Research Thrusts

At CCEI, we pursue an integrated approach to solving scientific and engineering problems that span across scales and disciplines. CCEI focuses its research efforts on realizing significant scientific impact that assists in enabling the U.S. to meet the energy challenges of the future by developing catalytic technologies for sustainable energy applications through a spectrum of processes envisioned in a future biorefinery.

Our research drives the science and technology that can lead to the conversion of cellulosic (non-food based) biomass and its derivatives to fuels, chemicals, and electricity. The center provides a multiscale integrated approach to solving scientific and engineering problems that spans across scales and disciplines, including (1) synthesis and characterization of novel catalysts, (2) development and application of multiscale modeling, (3) reaction and reactor evaluation, and (4) technology transfer.

Learn more about our current research thrusts below.

Adhesives

Research goal: Using pulp and paper waste derived chemicals to produce adhesives. This is an alternative to adhesives typically made from petroleum-derived chemicals.
Objectives:
Depolymerize the lignin (main component in pulp and paper waste) into smaller units called aromatic monomers at high purity and yield directly from raw biomass. The catalyst or depolymerizing lignin is a ruthenium metal supported on carbon (Ru/C). Designer molecules are added to each unit, attaching the units together, and finally, cast it onto sheets.

Learn more about adhesives

Waste-derived adhesives exhibit excellent adhesion to stainless steel without the addition of any tackifier or plasticizer, typically used in manufacturing petroleum derived adhesives. Our waste derived adhesives are just as competitive as commercial tapes. Application of this adhesives also include packaging, labels, sticky notes, and plastic wraps.

Research highlights

We have introduced a strategy toward the development of high-performance, pressure-sensitive adhesives (PSAs) from raw biomass deconstruction. By depolymerization of poplar wood, followed by minimal purification, we have produced two aromatic compounds, 4-propylsyringol and 4-propylguaiacol. Their efficient functionalization with either acrylate or methacrylate groups yield monomers that could easily be polymerized by a scalable, reversible, addition-fragmentation chain-transfer process to yield polymeric materials with high glass transition temperatures and robust thermal stabilities, especially relative to other potentially biobased alternatives.

Lubricants

Research goal: To develop innovative solutions to produce sustainable, durable, and high-performance bio-lubricants from inexpensive and sustainable renewables (non-food biomass, natural oils or waste cooking oils).
Objectives:

Learn more about lubricants

Lubricants represent a ~$61 billion global market at an annual consumption of 40 million tons. They have numerous applications in industrial machineries, automotive engines, agricultural equipment, aviation machinery, hydraulic fluids, hydropower and transformers. Petroleum-based lubricants consist of C20-C50 molecules and are formulated with additives.The high volatility of low-carbon fractions causes thickening over time, requiring frequent lubricant replacements. High-performance applications under extreme conditions (e.g., in gas turbines and nuclear reactors) demand rigid specifications (e.g., low pour point, high thermal stability, low volatility and high viscosity index). Synthetic, branched poly-alpha-olefin lubricants produced by olefin oligomerization meet some specifications, but selectively tuning their size and architectur is challenging.
Our strategy will enable use of less expensive, sustainable and versatile carbon feedstocks, control of size and molecular architecture, and a narrow molecular weight distribution to tune lubricant properties and avoid complex formulations. This will be achieved by advancing new frontiers of catalysis science.

Research highlights

We have developed a novel strategy  to produce three broad classes of bio-lubricants, from inexpensive and sustainable renewables (non-food biomass, natural oils or waste cooking oils). High yields, up to 90%, have been achieved. The number of carbons and molecular structure can be controlled with precision. These molecules contain furan rings, fully saturated furan rings, or fully deoxygenated branched alkanes. Their synthesis entails hydroxyalkylation/alkylation of 2-alkylfurans with aldehydes and subsequent hydrogenation and hydrodeoxygenation. The properties of these synthetic bio-lubricants are on par with or better than those of current mineral oils and synthetic lubricants.

