Stereo-selective hydrogenation of 3-hexyne over low-loaded palladium catalysts supported on mesostructured materials

This paper studies the effect of mesostructured materials in the stereo-selective hydrogenation of 3-hexyne at 298 K and 40 psig pressure of H 2 over Pd-supported catalysts at different substrate:palladium (S:Pd) molar ratios. The catalysts were prepared by impregnation using a toluene solution of Pd(acac) 2 to obtain a metal content close to 1 wt.% over SBA-15 with one-dimensional hexagonal structure, MCM-48 silica with cubic structure and three-dimensional pore system and MSU-γ alumina with a lathlike particle morphology. All the supports were characterised by nitrogen adsorption–desorption isotherms at 77 K, TEM, XRD and H 2 chemisorption and TEM measurements. The reactions were found to be zero order with respect to 3-hexyne concentration. The starting 3-hexyne produces primarily cis -3-hexene, which subsequently is either hydrogenated to hexane or isomerized to trans -3-hexene and 2-hexenes that are found in very small amounts depending on the nature of the support used. Palladium catalysts supported on SBA-15 was the most active and selective catalyst.