Synthesis of functionalized blend membranes for CO2 separation

Abstract

Anthropogenic climate change caused by the emission of green-house gases (GHG) is increasingly becoming a major environmental concern. As a major GHG, high levels of CO2 in the atmosphere are assumed to be primarily responsible for the global climate change. Application of green engineering principles could lead to substantial reductions in emissions. This can be done by design of sustainable separation and purification operations, reduction of the fossil fuel use for power sources and increasing the energy efficiency of existing processes. As far as the design of separation and purification systems is concerned, there is a strong need to develop techniques that are environmentally friendly, efficient and yet still cost effective. In recent years, scientific efforts and advances have been made in developing new technologies for effective and sustainable separation of CO2. In the field of membrane technology, significant research has focused on the synthesis of novel membranes for CO2 capture and on the design of more efficient membrane systems. Polymer blending is one of the techniques used to improve the separation performance of the existing membranes by combining the advantageous properties of individual polymers. Mixed matrix membranes (MMMs) comprising of inorganic fillers embedded in polymer matrix is another technique which is widely used to improve the performance of membranes. This thesis is mainly focused on the synthesis of novel polymeric blend and mixed matrix membranes with the objective to improve the performance of existing membranes. The whole thesis can be divided into two major parts (i) preparation and characterization of various compositions of Matrimid and fluorinated and sulfonated poly (ether ether ketone) (FSPEEK) blend membranes (ii) synthesis of MMMs by incorporation of zeolite 4A in the blend of FSPEEK and Matrimid. In first part of this research gas separation performance by synthesizing various compositions of Matrimid/FSPEEK blends was investigated at different operating conditions (temperature, pressure and feed composition). The results showed that the increasing the percentage of FSPEEK in the blend lead to increase in the permeability as well as CO2/CH4 and CO2/N2 selectivity of the membranes. In the presence of sulfonated group membranes showed excellent anti-plasticization properties on exposure to increasing CO2 loadings. In second part of thesis gas separation performance by incorporation of various compositions of zeolite 4A in 50:50 FSPEEK/Matrimid blend was studied. The results showed that the addition of porous fillers increases the permeability of the blend membranes. This is due to the increased diffusion of the gas molecules through the pores of the zeolite material. The effect of operating conditions to evaluate the commercial viability of the membranes was also studied in this thesis.