Proceedings of a Workshop—in Brief

Innovations in Catalysis to Address Modern Challenges

Proceedings of a Workshop—in Brief

INTRODUCTION

The National Academies of Sciences, Engineering, and Medicine (NASEM) Chemical Sciences Roundtable convened a workshop to discuss how the chemistry and chemical engineering communities can contribute practical solutions for improving chemical production through innovations in catalysis. Keynote presentations highlighted the implementation of sustainability in catalysis, including policy considerations and systems-level approaches to catalysis innovations. Throughout three presentation sessions, workshop participants discussed opportunities in various fields of catalysis, such as biocatalysis, electrocatalysis, and photocatalysis, as well as novel approaches to catalyst design and catalytic processes and reactions. The workshop also featured a session titled Vistas in Catalysis, in which 14 participants gave 3-minute presentations on topics ranging from photoelectrochemical water-splitting to machine learning in catalyst development. The workshop ended with a discussion, during which participants highlighted examples of gaps in the catalysis field, including communication between chemists and engineers. A meaningful definition for sustainability was yet to be formulated at the time of the workshop. Finally, perspectives related to discussed scalability of innovations were shared.

KEYNOTE PRESENTATIONS

Dr. David B. Berkowitz (National Science Foundation (NSF) and the University of Nebraska) presented updates from the Sustainable Chemistry Strategy Team in the White House Office of Science and Technology Policy, which recently formed the Joint Subcommittee on Environment Innovation and Public Health (JEEP) to promote federal cross-disciplinary research and development. The JEEP focuses on the discussion of sustainable chemistry (SC) within the federal landscape, which entails financial and economic considerations and U.S. Food and Drug Administration (FDA) toxicity considerations. On behalf of the White House, the JEEP reports to Congress on landscape and gap analysis, strategic planning, coordination of federal research, and recommendations of policy options. The JEEP recently released an SC Request for Information (RFI), which solicited feedback on a definition for SC, support technologies, fundamental research areas, metrics, financial and economic considerations, policy implications, and other investment considerations. Based on this RFI, the JEEP plans to develop a strategic plan for SC, which will be documented in a Report to Congress and will implement the plan using a cross-government approach. Metrics in the draft Report to Congress include life cycle analysis, kinetic and thermodynamic processes

of chemical development, and carbon footprints and byproducts. A major theme in both the RFI and the draft Report to Congress is recycling technologies that avoid petroleum stocks and balance greenhouse gases. The draft Report to Congress also discusses barriers to sustainability, which may be unlocked by catalysis innovations, such as harnessing solar and visible light energy, recycling sustainable polymers and plastics, enhancing research collaborations in biocatalysis and chemocatalysis, changing catalysis to earth abundant elements, and applying artificial intelligence for data-driven discovery.

Dr. Susannah Scott (University of California, Santa Barbara) presented research practices that can enable a more sustainable chemical enterprise. Her presentation focuses on aspects of economy of scale and carbon cycle. She proposed that the catalysis research community could employ a systems-level approach, in which sustainability is viewed as a property of the entire chemical production process rather than a property of catalysis alone. Such an approach can help integrate discovery into real-world applications rather than limit discovery to the ideal research setting. A systems-level approach can include collaborations among chemists, engineers, and social science researchers. Together, they can work to understand supply and demand policies, and policy-driven and market-driven approaches—an aspect of systems-level thinking that is unique from a sole research setting.

Dr. Scott also highlighted challenges related to using non-fossil carbon sources (e.g., switchgrass, waste plastic, and corn stover) to increase chemical output while reducing greenhouse emissions. Although non-fossil carbon reduces emissions, molecules from these sources usually have low thermal stability, low volatility, and low solubility compared to fossil carbons. Given these molecular constraints, new catalysts are needed to process non-fossil feedstocks. Dr. Scott also presented methods for heating polyethylene that eliminate the need for external hydrogen and produce long-chain alkanes and alkylaromatics, which can be used as lubricants and anionic surfactants. Furthermore, new research in machine learning and catalytic resonance (computational theory) was described. These approaches highlight the advantages of dynamic catalysis, in which various active sites can be utilized and binding properties can be electrically altered to accelerate the rates of multiple reactions that would otherwise be rate-limiting to each other. Dr. Scott concluded her presentation by noting that the outlook for chemical production involves embracing the heterogeneity of catalyst behavior, rigor and reproducibility of experiments, collaborations between fields, and cultural diversity among chemists in the field.

