Lewis/Bronsted 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, España

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, NaY) exhibited a poor activity and high selectivity to alfa-methylbenzyl ether (ET). The same happened with catalysts containing predominantly L acid sites of moderate and strong acidity (SiO2-Al2O3), which selectively transformed FE to ET that was sequentially converted to ES and heavier products (PP). Catalysts containing only strong Brönsted acid sites, such as HPA(28%)/SiO2, dehydrated FE directly to ET and also via the formation of ES; and both products were consecutively transformed to PP at high rate. Zeolites HY, HBEA and HZSM-5, which contain similar density of Brönsted (B) and Lewis (L) acid sites, converted initially FE into ES and ET, but in a higher degree to ES. Over larger size pore zeolites (HY, HBEA) all reaction products were formed while over HZSM-5, due to the shape selectivity, the S selectivity was boosted to a value higher than 93%.