High throughput experimentation (HTE) in catalysis has proven useful in expediting materials discovery via parallelized synthesis, characterization, and testing of candidate materials. However, even in a high-throughput manner, the combinatorial explosion of relevant parameters far exceeds our ability to study. To further complicate the problem, a large time investment and great deal of characterization is often required to build an in-depth understanding of catalytic materials. It follows that the field of heterogeneous catalysis is rich with examples of catalytic systems that have been developed using trial and error efforts for which a lot is known but context is lacking. Techniques such as machine learning and statistical design methodology can be used together with HTE to address this by facilitating more efficient and meaningful exploration of large parameter space problems. Here, two examples of oxidation catalysis will be highlighted where design of experiments was successfully paired with HTE to aid the catalyst development process and build novel synthesis-structure-activity relationships. First, synthesis factors important in the one pot colloidal synthesis of cobalt oxide nanoparticles including surfactant type, heating regimen, reducing agent, and reagent concentrations were studied with a series of factorial designs. Factors were linked to structural parameters including grain size and morphology as well as CO oxidation activity parameters such as light off temperature and activation energy. Ultimately, experiments revealed that the density of catalytically active grain boundaries and structure of the CoOx intermediates were the most important factors in enhancing the Co3O4 reactivity and provided models to tune these variables using synthesis conditions. Second, a series of co-promoters including Cs, Re, Sn, and Au were screened for use in the Cu-Ag/α-Al2O3 ethylene epoxidation system. Factorial design was used to screen component loadings, component impregnation order and reactant feed composition. It was found that the activity of the catalysts was sensitive to both the co-promoters used and the reactant feed composition which further experimentation revealed was linked to the Cu-Ag alloy behavior and Ag particle size.

Combinatorial study of oxidation catalysts: Uncovering structure-activity relationships

255th National Meeting (2018)

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