Dr. Bob Maughon (Saudi Arabia’s Basic Industries Corporation, SABIC) presented an industrial perspective on chemical production. He highlighted the contributions from catalysis research that have advanced chemical reactions. These improvements include enhanced selectivity, increase plant capacity, and reduced normalized energy input for the reaction or production. Although chemists’ understanding of catalysis applications has increased since 1940, the rate at which new catalysis applications are commercialized has significantly decreased. In contrast to academic advancements in modeling, in-situ monitoring, and synthesis, industrial innovations have been more evolutionary (slow and incremental) than revolutionary (fast and transformative). The reason for this gradual change is because petrochemicals offer stable opportunities, economic scale, and profitable growth. Echoing Dr. Scott’s message, the model systems lack a system-level approach, which impacts its translation into the industry scale. Model systems use 10 orders of magnitude lower pressure levels than industrial systems, with simplified components and catalysts and occur within sub-second to day-long timescales. In contrast, industrial systems are large-scale, have higher pressure, involve many complex components, and occur within months to decades.

Dr. Maughon emphasized that the catalytic industry, contributes a small quantity to the total GHG emissions of the chemical industry, compared to direct emissions from corporate facilities and indirect emissions from consumer residencies (e.g., for electricity, heating, and cooling). Dr. Maughon suggested that carbon dioxide (CO₂) emissions are an energy challenge related to thermodynamics and the application of heat to chemical

processes. He said that factors, such as the introduction of variable and localized feedstocks, reallocation of capital expenditure, and environmental regulations, necessitate a change in industrial chemical processes. Dr. Maughon outlined some opportunities improving catalysis, including operating at room temperature, using aqueous catalysts, and implementing small-scale processes. He also suggested that the chemical research and engineering communities could improve tools for translating research innovations to industrial systems.

During the open discussion, workshop participants expressed the need for policymakers to aid in making real-world innovations. Dr. Maughon stated that regulatory change rarely drives the initial steps of innovation and translation. Rather, regulatory change may help solidify innovations into policy that can reduce costs. Participants highlighted the need to build relationships between the chemical processing industry and academia. Dr. Maughon suggested that the catalysis community could develop joint investments between academics and industry to translate novel processes into industrial systems. Dr. Scott suggested that chemical engineering could be integrated into catalytic process design and collegiate chemistry curricula. Dr. Berkowitz highlighted the NSF Intern Program, which drives workforce development by providing NSF-funded graduate students with additional funding to complete 1-year industry internships. Dr. Berkowitz elaborated on NSF’s new Technology, Innovation, and Partnership Directorate, which will strive to enable use-inspired research and the translation of chemical processes to real-world applications through collaboration.

SESSION I: BEYOND CONVENTIONAL HOMO- AND HETEROGENOUS CATALYSIS—EMERGING TOPICS IN MAIN GROUP-, ORGANO-, AND BIO-/BIOHYBRID CATALYSIS

Dr. Todd Hyster (Cornell University) presented recent advances and future opportunities in biocatalysis. Biocatalysis uses enzymes as catalysts for organic synthesis that are highly selective, efficient, engineerable, and operate under mild conditions. In 2010, a pharmaceutical company provided evidence that biocatalysts could be directed toward useful targets for pharmaceutical manufacturing processes, using a transaminase developed from directed evolution. This approach reduced the number of steps needed to synthesize the drug, Sitagliptin. In recent years, the feasibility of biocatalysis has increased because of decreased costs for DNA sequencing and synthesis, and because of advances in directed evolution, high-throughput experiments, and bioinformatic techniques. However, the relatively slow process of protein engineering makes biocatalysis less viable compared to small molecule catalysis for chemical manufacturing. Dr. Hyster suggested options for shortening the timeline of directed evolution in protein engineering by designing more efficient mutant DNA libraries, accelerating DNA synthesis and protein expression, and improving analytic tools for screening libraries. In addition, Dr. Hyster suggested applying machine learning to predict enzyme structures and manipulated sidechain reactivities and to extract more information from mutant libraries.

