Quantification of Formate and Oxygen Coverages on Cu Under Industrial Methanol Synthesis Conditions

Methanol‐Assisted Autocatalysis in Catalytic Methanol Synthesis

“…We show here for the first time that methanol formation over the industrially applied Cu/ZnO/Al 2 O 3 catalysts is dominated by an autocatalytic pathway that involves methanol. At high SV the methanol synthesis is almost exclusively formed from CO 2 with the industrial Cu/ZnO/Al 2 O 3 catalyst . This is most likely also the case at lower SV, where the rate from a CO 2 ‐containing gas (>5 g MeOH g cat.…”

“…The heat generated in the exothermic reaction increases with conversion/product concentration regardless of the support, but here no significant temperature rise was observed, and the fact that TOF for Cu/Al 2 O 3 did not grow with conversion shows that the acceleration is not due to a temperature rise. As CO 2 is the primary reactant in methanol synthesis over pure Cu and Cu/ZnO(/Al 2 O 3 ) it is important to evaluate, if changes in CO 2 concentration can arise from the variations in conversion. CO 2 is consumed by methanol synthesis (reaction , subsequently denoted R1), but partly restored through water‐gas shift (reaction , subsequently denoted R2). …”

“…At higher conversion with greater water formation more methanol is formed by the CO→CO 2 →CH 3 OH sequence of R2 followed by R1, but the constancy in CO 2 concentration across the reactor (Figure S2) suggests that R2 is fast, and consequently methanol synthesis (R1) is always solely rate limiting. Adsorbed formate is present on the metal surface at methanol synthesis conditions, which suggests that the autocatalytic pathway could involve CO 2 ‐derived formate. Figure a shows that CD 3 OOCH was formed at low temperature, when Cu/ZnO/Al 2 O 3 with pre‐adsorbed HCOO (from exposure to HCOOH/N 2 at 303 K) was subjected to temperature programmed reaction (TPR) in a flow of CD 3 OD in He.…”

“…At high SV the methanol synthesis is almost exclusively formed from CO 2 with the industrial Cu/ZnO/Al 2 O 3 catalyst. [9,13,14] This is most likely also the case at lower SV, where the rate from a CO 2 -containing gas (> 5 g MeOH g cat.…”

“…CH 3 OH sequence of R2 followed by R1, but the constancy in CO 2 concentration across the reactor ( Figure S2) suggests that R2 is fast, and consequently methanol synthesis (R1) is always solely rate limiting. Adsorbed formate is present on the metal surface at methanol synthesis conditions, [14,21,22]…”