Synthesis of WO3/CeO2 Nanorod Catalyst via Ammonium Paratungstate

Nitrogen oxides (NOx), produced by burning of the biofossil fuels, have been recognized as an air pollutant that can cause a series of NH3-SCR has been demonstrated to be one of the state-of-the-art technologies.

However, there are some unavoidable defects of the traditional WO3 or MoO3 promoted V2O5/TiO2 catalyst, such as the narrow reaction temperature range, and the potential hazards of V2O5 to the environment and human beings et al.  Ceria has attracted much research attention for NH3-SCR reaction as an active component or support of catalyst due to its excellent oxygen storage capacity and the ability of easy shuttling between 3+ and 4+ oxidation states. For instance, CeO2/TiO2 catalyst had been synthesized with different methods for NH3-SCR, which exhibited excellent catalytic performances.

15 wt% WO3/CeO2 nanorod by wet-impregnation method using ammonium paratungstate (APT) as one of the raw materials has been conducted with excellent catalyst performance.

The synthesis process of 15 wt% WO3/CeO2 nanorod can be concluded as below:

For the preparation of the CeO2 rod, 1.736 g Ce(NO3)3·6H2O and 19.2 g NaOH were respectively added into 20 and 60 mL deionized water. Then, the former solution was added into the latter drop by drop. After stirring for 30 min, the solution was transferred into a 100 mL autoclave and then kept at 100 °C for 24 h. The obtained product was collected by filtration, washing, and drying. The final product was acquired after calcination at 450 °C for 4 h in a 10% O2/N2 mixture flowing at 50 mL/min.

The doping of WO3 and CeO2 were reached by the conventional wet-impregnation method. An equal mass of analytical grade ammonium paratungstate (APT), the precursor of WO3 and oxalic acid were added into the deionized water. The calculated amount of CeO2 was added into the above mixture and was continuously stirred for another 1 h. Then, the rotary evaporator was applied to evaporate off the excessive water. The obtained powder was dried at 110 °C for 12 h and calcined at 450 °C for 4 h.

In conclusion, 15 wt% WO3/CeO2 nanorod was successfully produced by wet-impregnation method using ammonium paratungstate (APT) as one of the raw materials. The TEM image of the WCR with a diameter of about 7 nm and a length between 14 and 60 nm. The HRTEM image of WCR indicated that the interplanar spacing, at 0.31 nm.

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