Goetz Veser - US grants

ABSTRACT

PI: Goetz Veser
Institution: University of Pittsburgh
Proposal Number: 0448147

Research:

This CAREER project aims to investigate, control and ultimately steer catalytic reactions through spatial confinement in a microchannel reactor. It is based on the development of a micromachined catalytic reactor system for detailed experimental and numerical investigations of coupled heterogeneous-homogeneous reactions, and specifically comprises the following steps:
Probe and identify contributions from homogeneous and heterogeneous reaction pathways by varying the microchannel diameter to either allow or gradually suppress homogeneous reactions;
Control heterogeneous-homogeneous reactions by quenching, i.e. completely suppressing, potentially explosive gas phase reactions, thus opening up new parameter ranges for exploratory studies of chemical reactions in these 'forbidden regimes';
Steer multiple reaction systems by selectively quenching reaction pathways and thus introduce process selectivity in a new, non-conventional way;
Investigate the reacting flow (and in particular boundary-layer kinetics) via non-invasive, in-situ IR spectroscopy over a wide range of realistic operating conditions.
The approach will be tested with high-temperature catalysis, a class of reactions with broad industrial and environmental impact as well as fundamental scientific significance. However, the developed system will be applicable well beyond these conditions to the study of a range of multiphase reaction systems.

Education:

Major parts of the research project are closely integrated into the education plan, which is based on the introduction of process intensification and microreactor engineering throughout the undergraduate curriculum. It will furthermore use microreactor engineering as an example to introduce students to 'multi-scale thinking' across the many length and time scales that characterize modern engineering problems. The plan will be integrated within a broader educational program for implementation at the University of Pittsburgh and beyond.

Broader Impact:

The project could have a major impact on the development of fuel reformers for hydrogen fuel cells and thus on the development of the 'hydrogen economy' through the successful demonstration of perfectly selective CO oxidation in CO/H2-mixtures (one of the planned test reactions). The detailed investigation of the quenching of explosive reactions in microchannel reactors, and hence the demonstration of intrinsic reactor safety, could have significant impact on the safety of industrial processes and, in particular, on a widespread and decentralized hydrogen distribution system.

Abstract

Proposal Title: Towards Understanding Nanocomposite Materials: Multiscale Tailoring for Thermally Stable and Accessible Nanoparticles

Proposal Number: CTS-0553365

Principal Investigator: Goetz Vesser

Institution: University of Pittsburgh

Analysis (rationale for decision):

This project will advance the fundamental understanding of nanocatalysis by developing a flexible and widely applicable template approach for synthesis that will lead to a systematic investigation of metal/oxide "nanocomposites." The approach is based on a microemulsion-templated synthesis and will involve the hierarchical multiscale tailoring of the characteristic dimensions of these materials across all length scales involved in a catalytic reaction. Specifically, the project comprises the synthesis of alumina- and silica-based nanocomposites which incorporate a wide range of metal nanoparticles; the investigation of the formation of the ceramic and metal nanoparticles and their interaction during nucleation and growth; and the reactive characterization of these materials at realistic reaction conditions for several energy-related high-temperature catalytic reactions.
The intellectual merit of the work is based on the fundamental challenge posed by the multiscale nature of catalytic reactions. The research will contribute a detailed understanding of how catalyst structures interact across different length scales. It will emphasize the crucial role of catalyst stability and transport inside nanostructured catalysts, rather than aiming mainly at activity and selectivity as targets for the catalyst development. Finally, the project will demonstrate a flexible and widely applicable multiscale approach towards an increased control over composition, structure, and function of nanocomposite catalytic materials.
The broader impact of the research will address the improved technological costs and catalyst stability, which are among the main limiting factors in the development of state-of-the-art fuel processors. The successful demonstration of highly active and stable nanocomposite catalysts for these environments will therefore have significant impact on future energy technology, including the possible realization of a "hydrogen economy". The project will feature an intensified participation of undergraduate students in research. Local high school students will also be involved in the research program, which will provide a basis for a new department-wide outreach effort.

Intellectual Merit: Periodically operated fixed-bed reactors are an emerging type of catalytic reactors with increasing application in energy and environmental applications. The present project aims to demonstrate the application of chemical looping, an emerging combustion technology, to the partial oxidation of methane to synthesis gas in a periodically operated fixed-bed reactor configuration. The resulting process has significant practical advantages (alleviating safety concerns in methane partial oxidation by avoiding direct contact between methane and oxygen, and allowing direct utilization of air without diluting the syngas with nitrogen), and will at the same time allow the investigation of the dynamics of coupled endothermal/exothermal gas-solid reactions in periodic fixed-bed reactors. The project team will furthermore extend the chemical looping principle onto a fully multifunctional reactor design by integrating desulfurization of the product stream, resulting in a strongly intensified, highly scalable, and efficient syngas process.

