Partial Hydrogenation of 2-Methyl-3-butyn-2-ol over Pd/ZnO: Effect of Reduction Temperature on Alloy Formation and Catalytic Response

We have investigated the catalytic effect of β-phase PdZn alloy on selective gas phase hydrogenation of 2-methyl-3-butyn-2-ol (MBY) over Pd/ZnO using Pd/Al2O3 as a benchmark. Activation (in H2) of Pd/ZnO to 973 K generated a Β-phase PdZn alloy (from XRD). Five intermediate samples with a modified surface PdZn/Pdδ- mol ratio (based on XPS) but similar metal nanoparticle size (mean size = 6 nm from HRSEM/STEM) were generated by changing the final activation temperature between 403 K and 973 K. Activation over the same temperature range increased metal nanoparticle size (6 → 10 nm) and lowered the surface Pdδ- content in the Pd/Al2O3 samples. In each case, regardless of the activation temperature, greater selectivity to target 2-methyl-3-buten-2-ol (MBE) was observed over Pd/ZnO relative to Pd/Al2O3. Both catalysts delivered a similar activity/selectivity trend characterised by enhanced MBE selectivity and lower activity over the systems activated at higher temperature. We associate this response to formatio...