Turning CO2 into di-methyl ether (DME) using Pd based catalysts – Role of Ca in tuning the activity and selectivity

Herein, we report high-performance Pd and Ca-promoted Pd nanoparticles (NPs) (~2–6 nm) over mesoporous CeO2 with dual functionality of converting CO2 to methanol and its dehydration to di-methyl ether (DME) in a single catalyst bed prepared by a single-pot sol–gel chelating (SGC) method. Moreover, Ca promotion (0.5wt. %, optimized value) greatly improved the catalytic performance (XCO2: 30.5 %, SDME: 70.5 % and space time yield (STYDME): 5276 mmol/kgcat.hr at 325 °C and 20 Bar) by increasing Pd0 content over CeO2 and tuned the redox properties of CeO2 as well as basicity/acidity of tested samples as evidenced by the characterization results. In situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) provided insights of the formation of DME and CH4 with visible respective IR bands along with the identification of various transient surface species emerged over the catalyst surface at actual reaction conditions which led us to propose a reaction mechanism following a formate route to methanol and its subsequent dehydration to dimethyl ether.