The approach builds on a combination of materials synthesis, reactor design and experimentation, and reactor modeling, and involves specifically the following steps:

- Design and construction of a fixed-bed reactor with high-resolution in-situ measurement of kinetics and spatio-temporal reactor dynamics;
- Synthesis, characterization, and evaluation of high-performance nanostructured materials as oxygen carriers and partial oxidation catalysts;
- Detailed reactor experimentation, including evaluation of key reactor operating parameters (co- and counter-current flow pattern, periodicity, etc.) on reactor dynamics and process efficiency;
- Integration of S-capture and separation, and
- Reactor modeling and detailed reactor simulation.

Overall, the main objectives of this research are (1) to advance our understanding of the dynamics of periodically operated fixed-bed reactors with heat-integration (specifically for gas-solid reactions) through a combination of experiments and reactor modeling; (2) to demonstrate the great potential of chemical looping (CL) beyond combustion (including integrated contaminant separation) and further establish the advantages of fixed-bed CL processes; and (3) to highlight the exciting possibilities of state-of-the-art nanomaterials as ?enablers? for advanced reactor engineering concepts .

The project will advance our knowledge and current understanding of periodically operated of fixed-bed reactors, specifically for gas-solid reactions, an area with importance well beyond chemical looping. It will furthermore highlight the enabling role that emerging nanomaterials can play in the realization of advanced reactor concepts. Finally, it will help to further establish and broaden ?chemical looping? applications by demonstrating the simultaneous use of chemical looping for a partial oxidation reaction combined with contaminants removal, and, through thorough experimental and model based analysis, lay the groundwork for extending the concept onto a broad range of new applications.

Broader Impact: Demonstration of a novel, compact, efficient, and safe reactor concept for natural gas utilization could have broad impact at a time where proven domestic gas reserves in the US are seeing explosive growth. Furthermore, this technology could enable the use of small-scale distributed sources, such as landfill gas and agricultural waste gas, resulting in tangible environmental benefits. The project will contribute to the education of graduate and undergraduate students, and involve outreach to high school students from underrepresented groups. Finally, active distribution of the developed methodologies and tools through collaborations, publications and conference contributions will help to foster partnerships and make the advances available to the scientific community at large.

Catalysts are used in the manufacturing of more than 60% of all synthesized chemicals and more than 90% of chemical industries use catalytic materials world-wide, with an estimated combined impact on the global economy of over $10 trillion per year. Furthermore, catalysis is essential to chemistry where reactants are efficiently converted to products while minimizing the production of by-products that are environmentally harmful. Yet, technological advancements in catalysis have frequently depended more on chemical intuition than fundamentals. The recent emergence of ?nano-characterization tools? has fundamentally changed this and is allowing the discovery of fundamental principles of catalysis via detailed characterization of catalysts and its correlation with their chemical reactivity.

In a collaborative program between the University of Pittsburgh, SUNY Binghamton, and Brookhaven National Laboratory, PIs Judith Yang, Goetz Veser and Guangwen Zhou will use state-of-the-art characterization tools including environmental transmission electron microscopy, in situ scanning tunneling microscopy, and X-ray photoelectron spectroscopy, complemented with reactivity studies using a specially designed spatially resolved microreactor in order to gain essential insights into catalytic structure-reactivity relationships. The PIs will focus on copper-containing catalysts, a class of catalysts with importance for existing and emerging energy technologies, such as partial oxidation of methanol and the water-gas-shift reaction. Experiments will be performed on simple model systems including Cu single crystals and Cu oxides produced by controlled oxidation of Cu surfaces in-situ. Correlations between the phases and surface and interface structure of Cu-based catalysts and their catalytic activity will be identified. The results will be compared with commercially available Cu/ZnO catalysts to provide a commercial base-line for these fundamental studies.

An important global topic such as energy production requires not only advances in scientific research, but trained people to aid in the transfer of these advances into industrial practice. The partnership between two major universities and a national laboratory will enrich the education of the students involved in this program. Graduate students will be trained in materials physics/chemistry and catalysis science and will learn about new microscopy, spectroscopy, kinetics and modeling techniques as well as materials issues that are at the forefront of current energy research. The training of graduate students in the broader area of clean energy technology, as well a fundamental scientific discipline (e.g., catalytic kinetics, materials science, physics, etc.), will result in future leaders that are better equipped to solve the complex energy and environmental problems that face society. Results from this project will also be incorporated into new graduate-level courses and high school outreach programs at both Universities.

