Scott M. Auerbach, Ph.D. - US grants

In this project in the Physical Chemistry Program of the Chemistry Division, Scott Auerbach of the Department of Chemistry of the University of Massachusetts-Amherst will model the microscopic dynamical processes that control hydrocarbon mobility and reactivity in X- and Y-zeolites. Specifically benzene hopping, diffusion and reorientation rates will be calculated for different substituted zeolites. The proton transfer rates between the oxygens and adsorbed butene in acidic zeolites will be simulated. The proton dynamics calculations will help understanding the mechanism of formation of hydrocarbons, which may suggest ways to improve the performance of these materials. The aim is to develop better understanding for the fundamental processes involved in the production of hydrocarbons in zeolites. This is of importance in the production of hydrocarbons from non-traditional sources.

CTS-9734153 Auerbach Most environmentally friendly technologies rely on separations that remove pollutants from benign materials. Zeolite molecular sieves, consisting of regularly spaced, molecular-sized cages shown below, are ideally suited for these separations. Although much is known about zeolites, no simple theory exists for accurately predicting how molecules diffuse through them. This is because of the difficulty in modeling infrequent event dynamics coupled with strong adsorbate-adsorbate interactions. Furthermore, zeolites are ignored by the single most important class in physical science: freshman chemistry. To address these issues, the Principal Investigator will develop novel educational techniques and molecular transport theories aimed at accelerating material and process screening of emerging chemical technologies. The mobility of many hydrocarbons in industrially important zeolites is exceedingly sluggish, precluding the use of straightforward molecular dynamics simulations, and hence requiring modeling techniques specialized for infrequent events. Previous transition state simulations of diffusion in zeolites were performed at low loadings, so that adsorbate-adsorbate interactions could be neglected. These conditions are irrelevant to industrial processes, which are carried out at essentially full hydrocarbon loading. To model transport in zeolites under industrial conditions, the Principal Investigator will develop a hierarchy of three new techniques with varying accuracy and speed. An accelerated molecular dynamics algorithm that adds a novel boost potential for reducing site-to-site activation energies will predict essentially exact diffusivities provided that the boost avoids transition states. A lattice Monte Carlo simulation will be developed that includes a new treatment of activation energies modified by adsorbate-adsorbate interactions. Finally, a completely analytical theory will be derived that synthesizes for the first time fluctua ting activation energies with the mean field theory of fluids. This new hierarchy provides the opportunity of choosing a model based on the need for speed or accuracy in process optimization. These models will be incorporated into a freshman chemistry module entitled: "Zeolites in Industry," involving new Web-based, interactive software that mimics the physical and chemical properties of these systems. This research will impact science and society on many levels. First, incorporating zeolite science and technology into freshman chemistry will excite and inform thousands of students about real-world benefits of industrial chemistry and engineering. Second, this novel combination of chemical reaction dynamics and mean field theory will yield the first truly molecular theory for transport in zeolites, elucidating how the competition between host-guest and guest-guest interactions controls these transport processes. This will guide and complement new diffusion measurements, and will accelerate screening of new chemical processes. Third, when applied to aromatic separations and hydrofluorocarbon separations in large-pore zeolites, these calculations will help guide scientists and engineers in choosing optimal zeolite Si:Al ratios, zeolite channel structures, temperatures and pressures for carrying out efficient and cost-effective separations.

EIA-9977540
Weinberg, Martin D.
Auerbach, Scott M.
University of Massachusetts Amherst

MRI: Acquisition of a High-Performance Parallel Computer to Support an Interdisciplinary Computational Science Center for Physical Science, Mathematics and Engineering

This is a proposal to construct a high-performance computing platform to enhance the state of scientific computing at the University of Massachusetts-Amherst. The computing platform will consist of 48 Pentium II processors. The purpose of this parallel computing platform is to: (i) facilitate the research of faculty members whose work involves computational simulation or massive data processing, (ii) encourage collaboration among faculty located in diverse departments and schools, (iii) provide a medium where new compiler technology and parallel processing research in the Computer Science Department can be tested and incorporated into state-of-the-art scientific applications, (iv) provide a testbed for new parallel algorithms and approaches and (v) allow graduate students quick access to parallel processing capabilities for use in classes or directly in research.

Abstract
CTS-0103010
P. Monson, U of Massachusetts Amherst

This proposal was submitted in response to solicitation "Nanoscale Science and Engineering (NSF 00-119)" and requests support for an interdisciplinary research program concerned with understanding the growth of nanoporous materials- focusing on zeolitic materials. A research program in this area will have immediate impact on an enormous worldwide effort for developing porous materials with properties tailored at the nanoscale for applications such as catalysis or separations. Moreover, a central feature in the growth of such materials is the assembly of supramolecular precursor particles to form complex organic-inorganic structures with crystalline order. This mechanism is paradigmatic for the synthesis of a whole range of new materials, ranging from substrates for quantum confinement and laser applications to biomaterial implants with controlled porosity and nanostructure.


