OXIDATIVE CLEAVAGE OF CYCLOHEXANE DERIVATIVES OVER TITANIUM-CONTAINING Y-ZEOLITES

The oxidative cleavage of trans-1,2-cyclohexanediol to adipic acid was studied with hydrogen peroxide as oxidant and titanium-containing Y z eolites as catalysts. These materials were obtained by treating zeolit e Y with ammonium hexafluorotitanate. Selectivities of up to 80% could be achieved at conversions of 50%. The catalysts could be reused seve ral times without activity loss. The titanation of Y zeolites is repro ducible. Independently prepared Ti-Y zeolites lead to the same catalyt ic results. Titanium is present as a species that causes a UV-VIS band at 260 nm. Bands indicating anatase or rutile were not observed. No l eaching of titanium was detected. The presence of mesopores in the cat alyst structure increases the conversion. Through variation of process parameters like temperature and reactant/catalyst ratio, the undesire d decomposition of the hydrogen peroxide can be partially suppressed. In comparison, cyclohexene oxide is cleaved with selectivities similar to those of trans-1,2-cyclohexanediol. By contrast, cyclohexanol and cyclooctene oxide are unselectively oxidized. Diffusion constraints se em to play a decisive role. (C) 1998 Elsevier Science B.V.