Surfactants

Research goal: To develop strategies to synthesize surfactants from bio-renewable feedstocks, as they have potential environmental benefits in addition to unique physicochemical properties that could improve performance and expand applicability.
Objectives:
One process in particular involves the acylation of furans, which has been reported to yield oleo-furan surfactants with superior properties compared to standard detergents. The indirect route, which uses the anhydride of a carboxylic acid as the acylating agent, is process intensive and carbon inefficient: stoichiometrically, half of the hydrocarbon backbone in the anhydride ends up as by-product. On the other hand, using the carboxylic acid as the acylating agent directly avoids this extra step, and yields only water as the by-product.

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Research highlights

We have shown that sugar-derived furans can be linked with triglyceride-derived fatty acid chains via Friedel−Crafts acylation within single layer (SPP) zeolite catalysts. These alkylfuran surfactants independently suppress the effects of hard water while simultaneously permitting broad tunability of size, structure, and function, which can be optimized for superior capability for forming micelles and solubilizing in water.

Furans

Research goal: The efficient transformation of sugars derived from cellulose and hemi-cellulose to various intermediates, such as furans and fuel-grade compounds.
Objectives:
  1. Sugar Transformations in Lewis Acid Zeolites and Molecular Analogues
  2. Integration of Lewis Acid Zeolite Catalysts into Tandem Reaction Schemes

Learn more about furans

The furans thrust aims at paradigm changing approaches for the selective transformations of sugars to furans and their further conversion to value added chemicals and fuels.

Research highlights

  • Inspired by an earlier demonstration of intermolecular Meerwein-Ponndorf-Verley (MPV) carbonyl reduction and Oppenauer alcohol oxidation (MPVO) in Sn-BEA, demonstrated sugar isomerization by an analogous intramolecular MPVO cycle. We have proposed that the Sn4+ centers catalyze the intramolecular H-shift to fructose similarly to the reaction catalyzed by D-xylose isomerase metalloenzymes.
  • Using 119Sn MAS NMR spectroscopy and reactivity studies with isotopically labeled (2H, 13C) reactants, fully characterized the Sn-BEA active site and showed the Sn centers in their “open” configuration ((-SiO)3-Sn-OH) can be distinguished from those in their “closed” configuration [(-SiO)4-Sn].
  • Using DFT calculations, elucidated the glucose-fructose isomerization mechanism and showed that the “open” framework stannanol (Sn-OH) sites are catalytically more active than the “closed” framework Sn sites and suggested that group-cooperativity—often encountered in enzymatic catalysis—determines selectivity to fructose, via 1,2-hydride shift, or to mannose (epimerization), via 1,2-carbon shift.
  • Validated the theoretically predicted site cooperativity by synthesizing molecular analogues of the Sn-BEA “open” and “closed” framework active sites in the form of sin-silsesquixanes, and in combination with DFT calculations studied structure-activity relations.
  • Contributed to the selective formation of 5-hydroxymethylfurfural (HMF) from fructose, with emphasis on understanding why certain organic solvents (e.g., DMSO, neat or as a co-solvent) accelerate fructose dehydration and minimize HMF degradation to levulinic and formic acids and polymerization to humins. Using quantum mechanics/molecular mechanics molecular dynamics simulations showed that rate-limiting elementary steps of the dehydration are profoundly influenced by solvent dynamics and re-organization, being accelerated as the dielectric constant of the medium decreases. We developed the COSMO-SAC modeling platform to predict solvents for reactive extraction and increase the yield of furans during dehydration. We introduced reactive adsorption and suitable adsorbents as an alternative to reactive extraction and shown that this can be a competitive process at lower temperatures. Finally, we developed the first kinetic model for dehydration of fructose to HMF and byproducts and used this to optimize operating conditions.
  • Elucidated the mechanism of formation of HMF in the isomerization of glucose to fructose and xylose to xylulose using metal salts as homogenous Lewis acid catalysts by employing speciation modeling, ab initio molecular dynamics, and a suit of experimental methods. We showed that the aldol-ketose isomerization mechanism is similar to that over Sn-BEA and proceeds via 1,2 hydride shift over a hydroxide form of the cation. Hydrolysis of the salt produces Brønsted acidity that drives fructose dehydration to HMF and further to formic and levulinic acids.
  • Developed methodologies that enable the synthesis of hierarchical zeolites. We introduced two representative hierarchical architectures (self-pillared MFI and 3-dimensionally-ordered-mesoporous-imprinted (3DOm-i) zeolites) with nanometer-sized microporous domains accessible through larger pores, ensuring coexistence of micropore activity and selectivity with fast mass transport. These hierarchical zeolites can be synthesized in pure silica or aluminosilicate form and now with metals (e.g., Sn) incorporated in the frameworks.
  • Achieved moderate-temperature (around 100 °C) retro-aldol reactions of various hexoses in aqueous and alcoholic media with catalysts traditionally known for their capacity to catalyze 1,2-intramolecular carbon shift reactions of aldoses, for example, various molybdenum oxide and molybdate species and alkali-exchanged stannosilicate molecular sieves, paving the road to alkyl lactates from renewables.