The proposal has its origin in a collaboration among some of the PI's on the problem of crystal growth of silicalitc-1 zeolite, in which important features of a growth mechanism involving the formation and assembly of subcolloidal zeolite particles were elucidated. The collaboration featured both experimental work and modeling of the growth process. As this work developed it became clear that further progress would be greatly enhanced with a larger research team. In particular, it was clear that expertise was required in detailed atomistic modeling of the growth process as well as in characterization by light scattering and atomic force microscopy. The NSF NIRT initiative has created an opportunity for this research team to come to full fruition. Our interdisciplinary team involves researchers in four departments at the Universities of Massachusetts and Delaware, partnerships with companies at the forefront of applications of nanoporous materials and collaboration with a government laboratory.

The project is divided into two main research areas:

Synthesis, Purification and Structure of Subcolloidal Particles:

Assembly of Subcolloidal Particles and Silicalite Crystal Growth

In addition to elucidating fundamental aspects of zeolite growth, we anticipate that in the longer term our research will lead to novel assembly methods and the development of new materials grown by assembly of subcolloidal zeolite particles. Each of our research areas will feature both experimental and modeling investigations. A spectrum of modeling techniques will be employed spanning length scales from the atomistic level, required to understand the formation and structure of subcolloidal zeolite particles, to the mesoscopic level, required to understand the crystal growth habit of zeolite materials.

The research program has substantial educational component including: the development of new graduate courses on nanoscale materials and on computational materials science at both partner Universities, industrial internships for graduate students and postdoctoral scholars, as well as involvement of undergraduate students in the research.

This proposal was received in response to the Nanoscale Science and Engineering initiative, NSF 02-148, category NIRT.

Recent advances in microwave synthesis that promise to revolutionize the time required to fabricate catalysts at the nanoscale. Zeolites, mixed metal oxides and mesoporous molecular sieves typically can require extended synthesis times because of slow nucleation and growth of ordered structures. This project promises to greatly reduce the time required for preparing an array of materials, and it will also fundamentally advance our understanding of nanoporous crystalline materials synthesis. A multidisciplinary team having an excellent track record in the proposed area of research, will address synthesis, characterization and theoretical aspects of catalysis by these materials. Graduate students will clearly benefit from the interdiscplinary environment, and there will be strong participation in the on-going Northeast Alliance REU program involving minority students. The research program will forge ties with industry also.

Proposal Title: Predictive Multi-Scale Modeling of Base Catalysis in Functionalized Zeolites
Proposal Number: CTS-0553577
Principal Investigator: Scott M Auerbach
Institution: University of Massachusetts Amherst


The coming paradigm shift from fossil fuels to biofuels - those derived from renewable biomass - requires significant research into new catalysts that selectively transform biomass to biofuels. Efficient biorefining requires shape-selective catalysts with strong basic sites, because of the significant oxygen content in biomass. Although standard zeolites contain weak base sites, functionalized zeolites offer strong base sites by replacing zeolite oxygens with bridging amine (NH) groups. Initial calculations conducted in the principal investigator's group suggest that base-catalyzed reactions are faster by a factor of 100,000 at room temperature by substituting amine groups into zeolites. As interest in amine-substituted zeolites continues to grow, several fundamental questions remain, which can be addressed by molecular modeling: What is the maximum basicity attainable by amine-substituted zeolites? How is catalytic activity in these functionalized zeolites influenced by ion exchange? This project will assess the relative base strengths of several zeolites (various frameworks and compositions) with and without amine substitution, by computing adsorption energies of various Lewis-acid guest molecules. Quantum chemical energy calculations will be performed on embedded clusters in collaboration with scientists at Gaussian, Inc. The research will establish convergence of these energy calculations by comparing 2-layer and 3-layer embeddings with fully periodic quantum calculations.


The calculations conducted in this research project will provide performance estimates for a burgeoning class of new catalysts: amine-substituted zeolites. This will assist zeolite chemists in the design and fabrication of advanced catalysts for biorefining applications. The collaboration with experimentalist C. Grey will help validate the theoretical predictions, and the collaboration with Gaussian, Inc. will lead to benchmarked software for the entire catalysis community to use for modeling reactions in zeolites. The research will be disseminated widely, especially through high school lectures entitled "High Octane Computing." Undergraduates and graduate students will be recruited from under-represented groups through two NSF-funded University of Massachusetts organizations: the Louis Stokes Alliances for Minority Participation, and the Northeast Alliance for Graduate Education. The broadest technical impact of this research translates to energy: shape-selective basic zeolites are important for catalyzing the future of biofuels.

