# Stabilizing Pd Catalysts for Liquid-Phase Hydrogenation of N‑Heterocyclic Hydrogen Carriers through Zeolite Encapsulation

## TL;DR

Researchers found that enclosing palladium nanoparticles in zeolites prevents them from clumping during hydrogenation reactions, improving catalyst stability for hydrogen storage.

## Contribution

The study introduces zeolite encapsulation as a novel method to stabilize Pd nanoparticles during liquid-phase hydrogenation.

## Key findings

- Pd nanoparticles in zeolites remain stable at <2 nm size during N-MID hydrogenation.
- Pd/SiO2 and Pd/Al2O3 catalysts suffer from sintering during the same reaction.
- Zeolite voids likely prevent Pd chelation and migration by N-MID molecules.

## Abstract

N-Heterocyclic aromatics can reversibly store H2 through
(de)­hydrogenation over supported Pd catalysts, but metal nanoparticles
often sinter during liquid-phase reactions. Here, we report that the
encapsulation of Pd nanoparticles in large-pore zeolites stabilizes
Pd catalysts during hydrogenation of N-methylindole
(N-MID). Flow reactor studies combined with post-reaction characterizations
show that Pd nanoparticles supported on SiO2 or Al2O3 sinter during hydrogenation of N-MID, while
Pd/zeolites (particularly Pd/Beta) retain <2 nm particles, likely
by suppressing the chelation and migration of Pd by N-MID. This work
highlights the potential of zeolitic voids to suppress metal catalyst
deactivation in liquid-phase reactions including H2 storage
in chemical bonds.