Synthesis of cyclic carbonates from epoxides:: Use of reticular oxygen of Al2O3 or Al2O3-supported CeOx for the selective epoxidation of propene

Reticular oxygen of Al2O3 or CeOx supported on Al2O3 was used for the epoxidation of propene without any double bond cleavage. In batch reaction, Al2O3 alone was able to convert propene into propene oxide (PO) with 100% selectivity and 2% conversion of propene with a close to 3:1 ratio with respect to the number of AI(111) reduced to elemental Al. When Ce2O3/Al2O3 or Ce2O3/Al2O3 was used, At remained in its +3 oxidation state. while the Ce oxide was the oxidant as demonstrated by XPS analyses. CeOx/Al2O3 was more active (propene conversion yield of 4-5%) but the selectivity was lower (70%) as PO was isomerized into acetone and propionaldehyde. Interestingly the use of reticular oxygen very much improves the selectivity with respect to the use of pure O-2. In fact, while propene was more efficiently oxidized (10%) with O-2 in presence of Al2O3 or CeOx/Al2O3, the selectivity was as low as 40% because C1 and C2 products were formed. However, the use of reticular oxygen represents a selective two-step technique for the use of molecular oxygen as oxidant of propene. The used oxides can be re-oxidized and the whole process can be further improved towards higher yields. PO is quantitatively converted into propene carbonate by reaction with Co-2 in presence of Nb2O5. (c) 2006 Elsevier B.V. All rights reserved.