Pd-ZSM-5复合膜的制备及其氢气分离性能

Fabrication of Pd⁃ZSM⁃5 composite membrane on porous alumina substrate and its hydrogen separation performance

为了能够在大孔氧化铝载体表面得到透氢性能良好的钯膜,利用二次生长法在多孔Al_(2)O_(3)载体上生长出一层连续完整的ZSM-5沸石分子筛修饰层,通过化学镀过程在ZSM-5沸石分子筛修饰的载体上沉积一层钯膜,从而得到Pd-ZSM-5复合膜。利用扫描电子显微镜(SEM)对载体、ZSM-5沸石分子筛修饰后的载体和Pd-ZSM-5复合膜的形貌进行详细分析,并通过X线能量色散光谱(EDX)对Pd-ZSM-5复合膜的表面和截面元素分布进行了研究。而且,为了确定该Pd-ZSM-5复合膜的H_(2)渗透性能,在623~773 K范围内,研究了操作温度、操作时间和测试压力对Pd-ZSM-5复合膜透氢性能的影响。研究结果表明,ZSM-5沸石分子筛修饰层能够有效改进载体的表面粗糙度和降低其表面孔径,有助于Pd膜的沉积。所制备的Pd-ZSM-5复合膜表面完整、致密,Pd膜层厚度约为5μm, ZSM-5沸石修饰层厚度约为3μm。当操作温度为773 K、渗透压力为0.1 MPa时,Pd-ZSM-5复合膜的H_(2)渗透通量和H_(2)/N_(2)渗透选择性分别为0.113 mol/(m·s)和468。而且,该Pd复合膜在773 K下,连续操作300 h后,其H_(2)渗透性能保持相对稳定。

In order to obtain a Palladium membrane deposited on the surface of a macroporous alumina support with good hydrogen permeation performance,a secondary growth method was employed to grow a continuous ZSM-5 zeolite modified film on the porous Al_(2)O_(3) support.A Palladium membrane was deposited on the ZSM-5 zeolite modified support using an electroless plating method,thereby obtaining a Pd-ZSM-5 composite membrane.Detailed analyses of the morphologies of the porous substrate,ZSM-5 modified substrate,and Pd-ZSM-5 composite membrane were carried out using scanning electron microscopy(SEM).Besides,the surface and cross-sectional elemental distributions were analyzed using energy-dispersive X-ray spectroscopy(EDX).Furthermore,to ascertain the hydrogen permeation performance of the composite membrane,the effects of operating temperature,duration,and test pressure on the hydrogen permeability of the Pd-ZSM-5 composite membrane were investigated within a temperature range from 623 K to 773 K.The results indicated that the ZSM-5 zeolite modification layer effectively reduced the roughness and surface pore size of the porous alumina support,facilitating the deposition of Palladium membrane.The prepared Pd-ZSM-5 composite membrane featured an intact and dense surface with a palladium layer of approximately 5μm and a ZSM-5 zeolite modification layer of about 3μm.At an operating temperature of 773K and a permeation pressure of 01 MPa,the hydrogen permeation flux and H_(2)/N_(2) permeation selectivity of the Pd-ZSM-5 composite membrane were 0113 mol/(m·s)and 468,respectively.Furthermore,the hydrogen permeation performance of the membrane remained relatively stable after 300 hours of continuous operation at 773 K.