Peter Lednor, Shell Research & Technology Ctr
Dick Nagaki, Union Carbide Corporation
- Criterion Catalyst Company L.P.
- Exxon Research & Engineering Company
- Norton Chemicals
- Shell Development Chemical Co.
- Union Carbide Corporation
Proceedings published as Volume 549
of the Materials Research Society
Symposium Proceedings Series.
* Invited paper
9:45 AM OPENING REMARKS 10:00 AM *FF1.1
SESSION FF1: STRUCTURED CATALYSTS
Chairs: Robert N. Carter and Peter W. Lednor
Monday Morning, November 30, 1998
Hampton A/B (S)
MONOLITHIC STRUCTURES AND HETEROGENEOUS CATALYSTS. Jacob Moulijn , Delft Univ of Technology, Dept of Chem Process Tech, Delft, NETHERLANDS.
Monolithic structures have a large potential in Heterogeneous Catalysis. In fact, the development of automotive converters has been one of the major successes of the chemical engineering and catalysis community. In the chemical industry they are not used to the same extent, in particular in multi-phase processes they are essentially absent.
Recently, the interest in these structures has increased. On the one hand the morphological aspects have been studied and engineering results have been obtained, enabling practical applications of these structures in industry. On the other hand, new materials have been successfully used as basis for structured reactors. An example is carbon supported Pt deposited on a cordierite monolith.
In the lecture the essentials of monolithic reactors in comparison with the conventional ones will be discussed. Synthesis methods will be highlighted and it will be attempted to summarize future trends.
10:30 AM *FF1.2
A NEW GENERATION OF CERAMIC FOAMS WITH SMALL PORE SIZE. Kenneth Butcher , Gary Pickrell, Porvair Advanced Materials, Hendersonville, NC.
Ceramic foams made by coating reticulated polyurethane are well known and are manufactured widely for several applications including catalysis. Cell sizes and pore sizes of these structures are generally several hundred microns in size.
A new method of manufacturing ceramic foams creates cell sizes of less than 100 microns with interconnecting pores in the 10 to 30 micron range. Low densities and high strenghts have been achieved.
This paper will review the structure and properties of these foams with special emphasis on potentials for catalytic applications.
11:00 AM FF1.3
HIGH SURFACE AREA RETICULATED CERAMICS FOR CATALYTIC APPLICATIONS. Truett B. Sweeting , Douglas L. Karst and David A. Norris, Vesuvius Hi-Tech Ceramics, Alfred, NY.
A high surface area reticulated (foam) ceramic has been developed that shows increased surface area while maintaining most of the strength of the original reticulated ceramic structure. This paper will discuss this modified microstructure which also enhances washcoat adhesion and allows more coating to be applied without spalling. Pore size distribution, volume percent porosity, BET surface area, and strength measurements are compared for different processing techniques against standard reticulates. Reticulated ceramics are expected to improve upon the efficiency of several catalytic reactions due to their high heat and high mass transfer as compared to other substrate structures. Catalytic steam reforming of methane, the oxidation of ethylene to ethylene oxide, methanol synthesis, and the oxidation of methanol to formaldehyde are some specific reactions that may benefit from the use of high surface area reticulated ceramics.
11:15 AM FF1.4
RETICULATED CERAMIC COATED WITH ZEOLITE. Herbert Giesche , NYSCC at Alfred University, Ceramic Eng and Material Science, Alfred, NY.
Reticulated ceramics have a wide variety of applications. The present study will show the possibility to coat these structures with zeolites. Physical characterization of the surface area and pore structure will be shown. The zeolite can be further doped with various metals in order to modify the acidity or catalytic activity.
11:30 AM FF1.5
ELECTROCHEMICAL TESTING AND STRUCTURAL CHARACTERISATION OF NICKEL BASED CATALYTIC COATINGS PRODUCED BY DIRECT SPRAYING. Stephen M.A. Sillitto , Nicholas J. E. Adkins, Ceram Research, Stoke-On-Trent, UNITED KINGDOM; David R. Hodgson, Eric Paul, ICI Chemicals and Polymers Limited, Runcorn, UNITED KINGDOM; R. Mark Ormerod, Keele University, UNITED KINGDOM.