Dr. Hyster detailed recent methods developed by researchers to overcome challenges in the pharmaceutical industry’s use of biocatalysis, including 1) de novo design of enzymes and 2) optimization of enzymatic cascades. In de novo enzyme design, researchers have incorporated non-natural amino acids into proteins, which produce a new enzymatic function for targeted catalysis. Next, Dr. Hyster provided an example of enzymatic cascade optimization (using mixtures of multiple biocatalysis included in the same reaction) employed in industry. In a process used by Merck Pharmaceutical, many of the protection and deprotection steps previously required to produce the drug, Islatravir, were eliminated from the synthetic route. Dr. Hyster also offered considerations for future enzyme cascade biocatalysis, including merging small molecule catalysts with biocatalysts in separate reaction steps, compartmentalizing other small molecules from biocatalysts, and avoiding Lewis acids.

Dr. Ive Hermans (University of Wisconsin-Madison) presented challenges and modern solutions to decarbonizing commodity chemicals. The catalysis community aims to implement technologies that can use new feedstocks and recycle waste by hydrogenation. He noted that recycling waste to higher feedstock purity may be a greener practice than using new feedstocks because

fewer chemical processes, hence less waste and less energy, are required to produce the end-product through recycling.

Dr. Hermans’ presentation showed industrial plants that produce olefins, such as ethylene, from steam cracking are currently responsible for 1 percent of global CO_2. Electrically heated furnaces can reduce CO₂ emissions by 90 percent and can be retrofitted to current industrial setups, thus reducing the capital expenditure necessary to integrate these furnaces. Dr. Hermans presented novel technologies for ethylene production, including a proprietary catalytic system and electrocatalysis from CO₂ and water feedstocks. However, this method cannot be retrofitted to current industrial setups due to scalability challenges. Dr. Hermans emphasized that electrocatalysis and electrically heated furnaces could reduce CO₂ emissions only if the source of electricity is also renewable.

The regeneration of catalysts needed to produce propylene using fluid catalytic cracking, accounts for approximately 30 percent of CO₂ emissions in a standard refinery. To reduce emissions from propylene production, Dr. Hermans’ team uses boron nitride as an oxidative dehydrogenation catalyst to produce propylene and hydrogen from propane. In hydrogen production, natural gas and coal still provide 99 percent of the industry energy needs. Dr. Hermans discussed conducting methane pyrolysis using solar-powered hydrogen panels, to reduce CO₂ emissions. However, hydrogen storage presents a challenge, because it requires high-energy conversion of hydrogen from gas to liquid that results in substantial hydrogen loss. Alternatively, hydrogen can be stored in artificial clathrate hydrates or as methanol. Dr. Hermans concluded that the catalysis research community could benefit from increased techno-economic and life cycle analyses, and collaboration between industry and academia.

Dr. Anita Mattson (Worcester Polytechnic Institute) presented three case studies involving small organic molecules in catalysis: n-heterocyclic carbenes (NHCs), hydrogen bond donors, and Bronsted acids. She observed that biological systems naturally produce acyl anions, such as polyketides from thiamine pyrophosphate and pyruvate. Recently, researchers have tuned these NHC-based catalysts to synthesize biologically active products with 99 percent product yields and 94 percent enantiomeric excess (ee). Next, in early research on hydrogen bond donors, a thiourea catalyst was used to add cyanide to an iminium ion generated in situ, discovering later that the mode of action was anion-binding which allowed for high facial selectivity. However, many of these anion-binding reactions used dilute concentrations of catalysts and occurred over long time scales. Over time, optimized hydrogen bond donor reactions—using various catalyst modifications, such as adding two thioureas to the catalyst backbone—decreased necessary catalyst concentrations and reaction times. Recently, chemists combined transition-metal and anion-binding catalysis to achieve an enantioselective reaction with a 94 percent yield and 97 percent ee. Lastly, in early research of Bronsted acids, phosphoric acids were introduced as catalysts for reactions with iminium ions and ketene silyl acetals. Recently, researchers have transitioned to Bronsted acid catalyst reactions with unactivated olefins rather than activated amines, finding that acidic catalysts are required to optimize the efficiency of olefin catalysis.

Dr. Mattson has centered her presentation on the concept of using organocatalysis to reduce the footprint of catalysis on precious and difficult to mine metals, while affording important and biologically relevant molecules, including chiral ones. She emphasized that through innovation, mechanistic understanding, and user-friendly machine-learning applications, designing novel organocatalysts and catalytic systems can potentially replace petroleum feedstocks in industry. In addition, collaborations between academia and industry can aid the translation of novel organocatalysts from the lab to industry. Dr. Mattson also suggested that the catalysis community could research enzyme biology to identify active sites that may be beneficial for designing smaller organic molecules able to mimic the active site functions of enzymes.

