Pd Nanoparticles Encapsulated in Mesoporous HZSM-5 Zeolite for Selective One-Step Conversion of Acetone to Methyl Isobutyl Ketone

Abstract

Here we report a bifunctional catalyst comprised of Pd nanoparticles encapsulated in a solid acid mesoporous HZSM-5 zeolite for one-step synthesis of methyl isobutyl ketone (MIBK) from acetone at 150 °C and atmospheric pressure. The Pd nanoparticles are encapsulated in conventional HZSM-5 and mesoporous HZSM-5, prepared using a carbon template procedure. The nanoparticles are encapsulated using in situ encapsulation during the zeolite synthesis and post impregnation to investigate the effect of preparation procedure, zeolite confinement and distribution of nanoparticles. Additionally, the influence of Si to Al ratio of HZSM-5 zeolite and hence the effect of acidity was also analyzed. The prepared materials are characterized with various techniques including SEM, TEM, XRF, nitrogen physisorption and XRD among others. Of different materials, palladium nanoparticles encapsulated inside mesoporous zeolite via in situ encapsulation (Pd@MesoHZSM-5) were found to be the most active and highly selective (> 99%) for the formation of MIBK with a conversion of 37%. Moreover, the mesoporous zeolite structure increased the mass transfer and thereby enabling acetone to diffuse easily to the active sites excluding the formation of by-products.