61st Annual Report on Research 2016

Our work has focused on understanding nanocatalyst properties that will selectively produce cyclohexanone, an intermediate in nylon polymer production, during the hydrogenation of phenol in the aqueous phase. We have been employing polyvinylpyrrolidone-capped palladium nanoparticles as model catalysts for this reaction. This past year, we sought to use kinetic studies to examine the role of the polymer stabilizer, as well as particle size and shape.

Over the past year, we synthesized differently sized and shaped colloidal Pd nanocatalysts stabilized by polyvinylpyrrolidone (PVP) using solution based reduction methods published in the literature.^1,2 Synthesized nanoparticles were characterized by transmission electron microscopy (TEM). We also worked to prepare supported catalysts by depositing the colloidal nanoparticles on the surfaces of silica microspheres.⁴ In order to determine the metal loading, we worked to develop a procedure using flame atomic absorption spectrometry (FAAS). This past year we generated reproducible standard curves and verified the loading of a commercial 5% Pd on silica catalyst. Our reaction studies during the past summer were again limited due to problems with the department’s gas chromatograph/mass spectrometer, despite installing a new column that improved the separation of cyclohexanone and cyclohexanol. We also worked to develop methods to measure the dispersion, or number of active sites, on the nanoparticle surfaces.

During the 2015–2016 academic year, two senior students, Josh Kauffman and Antoinette Issis worked on the project for independent research credit. Last summer, four students worked various times during the summer on different aspects of the project: Zachary Mrozek (reaction students), Katherine Gingrich (nanoparticle synthesis), Nathaniel Ginder (nanoparticle dispersion), and Kurt Mohn (palladium loading). At the end of the summer all students presented a poster at a regional scientific meeting. All students are continuing at Lebanon Valley College, with two exceptions. Josh Kauffman is currently enrolled in a Ph.D. program in chemistry at Pennsylvania State University, while Nathaniel Ginder has transferred to Case Western Reserve University to complete a 3+2 program in chemical engineering.

References

1. Li, Y.; Boone, E.; El-Sayed, M. A. Size Effects of PVP-Pd Nanoparticles on the Catalytic Suzuki Reactions in Aqueous Solution. Langmuir 2002, 18, 4921−4925.

2. Lim, B.; Jiang, M.; Tao, J.; Camargo, P. H. C.; Zhu, Y.; Xia, Y. Shape-Controlled Synthesis of Pd Nanocrystals in Aqueous Solutions. Advanced Functional Materials 2009, 19, 189–200.

3. Gude, K.; Narayanan, R. Colloidal Supported Metal Nanoparticles (CSMNs) as Effective Nanocatalysts for Liquid-Phase Suzuki Cross-Coupling Reactions. Journal of Physical Chemistry C 2011, 115, 12716−12725.