SESSION II: EMERGING TECHNIQUES AND THEIR APPLICATION PROSPECTS

Dr. Paula Diaconescu (University of California, Los Angeles) is the Director of the NSF Phase I Center for

Integrated Catalysis (CIC). The main goal of the CIC is to develop novel techniques in integrated catalysis, which refers to coupling synthetic cycles using switchable catalysis and spatiotemporally controlled reactions. Switchable catalysis allows two active states of a catalyst to perform orthogonal reactions. For example, redox this method can add different chemical blocks to a copolymer, depending on the redox state of the catalyst.

Dr. Diaconescu presented a CIC case study of polyketone produced from ethylene and CO/CO₂, which combines techniques in spatiotemporal control and theory. Spatiotemporal control is the ability to control when (e.g., chemo-responses, electron-switches, photo-switches) and where (e.g., surface attachment, flow systems, emulsion compartments, and gradients) catalytic reactions occur. Though polyketones are readily available and have many applications, they are not easily degradable and/or sourced from renewable feedstock. To advance approaches to polyketone production, the CIC’s teams focused on electrochemistry, polymerization reactions, and machine learning. They found that CO₂ could be reduced to CO by eliminating the use of use water during electrochemical reduction. Once reduced, CO was transferred to a separate vial containing the polymerization catalyst. Keeping the two processes separate is important because the electrochemical reduction of CO₂ would also reduce the catalyst. The polymerization team then generated non-alternating polyketones under low CO pressures at room temperature. At higher pressures and temperatures, the team was able to produce alternating polyketones. Finally, the machine learning team predicted whether a given catalytic compound would selectively produce alternating or non-alternating polyketones.

Moving forward, the CIC will focus on homogeneous and heterogeneous catalysis, catalyst synthesis, biocatalysis, reaction engineering, and computation. Integrated catalysis can address issues related to compatibility between catalysts, reactants, and products, and utilization of unstable intermediates. Dr. Diaconescu also suggested that the catalysis community could take advantage of interdisciplinary collaboration by fostering more communication around research opportunities.

Dr. Jeffrey Johnson (University of North Carolina at Chapel Hill) presented opportunities for productive merging of kinetic and thermodynamic control in stereoselective catalysis. He explained that molecular complexity is a driver for methods in modern catalysis. For example, the success of drug development is associated with an increase in molecular complexity, such that drugs that are brought to market have higher complexity than those in earlier development phases. Stereoconvergent synthesis is a means of increasing molecular complexity and represents an embodiment of Le Chatelier’s principle.¹ In addition, catalysts in stereoconvergent reactions can produce a single compound from multiple enantiomers.

As opposed to the asymmetric catalysis paradigm, in which selectivity is the most critical property, a merged approach that takes advantage of stereoconvergence, focuses on physical properties. Stereoconvergence with beta-dicarbonyls occurs through crystallization-induced diastereomer transformation (CIDT), which is similar to stereoconvergent catalysis; however, in CIDT reactions, selectivity arises from differences in crystallization. A merged approach enables higher-order molecular and reaction complexity by combining the transition state selectivity of enantioselective catalysis and the crystallization selectivity of CIDT. Dr. Johnson provided an initial proof-of-concept where a catalyst with two asymmetric centers was used to increase the complexity of the reaction. Although product separation can be resource intensive, this merged approach provides a distinct advantage because if the product crystallizes out of the reaction, then filtration methods can be used to reduce the burden of separation.

Dr. Johnson presented various challenges of employing stereochemistry as a broad tool in industry, including the need to better understand reaction mechanisms. It is currently not known what drives the production of

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a particular stereoisomer from a reaction. In addition, although density functional theory (DFT) tools can predict the solubility of stereoisomers, the standard error is large in predicting other properties such as melting point. Dr. Johnson suggested that these challenges in stereochemistry could also provide opportunities to merge kinetic and thermodynamic control to study asymmetric catalysis.