Hydrodeoxygenation
(HDO)

Research goal: The selective upgrade of furans and fuel-grade compounds to deoxygenated chemicals and transportation fuels.
Objectives:
  1. Kinetic and Spectroscopic Studies for Upgrading of Furan-Based Compounds
  2. Synthesis of Multisite/Multifunctional Materials with Nearly Atomic Scale Control

Learn more about HDO

The HDO Thrust aims to develop science and catalysts for the upgrade of furan-based compounds.
Furans, obtained via dehydration of sugars or pyrolysis of lignocellulose, and oxygenated fuel precursors, obtained via chain growth chemistry of furans, are important intermediate platforms of lignocellulosic biomass.
However, owing to their oxygen-rich content, their transformation to fuels and chemicals requires selective oxygen removal. Upgrade of furans requires transformative technology to improve product yields and introduce new chemicals and to reduce catalyst cost.

Research highlights

  • We are developing non-precious metal oxide catalysts for the ring-opening of furanics. We have demonstrated that the use of reduced Cu-Co-Al mixed metal oxides achieves the formation of 1,5-pentanediol with upward yields of 45% and 1,2-pentanediol with upward yields of 17%. This is the highest reported yield for 1,5-pentanediol when compared with other catalysts with a similar mechanism.
  • The design of a high-pressure flow reactor for studying reaction pathways for hydrodeoxygenation reactions.
  • Have developed new methods of catalyst activation for the synthesis of cobalt-oxide-overcoated Pt nanoparticles to target selective hydrodeoxygenation of oxygenated furans, while simultaneously suppressing the undesired side reactions of the desired product.
  • We are developing solid catalysts for the effective deoxydehydration of vicinal diols to olefins, a class of compounds with a multitude of uses. A first generation of catalysts was obtained by adopting transition metals and structural motifs from homogeneous catalysts, e.g., oxide-supported oxo-rhenium.
  • We are developing efficient and highly selective ring- opening catalytic pathways to convert biomass-derived furans and tetrahydrofurans into adipic acid, an essential monomer in 6,6-nylon.
  • Computational studies allowed CCEI researchers for the first time to establish catalyst design principles, which can ultimately lead to the discovery of the next-generation of C-O activation catalysts—metal core/oxide shell PtCoOx

Aromatics

Research goal: The selective upgrade of furans to aromatics.
Objectives:
  1. Achieving High Selectivity for Diels-Alder (DA) Furan Reactions
  2. Cycloaddition of Substituted Furans and Dienophiles

Learn more about aromatics

As steam cracker operators are capitalizing on the shale gas revolution and inexpensive natural gas liquids are pushing naphtha feedstocks aside, the development of alternative routes for the production of aromatics from renewables, such as biomass, is receiving considerable attention.
Of the possible routes garnering interest, CCEI scientists have proposed and been pursuing the dehydrative aromatization of the Diels-Alder product between bio-based furans with an appropriate dienophile; a tandem scheme where the cycloadduct obtained from the Diels-Alder is catalytically dehydrated to an aromatic. The strategy is showcased by the formation of p-xylene from 2,5-dimethylfuran and ethylene over the Brønsted-acidic catalysts H-Y and H-BEA, with yields as high as 90%. The same strategy has been used to convert methylfuran and ethylene to toluene over H-BEA; but methylfuran loss to side reactions (e.g., alkylation, hydrolysis and oligomerization) has an adverse effect on the selectivity (46%).

