Catalytic oxidative cracking of n-propane over nanosized gold supported La_2O_3 catalysts

摘要

Nanosized gold deposited bare and sulfated La2O3 samples were synthesized and utilized for catalytic oxidative cracking of n-propane. Bare La2O3 showed only 10% conversion with 15% olefin selectivity, however significant enhancement in the conversion of n-propane was observed when La2O3 support was deposited with 0.2 wt% gold (25% conversion and 39% olefin selectivity) at 550 degrees C. Further improvement in conversion (46%) and in 53% selectivity was observed with gold supported 10 wt% SO42-/La2O3 catalyst. Gold supported sulfated La2O3 catalyst showed stable activity even after 20 h and the catalysts are resilient to formation of the coke. Presence of partially oxidized gold species and sulfate ions resulted enhancement in Lewis and Bronsted acidity of the catalysts. Homogeneous dispersion of gold nanoparticles and presence of metal-sulfate interactive species was observed in case of gold supported sulfated La2O3 catalyst as evidenced by TEM, CO chemisorption and H-2-PR analyses. The enhancement of catalytic activity could be attributed to small particle size, balanced Lewis and Bronsted acid sites and high dispersion of gold nanoparticles, surface area and oxygen mobility of the catalysts.