Dr. Carsten Sievers (Georgia Institute of Technology) presented fundamentals of and opportunities in mechanochemistry, which is the principle of performing chemical reactions by providing energy in the form of mechanical impact instead of heat. Compared to traditional catalytic processes, mechanocatalytic processes occur in a ball mill and can occur under solvent-free conditions. He presented multiple mechanisms of transduction for mechanochemistry, including surface activation, heat transfer from collision, mechanical charge separation, and bond strain. In surface activation, ball mills generate catalytic activity from the rearrangement of surface domains in solids while a continuous flow of CO and oxygen gases is turned on and off. This analysis revealed that the rate of CO₂ production from calcium carbonate was dependent on the milling frequency and correlated with the apparent temperature during the milling process. In addition, heat transfer from collisions formed hot spots in the vessel that exceeded 800°C for short periods of time, with a thermal decay of 100 ms. Charge separation can occur through mechanical impact on piezoelectric materials, which change shape when an electrochemical potential is applied. Dr. Sievers’ group used milling balls to free electrons and protons from piezoelectric materials. Lastly, bond strain from mechanical impact during the milling processes can also break down large molecules, such as polystyrene, to form mechanoradicals.

Dr. Sievers presented multiple applications of mechanocatalysis, including ammonia synthesis and the depolymerization of cellulose and polyethylene terephthalate (PET). In ammonia synthesis, mechanocatalysis can be implemented by introducing continuous nitrogen and hydrogen gas flow into a milling chamber containing titanium. The milling process produces titanium nitride and, through the rapid heating and cooling of hot spots during the ammonia catalytic cycle. However, milling balls must be heated during this process to prevent the ammonia product from adhering to either the milling balls or the catalyst. Dr. Sievers’ group employed this method to depolymerize PET using a sodium hydroxide catalyst. Dr. Sievers estimated that integrating milling processes into industrial systems can produce an economic net present value of approximately $2.5 million total over 10 years of operation. When scaled up to 100 kg, attrition mills can reduce the energy required to initiate depolymerization processes by several orders of magnitude. Dr. Sievers said that mechanocatalysis provides new reaction pathways by creating unique, short-lived reactive environments and inducing reactions between two solids.

Dr. Ramesh Giri (Pennsylvania State University) presented alkene difunctionalization as a sustainable approach to organic synthesis. The drug development process, which involves discovery, preclinical and clinical research, FDA approval, and manufacturing, typically takes 10 years and can cost up to $2.8 billion. Currently, synthesizing organic molecules for pharmaceutical compounds involves several steps, and the volume-time-output (i.e., the amount of time and number of steps involved in chemical manufacturing) accounts for 40 percent of the cost distribution for drug manufacturing. Given the ever-growing demand for novel drugs, the large number of synthesis steps required to manufacture drugs is likely unsustainable. Moreover, reducing the number of synthesis steps can also reduce materials, which account for 15 percent of manufacturing costs, and expedite the pace of drug synthesis for emergent situations, such as the COVID-19 pandemic.

The current state of synthesis technology involves multiple steps to prime each pharmaceutical precursor for each intermediate reaction until the final marketable drug product is synthesized. The goal of future synthesis technologies is to combine multiple precursors in a single reaction, thereby reducing the number of intermediate molecules that must be primed for subsequent reactions. To achieve this goal, Dr. Giri’s group conducted alkene dicarbofunctionalization, which forms two carbon-

carbon bonds in a single synthesis step across an alkene. For the past 35 years, alkene dicarbofunctionalization has faced challenges in the formation of Heck reaction products during synthesis. Dr. Giri’s research introduced a coordinating group into alkene dicarbofunctionalization reactions to overcome this issue. However, using amines as the coordinating group, along with activated alkenes, does not significantly reduce the number of steps required for synthesis. Some outstanding challenges in alkene dicarbofunctionalization include understanding the importance of unactivated alkenes, internal alkenes, stereoselective reactions, tetrahedral hybridized carbon [C(sp³)] sources, and finding ways to remove coordinating groups remains. Dr. Giri’s group has addressed these challenges by combining secondary C(sp³) sources with internal alkenes, unactivated alkenes with a coordinating group, and unactivated alkenes with C(sp³) sources, as well as by eliminating the need for coordinating groups. For example, Dr. Giri’s group reduced the total number of steps required to manufacture 5-lipoxygenase activating protein (FLAP) inhibitors from 12 steps to 5 steps by using alkenyl arenes.

