Research Interests

Eric Karp is a chemical engineer in the National Bioenergy Center (NBC) at NREL. His work focuses on downstream process development for renewable specialty and commodity chemicals. Specific research interests include:

  • Nitriles and amine-based products

  • Separations in bioprocesses

  • Analytical tools for complex sample analysis

  • Surface science of catalytic reactions

  • Chemical process automation

  • Clean technology commercialization

Affiliated Research Programs

Areas of Expertise

Nitriles and Nitrile-Based Products

Recent work within the Renewable Carbon Fiber Consortium (RCFC) developed catalytic technology for the conversion of acrylate esters to acrylonitrile (AN). This breakthrough demonstrates the utility of the “nitrilation” chemistry in the processing of renewable feedstocks to nitrile-based chemicals. As a result, current research efforts are advancing to integrate this reaction to a variety of bio-derived carboxylates, esters, lactones, and anhydrides as a cost-advantaged and relatively non-hazardous approach for the production renewable nitriles and amines. Ultimately, the aim of this work is to produce nitrile and amine monomers for renewable polymers that are performance advantaged.

Catalytic scheme for ethyl 3-HP dehydration and nitrilation to produce ACN. Graph A shows steady-state yields of relevant reaction products produced when passing ethyl 3-HP over TiO2 as a function of reactor bed temperature. Complete reaction conditions and data set are provided in fig. S1. Section B shows the three reactions that are proposed to yield the results outlined in Graph A: dehydration, nitrilation, and overall. Flow chart C shows the proposed mechanism from DFT calculations for the aminolysis of ethyl acrylate to form acrylamide and gaseous ethanol in the nitrilation reaction. Flow chart D shows the proposed mechanism from DFT calculations for dehydration of adsorbed acrylamide to release gaseous acrylonitrile and water, the overall reaction in Section B.

A brief overview of the chemistry, which we dub “nitrilation,” is shown in the figure above. Panel A displays reaction products observed for increasing reactor temperature when vapors of ethyl 3-hydroxy propanoate (ethyl 3-HP) are passed over a TiO2 catalyst in the presence of ammonia. First, ethyl 3-HP dehydrates produce ethyl acrylate, then as the reactor temperature increases beyond 250°C, ethyl acrylate undergoes aminolysis and amide dehydration to form gaseous acrylonitrile. The sequence of reaction that occurs is shown in panel B, while panels C and D display the mechanistic steps for the nitrilation reaction.

Integration of the chemistry downstream of a biological cultivation process producing 3-HP: biological cultivation, dewatering, reactive distillation and nitrilation.

Integration of this chemistry downstream of a biological cultivation process producing 3-HP (above figure) allows a cost-comparative, renewable route to AN compared to the conventional propylene ammoxidation process. As such, future efforts continue with the aim of integrating this chemistry to other carboxylate producing bioprocesses as a means to access value-added nitrile and amine derivatives.

Separations in Bioprocesses

The recovery of neat product from fermentation broth is an expensive and often difficult unit operation in the production of bio-based chemicals. For most bioproducts, the cost of separations contributes ~30%–40% of the production cost. For bio-derived carboxylic acids, separations can contribute up to 60%–70% of the total production cost due to the added expense incurred for handling salts. Thus, there is substantial opportunity to develop new, intensified technologies for product separation that lowers the overall processing costs. To that end, work within our group focuses on the development of in situ product recovery (ISPR) technologies that separate neat products directly from fermentation broth during the cultivation process. The figure below illustrates an ISPR system where the bio-acid product is recovered directly from the liquid extractant via distillation.

In situ product recovery (ISPR) coupled distillation in a bioreactor, membrane contactor and distillation column: biological sourced carboxylic acids to acid extraction into an organic phase to recycle media and cells or recycle organic phase then acid vaporization and neat acid.

Benefits of this approach include decreased product inhibition to the microbial culture allowing for increased yields and productivities in smaller fermentation volumes and allows for avoidance of expensive salt-based separation methods. Economic analysis of this technology appears to provide a significant economic advantage over traditional post-processing separation schemes. Future work aims to apply this technology in high solids environments for waste-based bioconversion processes.

Analytical Tools for Complex Sample Analysis

Process streams that result from the chemical or mechanical deconstruction of biomass are often complex heterogeneous solutions composed of compounds with varying chemical functionalities over a large range of molecular weights. As such, developing analytical techniques to derive quantitative chemical information from these solutions is a long-standing challenge in the field of bioprocessing. This is particularly true for solutions rich in lignin (e.g., black liquor) due the metastable nature of solubilized lignins. Sensitivities to pH and solvent changes generally result in condensation reactions destroying the sample integrity. A research topic of continued interest is the development of non-destructive analytical techniques that can identify and quantify low molecular weight compounds present in these solutions. The below figure illustrates a non-destructive technique using a derivatization protocol adapted by our lab with a comprehensive two-dimensional gas chromatography (GCxGC) instrument to identify and measure low molecular weight compounds in weak black liquors in a non-destructive manner. While the utility of this method has been crucial to measuring the biological deconstruction of lignin-rich substrates, it is a time-consuming and difficult protocol to employ.

