New solid oxo-rhenium and oxo-molybdenum catalysts for the deoxydehydration of glycols to olefins

Several new solid oxo-rhenium and oxo-molybdenum catalysts were tested for the deoxydehydration (DODH) of 1,2-diols to terminal olefins employing aromatic solvents and reaction temperatures of 150–200 °C. A catecholato oxo-rhenium catalyst tethered to silica was prepared and found to have comparably high DODH activity to its soluble analog with triphenylphosphine as the reductant. Catalyst re-use and leach-test experiments show significant leaching into the liquid phase. Silica, ceria and, for the first time, alumina and iron oxide were tested as supports for perrhenate, with ceria producing the least active material in 1,2-decane diol DODH. Decene yields obtained with ReOx/SiO2, ReOx/Fe2O3, ReOx/Al2O3 were highest when triphenylphosphine was the reductant and reached 70 − 78% (at 90–100% conversion) at 150 °C. These three catalysts were also effective with gaseous reductants H2 or CO. Leaching of rhenium species occurred for all supports and was most pronounced for SiO2. New solid oxo-molybdenum catalysts were synthesized. At 200 °C, decene yields observed using MoOx/Fe2O3, MoOx/SiO2, MoOx/Al2O3, MoOx/TiO2 and MoOx/ZrO2 were comparable and did not exceed 20%. There were homogeneous contributions through leached molybdenum species.