Lewis/Brønsted balance as a key factor in the selective liquid-phase dehydration of 1-phenylethanol into styrene

NICOLÁS M. BERTERO; CARLOS R. APESTEGUÍA; ALBERTO J. MARCHI

Salamanca

Congreso; IX EuropaCat Congress; 2009

The liquid-phase dehydration of 1-phenylethanol (FE) was studied at 363 K on different acid solid catalysts. The catalyst activity and selectivity greatly depended on the nature and strength of surface acid sites. Samples containing exclusively Lewis (L) acid sites of moderate or weak strength (ZnO(20%)/SiO2) exhibited a poor activity and high selectivity to alfa-methylbenzyl ether (ET). SiO2-Al2O3, containing predominantly L acid sites of moderate and strong acidity, selectively transformed FE to ET that was sequentially converted to ES and heavier products (PP). HPA(28%)/SiO2, containing mainly strong Brönsted acid sites, dehydrated FE mainly to ET and to ES but in lower amount; then both products were consecutively transformed to PP at high rate. Zeolites HBEA and HZSM-5, which contain similar density of Brönsted (B) and Lewis (L) acid sites, converted initially FE into ES in a higher degree than to ET. Over larger size pore zeolite (HBEA) all reaction products were formed. Instead, over HZSM-5, probably due to the shape selectivity, the S selectivity was boosted to a value higher than 93%.