Synthesis and characterization of cobalt-containing aluminiumphosphate molecular sieves(CoAPO-5)

초록

According to XRD patterns,CoAPO-5 possesses essentially identical framework topology to AlPO4-5. In microwave heating synthesis, a very crystalline CoAPO-5 can be obtained at 180∼190℃ in 20 min. This demonstrates that CoAPO-5 can be synthesized very rapidly from a suitable substrate mixture using microwave heating. Rapid nucleation seems to be the major factor controlling the overall crystallization time of the AFI structure in this system. UV-vis. spectra of CoAPO-5 shows the triplet peaks at 500-700nm usually assigned to the characteristic transition of high-spin Co(Ⅱ) and the peaks at 300-500nm due to Co(Ⅲ)[4]. SEM photographs were taken to compare the crystal morphology of samples synthesized by microwave heating with conventional hydrothermal method. Both crystal samples were hexagonal-shaped(15㎛) and the samples also contain agglomerates of small particles. There was no visible particle size differences. In catalytic test, Autoxidation took off upon the addtion of the catalyst to the reaction mixture without any induction period. The selectivity of p-cresol to p-hydroxybenzaldehyde was 73% at 82% conversion for the reactions catalyzed by CoAPO-5, whilst with CoBr2 a selectivity for p-hydroxybenzaldehyde was 78%.