(64g) Competitive Transient Electrostatic Adsorption Mechanism for in Situ Regeneration of Poisoned Catalyst

Peng, Z. - Presenter, The University of Akron
Pan, Y., University of Akron
Shen, X., University of Akron
Yao, L., The University of Akron
Bentalib, A., The University of Akron
Poisoning is identified as one major cause of catalyst deactivation, resulting in billions of dollars loss every year for catalyst replacement and process shutdown. Due to strong chemisorption of poisoning species (impurities in reactant feeds or generated during reaction), active sites would be occupied and deactivated. Thus regeneration of poisoned catalysts becomes essential to recover the catalytic activity to enable their reuses. Till to date, off-site catalyst regeneration remains a common procedure in practice. However, off-site regeneration process requires periodic interruption of reaction for taking out deactivated catalyst materials for regeneration and replacing them with fresh ones, which often adds complexity over reaction control and additional operation cost. To overcome this issue, in situ catalyst regeneration is demanded.

Herein we report one new Competitive Transient Electrostatic Adsorption (CTEA) mechanism for energy-efficient and noninvasive in situ regeneration of poisoned catalyst. We utilize the Townsend discharge phenomena for Ar+ generation at a moderate DC voltage, and utilize CTEA of Ar+ for competition against chemisorbed poisoning species to regenerate the active sites. We verified effectiveness of this new concept by studying HCOOH decomposition as one model reaction and examining the effects of CTEA of Ar+ on the reaction properties. By applying a moderate DC voltage to create an electric field that generates Ar+ ions following the Townsend discharge mechanism, the deactivated Pt catalyst exhibited an immediate recovery of the activity. The extent of the catalyst activity recovery was discovered to increase proportionally to the measured Ar+ current, which was attributed to a larger number of Ar+ ions that facilitate the desorption of chemisorbed CO poisoning species to regenerate the active sites via the CTEA mechanism. DFT simulations together with Townsend discharge theory suggested that the electrostatic adsorption energy of Ar+ ions was dramatically bigger than the desorption energy of poisoning CO, which would force CO desorption to recover availability of the Pt active sites. The findings suggest CTEA mechanism offers a new, convenient and effective method to in situ regenerate poisoned catalyst materials, and shows a good potential to help reduce the operation cost associated with poisoned catalyst replacement in many reaction processes.