiley-VCH, 2000; 3rd edition 2007); Chemical Kinetics and Catalysis, with R.A. van Santen, Plenum, New York, 1995 and Concepts of Modern Catalysis and Kinetics, with I. Chorkendorff, (Wiley-VCH, 2003). 

Hans spent sabbaticals at the University of California at Berkeley (1994), and the Technical University of Denmark (2000, 2002). He was guest lecturer at the University Institute of Chemical Technology of Mumbai (2003), the EPFL Lausanne (2004) and several universities in South Africa, as the Eminent Visitor of the Catalysis Society of South Africa in 2005. He is currently Chairman of the International Advisory Board for the Institute of Chemical Engineering Sciences in Singapore. Hans was editor of CaTTech (1996-2001) and President of the European Federation of Catalysis Societies (1999-2001). He has been editor of the Journal of Catalysis since 1996. 

Lecture 

“Molecules and their Interactions on Surfaces”

Unraveling reaction mechanisms in terms of elementary reaction steps and determining their kinetic parameters is at the heart of understanding catalytic reactions at the molecular level. Such reactions take place between species adsorbed on surfaces. In catalytic modelling interactions between adsorbed species are generally ignored. However, in this lecture it is shown that lateral adsorbate interactions are very significant and play a key role in determining selectivity patterns of surface reactions. A thorough understanding of adsorbate interactions may eventually open the way to better control over selectivity in catalytic reactions. 

Location
The lecture will take place in room N020 in the Went-building, Sorbonnelaan 16 in Utrecht. 
After the lecture, drinks are being served.

The second Geus Lecture in honour of the honorary degree from Utrecht University awarded to

Prof. Avelino Corma

at

March 28, 2006 at 11.00 am

Professor Avelino Corma (1951) was born in Moncófar (Spain). He studied Chemistry at the Universidad de Valencia (1967-1973) and obtained his PhD at the Universidad Complutense de Madrid in 1976. He has worked with Professor Antonio Cortés Arroyo at the Instituto de Catálisis y Petroleoquímica (C.S.I.C.). Subsequently he moved to Queen’s University (Canada) as a post-doctoral fellow and returned to C.S.I.C. in 1979. In 1987 he became research professor at C.S.I.C. and in 1990 director of the Instituto de Tecnología Química of the Universidad Politécnica de Valencia. He has developed the institute to the highest ranks in the field of heterogeneous catalysis with emphasis on zeolites and mesoporous materials. He has covered an incredibly broad field of catalysis from oil refining, acid catalysis, selective oxidation, base catalysis and catalysis for synthesis of fine chemicals. The synthesis of many new microporous and mesoporous materials has been combined with excellent characterization and catalysis studies.

Professor Avelino Corma has received numerous awards and honours such as the Dupont Award (1995), G. Ciapetta Award of the North American Catalyst Society (1998), the Francois Gault European Award on Catalysis (2001), the Houdry Award of the North American Catalysis Society (2003) and the Breck Award of the International Zeolite Association (2004). He has served on the board of many prestigious journals such as Chemical Communications, the Journal of Catalysis and Catalysis Reviews.

He has published more than 500 papers in high-quality journals (e.g.. Chemical Communications, Journal of the American Chemical Society, Angewandte Chemie and Nature) and has been listed as inventor on about 100 patents, many of which are or have been applied commercially. His publications have been cited more than 15,000 times. Professor Corma combines excellent fundamental work in heterogeneous catalysis with innovation that has led to many industrial applications.

