EFFECTS OF THIOPHENE AND SO2 ON ACROLEIN HYDROGENATION OVER CO SIO2 CATALYSTS/

Infrared spectra are reported of adsorbed species and gaseous products in the reactions over S-2,-modified Co/SiO2 of acrolein, propanal, al lyl alcohol and propan-1-ol with and without hydrogen. Low coordinatio n edge or step sites in high index planes contain Con+ Co-O sites whic h are active for C=O hydrogenation but are completely poisoned by SO2 pretreatment. Formation of 2-methylpenten-2-al from propanal by an ald ol reaction over oxidic cobalt sites was promoted by SO, but inhibited by hydrogen. Low index planes contain Co-O sites which are available for C=C hydrogenation of acrolein but are inactive for allyl alcohol h ydrogenation because of strong chemisorption of allyl alcohol on the S O2-treated surface. Propanol was the dominant product from acrolein, p ropanal and allyl alcohol hydrogenation over unmodified Co/SiO2 but wa s not formed over SO, modified catalyst. The acrolein reaction gave pr opanal alone. Thiophene caused partial poisoning of both low coordinat ion and high coordination sites on Co/SiO2, the hydrogenation of acrol ein giving propanal and propan-1-ol but at lower rates than for unmodi fied Co/SiO2. (C) 1998 Elsevier Science B.V. All rights reserved.