Synthesis of Co-rich CoAPO-5 molecular sieves: A comparison between glycerol and water as solvent

CoAPO-5 molecular sieves have been synthesized with glycerol and water as solvent in order to maximize the degree of isomorphous substitution of Co2+ ions in the AFI framework. These CoAPO-5 molecular sieves have been characterized with X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, electron microprobe microanalysis, N-2 sorption, and UV-visible-NIR-diffuse reflectance spectroscopy techniques. Optimum conditions for the synthesis of Co-rich single-phase and highly crystalline CoAPO-5 molecular sieves were obtained by varying the [Co]:[Al] ratio in the synthesis gel and the synthesis time. It will be shown that highly crystalline hexagonal single-phase CoAPO-5 crystals with a size between 3 and 10 mum and a substitution degree of about 13% can be obtained from a 0.7CoO.0.65Al(2)O(3).1P(2)O(5).1(C2H5)(3)N.40HOCH(2)CHOHCH(2)OH gel at 190 degreesC after 14 days of synthesis. This substitution degree is substantially higher than that for CoAPO-5 materials synthesized in the presence of water (i.e., about 7.5%).