The electrolysis of brine to chlorine, sodium hydroxide and hydrogen is the world's largest electrolytic industry. Energy requirements of the process are currently 4 107
MWh of electricity world wide. This high energy demand is due mainly to the scale of the process, with some 40 million tonnes of chlorine being produced each year. Nevertheless, inefficiencies in converting the electrolyte to products consumes a significant amount of power because of the 10 extra voltage that is required to drive the reaction in the preferred direction. Coating the electrode with a catalyst can reduce this extra voltage.
In this paper a novel processing technique has been used to produce a range of nickel based electrocatalytic coatings with low overpotentials. These coatings include pure nickel as well as Raney nickel alloys, with particular focus upon the beneficial effects of molybdenum additions to Raney nickel. characterisation of all coatings has been carried out using X-ray diffraction for quantitative phase identification, backed up by optical and electron microscopy for analysis of phase distribution. Measurement of the coatings' electrochemical properties has been performed in fully functioning micro-pilot scale electrolysis cells.
This project is jointly funded by the DTI and the EPSRC through the PTP scheme.
1:30 PM *FF2.1
SESSION FF2: CATALYTIC COMBUSTION
Chairs: Peter W. Lednor and Jacob Moulijn
Monday Afternoon, November 30, 1998
Hampton A/B (S)
CATALYTIC COMBUSTION TECHNOLOGY DEVELOPMENT FOR GAS TURBINE ENGINE APPLICATIONS. Lance L. Smith, Hasan Karim, Marco Castaldi, Shah Etemad, George Muench, Samuel Boorse, Paul Menacherry, William C. Pfefferle, and Robert N. Carter , Precision Combustion, Inc., New Haven, CT.
Catalytic combustion is one means of meeting increasingly strict emissions requirements for ground-based gas turbine engines for power generation. In conventional homogeneous combustion, high flame temperatures and incomplete combustion lead to emissions of oxides of nitrogen (NOx), carbon monoxide (CO), and unburned hydrocarbons (UHC). However, catalyst-assisted reaction upstream of a lean premixed homogeneous combustion zone can increase the fuel/air mixture reactivity sufficiently to provide low CO/UHC emissions. Additionally, catalytic combustion extends the lean limit of combustion, thereby minimizing NOx formation by lowering the adiabatic flame temperature. An overview of this technology is presented including discussion of the many materials science and catalyst challenges that catalytic combustion poses ranging from the need for high temperature materials to catalyst performance and endurance. Results of ongoing development efforts at Precision Combustion, Inc. (PCI) are presented including modeling studies and experimental results from both bench-scale and combustor-scale studies.
2:00 PM *FF2.2
CATALYTIC COMBUSTION OF METHANE OVER METAL OXIDE CATALYSTS. Koichi Eguchi Department of Molecular and Material Sciences, Graduate School of Engineering Sciences, Kyushu University Kasuga, Fukuoka, JAPAN.
Catalytic combustion of methane has been investigated as a clean and efficient method for the application to gas turbines. As the combustion is operated at high temperatures and high space velocity, the catalyst material used for this purpose should maintain large active surface area in severe operating condition to attain high combustion efficiency. A series of hexaaluminate compounds have been investigated as heat-resistant catalysts which maintain large surface area at high temperatures. The design of the heat resistant microstructure and the active hexaaluminate catalysts has been reported. On the other hand, the ignition of methane at low temperature is also requested for the catalysts to reduce NOx emission. Palladium catalysts were generally employed for the combustion of methane below 1000Åé. A stable activity over a wide conversion and temperature range is one requested property for combustion catalysts, whereas the Pd catalysts are often suffered from the activity degradation at high conversion level due to depletion of oxygen at high temperatures. A large effect of support oxide on the activity of Pd could be observed, especially Pd/SnO2 was very active for oxidation of methane at low temperatures.
2:30 PM FF2.3
CATALYTIC COMBUSTION WITH NANOSTRUCTURED BARIUM HEXAALUMINATE-BASED SYSTEMS. Andrey J. Zarur and Jackie Y. Ying. Massachusetts Institute of Technology, Dept. of Chemical Engineering, Cambridge, MA.