Sankaran Thayumanavan, Scott Auerbach, Jeanne Hardy and Dhandapani Venkataraman of the University of Massachusetts Amherst and Mark Johnson of Yale University are supported by an award from the Chemical Bonding Centers (CBC) Phase I program to carry out research addressing several fundamental aspects of proton transport, the molecular level process which underlies a number of important biological phenomena as well as the functioning of a central component in fuel cells. Proton transfer is a key aspect of a broad array of chemical problems, including acid-base reactions, energy storage and utilization, and catalysis. The center is focusing its investigation of the chemistry of proton conduction via site-to-site jumps and well-defined scaffolds. The main objectives are to (i) identify optimal functional groups and the underlying dynamics of facile proton transfer; and (ii) fabricate ideal scaffolds that produce stable and rapid proton conduction.

An important application area of this research is the design of better membranes for fuel cells. In keeping with this goal, the CBC will create a web-based entity, the National Chemical Energy Research Network, NCERN, that will (i) act as a dynamic interface among energy researchers and research centers; and (ii) foster better communication between chemists working on energy-related research and the general public. NCERN will facilitate the creation of wiki pages and will moderate interactive chats on these subjects. The center is having a broad impact both through the activities of NCERN as well as through its function as an interdisciplinary training center for graduate students and postdoctorals.

Abstract

PI Name: George Huber
Institution: University of Massachusetts Amherst
Proposal Number: 0937895

EFRI-HyBi Green Aromatics by Catalytic Fast Pyrolysis of Lignocellulosic Biomass


This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)

Intellectual Merit
Cellulosic biomass has tremendous potential as a feedstock to produce liquid fuels due to its low cost, sustainable production and abundance. The PIs have recently developed a new process, called catalytic fast pyrolysis (CFP), to convert solid biomass directly into gasoline range aromatics. The advantages of CFP include short residence times (2-10 s), reaction that occurs in one single step, inexpensive catalysts, and fuel products that already fit into existing infrastructure. The objective of this project is to investigate the underlying physical and chemical mechanisms that control the CFP of biomass to fuels. CFP involves the direct conversion of solid biomass into gasoline-range aromatic compounds in a fluidized bed reactor. This complex process involves thermal decomposition of the biomass particles, transport of the resulting gaseous species and reactions in the gas phase surrounding the particles, and transport and reactions of the pyrolysis products inside the zeolite catalyst particles to yield gasoline-range aromatic compounds. The complexity of the process requires an interdisciplinary approach that will enable a better understanding of the underlying physical and chemical phenomena and lead to the development of accurate multi-scale reaction-transport models that can be used to guide reactor design, scale up, and optimization. The PIs have assembled a multi-disciplinary research team that includes experts on catalysis, reaction engineering, theoretical chemistry, fluid mechanics, gas-particle flows, heat transfer, cogeneration, and transport phenomena, aiming to understand the fundamental mechanisms underlying the CFP of biomass to fuels. They will also develop a cogeneration strategy that integrates a CFP process with a power cycle for maximum utilization of the energy content of the biomass feedstock. They propose a combination of kinetic and hydrodynamic experiments that will enable validation of multi-scale reaction-transport models. These models will accurately represent microscopic interactions occurring in the pores of catalyst particles and couple them to reactor-level descriptions of momentum, energy, and mass transport. The ultimate objective is to develop more efficient catalysts and design new reactors for CFP of solid biomass to fuels and cogeneration of electricity. The researchers in the team have a broad range of complementary research expertise to effectively address the challenges posed by the complexity of the proposed project.

Broader Impacts
The proposed program integrates research on biofuels with an educational and outreach component that are designed to demonstrate the importance of engineering in the area of biofuels and renewable energy. While it is generally accepted that biology and biotechnology are vitally important for biofuels production, it is less well known that catalysis and reaction engineering are equally important. The PIs? research on biofuels has received significant media attention and provides an opportunity to educate the public on the topic and excite interest in high school students to pursue careers in science and engineering. They plan to host in their laboratories underprivileged students from Springfield, MA, area high schools and collaborate with science teachers to develop teaching modules on sustainable energy. They also plan to recruit, mentor and support minority graduate students by collaborating with the Northeast Alliance for Graduate Education and the Professoriate (NEAGEP) at UMass, which supports efforts to recruit and mentor doctoral students from population groups that are underrepresented in science, technology, engineering, and mathematics (STEM) fields.

