Zeolit katkılı polimerik gaz ayırma membranları

Özet

Bu çalışmada belirli zeolitlerin farklı polimer matrislerine katılmasının çözünme-difüzyon tipi polimerik membranların seçici ayırma özelliklerine etkilerinin araştırılması, zeolit katkılı polimerik membranlarda gazların taşınım mekanizmalarının incelenmesi ve bu bilgiler doğrultusunda yüksek ayırma performansına sahip membran malzemelerinin hazırlanabilmesi amaçlanmıştır. Uygun polimer/zeolit çiftinin seçimi, zeolitlerin moleküler elek özelliklerine karşın kinetik ve adsorpsiyon seçiciliklerinin önemi ve zeolit/polimer arayüzeyindeki etkileşimler incelenmiştir. Sonuçlar hedeflenen bir uygulama için başarılı bir zeolit katkılı membran tasarımında en önemli unsurun zeolit ve polimer arasında yer alan arayüzeyin tasarımı olduğunu ortaya koymuştur.

Abstract

Due to the limitations on current polymeric gas separation membranes for many commercially attractive applications, mixed-matrix composite (MMC) membranes, prepared by incorporating size and shape selective zeolites into solution-diffusion type polymeric membranes, has been a focus of attention in recent years. The goal of this work is to investigate the effect of specific zeolite fillings on the selective permeation rates of the polymeric solution-diffusion type gas separation membranes, to get an understanding of the transport mechanism, and, through this knowledge, to develop membrane materials with high separation performance for a desired application. For this purpose, synthetic zeolites with different pore opening and geometry, Si/Al ratio and hence surface polarity and hydrophilicity were chosen as fillers, and polydimethyl-siloxane (PDMS), a rubbery polymer, and poly(vinyl acetate) (PVAc), a glassy polymer were chosen as polymeric phases. The separation properties of MMC membranes prepared were characterized by steady-state gas permeability measurements and morphological characterization was carried out using scanning electron microscopy (SEM). Proper selection of the polymer/zeolite pair, the importance of molecular sieving versus kinetic and sorption selectivities of the zeolite filler, and the transport properties and morphology of the zeolite/polymer interphase are addressed. The results indicate that the key issue in the design of succesful MMC gas separation membranes for target applications is the design of the interfacial region between the zeolite and the polymer.