Research highlights

Lewis acid catalysis. In order to curtail undesired side reactions promoted by Brønsted acids, the CCEI researchers have turned their attention to Lewis-acidic zeotypes, specifically isomorphically substituted zeotypes with Lewis-acidic centers, such as Sn-BEA, Zr-BEA, Ti-BEA, Hf-BEA and Zn-BEA. This multi-institution effort led to the synthesis of numerous aromatics: methyl 4-(methoxymethyl)-benzoate from ethylene and methyl 5-(methoxymethyl)-furoate; dimethyl terephthalate from ethylene and the dimethyl ester of 2,5-furandicarboxylic acid; as well as p-xylene.
These efforts led to the remarkable finding that Lewis-acidic zeotypes are as effective as the Brønsted-acidic H-BEA in influencing the rate of the tandem scheme, and in particular the dehydration of oxanorbornene derivatives.
Catalysis of the Diels-Alder. The fleeting existence of the Diels-Alder cycloadduct has not allowed the CCEI engineers to decouple the two steps of the tandem scheme and thus elucidate whether the zeotypic Brønsted and Lewis acids have any effect on the rate of the Diels-Alder step itself. With furans being among the less reactive dienes, accelerating the cycloaddition reaction will be a pivotal step in the success of producing aromatics by dehydrative aromatization of the Diels-Alder product of biomass-derived furans and appropriate dienophiles.
Brønsted and Lewis acids are known to accelerate a variety of Diels-Alder reactions. The mechanism by which they influence the rate of the DA reaction can readily be explained in terms of the famous Fukui theory of frontier molecular orbitals. In the so-named normal electron demand mode of the reaction, protonation of the dienophile or complexation with the Lewis acid lowers the energy of its lowest occupied molecular orbital and closes the gap to the highest occupied molecular orbital of the diene, increasing the interaction between the two orbitals and thus the rate of the reaction.
Calculations by CCEI scientists have, however, asserted that when ethylene is the dienophile, neither Brønsted nor Lewis acid zeotypes can influence the rate of the Diels-Alder step, because the furanic molecule binds more strongly to the active site of the catalysts.
Breaking through. Recently, CCEI catalysis experts have achieved to synthesize methylbenzoate by Diels-Alder aromatization of furan and methylacrylate over the zeotypic Lewis acids Sn-BEA, Zr-BEA, and Hf-BEA. With the aid of computational chemistry, they were able to show that these Lewis acids are capable of accelerating the Diels-Alder reaction heterogeneously.
In order to curtail by-product formation, CCEI researchers have also been exploring phosphorous-containing siliceous zeolites. The have been able to synthesize zeolites with BEA (P-BEA) and MFI topology (P-SPP) and found that these catalysts are highly selective and stable for this reaction with an unprecedented p-xylene yield of 97%. The superior properties of phosphorous-containing siliceous zeolite catalysts are attributed to the nature of the acid sites which exclusively catalyze the dehydration of cycloadduct intermediate, and remarkably minimize the alkylation and oligomerization reactions.
Impact. Given the importance of the Diels-Alder cycloaddition as a tool in synthetic organic chemistry and in particular its significance for the development of a technology for the sustainable conversion of furans to aromatics, these are significant steps toward overcoming a number of undesirable or inconvenient features of traditional Lewis acids (e.g., BX3, AlX3, TiX4, SnX4 and LiClO4), such as sensitivity to water, or strong binding between the Lewis acid and the electron withdrawing group of the dienophile and of the product, which can slow down exchange and catalyst turnover.