(3gy) Lessons Learned: Making Biodiesel with the Nbb, Lignocellulosic Pretreament at a Start-up, Rational Catalyst Design during a Ph.D., and Now, Catalysis for Plastics Upcycling

If Jacques Monod, the 20^th century biochemist, were alive today and applied his microbial growth model to our human population on earth today, he would conclude that this population has transitioned into what he called, a retardation phase. He characterized the retardation phase of microbial growth as one where nutrients for growth are starting to become limited and there is a build-up of toxic products. This is not to imply the human race is headed toward a death phase. However, we all could agree there is a convergence of challenging problems that our society currently faces. From the dire predictions of global warming, to the estimate that there will be more plastic in the ocean than fish by 2050, there has never been a more critical time for technological innovation to pull humans toward more sustainable habitation on earth. Chemical Engineers have a unique ability to provide inventions capable of monetizing the waste we generate (e.g. carbon dioxide, waste plastics, etc.) by developing catalysts and processes that transform these cheap feedstocks into value-added or upcycled products. In this poster I will present my current Postdoctoral research efforts on two new plastic upcycling catalyst systems and the lessons I learned from a Ph.D. focused on tuning the near-surface environment of catalysts using self-assembled monolayers (SAMs).

As a Director’s Postdoctoral Fellow at the National Renewable Energy Laboratory, this is the focus of my current research; catalysis to further plastics upcycling. I’ll be presenting research efforts to develop a fully heterogeneous catalyst system capable of depolymerizing polyethylene to a distribution of alkane products at temperatures below 200°C by leveraging two chemistries that operate in tandem. Tandem dehydrogenation and olefin cross metathesis is capable of depolymerizing polyethylene to a tunable distribution of alkane products by varying certain process parameters, like the solvent. We have been able to develop a series of different catalysts capable of performing these chemistries together. The role of support, promotors, process conditions, and catalyst pretreatment will be presented.

We are also pursuing hybrid, biological and chemical processes for plastics upcycling. To successfully launch a “plastics biorefinery,” a variety of products and associated processes will be needed to remain financially solvent during market fluctuations (a lesson the biofuels industry learned the hard way). Our interdisciplinary team of catalysis engineers and molecular biologists has developed a process capable of depolymerizing mixed waste plastics to a distribution of intermediates that is then biologically funneled toward single product. Our focus has been to provide for maximal depolymerization yield of plastics, but with minimal inhibition to biological catalysts capable of consuming this mixture. I’ll be presenting our achievements in catalyst and process development for this yet to be published work.

My interest in using science & engineering to combat the challenges of global warming and poor waste management did not begin during my postdoc. This has been true since I was undergraduate student when I founded a student group to make biodiesel from waste vegetable oil on campus and continued as a M.S. student when I co-founded the Next Generation Scientists for Biodiesel in partnership with the National Biodiesel Board to organize educational webinars about biodiesel chemistry. I continued my interest in furthering the commercial viability of biofuels production while working as a research associate at a cellulosic ethanol start-up company (Mascoma Corporation) with a focus on pretreatment technologies. My time at Mascoma, ignited an excitement for developing catalytic technologies to facilitate the 1^st and 2^nd generations of the biorefinery industry, which led to my Ph.D. work in rational catalyst design.

My Ph.D. focused on rational catalyst design to further dehydration reactions, those needed to provide value-added products to industries like biodiesel (i.e. glycerol valorization). With a fundamental focus, I sought to understand how self-assembled monolayers (SAMs) could be utilized to tune catalyst properties such as adsorption orientation or site-selection. These strategy of controlling the near-surface environment were developed for noble metal catalysts with thiolate SAMs and has been utilized with great success. However, this strategy had not been demonstrated for inexpensive metal oxide catalysts, which are most useful for acid-base catalyzed reactions such as dehydration. My Ph.D. demonstrated that this methodology for controlling the near-surface environment of metal oxide catalysts using SAMs was viable with four strategies demonstrated, 1) active site selection, 2) steric hindrance, 3) site creation, and a new strategy 4) tuning surface electronics. In this new strategy, tuning surface electronics, SAM molecules were selected with varying dipole moments. This created a tunable near-surface electronic environment, which increased reaction rates by changing transition state geometry.

My Ph.D. taught me numerous lessons in rational catalyst design. My postdoc taught me I can use this knowledge to develop innovative solutions for challenging problems like waste plastic upcycling. My future work will continue to use these lessons to tackling global problems through designing catalyst systems, hopefully creating a phase of growth that Jacque Monod never found, sustainable growth.