After building the mechanisms in RMG, models were simulated using Cantera All surface reactions were 'turned off' for the first 10 mm of the PFR by setting the multipliers to zero, as there are no surface reactions if there is no catalyst. Surface reactions were turned on by setting multipliers back to 1.0 for 10 mm to 20 mm and back to zero for the remainder of the reactor. Gas-phase reactions remained 'on' for the entirety of the PFR.