Zeolite Membranes for Gas Separations

Gas-separation Problems Combined with Membrane Reactors 

Membrane Separation T (°C) Feed water ( wt%) J (kg ) Separation factor 

The current commercial zeolite membranes, developed for pervaporation, are not yet useful in gas separations (H2/CO2 selectivity for NaA membranes of Mitsui and Inocermic are 6 and 5.6, respectively) because of the presence of large inter-crystalline defects. They, furthermore, participate in the separation process. During pervaporation the water fills the intra-crystalline and intercrystalline pathways. However, much effort is in progress to produce defect free zeolitic membrane also for gas separations. In this chapter the application of zeolite membranes in gas separations is reported and deeply discussed. The main strategic methods used for the membrane preparation and mass transport through zeolite membranes are also dealt with. 

---

We have divided the applications of zeolite membranes for gas separations into two main groups based on and depending on whether there is molecular exclusion or not in one of the components to be separated. 

Zeolite Membranes for Gas Separations Table 17.9 Separation selectivities and mechanisms of some binary mixture... 

Supported LTA membranes have been successfully installed during the last 10 years worldwide in about 25 plants for the dewatering of (bio)ethanol and i-propanol. Whereas there are outstanding separation performances of a new generation of zeolite membranes type SAPO-34 and DD3R on the lab scale, no short-term large-scale industrial application of zeolite membranes for gas separation can be predicted. 

Efforts are ongoing to find a way to avoid, reduce or eliminate the presence of inter-crystalline defects, which, aside from poor synthesis reproducibility, are the main obstacle to the industrial application of zeolite membranes for gas separation. 

J.P. Boom, D. Bargeman, and H. Strathmann, Zeolite filled membranes for gas separation and pervaporation. Zeolites and related microporous materials State of the art 1994 Part B, Proc. 10th Int. Zeol. Conf., Garmisch-Panenkirchen (J. Weitkamp, H.G. Kaige, H. Pfeifer, and W. Holderich, eds.), Elsevier, Amsterdam, 1994, p. 1167. 

Glassy Perfluorolymer-Zeolite Hybrid Membranes for Gas Separations... 

Despite their advantages, inorganic membranes have not so far found major industrial importance in gas separation. However, about 20 years ago, there was much enthusiasm about the development of supported thin zeolite layers as membranes for gas separation. 

Song Q, Nataraj S, Roussenova M, Tan J, Hughes D, Li W, et al. Zeolitic imidazolate framework (ZIF-8) based polymer nanocomposite membranes for gas separation. Energy Environ Sci 2012 5 8359-69. 

Boom, J. P., Bargeman, D., and Strathmarm, H. (1994). Zeolite-filled membranes for gas separation and pervaporation. Stud. Surf. Sci. Catal. 84, 1167-1174. 

Marand, E., and Pechar, T. W. (2003). Zeolite-polyimide mixed-matrix membranes for gas separations. U.S. Patent 2003220188. 

Mixed matrix hollow fiber membranes made with modified HSSZ-13 zeolite in polyetherimide polymer matrix for gas separation. /. Membr. Sd., 288, 195-207. 

Gorgojo, P., Uriel, S., Tellez, C., and Coronas,). (2008) Development of mixed matrix membranes based on zeolite Nu-6(2) for gas separation. Micropor. Mesopor. Mater., 115, (1-2), 85-92. 

---