VAPO as catalyst for liquid phase oxidation reactions Part I: preparation, characterisation and catalytic performance

VAPO as catalyst for liquid phase oxidation reactions. Part II: stability of VAPO-5 during catalytic operation

“…Solutions of substrate and oxidants were described earlier by the authors in a previous article [9]. For the first cycle 70 ml of 3-phenyl-2-propen-1-ol (0.45 M) and 35 ml of TBHP-solution (0.9 M) were combined and heated to 50°C.…”

“…Well dried VAPO-5 (S-P3) (12.5 g) was added and allowed to react for 24 h. Then the VAPO-5 was filtered off at 50°C and washed with acetonitrile. The VAPO-5 was dried overnight at 80°C and used again in a new cycle or calcined in air at 500°C for 3 h using a standard temperature program [9]. After the first, second, fourth, seventh, tenth and fourteenth cycle a calcined sample of about 0.8 g was kept apart for analysis by XRD, SEM, PV, DRUVVIS, ESR, AAS and a test reaction with 3-phenyl-2-propen-l-ol under standard conditions ([V] =300 mg/l) [9].…”

“…The VAPO-5 was dried overnight at 80°C and used again in a new cycle or calcined in air at 500°C for 3 h using a standard temperature program [9]. After the first, second, fourth, seventh, tenth and fourteenth cycle a calcined sample of about 0.8 g was kept apart for analysis by XRD, SEM, PV, DRUVVIS, ESR, AAS and a test reaction with 3-phenyl-2-propen-l-ol under standard conditions ([V] =300 mg/l) [9]. For every large scale reaction the amounts of reactants were adapted to the amount of VAPO-5 remained to keep the ratio [substrate]/[V] and [TBHP]/[V] constant.…”

“…A similar procedure was carried out to obtain a large amount of a VAPO-5 used for the oxidation of 3-octanol. Alternatively, an used VAPO-5 was Soxhlet extracted with acetonitrile for 5 days and then dried at 80°C before it was used again as catalyst for a new reaction under standard conditions [9].…”

“…The concept "reactions in micropores" might not be applicable in case of VAPO-5 because the actual reaction takes place in solution. A low activity compared with a similar amount of homogeneous catalyst and minor influence of the pore structure on activity and selectivity [9] are arguments in favor of this hypothesis, but also the intrinsic activity of vanadium sites in the pores may be low. In this article it will be shown that stability tests might give useful information whether or not the concept is valid in case of VAPO.…”