Lecture: "A parallelism between homogeneous and heterogeneous catalysis with gold catalysts"

Major improvements in catalysis will require the understanding of the reaction mechanism and the design of catalysts at the molecular level. Transition metal complexes allow to design the electronic and geometrical characteristics of active sites, and from this we can better understand and design solid catalysts. While metallic gold is chemically inert, and therefore of limited use for adsorption and catalysis, Au(III) and Au(I) can act as Lewis acids and also may go through a redox process. Interestingly, their d8 electronic structure is the same than Pd(II) and Pd(0) respectively. Even though their chemical potential and softness-hardness are different respectively. All this opens the possibility to use Au(III) and Au(I) as active catalytic species. Following the above will show that gold metal complexes can catalyze hydrogenations, oxidations and C-C bond formation reactions, being possible to change the product distribution by changing Au(III) by Au(I), in excellent parallelism with the corresponding Pd complexes. Thus, we will present that when stabilizing Au(III) and Au(I) species on solid supports by interplaying with the size of gold particles and the nature of the support, it is possible to catalyze the same reactions that with the gold metal complexes. Raman and XAFS spectroscopies allow to establish the nature of the gold reactive species in solid based gold catalysts.

 

The first lecture has been given by 

Prof. Dr. Ir. J.W. Geus

at

April 29, 2005 at 4.00 p.m. 

Prof. J.W. Geus 
John W. Geus (1933) was educated at the Technical University of Delft where he studied chemistry from 1951 to 1957. His graduate work, guided by Prof. Dr. W.G. Burgers concerned precipitation processes in solids. He graduated “cum laude’.
From 1959 to 1971 he was employed by DSM at the catalyst department of The Central Laboratory. After a period in which he focused on fundamental work on the effect of adsorption on physical properties of metals, he concentrated on processes for the production of solid systems with controlled structures and properties. Though his main activities concerned solid catalysts and catalytic reactions, he also developed new magnetic materials and inorganic pigments. With his newly developed synthesis procedures he succeeded in the preparation of new and better catalysts with which he could considerably improve a number of catalytic processes. Thus equipped with impressive experimental and theoretical skills and a profound insight in the conduct and policy of industrial companies and institutions, he started in 1971 his work at Utrecht University as professor in Inorganic Chemistry and Heterogeneous Catalysis. There he guided 80 PhD students and at least 400 undergraduates. With them he contributed considerably to important developments in the fields of synthesis of solid catalysts, oxidation catalysis, sulfur processes and gas treating, synthesis gas processing, carbon fibrils, hydrogenation and de-hydrogenation, synthesis and employment of clay based catalysts and physics and chemistry of (mono crystalline) surfaces.
For his work on the “SuperClaus “ process he was awarded with the Dow Chemical Energy Prize in 1991 and in 1995 he accepted his honorary degree at Delft University. On that occasion he said: ”All that work, we did it together, we all deserve this honour.”
As an Emeritus (1998) he acts as a consultant to industry and studies catalysts using electron microscopy. 

Lecture: "Selective Catalytic Oxidation of Hydrogen Sulfide to Elemental Sulfur"
Purification of natural gas and hydrotreating of crude oil fractions lead to huge flows of highly poisonous and badly smelling hydrogen sulfide. The Claus process in which hydrogen sulfide reacts to non-poisonous elemental sulfur involves the following equilibrium: 

2 H2S + SO2 = 2H2O + 3/n Sn

However, at temperatures where the catalysts (titania and alumina) are sufficiently active, equilibrium limits the sulfur recovery to 96 to 97%. Therefore, a process increasing the sulfur recovery to about 99% is required. Earlier developed Claus tail gas processes are calling for high investments and consume much fuel gas and power. An alternative was therefore highly desired. An appropriate process can be based on the selective oxidation of hydrogen sulfide:

2 H2S + O2 = 2 H2O + 2/n Sn

By raising the hydrogen sulfide to sulfur dioxide ratio of the process the sulfur dioxide content of the tail gas can be lowered. The selective oxidation of the remaining hydrogen sulfide will considerably enhance the sulfur recovery.
The constraints of the selective oxidation process will be dealt with. The catalyst must be selective with an excess of oxygen in the presence of about 30 % water vapour and within a temperature window where condensation of elemental sulfur and gas phase oxidation of sulfur do not proceed. Since the process to be developed should had to be performed within the third catalytic Claus reactor of the usual Claus plants, the development of the catalyst was crucial.
Moreover, to reduce emission of sulfur dioxide completely a process and an absorbent had to be developed to remove the small remaining amounts of sulfur dioxide.