Support composition and annealing temperature of NH4ReO4/Al2O3-SiO2 systemeffect rhenium heterogeneous metathesis catalyst properties

NH4ReO4, supported in wt. 3.3% quantity on laboratory made amorphous alumin a-silicas composed of wt. 20, 40, 60, 80 and 100%(wt) of Al2O3, was anneale d at 200, 300, 400, 500, 600 and 700 degrees C for 2 h under air and I h un der nitrogen. This way prepared catalysts, after modification with tetraeth yllead (Et4Pb), were tested in the hexene-l metathesis reaction. Both the s upport composition as well as calcination temperature affects the prepared catalyst activity. Low content Al2O3 catalysts are relatively more active w hen prepared by annealing at relatively lower temperatures. Contrary, the h igh content Al2O3 catalysts exhibit relatively higher activity after prepar ation at relatively higher temperatures. All catalysts, containing alumina- silica as supports and prepared between 300-500 degrees C, demonstrated the highest activity. When alumina is the catalyst support, the activity incre ased according to the calcination temperature growth.