Atomic layer deposited Palladium nanoparticle catalysts supported on Titanium dioxide modified MCM-41 for selective hydrogenation of acetylene

Abstract

In the chemical industry palladium-based catalysts are commonly used to remove trace amounts of acetylene from ethylene feed. In this work atomic layer deposition (ALD) is utilized to synthesize uniformly dispersed Pd nanoparticles inside the meso-pores of a silica molecular sieve MCM-41. The space confinement effect from the internal channels of the molecular sieve leads to a very narrow size distribution (2–3 nm) of Pd nanoparticles and effectively prevents the particles from sintering during high temperature treatments. In selective hydrogenation of acetylene the ALD Pd nanoparticle catalysts exhibit excellent catalytic performances under ambient temperature and pressure. The excellent performance of the ALD catalyst is attributed to small Pd nanoparticles uniformly dispersed in the meso-pores of MCM-41 so that more Pd surface sites are available for the catalytic reaction. The strong metal support interaction between Pd and TiO2 can be induced by high temperature treatments, which suppresses the surface adsorption of both acetylene and ethylene, leading to decreased acetylene conversion and improved ethylene selectivity. The high temperature treatment also helps improve the stability of the catalysts.