碱对硅藻土水热合成ZSM-5分子筛的影响

以硅藻土为原料,以氢氧化钠或氨水为碱源,分别水热合成出具有较高相对结晶度的钠型ZSM-5分子筛和氢型ZSM-5分子筛。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、吡啶吸附红外光谱(Py-IR)和N2-吸附脱附等手段,对所合成的样品进行了表征。结果表明,合成的Na ZSM-5分子筛和HZSM-5分子筛均具有较高的结晶度,但有不同的酸性、孔结构、形貌和粒径,粒径分别约为500 nm或7μm。相比硅藻土,晶化产物的比表面积、微孔表面积和微孔孔容均明显增大。用Na OH合成样品的比表面积、孔容大于用NH3?H2O合成的样品。采用氨水合成的ZSM-5分子筛经焙烧后可直接转化成氢型分子筛。

Effect of Alkalion on Hydrothermal Synthesis of ZSM-5 Zeolites From Diatomite

NaZSM-5 zeolites and HZSM-5 zeolites were synthesized from diatomite with NaOH and NH3·H2O as the alkali source respectively by hydrothermal crystallization method.The synthesized samples were characterized by X-ray diffraction,scanning electron microscope,Py-IR,and N2 adsorption and desorption.The results showed that the prepared NaZSM-5 and HZSM-5 zeolites with high crystallinity had different acidity,porosity and morphology,the particle size was about in the range of 500 nm ～7 μm.Compared with diatomites,the synthesized samples had larger BET specific surface area and micropore volume.The specific surface area and pore volume of the samples prepared by NaOH were higher than that of the samples prepared by NH3-H2O.The as-prepared NH4-ZSM-5 by using ammonia solution can be converted into the H-form zeolite by direct calcination.