Method for producing epoxides through olefin oxidation with air or oxygen

The present invention provides a process for the epoxidation of alkenes of the formula (1)where R1, R2, R3 and R4 are, independently of one another, hydrogen, C1-C20-alkyl, C1-C12-alkoxy, C6-C10-aryl, -CHOH-CH3, -CH-NH2-CH3 or carboxy, using air or oxygen over a catalyst comprising compounds of the formula (2)wherex is 1, 2 or 3,y is an integer from 0 to 2x+1,z is an integer from 1 to 2x,where the ligand L is a compound of the formula (3) or (4)whereX is a nitrogen, oxygen or sulfur atom,Y is hydrogen, C1-C8-alkyl, C1-C8-alkoxy, F, Cl, Br, I, COOCH3, C6-C14-aryl or C3-C8-cycloalkyl,R7 and R8 form a ring containing from 4 to 8 carbon atoms onto which one or two aromatic rings may be fused,R5 and R6 are hydrogen, branched or straight-chain C1-C12-alkyl or branched or straight-chain C1-C12-haloalkyl which are substituents on the ring formed by R7 and R8 and/or the rings fused onto this ring,or the ligand L is a compound of the formula (5), (6) or (7)where R is hydrogen, C1-C8-alkyl, C1-C8-haloalkyl, C1-C8-alkoxy, COOCH3, C6-C14-aryl or C3-C8-cycloalkyl and n is 1 or 2 and m is from 1 to 6, wherein the reaction is carried out in a pressure vessel which is completely lined with an inert material.