Catalytic oxidative dehydrogenation of 1-butene to 1,3-butadiene with CO 2 over Fe 2 O 3 /γ-Al 2 O 3 catalysts: the effect of acid or alkali modification

Fe2O3/γ-Al2O3 catalysts were modified by acid and alkali (H2SO4, LiOH, NaOH and KOH) and were investigated for 1,3-butadiene (BD) synthesis through the oxidative dehydrogenation of 1-butene with CO2. Nitrogen sorption and XRD results revealed that physical and original crystalline structure of Fe2O3/γ-Al2O3 catalysts remained intact after the modification. The acidity and alkalinity of the catalysts were determined quantitatively and qualitatively by NH3-TPD and CO2-TPD, respectively. The sequence of catalyst activity for these five catalysts was: Li–Fe2O3/γ-Al2O3 > S–Fe2O3/γ-Al2O3 > Fe2O3/γ-Al2O3 > K–Fe2O3/γ-Al2O3 > Na–Fe2O3/γ-Al2O3. The catalytic activity (BD rate) of Fe2O3/γ-Al2O3 catalysts was improved ~41% after the modification of LiOH. Results indicated that too little amount of acid sites as well as the strong basic sites over catalyst surface were not facilitate to the formation of BD. TG characterization results illustrated that the coke resistant ability of the catalysts was enhanced with the catalyst alkalinity.