Catalytic benzene hydroxylation over copper-substituted aluminophosphate molecular sieves (CuAPO-11)

Copper-substituted aluminophosphate molecular sieves (CuAPO-11, AEL topology) containing various copper fractions, which have been synthesized by hydrothermal crystallization, were characterized using several physicochemical techniques, Such as XRD, SEM, FTIR, Al-27 and P-31 MAS NMR, etc. In combination of early reported characterization results, the isomorphous substitution of copper in the framework of the parent AlPO4-11 was further confirmed. For example, FTIR spectroscopy provides clear evidence of copper incorporation into the framework of the AEL structure due to the occurrence of a new absorption hand around 1050 cm(-1) as compared with the pure AlPO4-11. which may be tentatively attributed to some stretching vibration related to the lattice oxygen-coordinated copper species. The selective oxidation activity of CuAPO-11 was evaluated using liquid phase-H2O2 hydroxylation of benzene as a probe reaction and compared with another redox analog CuAPO-5 (AFI topology). The catalytic test results suggest that comparable benzene conversion over these copper-containing materials was associated with the framework-incorporated copper atoms whereas different product distributions were governed by the structure type, viz. AEL or AFI topology. (C) 2009 Elsevier Inc. All rights reserved.