Although alkene dicarbofunctionalization provides opportunities to synthesize products with multiple components, Dr. Giri noted that a better fundamental understanding of these reactions is needed to enable expanded applications in pharmaceutical, natural, and bioactive production.

Dr. James Mack (University of Cincinnati) presented on improving catalysis through mechanochemistry processes. Mechanochemical reactions typically are faster than chemical reactions with common solvents, such as dimethylformamide, often synthesizing products in less than half the time of chemical reactions. Solvent-based reactions may be converted into mechanochemical ones, through the milling of precursors in the solid phase, with solvents being absent or added in substoichiometric quantities. However, mills have different energetic properties, and the yield efficacy of a reaction is dependent on both milling frequency and milling ball temperature. Dr. Mack’s group compared the percent yield of Suzuki and Sonogashira reactions under various temperature conditions. These reactions can also be combined in a “two-step, one pot” process, in which a single mill is used in synthesis. In addition, reactions can be modified by using vials and balls made of various metals, as well as by adding ligands to switch catalytic activity.

Dr. Mack suggested that mechanochemistry is a powerful tool to conduct chemical reactions. Because mechanochemical reactions often involve similar catalysts, these reactions are similar to solution-based reactions. However, mechanochemistry may present a more sustainable means for conducting large-scale catalytic reactions. Dr. Mack emphasized that more research is needed in mechanochemistry to conduct large-scale catalytic reactions and improve mechanistic analysis tools. Mechanochemical reaction analysis tools, such as in situ x-ray diffraction and infrared imaging present an opportunity for the chemistry community to potentially consider developing new tools suitable for these types of reactions. Dr. Mack also suggested that the mechanochemistry research community could collaborate with chemists in other fields to develop tools and understanding of chemical mechanisms that can improve catalysis.

SESSION III: CARBON AND OTHER RESOURCES FOR THE FUTURE

Dr. LaShanda Korley (University of Delaware) presented opportunities for re-imagining plastics waste as valuable feedstocks. Plastics are used in chemical production and manufacturing because of their high strength-to-weight ratio for transportation, low thermal conductivity that reduces heat loss, good barrier properties for food and medicine, and high processability. However, plastics create environmental pollution and consume energy during production.

The wide range of bond energies in polymers can dictate catalytic strategies to replace either discarding or incinerating plastics. For example, polyethylene, which is relatively homogeneous in bond energy, is well-suited for deconstruction, whereas PET is more heterogeneous and thus better suited for depolymerization. Dr. Korley presented a case study on plastics deconstruction that

combined atomic layer deposition (ALD) and capillary rise infiltration to measure the effect of surface chemistry and power penetration on catalysts. Researchers calculated the contact angles of polystyrene to study the conversion kinetics of deconstruction, making ALD-infiltration a powerful tool for benchmarking catalyst surface characteristics. Other groups have found that hydrocracking and hydrogenolysis can lower the energy demand of deconstruction and produce isomerized products, such as waxes and modifiers. Olefin metathesis can also produce smaller molecule products for other high-value feedstocks. Dr. Korley emphasized that combining these strategies can replace traditional chemical routes to match desirable feedstock chemicals with plastics waste inputs.

Dr. Korley noted that innovations in plastics catalysis and sustainability occur through scientific advancements and partnerships with community, industry, and public policy stakeholders. Innovations may occur at multiple scales, including molecular modeling, machine learning, applied experiments, systems analysis, and large-scale data science. In addition, plastics catalysis faces barriers to sustainability, such as identifying tailorable product streams and processes, addressing the complexity of waste (e.g., additives that affect catalytic activity), and maximizing value in processes while reducing environmental impact. Globally, the catalysis community may consider designing materials with polymers that reduce end-of-life burden and change consumer perspectives about plastics use. In addition, identifying differences in plastics waste between geographical locations may help with targeted approaches to waste conversion. Dr. Korley also suggested that engineers in catalysts, polymers, and process analysis could collaborate to drive success in valorization strategies.