Representative chromatogram of APL sample illustrating a non-destructive technique using a derivatization protocol adapted by NREL with a comprehensive two-dimensional gas chromatography (GCxGC) instrument to identify and measure low molecular weight compounds in weak black liquors in a non-destructive manner.

In collaboration with researchers at the National Institute of Standards and Technology, gradient elution moving boundary electrophoresis (GEMBE) was adapted to provide the same chemical information as that obtained using the above protocol in a fraction of the time. Research continues with an aim to develop GEMBE methods to analyze a wide variety of bioprocess streams, including sugar-rich solutions generated from lignocellulosic feedstocks. The GEMBE device and developed methods could be an important tool for rapid analysis of complex process streams derived from biomass deconstruction operations.

Flow chart with molecular formulas showing the gradient elution moving boundary electrophoresis (GEMBE) analysis.

Surface Science of Catalytic Reactions Germane to Bioprocessing

Surface science studies of the interaction between adsorbates and catalytic materials have been invaluable in understanding the fundamentals of heterogeneous catalytic systems. The decades of research in catalytic surface science has predominately focused on reactions that are germane to petrochemical refining (e.g., alkane activation, olefin hydrogenation, and oligomerization). As research trends toward the chemical conversion of renewable feedstocks to fuels and chemicals, new catalysts developed for these processes face a different set of operational challenges. For example, lignin or sugar streams from lignocellulosic biomass usually contain a high water content, high salt loads, oxygenates, and a large fraction of non-target organics. These features of bioprocess streams are usually detrimental to catalytic activity via poisoning and the damaging effects of water to catalytic materials at severe process conditions. Thus, understanding the fundamental nature of how these catalysts operate is key to enabling design of tolerant materials that can maintain activity under these conditions.

Our recent LDRD award aims to gain fundamental insight into the nature of dopants in mixed metal oxides for facilitating the ketonization reaction. The ketonization reaction is interesting because it is a C-C coupling reaction joining two carboxylates to form a longer chain ketone. Thus, this reaction holds promise for the production of fuels from carboxylate-rich bioprocess streams. Oxides are better suited to handle the harsh conditions needed for conversion of bioprocess streams and understanding the link between dopants and catalytic activity in these materials is crucial to achieving high performance for oxide catalysts that is on par with industrial catalysts used for petrochemical upgrading. The image below displays the ultra-high vacuum chamber that this work is performed in and low energy electron diffraction patterns of well-defined oxides that our team has grown.

Ultra-high vacuum chamber and three low energy electron diffraction patterns of well-defined oxides.

Chemical Process Automation

A key component to all of the work our team engages in is the automation of chemical processes. Below are images of a custom flow reactor system our team designed, built, and automated. The automation of this instrument was achieved through custom software our team wrote in OPTO-22. This reactor system allows for rapid and unattended collection of data and was crucial to our team’s success in the Renewable Carbon Fiber Consortium project. Work within other projects follows the same automation philosophy. All custom-built equipment is designed to operate safely in an unattended manner allowing for rapid data collection and quick turnaround of project deliverables.

Custom flow reactor in the laboratory (left) and the systems control area with computer monitors (right).


  • Ph.D., Chemical Engineering, University of Washington, 2012

  • M.S., Chemical Engineering, University of Washington, 2010

  • B.S., Chemical Engineering, University of Colorado – Boulder, 2007

Featured Publications

  1. "In situ recovery of bio-based carboxylic acids," Green Chemistry (2018)

  2. "Renewable Acrylonitrile Production," Science (2017)

  3. "Gradient Elution Moving Boundary Electrophoresis Enables Rapid Analysis of Acids in Complex Biomass-Derived Streams," ACS Sustainable Chem. Eng. (2016)

  4. "Quantification of acidic compounds in complex biomass-derived streams," Green Chem. (2016)

  5. "Alkaline Pretreatment of Corn Stover: Bench-scale Fractionation and Stream Characterization," ACS Sustainable Chem. Eng. (2014)

  6. "Bond Energies of Molecular Fragments to Metal Surfaces Track Their Bond Energies to H Atoms," J. Am. Chem. Soc. (2014)

  7. "Energy of Adsorbed Methanol and Methoxy on Pt(111) by Microcalorimetry," J. Am. Chem. Soc. (2012)

View all NREL Publications for Eric Karp.

Awards and Honors