0932777
Auerbach

Intellectual Merit:
Objectives: The PI will continue developing and applying methods of theoretical chemistry to assist in the design of zeolites as biofuel and bioproduct catalysts. In previous work, he has modeled the spectroscopic signatures and formation/stability kinetics of nitrogen-containing zeolites X/Y/ZSM5 - i.e., zeolites with some bridging oxygens replaced with bridging amine (-NH-) groups - which show promise as shape-selective base catalysts for biofuel production. In this work he will continue study of nitrogen-containing zeolites by directly modeling size- and shape-selectivity of aldol condensation (a carbon-carbon bond forming reaction) in both acidic and basic zeolites X/Y/ZSM5, to identify how zeolite chemistry impacts catalyst selectivity and activity. In a new direction, he will perform cutting-edge modeling to investigate size- and shape-selective adsorption in these zeolites under the high-temperature conditions of catalytic fast-pyrolysis (CFP), a process that Huber has shown converts cellulose directly into biofuels. He will quantify thermal distortions of the sizes and shapes of zeolite pores, and how such distortions impact adsorption and diffusion of relevant biofeeds and biofuels.

Approaches: (i) Aldol Condensation: The PI will model the aldol condensation of furfural (C5) and acetone (C3) to the C8 product (so-called "monomer"). He will also model an additional condensation of C8 monomer and furfural to a C13 "dimer" product. Such reactions are promising routes for upgrading biomass-derived feeds into gasoline-range fuels. He will learn how to tune the monomer/dimer selectivity by computing the reaction pathways in medium-pore (ZSM5) and large-pore (X/Y) zeolites. He will learn how to tune activities by modeling these reactions in both acidic and basic versions of these zeolites. Electronic energies will be computed using embedded cluster (QM/MM) techniques; complex reaction pathways will be discovered using the "climbing image nudged-elastic band" method, which he has recently implemented in an efficient way with the Gaussian computational chemistry program.
(ii) High-temp Adsorption: The PI will perform periodic electronic structure calculations with various unit cell sizes to parameterize a new forcefield that reproduces zeolite thermal expansion. Using this new forcefield, he will perform statistically rigorous constant-pressure simulations to determine how zeolite distortions may accommodate the adsorption of relatively large molecules such as glucose and levoglucosan, and the formation of relatively large species such as naphthalene, during CFP.

Scientific Impacts: The PI's computational studies of aldol condensation will shed light on how to exploit the shape-selective properties of zeolite catalysts to produce biofuels of desired lengths. His work will directly impact, and will benefit from, collaboration with the Huber group at UMass (see support letter), which is experimentally studying these same reactions. His modeling of high-temperature adsorption will help to explain whether CFP products such as naphthalene are formed inside or outside of zeolites, providing the insights necessary to further improve and optimize CFP. This project will directly impact, and benefit from, our collaboration with the Grey group at SUNY Stony Brook (see support letter), which is using X-rays to measure zeolite expansion.

Broader Impacts:
The PI will continue to recruit under-represented students to this program, exploiting existing NSF-funded REU and NEAGAP programs at UMass. He will continue to collaborate with the Center for Talented Youth to engage in middle-school outreach using Biofuels as the hook for young minds. The PI will deliver an undergraduate course on Renewable Energy in Fall 2009, in which Biofuels will play a prominent role. In parallel, the PI is leading a committee at UMass to develop a new interdisciplinary concentration (like a minor) on Renewable Energy. This proposal will support undergraduate research as a capstone experience of the Renewable Energy concentration.

1033179
Ford

This project provides funding for the purchase of a 32-processor, 192-core computer cluster for research in molecular and materials modeling in the Chemical Engineering Department at the University of Massachusett, Amherst.

Intellectual Merit: This computing facility allows the study of large model systems across multiple length and time scales, as well as systematic parametric analyses using a range of modeling techniques including molecular computer simulation and quantum chemistry. The equipment will serve the computation needs of at least seven research projects in the groups of five faculty members. David Ford's group will use the cluster for classical density functional theory calculations on solid-fluid equilibrium and also for stochastic modeling of colloidal self-assembly processes. Peter Monson's group will use the new facilities for research projects on the dynamics of fluids confined in porous materials. Dimitrios Maroudas' group will use the equipment for their research on multiscale modeling related to the surface engineering of metals and semiconductors and plasma processing of carbon nanostructures. Furthermore, several collaborative projects across the groups will be supported. T.J. (Lakis) Mountziaris works with Maroudas on modeling the doping and synthesis of core/shell semiconductor nanocrystals, while Scott Auerbach works with Monson to model the self-assembly of ordered nanoporous materials, specifically zeolites.