Dr. William Tarpeh (Stanford University) presented on converting pollutants in wastewater to products using electrochemical techniques. Current nitrogen management poses environmental and equity challenges. Toxic algal blooms resulting from fertilizer runoff and nutrient pollutants have increased over the past seven decades. However, less than 100 Haber-Bosch facilities produce nitrogen fertilizers around the world, resulting in inequitable nitrogen transport costs and higher emissions from long-distance transport. Dr. Tarpeh’s group focuses on advanced wastewater treatment (i.e., the removal of nitrogen, phosphorus, and pharmaceutical waste), as opposed to primary and secondary treatment (i.e., the removal of solids and dissolved organics, respectively), to resolve these nitrogen management challenges. To offset nitrogen cycle disruptions caused by Haber-Bosch reaction, Dr. Tarpeh’s group works on electrocatalysis to recycle reactive nitrogen (e.g., ammonia and nitrite) or convert reactive nitrogen into valuable intermediates. Dr. Tarpeh’s group also designs electrocatalytic processes by selecting the target pollutant from available wastewater sources, the target product, and the electrochemical tools that can best aid the conversion of target pollutant to target product.

Dr. Tarpeh elaborated on his research in electrochemical stripping, electrodialysis (ED), and nitrate reduction (NR) techniques. His group uses electrochemical stripping to selectively recover nitrogen, with approximately 90 percent efficiency, from ammonium-laden wastewater based on charge and volatility. The group also developed a combined EDNR process, which enables ammonia production from mixed sources of ammonia- and nitrate-laden wastewater. In this process, ammonia is selectively recovered from ammonia-laden wastewater using ED or synthesized from nitrate-laden wastewater using NR. The group optimized the EDNR process by reducing the electrolyte pH, increasing the concentrations of sodium and perchlorate, and purposefully forming titanium hydride at the electrode, which resulted in a 3.4-fold efficiency increase. The group also conducted a prospective life cycle analysis, which showed that electrolyzers can reduce environmental impacts from regenerating water treatment adsorbents.

Dr. Tarpeh observed that electrochemical reactive separations are well-suited for selective wastewater refining because they are flexible with scale, integrate with renewable energy, replace chemical inputs with electricity, and facilitate process control (e.g., current and potential control). Catalytic cascades, which are common in biocatalysis, could also improve

the capabilities of synthesizing various chemical products from wastewater treatment. In addition, to improve wastewater treatment in the U.S. Midwest, electrocatalytic sensors can detect and measure concentrations of waste in farm wastewater and potentially recover ammonia themselves.

SESSION IV: VISTAS IN CATALYSIS

Selected participants shared the results of their research via a rapid-fire virtual session, with participants receiving 3 minutes for each of the following presentations:

Dr. Estak Ahmend (Michigan State University) presented on electrocatalytic ammonia oxidation using a low coordinate copper complex, which forms stable polyamine copper species, facilitates the deprotonation of copper to ammonia, and prevents bisammine formation.

Dr. Anastassia Alexandrova (University of California, Los Angeles) presented on dynamic active sites of catalysts and how ensembles of metastable states define various mechanisms of catalysis.

Dr. Louise A. Berben (University of California, Davis) presented on aluminum-ligand cooperative bond activation, which can be applied at low cost to amine oxidation, formic acid dehydrogenation, and transfer hydrogenation.

Dr. Daniela E. Blanco (Sunthetics) presented on leveraging small chemistry datasets to optimize reactions, catalysts, and material properties using proprietary machine learning algorithms.

Dr. Joseph Gair (Merck) presented on implementing electrostatic interactions to enhance generality in asymmetric catalysis by increasing the stereo control of substrates with varying sizes.

Dr. Long Qi (Ames National Laboratory) presented on a novel nitrogen-doped carbocatalyst, which releases hydrogen at room temperature without transition metals, for strong bond activation of liquid organic hydrogen carriers.

Dr. Hongyuan Sheng (University of Wisconsin–Madison) presented a linear paired strategy for electrochemical valorization of glycerol, in which glycerol can undergo oxidation at both the cathode and anode from Electro-Fenton hydroxide generation.

Dr. Yogesh Surendranath (Massachusetts Institute of Technology) presented on multiple mechanisms for uniting heterogeneous, molecular, and biological catalysts (e.g., graphite-conjugated catalyst), as well as thermochemical, electrochemical, and photochemical modes of energy input (e.g., spontaneous polarization).

Dr. Jenny Y. Yang (University of California, Irvine) presented on installing internal electric fields at active sites using proximal cations, which results in C-H oxidation at milder potentials and an inverse linear free energy relationship.

