Synthesis And Characterization Of Heteroatom-substituted Alumino-Phosphates Molecular Sieves And Catalytic Application On Hydroxylation

With regular nano-pore structure and high internal surface area, zeolite has widely used in petrochemical and fine chemical industry, acted as catalyst, adsorption-desorption as well as ion exchange materials. After the traditional aluminosilicate zeolites, aluminophosphate molecular sieves have been extensively studied due to their rich structural framework and thermostability. But aluminophosphate molecular sieves have many defects like poor ion exchange performance and weak acidity. So the heteroatom-substituted aluminophosphate molecular sieves not only develop new compositions and novel structures, but also have exhibited special catalytic properties because of the creation of heteroatom. In addition, the hierarchical molecular sieves combined the advantages of microporous and mesoporous, which improved the catalytic mass transfer efficiency. Recently, the heteroatom-substituted and hierarchically structured aluminum phosphate molecular sieves has been attracting significant attention. In this work, the heteroatom-substituted and hierarchically structureed aluminum phosphate molecular sieves were synthesized with direct hydrothermal method and ionothermal methods. The main contents are as follows:The heteroatom-substituted and hierarchical Fe/CuAPO-11molecular sieves with AEL topology structure have been synthesized by direct hydrothermal method. Using starch, glucose and GO as the mesoporous structure-directing agents. The as-prepared materials were characterized by X-ray powder diffraction(XRD), N2low physical adsorption, scanning electron microscope (SEM), UV-visible diffuse reflectance (UV-vis) and elementary analyzer. The results showed that the sample has a AEL topology structure with good crystallization and little mesoporous. With Fe/Al value is increasing, the content of Fe in molecular sieves is increase. The UV-vis result reveals that it existed isolated framework of Fe3+as well as exoskeleton of Fe3+. SEM results showed that the nano-layered stacked crystal with an irregular morphology.Moreover, the Fe/CuAPO-11molecular sieves material prepared by phenol hydroxylation reaction. The results showed the pore structure of material is unideal, but the sample has high activity during the reaction. Such as the conversion rate of phenol is above60%under the conditions of60-80℃for2h. When the content of Fe is2.74%, the conversion rate of phenol is62%and have the best catalytic stability. With the same amount of Fe/Cu, the composites have the similar catalytic activity compared Fe/CuAPO-11molecular sieves. That is to say, Fe3+/Cu2+have the best catalytic stability during phenol hydroxylation reaction. Hierarchical structured CuAPO-5molecular sieve has been ionothermally synthesized by microwave irradiation and using eutectic mixture based on succinic acid, choline chloride and tetraethyl ammonium bromide (TEABr) in a molar ratio of8:8:1as solvent and template. Among the synthesis parameters investigated, P2O5/Al2O3ratios, HF/Al2O3ratios and CuO/Al2O3ratios, aluminum and copper source had impact on the crystallization of CuAPO-5. The resulting CuAPO-5molecular sieve was characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscopy (TEM), and N2physical adsorption-desorption, respectively. SEM analysis revealed that CuAPO-5molecular sieve with hexagonal nanometer-disc morphology could be synthesized under specific synthesis conditions. N2physisorption, SEM and TEM characterizations show that the resultant material is one kind of hierarchical structured aluminophosphate molecular sieve possesses both micropore and mesopore.