Catalytic combustion of methane has been widely studied as an alternative to gas phase homogeneous combustion. It allows combustion to occur at high levels of excess air, leading to more complete reaction and reduced hydrocarbon emissions. Furthermore, it enables combustion to proceed at lower temperatures, significantly reducing the NOx
production. Traditionally, noble metal systems, such as platinum and palladium, have been used as combustion catalysts. However, noble metal clusters tend to sinter or vaporize at the high combustion temperatures of >1000 C. Our research objective is to develop complex metal oxide systems that offer superior thermal resistance and high catalytic activity simultaneously. To achieve this, we have successfully synthesized nanocrystalline barium hexaaluminate (BHA) materials using a novel reverse micelle-mediated sol-gel technique. In this novel approach, a nanoemulsion is used to effectively confine the hydrolysis and polycondensation reactions to nanometer-sized aqueous domains. The resulting controlled nanostructured morphology and improved chemical uniformity enable nanocrystalline BHA to maintain surface areas in excess of 100 m2
/g even upon extended exposure at 1300 C. We have also significantly improved the low-temperature catalytic activity of BHA through the introduction of transition metal oxide dopants.
2:45 PM FF2.4
AEROGEL-DERIVED BARIUM HEXAALUMINATE COMBUSTION CATALYSTS. Lin-chiuan Yan and Levi T. Thompson , University of Michigan, Dept of Chemical Engineering, Ann Arbor, MI.
High temperature catalytic combustion catalysts are being developed to reduce NOx
emissions produced during conventional flame combustion. Currently available combustion catalysts such as noble metals or perovskites are not suitable to be used in high temperature environments due to sintering problems. Cation-substituted hexaaluminates have been identified as promising candidates for use in high temperature catalytic combustors. Hexaaluminates produced using conventional solid-state reaction methods including the reaction of mixed oxides have relatively low surface areas. In this research sol-gel techniques have been employed to synthesize high surface area cation-substituted hexaaluminates. The xerogel-derived hexaaluminates had higher surface areas and better heat resistance at high temperature than materials synthesized using conventional solid state reaction methods. Properties of the aerogel-derived hexaaluminates were superior to those of both the xerogel and conventionally prepared materials. All of the materials were active for the combustion of methane. The presence of Co and Mn in the lattice decreased the light-off temperature by more than 150C when compared to the unsubstituted Ba-hexaaluminates. There appeared to be an extraordinary increase in the catalytic performance when more than one substitution cation was present in the materials. For example, the Co-Mn substituted Ba-hexaaluminate was more active than either of the corresponding Co or Mn substituted hexaaluminates (identical total cation loadings). Results from temperature programmed reduction and oxidation indicate a strong correlation between the metal oxygen bond strength and the combustion activity. This and other correlations will be discussed.
3:30 PM FF3.1
SESSION FF3: PHOTOCATALYSIS
Chairs: Robert N. Carter and Jacob Moulijn
Monday Afternoon, November 30, 1998
Hampton A/B (S)
PHOTOCATALYSIS USING SEMICONDUCTOR NANOCLUSTERS. J.P. Wilcoxon and T.R. Thurston, Sandia National Labs, Albuquerque, NM.
In addition to their large specific surface areas, nanoclusters often have unusual surface morphologies and bonding arrangements which can them effective catalysts. We first discuss inverse micelle synthesis and surface modification of nanoclusters to produce size selected materials. After purification of the nanoclusters using high pressure liquid chromatography and/or extraction the nanoclusters can be used as catalysts. As an example of photocatalysis we discuss the photo-oxidation of organic pollutants using such nanoclusters as MoS2 and WS2. We have demonstrated that we can vary the redox potentials of these small semiconductors by adjusting their size and studies of the photooxidation of organic molecules have revealed that the rate of oxidation increases with increasing bandgap (i.e. more positive valence band and more negative conduction band potentials). However, since too wide a bandgap doesn't permit enough visible light to be absorbed, we have found the optimum performance for MoS2 occurs for a size of 4.5 nm This material has an absorbance edge of 550 nm, or a bandgap of 2.2 eV (compared to the bulk value of 1.2 eV). Moreover, when combined with TiO2 as a support material we have sucessfully oxidized phenol using only visible light (>450 nm) and d=8 nm MoS2 with an absorbance onset of 700 nm. In this case we are taking advantage of charge carrier transfer between the nanocluster MoS2 and TiO2 powder. It is possible to modify MoS2 nanoclusters by deposition of metals such as Pt and Ru and we will report on their photocatalytic behavior. Because these photocatalysis reactions can be performed with the nanoclusters fully dispersed and stable in solution, chromtography can be used to determine both the intermediate reaction products and the state of the nanocluster during the reaction. We have demonstrated that the MoS2 nanoclusters remain unchanged during the photooxidation by this technique.
