Fluorinated CuO/ZnO/MgO Catalyst Systems for the Direct CO 2 Hydrogenation to DME

The direct hydrogenation and conversion of CO 2 to dimethyl ether (DME) combines CO 2 valorization and climate change mitigation. This process requires a bifunctional catalyst (CtM//MtD) with a CO 2 ‐to‐MeOH (CtM) and a MeOH‐to‐DME (MtD) component, in which the CuO/ZnO/ZrO 2 (CZZ) CtM‐catalyst is better suited for CO 2 rich feed gases than the industrial CuO/ZnO/Al 2 O 3 (CZA) catalyst optimized for classical CO/H 2 syngas. Dehydration MtD‐catalysts include commercial zeolites (ZSM5, FER) and heteropolyacid‐coated alumina and zirconia (HPA@Al, HPA@Zr). However, ZrO 2 is significantly more expensive than Al 2 O 3 . Therefore, a novel fluorinated CuO/ZnO/MgO (CZMg‐F) system was tested for direct DME synthesis under gas hourly space time velocities (GHSVs) of 4950−158000 NL kg cat −1 h −1 at 250°C and 40 bar in a CO 2 /3H 2 stream. The study showed that CZMg‐F combined with ZSM5 and FER achieved similar activities to CZZ‐based catalysts. CZMg‐F//HPA@Zr exhibit superior DME selectivity (50%) at high GHSV, outperforming all other tested CZMg‐F and CZZ hybrid catalysts. The only exception was CZMg‐F//HPA@Al, which exhibits significantly lower DME activity, most likely due to unfavorable interactions with Al 2 O 3 . Compared to the low activity of CZZ//FER at high GHSV, CZMg‐F//FER showed much higher DME activity, making CZMg‐F a better alternative in combination with FER at high GHSV.