Nickel Doped Aluminophosphate-5 as an Efficient Heterogeneous Catalyst for Imine Synthesis by Direct Condensation of Alcohols and Amines at Room Temperature

Ni doped hierarchical micro-mesoporous AlPO-5 molecule sieve (HP-NiAlPO-5) was prepared and evaluated as the heterogeneous catalyst for the synthesis of imines by direct condensation of amines and easily accessible alcohols. The catalyst exhibits encouraging efficiency with isolated yields up to 95% and turnover frequency (TOF) number up to 10.7h(-1) for a variety of amines and alcohols with varied substrates and properties. The moderate reaction conditions, namely, room temperature of 303K and air as the oxidant, together with the decent stability and reusability after cycles, make HP-NiAlPO-5 a promising alternative for the future large-scale applications. Characterizations and detailed comparison among catalysts with different compositions revealed that the superiority of HP-NiAlPO-5 can be attributed to synergistic effects of the uniform framework of the AlPO-5 molecular sieve and readily accessibility of highly dispersed Ni nano particles on hierarchical micro-mesoporous support. It was found that the levels of H-2 consumption on several metals during H-2 temperature programmed reduction are directly related to their catalytic performances.