Broader Impact: A commonality among the research projects to be supported by the new computing facilities is fundamental research in molecular and materials modeling in areas where there is a close connection with practical application. As an example, the development of new types of porous materials with properties tailored for specific applications is a major area of research throughout the world. Understanding of how the collective behavior of adsorbed
molecules is influenced by the microstructure of the porous material can contribute significantly in this effort. The investigators have reached the point where adsorption experiments can be accompanied by a much more sophisticated understanding of the structure. Monson's projects in this area could provide a foundation for new approaches to the characterization of porous materials. The range of potential impact extends across the range of applications of porous materials. Similar connections to application exist for all of the fundamental research projects to be impacted by the new facilities.

Research in the department has consistently had a strong educational component through the involvement of graduate students, postdoctoral scholars and undergraduates. The equipment requested will be used by 20 graduate students and 6 postdoctoral researchers, as well as undergraduates engaged in independent study projects. The junior researchers involved will learn important techniques in parallel computation for engineering applications. The faculty involved have an established record of bringing molecular and materials modeling into the Chemical Engineering curriculum and these activities will be supported by the new facilities.

There are daunting technological challenges in bringing the potential of renewable energy such as solar energy and biofuels to fruition, requiring collaboration among leaders in science, engineering, and social science. Despite this need for multidisciplinary integration, university science education remains firmly rooted in separate silos. The University of Massachusetts Amherst (UMass) is tackling this issue through the Integrated Concentration in Science (iCons) program, a new national model of integrative education that sets multidisciplinary student teams to work on current societal problems such as renewable energy. Holyoke Community College (HCC) has likewise developed its own integrative 2-year clean energy program. Jointly they develop a renewable energy laboratory course. The course trains students to design and carry out unique experiments on subjects such as algae biofuels, plastic solar cells, and new energy-efficient building materials. This new UMass/HCC partnership produces students with leadership and laboratory experience in clean energy problems, able to cross disciplinary boundaries in search of useful solutions. The resulting laboratory modules will be disseminated nationally and globally for broadest impact. The partnership produces new pathways for HCC students to transfer to 4-year programs. And most important, the UMass/iCons and HCC programs produce the next generation of leaders in science with the attitudes, knowledge, and skills needed to solve the inherently multidisciplinary technology problems facing our nation.

Auerbach (1512442) - The study involves theoretical calculations aimed at understanding the complex catalysis involved in converting biomass-derived organic compounds to liquid fuel precursors in the confined spaces of zeolites while avoiding deactivation due to coke formation. A novel theoretical approach will be employed that will be benchmarked against experimental data. The PI will also incorporate aspects of his research into educational and outreach programs including an immersive summer science experience for middle- and high-school girls.

The proposal builds on recognition that selective conversion of biomass-derived organic species to longer-chain liquid fuel precursors and the undesired reaction to form coke, are both examples of carbon-carbon bond forming reactions, and thus amenable to theoretical methods that provide insight into fundamental mechanisms of carbon chain growth as affected by zeolite structure and chemical properties. Thus, the proposed work addresses both phenomena, but through a unique theoretical approach - "metadynamics in reverse" - by examining the more-straightforward carbon-carbon bond breaking process and appealing to microscopic reversibility to gain insight into the carbon addition reactions. To this end, the PI will employ and extend several aspects of computational catalysis developed in his lab (in collaboration with the software firm SCHROEDINGER) to obtain accurate energetics of carbon bond forming and breaking while incorporating effects of framework dynamics and long-range forces, all while keeping simulation times manageable. Specifically, the work will address how confinement effects in the zeolite cage influence the balance between the activation and condensation steps in aldol condensation. The theoretical predictions will be benchmarked against related experimental studies carried out by his collaborator, Paul Dauenhauer.

The broader impact of the research is in the general insight it will provide on organic reactions in zeolite structures, especially the factors that control selectivity between condensation reactions to produce desired specific carbon-number products and unchecked carbon condensation to form coke. In addition to the direct insight into the aldol condensation process, the theoretical techniques that will be developed and refined should have broad applicability to reaction processes in the confined environment of zeolite cages. The PI has developed a strong education and outreach plan that incorporates aspects of his research while addressing studies showing that interest in science and math dwindles amongst girls during their middle-school years. He also directs an inter-disciplinary program for undergraduate students at U Mass Amherst that forms teams of students to address real-world scientific issues, especially those dealing with biomedicine and renewable energy.