Isotope effect in formaldehyde steam reforming on Pt/m-ZrO2: Insight into chemical promotion by alkalis

Infrared spectroscopy, temperature programmed reaction mass spectrometry (TP-reaction/MS), and catalyst testing were used to investigate alkali promotion of dehydrogenation selectivity during formaldehyde steam reforming (FSR) on Pt/m-ZrO2. In a preferred pathway, formaldehyde reacts with water forming hydrogen and formate, followed by forward formate decomposition to CO2 and H2. Alkali-doping of 2 wt% Pt/m-ZrO2 increases catalyst basicity, which weakens the formate CH bond promoting formate dehydrogenation / decarboxylation. Promotion by alkali in FSR was observed through a formate ν(CH) band shift to lower wavenumbers in infrared spectroscopy, and through a decrease in the normal isotope effect in switching from H- to D-labeled formaldehyde in TP-reaction/MS. [Display omitted] •Alkalis promote formate decarboxylation / dehydrogenation in FSR over Pt/m-ZrO2.•Alkali doping of Pt/m-ZrO2 increases catalyst basicity.•The -O2C of formate intermediate is held more tightly, weakening the CH bond.•In IR spectroscopy, the formate ν(CH) band is shifted to lower wavenumbers.•Adding alkali decreases the normal isotope effect for formate CH bond scission.