CBET 1236258
The present project aims to advance the current understanding of nanomaterials toxicity with a specific focus on size-dependent toxicity of metal nanoparticles (NPs) in the "non-scalable regime" (1 nm - 10 nm). The approach is based on the combination of the synthesis of finely controlled and well-characterized metal nanoparticles, with the use of zebrafish models for fast toxicological screening and mechanistic studies It builds onto the expertise of an engineer who is an expert on nanomaterials synthesis, characterization, and application, combined with that of a medical researcher who is an expert on zebrafish models of human disease. The proposed work exploits a number of unique reagents and facilities, including the University of Pittsburgh's zebrafish facility, one of the largest in the world. The proposed approach will be applied to three metals with broad relevance in nanomaterials application in consumer products and industrial processes (Ag, Fe, and Ni), and comprises specifically the following steps:
- Size-controlled synthesis of metal nanoparticles with dimensions in the 1 - 10 nm range (plus controls in the size range of 30 - 100 nm), and careful and extensive characterization of these materials prior to toxicological studies.
-Identification of size- and dose- dependent toxicity of these engineered NPs via zebrafish studies.
- Mechanistic studies of organ-specific toxicity to identify target organs in comparison to the respective free metal salt and as function of particle size.
- Finally, investigation of the impact of porous silica coatings on the toxicity of metal nanoparticles as a potential means to mitigate NP toxicity without impacting accessibility and hence functionality of the engineered NPs.
Overall, the proposed approach aims to develop methodology for fast and reliable screening of nanoparticle toxicity, improve understanding of nanotoxicity in the "non-scalable" size regime (<10 nm), and demonstrate an approach towards mitigating nanoparticle toxicity via porous coatings.

Intellectual Merit The project directly addresses the fundamental challenge posed by the multidisciplinary nature of nanotoxicological studies. By focusing on two aspects of scientific significance as well as great practical importance: the systematic study of size-dependent nanotoxicity in the "non-scalable" regime, which has been largely neglected to-date, and the study of porous coatings as a means towards mitigating the toxicity of metal nanoparticles, it aims to enable significant advances towards a better fundamental understanding of the toxicity of metals at the nanoscale. The project will furthermore establish zebrafish studies as a fast and robust screening tool for nanotoxicological studies. By using transgenic zebrafish lines expressing reporter genes under tissue specific promoters, rapid evaluation of potential target organs for (size-specific) NP toxicity will be possible for the first time. This will enable establishing whether nanomaterials are subject to size-dependent fundamental changes in toxicity and target pathways, similar to the well-established fundamental changes in chemical reactivity for metal NPs in the sub-10 nm range.

Broader Impact Demonstration of fast and reliable screening tools for nanotoxicity and development of an improved fundamental understanding of the toxicity of materials in the nanoscale regime could have profound impact on the development and implementation of safe "nano-enabled" consumer products. Fast and cost-efficient screening would pave the way towards robust and responsible implementation of NPs in nanomaterials-based consumer and industrial products, further accelerating the market penetration of these materials with potentially huge impact on quality of life. An improved understanding of the basic principles of nanotoxicity would furthermore help to (pre-emptively) guide the design of novel nanomaterials with safety built into their design. Finally, such an understanding could yield reliable guidelines for legislative action on nanomaterials.

The scientific field of computational chemistry uses computer simulations to calculate the structures, properties, as well as, reactions of molecules and materials. These simulations can be envisioned as virtual experiments that generate rich information about the materials behavior with a great level of accuracy. Elucidating the mathematical functions that describe how the materials properties depend on their structural characteristics allows us to design optimal materials for targeted applications (structures that maximize a desired property). This methodology significantly reduces the need to perform numerous, time-consuming, and costly experiments in the lab, which are often based on extensive trial and error. This Design of Engineering Material Systems (DEMS) award supports fundamental research to design nanoparticles that consist of two different metals and are able to capture carbon dioxide, a molecule contributing to the greenhouse effect. The predictions from the computational research will be validated with targeted experiments in the lab. Since metal nanoparticles find a wide range of applications, it is expected that results from this research will affect the U.S. economy, society and the environment. A website will be developed to allow free access to a library of simulated structures. The multidisciplinary nature of this research, involving computational chemistry, materials design, optimization, scientific computation, materials synthesis and catalysis, will help broaden engineering education and attract underrepresented students to research. In addition, animation modules will be generated for incorporation in high school classes.

This project creatively integrates first-principles calculations with rigorous engineering design methods, in order to develop a systematic framework to optimize nanoparticles in light of a performance metric (demonstrated via carbon dioxide adsorption), while also taking into account nanoparticle stability aspects. A novel design of experiments approach, tailored to the intricacies of this specific materials class, will be developed, while the computational predictions will be validated experimentally through targeted nanoparticle synthesis, characterization, and carbon dioxide adsorption experiments. Developing the capability to computationally identify nanoparticles that maximize their performance for a given application in a multi-dimensional composition-morphology space is crucial to guide future research efforts and accelerate nanomaterials discovery. However, efforts to-date have been focused entirely on one-dimensional optimizations (almost exclusively focused on metal composition). The present project will demonstrate the first strategy that truly explores the vast parameter space and hence enables true design of functional nanoparticles. In addition, this research advances the state-of-the-art in the study of bimetallic nanoparticles by developing structure-property relationships that will be applicable to any nanoparticle morphology. Finally, this project advances environmental science by designing bimetallic nanostructures for capturing and activating carbon dioxide, a key greenhouse gas.