3:45 PM FF3.2
PHOTOCATALYTIC REDUCTIONS OF NITRIC OXIDE IN GAS PHASE AND NITRATE ION IN WATER WITH REDUCING AGENTS ON HOLLANDITE-CATALYST. Toshiyuki Mori , Jun Suzuki, Mamoru Watanabe, National Institute for Research in Inorganic Materials, Ibaraki, JAPAN; Kenjiro Fujimoto, Trainee from Science University of Tokyo, Chiba, JAPAN; Yoshio Hasegawa, KAKEN Co.Ltd., Ibaraki, JAPAN.
Photocatalysis is an effective approach in decomposing a variety of environmental pollutants. Nitric oxide (NO) is the origin of ``acidic rain'' to change into the nitrate ion (NO3-
) in rain. NO in gas phase and nitrate ion in water are hazardous chemicals to human. Recently, it was reported that titanium oxide (TiO2
) photocatalyst performed the oxidative decomposition of NO into nitrate. However, the ideal photocatalysis of NO removal would be a reductive decomposition of NO to N2
with high selectivity by photocatalyst. The authors have found an attractive catalytic property under heating conditions with respect to hollandite-type compounds that are characterized by one-dimensional tunnel structure. In this study, the surface activity of the hollandite-type compounds was applied to photocatalysis under UV irradiation. Fine powders of hollandite K2.0
(KGSO) were prepared by sol-gel method. The product was obtained as single-phase at 700C and showed meso-porous characteristics. The photocatalytic reaction in gas phase was performed using a closed gas-circulating system. NO (0.15mmol) and 13
(0.30mmol) as a reducing agent were introduced into this system and irradiated with a 400W mercury lamp. The photocatalysis in water was carried out in batch reaction manner. The catalyst powder was dispersed in an aqueous solution containing NO3-
(10ppm) and CH3
OH (10ppm) as a reducing agent and irradiated with a 400W xenon lamp.
The hollandite catalyst exhibited the reductive decomposition of NO with high selectivity for the formation of N2
in gas phase. Moreover, this catalyst also showed the reductive decomposition of nitrate ion into nitrite ion and N2
in water. Therefore, it is expected that KGSO is a unique photocatalyst, which can realize the photocatalytic reductions of NO in gas phase and NO3-
in water with reducing agents, in comparison with traditional photocatalyst such as TiO2
4:00 PM FF3.3
SYNTHESIS AND CHEMICAL PROPERTIES OF DYE-DOPED MESOPOROUS TRANSITION METAL OXIDES. Itaru Honma and H.S.Zhou, Electrotechnical Laboratory, AIST, Tsukuba, Ibaraki, JAPAN.
The functional inorganic materials with molecular-to-nano size structure has attracted much attention for devices with excellent properties. We present, in this paper, a new synthetic route of self-organization process to produce self-assembled dye molecules doped in mesoporous transition metal oxides. The material provide dye-ceramic nanocomposites, where the dye-molecules such as Porphyrins was doped in mesoporous inorganic materials such as silicate V2O5, WO3, MoO3 and TiO2 frameworks. The hydrophobic Porphyrin molecules were desolved in side C16TMA micelles in H2O solution and hydrolized with a silicate precursor (TEOS) or other metal oxides precursor (NH4VO3, (NH4)3PO4/12WO3/3H20, (NH4)3/PO4/12MoO3/3H2O) to form dye-doped mesoporous materials of transition metal oxides frameworks, where the dye molecules are doped and self-assembled in a nanochannels. The colored product shows amorphous, lamellar and hexagonal mesophase depending on the preparation conditions. Only hydrophobic molecules were doped within C16TMA micelles and self-assembled in the channels. The dye-doped mesoporous thin film structure has been also made through a spin casting method by modified sol-gel processing. The nanostructure, optical absorptrion spectra, electrical conductivities and chemical properties including sensing/catalytic activities of those dye-doped mesoporous inorganic materials are investigated and will be reported.