Dr. Peter Zhang (Boston College) presented on metalloradical catalysis, which can control the reactivity and selectivity of one-electron homolytic radical chemistry.

Samay Garg (Columbia University) presented on tandem catalysis processes, including electrocatalytic and thermocatalytic processes, for the rapid decarbonization of chemicals that contribute more than 50 percent of emissions, such as ammonia, methanol, olefins, and benzene, toluene, ethylbenzene, and xylene (BTEX).

Dr. Randall Snurr (Northwestern University) presented on data-driven and computational discovery of metal-organic framework (MOF) catalysts using DFT tools to predict the relationship between active site stability and reactivity.

Dr. Emily Sprague-Klein (Brown University) presented on a dual wavelength-dependent photo-electrochemical process for water-splitting, which has broad impacts on light-driven redox chemistry and photocatalysis.

Dr. V. Sara Thoi (Johns Hopkins University) presented on molecular strategies to modulate the electrode-electrolyte interface in heterogeneous electrocatalysis,

which have applications for developing molecular additives, sustainable urea production, and pulsed potential electrocatalysis.

Following the rapid-fire session, workshop participants and presenters engaged in an open discussion. Several participants shared their thoughts for advancing innovations in catalysis, including improving communication between chemists and engineers, scalability of innovations, and sustainability in catalysis. Participants discussed effective multidisciplinary collaboration and communication between catalysis researchers and chemical engineers for translating innovations to industry. Although undergraduate chemical engineering programs require courses in chemistry, the current curriculum for chemistry programs lacks engineering courses. These courses could provide critical language to enable communication between chemists and engineers and opportunities for integrating novel catalysis into industrial systems. In addition, funding for industry internships, such as the NSF Intern Program, could provide further real-world educational opportunities for undergraduate chemistry students.

Several participants noted that multidisciplinary partnerships, with considerations to equity, diversity, and inclusion can provide opportunities for scaling laboratory innovations to industry, such as researching stable industrial conditions for novel catalysts and implementing energy-efficient catalysis approaches. Furthermore, although sustainability is portrayed to the public as having large economic impacts on industry, it is unclear how the catalysis community has contributed to sustainability. Defining sustainability in detail, rather than with broad concepts, could enable the catalysis community to accurately quantify the impacts of catalysis on industry and provide focus to prioritizing future research efforts in catalysis.

DISCLAIMER This proceedings of a workshop—in brief was prepared by Rose Li Associates as a factual summary of what occurred at the workshop. The statements recorded here are those of the individual workshop participants and do not necessarily represent the views of all participants, the planning committee, the Chemical Sciences Roundtable, or the National Academies. To ensure this proceedings meets institutional standards for quality and objectivity, it was reviewed in draft form by December 2022 and January 2023. The review comments and draft manuscript remain confidential to protect the integrity of the process.

ABOUT THE CHEMICAL SCIENCES ROUNDTABLE The Chemical Sciences Roundtable provides a neutral forum to advance the understanding of issues in the chemical sciences and technologies that affect government, industry, academic, national laboratory, and nonprofit sectors and the interactions among them and to furnish a vehicle for education, exchange of information, and discussion of issues and trends that affect the chemical sciences. The Roundtable accomplishes its objectives by holding annual meetings of its members and by organizing webinars and workshops on relevant important topics.

REVIEWERS To ensure that it meets institutional standards for quality and objectivity, this Proceedings of a Workshop—in Brief was reviewed by Michael Fulller, Chevron and Audrey Moores, McGill University. We also thank staff member Brittany Segundo for reading and providing helpful comments on this manuscript. The review comments and draft manuscript remain confidential to protect the integrity of the process.

STAFF Linda Nhon (Program Officer), Jessica Wolfman (Research Associate), Ayanna Lynch (Research Assistant), and Kayanna Wymbs (Research Assistant).

SPONSORS This workshop was supported by the Department of Energy (AWD-002011) and the National Science Foundation (AWD-001027).

For additional information regarding the workshop, visit https://www.nationalacademies.org/event/10-24-2022/innovations-in-catalysis-to-address-modern-challenges-a-workshop.

SUGGESTED CITATION National Academies of Sciences, Engineering, and Medicine. 2023. Innovations in Catalysis to Address Modern Challenges: Proceedings of a Workshop—in Brief. Washington, DC: The National Academies Press. https://doi.org/10.17226/27161.

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