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, 27Al and 31P 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 band 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.