Green methanol is made by hydrogenating captured CO₂ with hydrogen from renewable electrolysis, over a copper/zinc-oxide/alumina (Cu/ZnO/Al₂O₃) catalyst bed — the gold band in the reactor. Grey-red spheres are CO₂ molecules, small blue spheres are H₂, entering at the top and falling through the bed. Where a CO₂ molecule meets at least three H₂ molecules inside the catalyst band, they can react to form one methanol molecule (green) and one water molecule (cyan), which exit at the bottom. Anything that passes through unreacted is recycled back to the feed, just like the real recycle loop around an industrial methanol converter.
CO2 + 3 H2 ⇌ CH3OH + H2O ΔH < 0 (exothermic)
conversion ∝ kinetics(T) × equilibrium(T, P)
- Temperature — higher temperature speeds up the reaction kinetically, but the equilibrium itself is exothermic and shifts *back* toward CO₂ + H₂ as temperature rises. The visible conversion rate peaks around 230–260 °C, the same sweet spot real Cu/ZnO/Al₂O₃ plants target.
- Pressure — the reaction converts 4 moles of gas into 2, so by Le Chatelier's principle higher pressure pushes the equilibrium toward methanol. Raising the slider visibly increases the reaction rate in the bed.
- H₂:CO₂ feed ratio — the stoichiometric ratio is 3:1. Too little H₂ starves the reaction of a reactant it needs three of; too much just dilutes the bed with unreacted hydrogen that gets recycled.
- Feed rate — how fast fresh CO₂ and H₂ enter the reactor; higher throughput fills the vessel faster but does not by itself change the fraction that converts.
Real-world relevance: this is the core chemistry behind e-methanol plants that pair direct-air-capture or point-source CO₂ with electrolytic hydrogen to make a carbon-neutral drop-in fuel, increasingly used for shipping.