8:30 AM *FF4.1/CC3.1
SESSION FF4/CC3: JOINT SESSION:
COMBINATORIAL METHODS IN CATALYSIS I
Chairs: Ralph Nielsen and Patricia Watson
Tuesday Morning, December 1, 1998
Hampton A/B (S)
SYNTHESIS AND SCREENING STRATEGIES FOR THE DISCOVERY OF NEW OLEFIN POLYMERIZATION CATALYSTS. Thomas Boussie, Timothy Powers, Howard Turner, Vince Murphy . Symyx Technologies, Santa Clara CA.
The application of combinatorial techniques to the discovery and optimization of olefin polymerization catalysts is an area that promises to be of great importance to the olefin polymerization industry. In this paper, we address the parallel synthesis of ancillary ligands for olefin polymerization catalysts, and the preparation of resultant metal alkyl libraries. In addition, catalyst screening methods and potential encoding strategies will be discussed.
9:00 AM *FF4.2/CC3.2
USING THE METHODS OF COMBINATORIAL CHEMISTRY IN CATALYSIS. Paul J. Fagan , George Li and Elisabeth Hauptman, The Dupont Co., Dept of Biochemical Sciences and Engineering, Experimental Station, Wilmington, DE.
The use or combinatorial chemistry in the initial stages of catalyst discovery wlll be discussed. The development of new ligand synthesis on both solid supports and in solution provides the basis for the production of hundreds to thousands of catalysts. Several examples will illustrate the chemistry and techniques which have aided our catalysis efforts. The screening of these catalysts and the kind of results that can be obtained will be presented.
9:30 AM *FF4.3/CC3.3
SYNTHESIS AND CHARACTERIZATION OF POLYMERS USING COMBINATORIAL TECHNIQUES. Adam L. Safir , Peter Huefner, Ralph Nielsen, Tom Lee, Symyx Technologies, Santa Clara, CA.
While combinatorial synthesis techniques have been adapted to several areas of material science, characterization of polymeric materials formed has been almost exclusively limited to traditional methods. Our focus has been on developing rapid screens for the determination of polymer chemical properties such as molecular weight. We will discuss these techniques and show their application in the characterization of polymer libraries synthesized by Atom Transfer Radical Polymerization (ATRP).
10:30 AM *FF4.4/CC3.4
APPLICATION OF LOW-FREQUENCY QUARTZ RESONATORS TO PARALLEL MONITORING OF POLYMERIZATION REACTIONS IN COMBINATORIAL REACTOR. Leonid Matsiev , James Bennett, Eric McFarland, Symyx Technologies, Santa Clara, CA.
An important step in combinatorial exploration of polymerization catalysts is the determination of catalyst activity and conversion rate. Common laboratory techniques may not be applicable for combinatorial arrays of reactor vessels, so it is important to provide high throughput methods for measurement of polymer concentration and molecular weight during reaction run-time in each vessel.
Both catalyst activity and conversion rate can be estimated by monitoring physical parameters such as viscosity and dielectric constant of the polymer solution in presence of catalyst and monomer. We have found that real-time monitoring of both viscosity and dielectric constant can be provided using just one sensor: low-frequency quartz tuning fork. The viscosity and dielectric constant measurements performed using 32.7 kHz tuning fork for a set of 12 organic solvents gave very good agreement with standard values from CRC. For a set of polystyrene-toluene and hexane-isobutilene solutions at various concentrations and molecular weight, the tuning fork response was quite sensitive to both concentration and MW of polymer below 1M, above 1M the response displays saturation and depends only on concentration.
Low operation frequency of such resonators makes electronics simple and low-cost. These factors make such resonators suitable to be incorporated into a polymerization reactor for real-time monitoring, especially for combinatorial reactors. Using electronics and a PC it is possible to provide about one reading per second of solution parameters from a few hundred reactor vessels simultaneously, which gives valuable information about kinetics of hundreds polymerization reactions in a single experiment. Ethylene polymerization reactions have been monitored in a parallel multi-well reactor using tuning fork resonators. The results indicated that a tuning fork sensor gives a possibility to monitor reaction kinetics including the onset of polyethylene precipitation from the solution.
