Gp. Schindler et al., OXIDATIVE CLEAVAGE OF CYCLOHEXANE DERIVATIVES OVER TITANIUM-CONTAINING Y-ZEOLITES, Applied catalysis. A, General, 166(2), 1998, pp. 267-279
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.