One of the major global challenges urged by the climate change and the desired paradigm shift from the fossil-fuels dependent society to a more sustainable one is the carbon management. This is closely related to how efficiently we utilize the carbon dioxide (CO2) being emitted and accumulated in the atmosphere. In the last decades, catalytic transformation of CO2 into useful chemicals such as organic and inorganic carbonates via non-reductive CO2 transformations has been widely investigated. Particularly, dimethyl carbonate (DMC) is of wide interest due to its highly attractive chemical characteristics. Direct methanol carboxylation reaction with CO2 represents a safer and cleaner way for DMC production, eliminating the use of toxic phosgene or CO while providing an extremely high atom efficiency based on the reaction stoichiometry. However, the reaction is severely thermodynamically-limited and efficient removal of co-product, water, is necessary to achieve high DMC yield. Up to date, the most successful finding involves the use 2-cyanopyridine (2-CP) as a dehydrating agent, demonstrating outstanding catalytic performance in terms of methanol conversion and DMC selectivity and we have recently demonstrated direct DMC synthesis in a fixed bed reactor over ceria (CeO2) catalysts in the presence of 2-CP with &gt;90% methanol conversion and &gt;95% DMC selectivity. Despite the extraordinary results, a severe catalyst deactivation at the time-scale of days was observed and molecularly adsorbed 2-picolinamide (2-PA, 2-CP hydration product) was identified as the origin of deactivation. In this contribution, the continous appraoch to synthesize DMC in the presence of 2-CP is described and effective strategies to prevent catalyst deactivation are presetned. The nature of catalytic active sites are also investiagted by means of various operando spectroscopic techniques (DRIFTS, Raman, XAFS) to explain why CeO2 is the unique material active in this reaction. Highlights on the catalytic activity, stability, regeneration strategy and catalytic active sites will be presented and discussed.

Continuous synthesis of DMC from CO2 and methanol over CeO2 using 2-cyanopyridine as dehydrating agent: Catalyst stability and the reaction mechanism

256th National Meeting (2018)

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