Abstract
Characterization of acid-base centers and catalytic dehydration of 2,3-butanediol (BDO) was performed over a wide range of silica-supported alkali phosphates (M_P/SiO2; M = Na, K, Cs; M:P = 0.5–3 mol:mol). Selectivity to 1,3-butadiene (BD) and 3-butene-2-ol (3B2OL) formed by elimination correlates with the densities of conjugated acid-base pairs and increases in the order Na < K ≈ Cs. Selectivity to 2,3-epoxybutane (BTO) formed by dehydrative epoxidation increases with the M/P ratio in the order Na < K ≤ Cs. Methyl ethyl ketone (MEK) and isobutyraldyde (IBA) formed by the rearrangement are produced by isolated Brønsted acid centers. Conjugated acid-base pairs are probably composed of the end groups of polyphosphates having both acid P-OH and base PO−⋯M+ moieties. Isolated Brønsted acid centers are probably silica grafted phosphoric acid molecules at low M/P and PO(OH)2 end groups of oligophosphates at M/P > 1.5.Deactivation rate increases with the increase of M/P ratio in order Na < K < Cs. Deactivation patterns imply that sites responsible for elimination are active in dehydrative epoxidation. Dehydration of 3B2OL smoothly proceeds to BD, but the catalysts deactivate faster compared to BDO dehydration.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call