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Title: Analysis of gas membrane ultra-high purification of small quantities of mono-isotopic silane

A small quantity of high-value, crude, mono-isotopic silane is a prospective gas for a small-scale, high-recovery, ultra-high membrane purification process. This is an unusual application of gas membrane separation for which we provide a comprehensive analysis of a simple purification model. The goal is to develop direct analytic expressions for estimating the feasibility and efficiency of the method, and guide process design; this is only possible for binary mixtures of silane in the dilute limit which is a somewhat realistic case. In addition, analytic solutions are invaluable to verify numerical solutions obtained from computer-aided methods. Hence, in this paper we provide new analytic solutions for the purification loops proposed. Among the common impurities in crude silane, methane poses a special membrane separation challenge since it is chemically similar to silane. Other potential problematic compounds are: ethylene, diborane and ethane (in this order). Nevertheless, we demonstrate, theoretically, that a carefully designed membrane system may be able to purify mono-isotopic, crude silane to electronics-grade level in a reasonable amount of time and expenses. We advocate a combination of membrane materials that preferentially reject heavy impurities based on mobility selectivity, and light impurities based on solubility selectivity. We provide estimates for the purificationmore » of significant contaminants of interest. In this study, we suggest cellulose acetate and polydimethylsiloxane as examples of membrane materials on the basis of limited permeability data found in the open literature. We provide estimates on the membrane area needed and priming volume of the cell enclosure for fabrication purposes when using the suggested membrane materials. These estimates are largely theoretical in view of the absence of reliable experimental data for the permeability of silane. And finally, future extension of this work to the non-dilute limit may apply to the recovery of silane from rejected streams of natural silicon semi-conductor processes.« less
 [1] ;  [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division. Chemical Separations Group
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division. Applied Technology Group
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Membrane Science
Additional Journal Information:
Journal Volume: 527; Journal ID: ISSN 0376-7388
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); USDOE Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Dense polymeric membrane; Polydimethylsiloxane (PDMS); Cellulose acetate; Purification; Mono-isotopic silane; Gas separation
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1397917