Polymer Membranes for Hydrogen Separations

Abstract

The development of a hydrogen-based economy would generate a substantial necessity for efficient means of collecting hydrogen with a relatively high purity. Membrane separations play a major role in the separation of hydrogen gas from various gas mixtures, and this article discusses the use of polymeric materials to produce these membranes. After a review of the historical use of polymeric membranes and some background information regarding mechanisms of gas transport in membranes, this article will review the work that has been done in the two major classes of hydrogen separation membranes: hydrogen-selective membranes and hydrogen-rejective membranes. In hydrogen-selective membranes, the very small size of the hydrogen molecule is exploited to allow rapid diffusion of hydrogen through the membrane while excluding other gases. Hydrogen-rejective membranes use the significantly higher sorption of other gases to overcome the advantages of the small size of the hydrogen molecule. The discussion of these two types of membranes will be followed by a presentation of the current state of the art with regard to polymeric membranes for hydrogen separation and a discussion of the predictions for future applications and advancements in this area.

A Review on the Production and Purification of Biomass-Derived Hydrogen Using Emerging Membrane Technologies

“…However, gas separation polymeric membrane systems could not be commercialized before overcoming the problems of their large-scale manufacture and their poor permeability in the 1980s [16,17,[32][33][34][35][36]. Since the first publication of Monsanto's commercial system, the polymeric gas separation membrane has undergone a very fast expansion benefitting from technological improvement and application development.…”

“…The application for hydrogen recovery was the initial target for polymeric gas separation membrane, and in turn, the first large-scale commercial polymeric gas separation membrane system was also employed for hydrogen recovery in the ammonia manufacture industry [33]. Compared with metal and inorganic membranes, polymeric membranes dominate the hydrogen separation membrane market at present [32,35] because of their lower material and manufacturing cost, easy accessibility and mild operation conditions [36].…”

“…Hydrogen has a very high diffusivity coefficient in polymer membrane structures due to its smallest gas molecular size among all the gases, but it has very low solubility because of its weak affinity to all the known polymer materials [32]. From this perspective, the polymeric hydrogen separation membranes could be further divided into two types, hydrogen-selective membranes and hydrogen-rejective membranes [35]. For hydrogen-selective membranes, the principle is to enhance the hydrogen selectivity by maximizing its diffusivity benefits relative to the other gases within the rigid matrix of glassy polymers.…”

“…For hydrogen-selective membranes, the principle is to enhance the hydrogen selectivity by maximizing its diffusivity benefits relative to the other gases within the rigid matrix of glassy polymers. In contrast, hydrogen-rejective membranes have a reverse selectivity with respect to hydrogen because they take advantage of the solubility differences among gases but weaken the diffusivity differences with the large free volumes in the rubbery polymer structure [34][35][36].…”

“…The first strategy is to design new polymer materials to either maximize the diffusivity selectivity for hydrogen-selective membranes or, inversely, to enhance the solubility selectivity for hydrogen-rejective rubbery membranes [35]. Budd and McKeown et al developed a series of membranes with porous intrinsic micro-porosity (PIMs) polymers for gas separation [53,54].…”