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UBC Theses and Dissertations

Toward carbon-neutral hydrogenation using a palladium membrane reactor Jansonius, Ryan


Organic chemicals are the building blocks for plastics, clothing, fertilizers, pharmaceuticals and fuels. Nearly all these materials are manufactured at high temperatures, using fossil fuels to heat the reactors. These processes are resultantly carbon intensive. This thesis presents a technology, called an electrocatalytic palladium membrane reactor (ePMR), that can reduce the carbon impact of chemical manufacturing by using only water and electricity to produce hydrogenated chemicals. This reactor generates reactive hydrogen atoms from water electrolysis, the hydrogen atoms then pass through a palladium membrane to react with an unsaturated feedstock at the opposite surface of the metal. By using an electrochemical driving force, the ePMR can perform hydrogenation without any fossil-derived inputs or high temperatures or pressures. I first focused on the palladium electrode at the center of the ePMR. I investigated how the spacing between palladium atoms influences the rate that hydrogen is produced during electrolysis, and also the amount of hydrogen that absorbs into the palladium electrode. I designed an electrochemical cell that applies mechanical strain to the palladium lattice and used electrochemical measurements to show that tensile strain increases the hydrogen production rate, and decreases the amount of hydrogen that absorbs into the lattice. I then focused on increasing the rate of hydrogenation in an ePMR through electrochemical flow cell design. I developed a flow reactor to enable up to 15-fold faster hydrogenation rates than can be achieved in a conventional palladium membrane reactor. This flow cell also enabled me to study how hydrogen in the membrane influences reaction rate and selectivity. Hydrogenation rate is proportional to the hydrogen loading in the membrane, while selectivity for the alkene intermediate is inversely proportional to hydrogen content. Finally, I show that hydrogenation reactivity can be influenced by depositing secondary metals on the hydrogenation surface of the palladium membrane. This approach was designed to increase reactivity for harder-to-reduce C=O functionalities. I found that thin films of iridium, gold and platinum all increase hydrogenation rates for carbonyl groups, while only platinum increases hydrogenation rates for C=C unsaturations. This work provides a new catalyst design strategy for tailoring reactivity in the ePMR.

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