(6bp) Enabling New Chemistries through Catalyst Design

Authors: 
Lusardi, M., California Institute of Technology
Davis, M. E., California Institute of Technology

Enabling New Chemistries through Catalyst Design

Marcella Lusardi

Research Interests:

Economies revolve around carbon-based chemicals and their derivatives. The concentrated distribution of traditional carbon resources (e.g., petroleum) renders the consumer goods, food and agriculture, and transportation industries, among others, vulnerable to fluctuations in a global carbon economy and volatile geopolitical relations. Capitalizing on unused, ubiquitous carbon feedstocks—like biomass, which most often finds its way into waste streams—addresses these economic challenges, while also adding a foundational brick to the construction of a closed carbon cycle. Unfortunately, existing processes for producing valuable chemical intermediates are only suited to handle the specific physicochemical properties of traditional feedstocks, which are starkly different (e.g., molecular weight, oxygen content) from those of alternative feeds. Thus, practically leveraging these diverse feeds requires extensive development of fundamentally new chemical processes. My work addresses this by designing the equally diverse set of catalysts that are critical to such conversion technologies.

My research approach is to understand the fundamental origin of activity within catalytic materials through rigorous materials characterization, and then use this insight to design catalysts with physicochemical properties tuned for specific chemical routes. This characterization-synthesis-reactivity cycle systemizes the discovery of structure-activity relationships across a matrix of structure parameters. A key component to my research efforts is the strong focus on in-depth, tailored synthesis techniques that enable the creation of materials with desired catalytic properties.

Catalytic material development requires a hand-in-hand partnership between synthesis and characterization. To this end, my research has focused on using intensive syntheses of organic, inorganic, and hybrid materials that carefully control the interaction among solvents, structure-directing agents/ligands/surfactants, and molecular precursors to tailor properties like porosity and active site distribution. These techniques, in conjunction with rich in-situ and ex-situ characterization methods (e.g., IR, NMR), alter and elucidate catalytically-dependent electronic and spatial environments of physicochemically-diverse materials. Examples of applications of this methodology from my prior research, along with the corresponding impact, include the following:

  • Production of xylene analogs from an ethanol derivative [1]: Next generation catalysts can use insight regarding the specific roles of acid and base centers to optimize site coordination for selective production of the para- isomer, which could be a direct drop-in intermediate in the synthesis of terephthalic acid (40 MT/yr demand for PET plastics and polyester fabrics).
  • Application of SSZ-13 as a dimethyl ether carbonylation catalyst [2]: The turnover rate for methyl acetate production over this commercially-available material (aluminosilicate with the chabazite framework) rivals that measured over the state-of-the-art zeolite carbonylation catalyst, mordenite.
  • Quantitative mapping of solvent-surfactant-precursor recipes for porous carbon nitrides [3]: The facile, one-pot synthesis method developed in this work yielded the highest reported surface area for a soft-templated carbon nitride (C/N ~ 0.75). These textural properties facilitate enhanced molecular and electronic transport in photocatalytic applications.

Physicochemical properties that impact catalytic reactivity expand beyond surface chemistry and porosity. The design of hybrid hydrophilic-hydrophobic materials, for example, could provide an avenue for executing conversion reactions that are often thwarted by the presence of water in nonconventional carbon feedstocks. Such hybrid materials could be realized through the synthesis of acid centers connected to nonpolar organic linkers, encapsulated in an inorganic scaffold of hydrophobic domains. Research in my group moving forward will continue to approach practical challenges in catalyst development for new chemical routes through optimized synthesis protocols and extensive structure elucidation.

Teaching Interests:

Teaching both undergraduate and graduate students is one of the main reasons I am interested in pursuing a career in academia. I am qualified to teach introductory chemical engineering courses, materials and energy balances, and upper-level undergraduate and graduate courses in thermodynamics. Additionally, I am interested in building a new course centered on materials characterization. Often, techniques like XRD and SEM are not encountered unless a student’s research directly requires it. Exposure in a classroom environment (in an upper-level undergraduate/graduate course) to such methods could excite and attract students who might otherwise not get exposed to a major component of materials education and research. The course would be a combination of theoretical background (e.g., the mathematics of crystal periodicity), instrument design (e.g., incident/diffracted x-ray beam, goniometer), and examples for practical application (e.g., crystallography in pharmaceuticals, catalysis, semiconductors). This course would benefit students interested or currently conducting research in a variety of chemical engineering subdisciplines.

References:

[1] Lusardi, M., Struble, T., Teixeira, A., and Jensen, K. F. “Identifying the roles of acid-base sites in formation pathways of tolualdehydes from an ethanol derivative over MgO-based catalysts.” In submission.

[2] Lusardi, M., Kale, M., Kang, J. H., Chen, T., Neurock, M., and Davis, M. E. “The origin of catalytic reactivity in chabazite-type zeolites in the carbonylation of dimethyl ether to methyl acetate.” In preparation.

[3] Peer, M.,†Lusardi, M.,† and Jensen, K. F. “Facile soft-templated synthesis of high-surface area and highly porous carbon nitrides.” Chem. Mater. 2017, 29, 1496−1506. †indicates co-first authorship.