(707f) Zr Doping Effect On CeO2 As the Catalyst in the CO2 – Ethylbenzene Reaction
AIChE Annual Meeting
Thursday, November 7, 2013 - 2:20pm to 2:40pm
Under the thermodynamic limitation , dehydrogenation of ethylbenzene (EB) to styrene (ST) with CO2 is widely investigated. The lattice oxygen mobile capacity of catalyst is the important influencing factors in the CO2-EB reaction. CeO2 of the CaF2 structure with the excellent oxygen storage/release capacity (OSC) is preferred as the catalyst. The addition of Zr4+ to the cubic structure of CeO2 can greatly increase the OSC and improve its surface area, thermal stability, mechanical strength and surface acidity. The Zr content of CexZr1-xO2 solid solutions strongly influence the crystal structure, the mobility of lattice oxygen and the catalytic performance. CexZr1-xO2 solid solutions replacing the pure CeO2 as the catalyst could be used in oxidative dehydrogenation of EB to ST with CO2 for changing the lattice structure of CeO2 and improving the transmission capacity of lattice oxygen.
In this work, CexZr1-xO2 solid solutions with different Zr proportions were synthesized using hydrothermal method. The synthesized catalysts were characterized by X-ray power diffraction pattern, Raman spectroscopy and N2-adsorption. It was found that the catalysts were solid solution mixture having specific surface area more than 100 m2/g. By the means of the H2 temperature-programmed reduction, the lattice oxygen mobile capacity was calculated, corresponding to the order is Ce0.5Zr0.5O2 > Ce0.7Zr0.3O2 > Ce0.3Zr0.7O2 > CeO2. The performance of the catalysts for dehydrogenation of EB to ST was evaluated in a fixed-bed reactor under the conditions 823 K, 1 atm, and 20 of the CO2/EB molar ratio. Results showed that the lattice oxygen mobile capacity of CexZr1-xO2 influenced the catalytic activity and promoted activity of CO2. The Ce0.5Zr0.5O2 showed the highest activity with the EB conversion of 50% and the ST selectivity above 96%. The mechanistic model of EB dehydrogenation with CO2 over the CexZr1-xO2 catalysts was proposed.