Preparation And Properties Of SPEEK/Zeolite A Composite Proton Exchange Membranes

SPEEK is widely concerned because of its excellent methanol resistance,high proton conductivity,excellent mechanical properties,relatively simple preparation process and low cost.However,pure SPEEK proton exchange membrane(PEM)is limited by poor dimensional stability at high degree of sulfonation(DS),and it is difficult to combine the conductivity with methanol resistance.In this paper,doping modification method is used,in which inorganic particle zeolite A served as the dopant,giving rise to a series of SPEEK/zeolite composite proton exchange membranes.After that,the performance of the composite PEM is summarized in this paper from perspectives of dimensional stability,water absorption,proton conductivity,methanol permeability and etc.Hydrothermal method and ion exchange method are used to prepare zeolite A with different particle sizes(4A/4a)and different pore sizes(4a/3a).The SPEEK/A zeolite composite proton exchange membrane is prepared by solution casting method.It is found that the zeolite modified SPEEK/4a composite membrane with a particle size of 1 ?m is superior to the SPEEK/4A composite membrane and the conductivity is increased by 60.4% at 20 ?.The temperature dependent conductivity of zeolite-modified SPEEK/4a membrane and SPEEK/3a membrane with different pore size are almost the same.However,the pore diameter of the zeolite 3a lies between water molecule and methanol molecule,and therefore the methanol resistance and selectivity of the SPEEK/3a-10.0 membrane exceeds that of the SPEEK/4a-10.0 membrane.Moreover,HPW is added to the system as proton conductor in preparing the SPEEK/HPW@3a composite membrane for the purpose of enhancing performance of the SPEEK/3a composite PEM.It is observed that the conductivity of SPEEK/HPW@3a is slightly higher than that of SPEEK/HPW/3a film at 60°C.It is probable that HPW and zeolite 3a are tightly combined,reducing the loss of HPW in the pretreated HPW@3a.Finally,this paper investigate the impact of zeolite on the internal microstructure of the SPEEK membrane.It is noted that the proton transport channel of the SPEEK composite membrane links to an extend degree due to addition of 3A zeolite,and the intersections of channels increase,resulting in a more coherent network structure that is formed in the SPEEK/4a composite membrane.The zeolite disperses and thus the methanol molecular meanders,featured by lower methanol permeability.The SPEEK/A type zeolite composite membrane is prepared by blending,and the dissociation characteristics of the zeolite in an acidic environment are utilized to solve the problem that a large number of nanoparticles are easily agglomerated,so that the blending ratio reaches 10.0 wt.%;using the hydrophilicity and porosity of the zeolite are utilized to improve the hydrophilic channel structure and methanol-blocking properties of the composite membrane,and obtain a composite proton exchange membrane with good comprehensive performance,which provides a new idea for the practical application of SPEEK.