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Extraction of ethane from natural gas by adsorption on modified ETS-10 N.B.K. Magnowski, A.M. Avila, C.C.H. Lin, Meng Shi, S.M. Kuznicki PII: DOI: Reference: To appear in: Received date: Revised date: Accepted date: S0009-2509(11)00015-7 doi:10.1016/j.ces.2011.01.005 CES 9506
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Chemical Engineering Science 21 July 2010 22 December 20106 January 2011

Cite this article as: N.B.K. Magnowski, A.M. Avila, C.C.H. Lin, Meng Shi and S.M. Kuznicki, Extraction of ethane from natural gas by adsorption on modified ETS-10, Chemical Engineering Science, doi:10.1016/j.ces.2011.01.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of themanuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Extraction of ethane from natural gas by adsorption on modified ETS-10N.B.K. Magnowski, A.M. Avila, C.C.H. Lin, Meng Shi, S.M. Kuznicki* Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2V4 * Corresponding author. Tel.: +1.780.492.8819, Fax.: +1.780.492.8958 E-mail address: steve.kuznicki@ualberta.ca Abstract Ethane was extracted from a synthetic natural gas mixture at 298 K and 101.3 kPa using modified ETS-10 as apacked bed adsorbent. Ethane was completely separated from the mixture for a prolonged period until the initial stages of breakthrough. The adsorptive properties of several cation-exchanged forms of ETS-10, a large-pored titanosilicate molecular sieve, were compared. Na-, Ba- and Ba/H-ETS-10 were all found to be selective for ethane over methane. Na-ETS-10 showed the highest Henry’s selectivity (α =52) for ethane over methane of the three ETS-10 materials tested. Ideal adsorbed solution theory (IAST) models indicate that significant selectivity should persist at high pressures. Ethane is commonly removed from raw natural gas by energy-intensive cryogenic methods and these results reflect the potential for an alternative and efficient separation process using cation-exchanged ETS-10 as anadsorbent.

KEYWORDS: adsorption, gas separation, ion exchange, selectivity, zeolites, natural gas

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Introduction Ethane, the second largest component of raw natural gas (ranging from 0.7 to 6.8% by volume), is an important source of feedstock for ethylene production via industrial scale cracking processes (Ren et al., 2006). Annual global demand for ethylene, a precursor in the productionof films, rubber and plastics, exceeds 100 million tonnes (Storck, 2006). The recovery of natural gas liquids (NGLs), such as ethane, from natural gas typically involves absorptive or energy-intensive cryogenic separation methods (Rojey, 1997).

In absorptive separation, natural gas is brought into contact with a “lean” absorption oil which picks up NGLs by gas-liquid absorption of likehydrocarbon compounds. The resulting “rich” absorption oil contains propane, butane and heavier hydrocarbons, while leaving lighter ethane fractions in the natural gas. Although alternative oil absorption methods which use a refrigerated absorption oil allow for the recovery of some of the ethane, they are still less effective than cryogenic methods (Chebbi et al., 2010)

Cryogenic methods allow for asmuch as 90% or more of the ethane present in a natural gas stream to be recovered (Pitman et al., 1998). Cryogenic processes generally involve cooling a natural gas stream to temperatures near 188 K. These low temperature requirements have high associated energy consumption costs. For example, one common approach to lowering the temperature of a natural gas stream is to use a turbo expansion...