Influence of pretreatment temperature on catalytic performance of rutile TiO2-supported ruthenium catalyst in CO2 methanation

• R-TiO2 was able to stabilize Ru nanoparticles even after pretreatment at 800 °C.
• Activity was depended on encapsulation extent by TiOx layers and hydroxyl group amount.
• The maximum reaction rate was observed over the catalyst pretreated at 600 °C.

Catalytic hydrogenation of CO2 to methane was investigated over Ru/rutile TiO2, focusing on the influence of the pretreatment temperature on the activity. Rutile TiO2 stabilized Ru nanoparticles even after pretreatment at 800 °C; therefore it was possible to establish the structure–activity relationship without considering the particle size effect. The CO2 turnover frequency initially increased with increasing pretreatment temperature from 300 to 800 °C, and reached a maximum value of 1.59 s−1 on Ru/rutile TiO2 pretreated at 600 °C; it decreased to 1.16 s−1 for the sample pretreated at 800 °C. The characterization results indicated that the activity depended on both the extent of encapsulation of Ru particles by TiOx layers and the number of hydroxyl groups on the TiOx surface. The mechanism of CO2 methanation was discussed based on in situ diffuse-reflectance infrared Fourier-transform spectroscopy results.

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