11:00 AM *FF4.5/CC3.5
DESIGN AND DEVELOPMENT OF NEW ASYMMETRIC CATALYTIC REACTIONS. THE DIVERSITY APPROACH. Marc Snapper , Boston College, Department of Chemistry, Chestnut Hill, MA.
Various approaches for the discovery and development of new C-C bond forming reactions will be presented. The more established mechanism-based approach to reaction discovery will be contrasted to some of the more recently developed diversity-based protocols for identification of novel asymmetric processes.
1:30 PM *FF5.1/CC4.1
SESSION FF5/CC4: JOINT SESSION:
COMBINATORIAL METHODS IN CATALYSIS II
Chairs: Robert C. Haushalter and Tom Lee
Tuesday Afternoon, December 1, 1998
Hampton A/B (S)
HIGH THROUGHPUT SCREENING OF COMBINATORIAL HETEROGENEOUS CATALYST LIBRARIES. Peijun Cong , Robert Doolen, Daniel Giaquinta, Shenheng Guan, Eric McFarland, Kyle Self, Howard Turner, Henry Weinberg, Symyx Technologies, Santa Clara, CA.
The application of combinatorial methodologies to the discovery of new catalysts requires a means of rapidly ascertaining the performance of large number of new materials. To meet this challenge, we have developed a high-throughput heterogeneous catalyst-screening instrument that is capable of measuring the activity and selectivity of a single catalyst in less than one minute. The instrument is equipped with a mass-selective detector and an optical detector, thus offering a wide range of highly sensitive and selective detection schemes for the relevant reactants, products, and side-products. Numerous model catalyst systems have been explored with this instrument, such as metal alloys and metal oxides. The complexity of reactions involved ranges from simple complete combustion to delicate hydrocarbon partial oxidation. In this presentation, we will discuss the main design features of the high-throughput screening instrument. By comparing results from this instrument with those from conventional laboratory-scale micro-reactors, we show the validity of the combinatorial approach to catalyst research. We further demonstrate the power of this new technology by highlighting some of our recent results from discovery libraries.
2:00 PM FF5.2/CC4.2
DETECTION OF CATALYTIC ACTIVITY IN COMBINATORIAL LIBRARIES OF HETEROGENEOUS CATALYSTS. Arnold Holzwarth , Hans-Werner Schmidt, Wilhelm F. Maier, Max-Planck-Institut fuer Kohlenforschung, Muelheim/Ruhr, GERMANY.
Emissivity corrected infrared thermography is applied to display the heat evolution of heterogeneously catalyzed gas phase reactions on combinatorial catalyst libraries with microscopic amounts of catalysts. Catalytic hydrogenation of 1-hexyne at 100C and oxidation of isooctane and of toluene at 350C were chosen as test reactions. Our 37 member model library was based on the sol-gel procedure for the preparation of amorphous microporous mixed oxides (AMM). The individual sols were deposited in microliter amounts corresponding to less than 200 g of final catalyst spots in the small wells on the surface of the library substrate, followed by controlled drying and calcination of the library. To increase the temperature resolution of our thermographic experiments a special correction procedure was applied to account for the differences in emissivity on the library surface. Misinterpretation of emissivity differences on the library surface as temperature differences was thereby prevented and small temperature differences down to 0.1 K due to catalytic activity could easily be identified. Special care was also taken to prevent reflections from the library surface and to reduce the effect of thermal infrared emissions of the reactant gases, since they can cause changes to the infrared image unrelated to catalyst temperature. On the basis of our experiments the application of infrared thermography to high throughput screening for catalytic activities of large materials libraries is now a realistic possibility.
2:15 PM *FF5.3/CC4.3
SELECTION AND TESTING RESULTS OF CATALYTIC MATERIALS - A COMBINATORIAL AND EVOLUTIONARY APPROACH. Manfred Baerns , Olga Buyevskaya, Uwe Rodemerck, Dorit Wolf, Institute for Applied Chemistry Berlin-Adlershof, Berlin, GERMANY.
Various catalytic compounds for selective hydrocarbon oxidation to oxygenates were pre-selected by means of a knowledge-based expert system.