Zeolite Membrane Separation at Low Temperature
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
The energy consumption of separation process accounts for a large part inchemical industry. Membrane processes use much less energy compared to thecurrently used thermally driven processes and could thereby reduce energyconsumption in industry significantly. Zeolite membranes have severalsuperiorities over the commercially available polymeric membranes, e.g. higherflux, higher chemical and thermal stability. There have been extensive studieson zeolite membrane separation at high temperature during the past decades,whereas scientific reports at low temperature are rather scarce. It is of interest toexplore the performance under this condition.Zeolite membranes were for the first time evaluated for gas separation atcryogenic temperature in the present work. Air separation by ultra-thin MFImembranes was carried out with a feed pressure varying from 100 mbar to 5 barover the temperature range of 62– 110 K. The membranes were found to beoxygen selective at all the conditions investigated. The observed results werewell above the upper bound in the 2008 Robeson selectivity-permeability plotwhen the feed pressure was not higher than 1 bar. The O2/N2 separation factorreached 5.0, corresponding membrane selectivity 6.3 at 67 K and a feed pressureof 100 mbar, with a high O2 permeance of 8.6 × 10-7 mol m-2 s-1 Pa-1. Theperformance of our membrane (in terms of selectivity and permeability in Barrer)was comparable to that recently reported in Science by Carta et al., but 100times higher in term of permeance or flux.The selectivity to O2 should primarily emanate from condensation of O2 in thezeolite pores blocking the transport of N2. In addition, the O2/N2 selectivityincreased with decreasing feed pressure. Thus, the selectivity should also beenhanced by a weaker adsorption of N2 at the relatively lower feed pressures.The present work has therefore indicated the optimum conditions for airseparation using MFI membranes, namely low feed pressures and cryogenictemperatures.Synthesis gas generated from biomass or waste is a renewable energy resource,mainly consisting of CO, CO2, H2 and H2O. It is necessary to remove some CO2from the synthesis gas to arrive at optimum composition of the gas for e.g.methanol synthesis. In this work, zeolite membranes were also studied for CO2separation from H2 and CO at low temperatures down to 238 K with a feedpressure of 9 bar. The highest separation factor was 109 for CO2/H2 separationat 238 K and 21 for CO2/CO separation at 258 K, significantly higher than thatat room temperature. This is attractive for practical CO2 separation.In summary, the present work has demonstrated the potential of MFI zeolitemembranes for O2/N2 separation and CO2 separation from synthesis gas at lowtemperature.
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2014.
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Research subject Chemical Technology
IdentifiersURN: urn:nbn:se:ltu:diva-26267Local ID: d684df5f-1506-4f94-8c8d-a62a1506ae83ISBN: 978-91-7586-001-8ISBN: 978-91-7583-002-5 (PDF)OAI: oai:DiVA.org:ltu-26267DiVA: diva2:999429
Godkänd; 2014; 20140506 (andbra); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Pengcheng Ye Ämne: Kemisk teknologi/Chemical Technology Uppsats: Zeolite Membrane Separation at Low Temerature Examinator: Professor Jonas Hedlund, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Ph.D. Linda Sandström, Energy Technology Centre in Piteå Tid: Måndag den 6 oktober 2014 kl 10.00 Plats: C305, Luleå tekniska universitet2016-09-302016-09-302016-10-20Bibliographically approved