Understanding the Reactive Adsorption of H2S and CO2 in Sodium-Exchanged Zeolites

Evgenii O. Fetisov, Mansi S. Shah, Christopher Knight, Michael Tsapatsis, J. Ilja Siepmann

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Purifying sour natural gas streams containing hydrogen sulfide and carbon dioxide has been a long-standing environmental and economic challenge. In the presence of cation-exchanged zeolites, these two acid gases can react to form carbonyl sulfide and water (H2S+CO2⇌H2O+COS), but this reaction is rarely accounted for. In this work, we carry out reactive first-principles Monte Carlo (RxFPMC) simulations for mixtures of H2S and CO2 in all-silica and Na-exchanged forms of zeolite beta to understand the governing principles driving the enhanced conversion. The RxFPMC simulations show that the presence of Na+ cations can change the equilibrium constant by several orders of magnitude compared to the gas phase or in all-silica beta. The shift in the reaction equilibrium is caused by very strong interactions of H2O with Na+ that reduce the reaction enthalpy by about 20 kJ mol−1. The simulations also demonstrate that the siting of Al atoms in the framework plays an important role. The RxFPMC method presented here is applicable to any chemical conversion in any confined environment, where strong interactions of guest molecules with the host framework and high activation energies limit the use of other computational approaches to study reaction equilibria.

Original languageEnglish (US)
Pages (from-to)512-518
Number of pages7
JournalChemPhysChem
Volume19
Issue number4
DOIs
StatePublished - Feb 19 2018

Bibliographical note

Funding Information:
This work was supported by the National Science Foundation through Grant CHE-1265849 for the development of the RxFPMC methodology (EOF & JIS) and by the Department of Energy Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-12ER16362 for the set-up of the zeolite structures and part of the analysis (MSS, MT & JIS). EOF and MSS acknowledge support from University of Minnesota through Graduate School Doctoral Dissertation Fellowships. This research used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357. Additional computer resources were provided by the Minnesota Supercomputing Institute.

Publisher Copyright:
© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Keywords

  • Monte Carlo simulation
  • density functional calculations
  • reactive equilibria
  • sour natural gas
  • zeolites

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