Epoxidation of cyclic alkenes with hydrogen peroxide and tert-butyl hydroperoxide on Na-containing Ti beta zeolites

The liquid-phase epoxidation of a series of cyclic alkenes with H2O2, and T BHP over Na-Ti beta zeolites without undergoing further acid-treatment has been carefully investigated. Many factors such as the time, the conversion, the solvent, the Si/Na ratio, the Si/Ti ratio and the Ti/Na ratio, have be en found to take effects on the conversion of cyclohexene and H2O2 as well as the selectivity to epoxide. Lower conversion (about 6.2 mol%) of cyclohe xene has shown an improvement for the selectivity to epoxide (about 90%). T he solvent having bigger dielectric constant is very helpful to enhance the reactivity of substrate, particularly MeCN is an optimal choice for improv ing the selectivity to epoxide (up to 59%). The reactivity of cyclic alkene s decreases with increasing carbon number from C6 to C12, the selectivity t o corresponding cyclic epoxides is C12 approximate to C8 (100%) > C7 (71%) > C5 (20%) > C6 (1.2%), where the exception of C5 is related to its low dis solubility and steric conformations of reactant and products molecules. Lin ear alkene shows the higher reactivity and the lower selectivity to epoxide than cyclic alkene with the same carbon number. TBHP as the oxidant signif icantly retards the reactivity of C6, C7 and C12, and shows more beneficial to the selective production of epoxide than H2O2 (C) 2001 Elsevier Science B.V. All rights reserved.