Ceramic-supported organic composite membranes for gas separation

Organic-inorganic composite membranes have received increasing attention for molecular separation. In this chapter, recent progresses on ceramic-supported organic composite membranes for gas separation are briefly reviewed. The organic separation layer of the composite membranes includes traditional polymeric membrane materials such as polydimethylsiloxane (PDMS), poly(ethylene glycol) (PEG), and poly(amide-b-ethylene oxide) (PEBA), as well as emerging twodimensional graphene-based membrane materials. Fabrication method, physicochemical property, and gas separation performance of the membranes are discussed. Compared with the state-of-the-art, the developed ceramic-supported organic composite membranes exhibited excellent gas separation performance for carbon dioxide and hydrogen separation, suggesting great potential for practical application. Although the gas permeation performance for various membranes mainly depends on the properties of the membrane materials, the types of membrane structure also have an influence on the membrane performance which should not be neglected. In industrial application, composite membranes that consist of a porous support layer with a thin dense skin layer on top are predominantly used because of their higher gas permeability and mechanical strength compared to symmetric dense membranes. The stability of the composite membranes is determined by not only the separation layer but also the interface between the separation and support layers. In the cases of high temperature or high pressure, polymeric supports cannot constrain the shear stress at the interface; thus the separation layer may delaminate from the support with elapse of the operation time. However, the rigid ceramic supports can confine the polymer that penetrates into the pores, which improves the stability of the composite membrane with the confinement effect. In addition, ceramic supports can provide sufficient mechanical stiffness to support a thin selective polymeric layer even at high pressure. The low transport resistance of ceramic support could enhance the gas permeance as well. Because of the above-mentioned advantages of ceramic supports, numerous studies have been focused on the preparation of organic- inorganic composite membranes, which combine the advantages of both organic and inorganic membranes. Our group has developed a series of ceramic-supported polymeric composite membranes.¹ The separation materials include PDMS, ^2-4 poly(vinyl alcohol) (PVA), ⁵ and polyelectrolytes. 6 The applications of these composite membranes contain the bio fuels recovery, ⁷ gasoline desulfuration, ⁸ pervaporation coupled process, ⁷ and dehydration of alcohols and esters.^{9, 10} Those ceramic-supported polymeric composite membranes exhibit remarkable high performance, especially high permeate flux. This is attributed to the thin polymer separation layer and ceramic support with low transport resistance. This chapter summarized recent progresses in ceramic-supported organic composite membranes for gas separation. The separation layer includes polymers such as PDMS, PEG and PEBA, and also two-dimensional materials such as graphene oxide.