(36e) Challenges in Implementing in2O3 Catalyst for CO2 Hydrogenation to Methanol: H2o Effect and Stability | AIChE

(36e) Challenges in Implementing in2O3 Catalyst for CO2 Hydrogenation to Methanol: H2o Effect and Stability


Jiang, X. - Presenter, Oak Ridge National Laboratory
Nie, X., Dalian University of Technology
Purdy, S., Oak Ridge National Laboratory
Guo, X., Dalian University of Technology
Walton, K., Georgia Institute of Technology
Song, C., Pennsylvania State University
Wu, Z., Oak Ridge National Laboratory
Catalytic CO2 conversion to chemical feedstocks and transportation fuels attracts great attention. In2O3 is a promising candidate for CO2 hydrogenation to methanol, and is characteristic of high methanol selectivity. However, an atomic level understanding of surface nature and structural evolution under reaction conditions and changes with time-on-stream (TOS) is lacking. This work studied the activity of In2O3 catalysts in the presence of additional moisture in feed gas and long-term stability.

The effect of additional moisture in the feed gas was studied on In2O3 and In2O3/ZrO2. Adding 0.1 mol% H2O significantly enhances CH3OH formation rate from 2.75 to 3.42 mol-kg-1-h-1 over In2O3/ZrO2. Similar enhancement is evident on In2O3. Characterization (STEM/EDS and CO2-TPD) confirms the preservation of In-Zr strong interaction in the presence of additional H2O and H2O-induced oxygen vacancies, which improves CO2 adsorption capacity. XPS reveals the formation of InOOH species due to H2O addition, which appears to correlate to H2O-dependant CH3OH enhancement. Density functional theory calculations demonstrate that adding H2O is found to facilitate surface InOOH formation, suppress COOH* pathway and thus CO formation, and promote CH3OH formation via HCOO* intermediate. However, excess H2O in the feed gas leads to aggregation of In species and reduction of surface In0 sites for H2 dissociation.

Long-term stability tests were conducted as well. After 100-h TOS, CH3OH formation rate on In2O3 drops significantly by 36%, while In2O3/ZrO2 remains stable. In situ X-ray absorption spectroscopy (XAS) results demonstrate that the stability originates from the interaction between In2O3/In2O3-x and ZrO2, which prevents deactivation through the over-reduction of In2O3 to In0. Structurally, ZrO2 plays a role in kinetically trapping In2O3/In2O3-x in an oxygen deficient state under reaction conditions.

These findings would be of importance for developing fundamental understanding of reaction chemistry involving in CO2-to-CH3OH and for shedding light on implementing In2O3 catalysts in practical process technology.