Work out surface area of catalyst instantly with clear inputs, formula shown and shareable results.
BET analysis converts the gas volume needed to lay down one molecular layer into surface area. The volume at STP gives moles, moles give molecules through the Avogadro constant, and each molecule covers a known footprint - 0.162 nm2 for nitrogen at 77 K. A 2.5 cm3 monolayer on 0.2 g of catalyst works out near 54 m2/g.
Monolayer amount
n(m) = V(m) / 22414 cm3 per mol
Specific surface area
S = n(m) x NA x sigma / sample mass
It adsorbs weakly enough to form a well-defined monolayer, its cross-section is well established, and 77 K is easy to hold.
A few m2/g for dense oxides, 100-300 m2/g for alumina supports, and over 1000 m2/g for activated carbons and zeolites.