CONICET | Buscador de Institutos y Recursos Humanos

The liquid-phase dehydration of alcohols is widely used in chemical industry because it forms valuable unsaturated organic molecules. Commercial processes for this reaction use strong mineral acid catalysts, such as H2SO4, KHSO4 or p-toluensulfonic acid that entail concerns related to high toxicity, corrosion, and material disposal. New industrial strategies demand the replacement of liquid acids by solid catalysts. However, studies on alcohol dehydration over solid acids have been essentially performed in gas phase, at relatively high temperatures. In particular, 15 % of the worldwide production of styrene is obtained via the dehydration of 1-phenylethanol (PhE), a byproduct in the propylene oxide synthesis process. 1-Phenylethanol dehydration is also a useful test reaction because 1-phenylethanol is structurally similar to much more expensive alcohols widely used in Fine Chemicals. One example is the dehydration of indanols to produces indenes [1]. However, very few papers deal with the liquid-phase dehydration 1-phenylethanol [2] and knowledge on the exact requirements of density, nature and strength of surface acid sites for improving the styrene yield and selectivity on solid acids is lacking. Figure 1 shows the reaction pathways involved in 1-phenylethanol conversion reactions. 1-Phenylethanol may be converted by intramolecular dehydration to styrene (S) but also may simultaneously form alpha-methylbenzene ether (AME) via an intermolecular dehydration/condensation reaction. Both products are consecutively converted to heavy products (HP). In this work, we studied the liquid-phase conversion of 1-phenylethanol on samples containing only either strong Brønsted (HPA/SiO2) or Lewis (ZnO/SiO2) acid sites, and catalysts containing both Lewis and Brønsted acid sites of either strong (zeolites HZSM5 and HBEA) or moderate (SiO2-Al2O3, Al-MCM-41) strength.