Greening Ammonia toward the Solar Ammonia Refinery

Lu Wang, Meikun Xia, Hong Wang, Kefeng Huang, Chenxi Qian, Christos T. Maravelias, Geoffrey A. Ozin

Research output: Contribution to journalReview articlepeer-review

181 Scopus citations

Abstract

In light of the targets set out by the Paris Climate Agreement and the global energy sector's ongoing transition from fossil fuels to renewables, the chemical industry is searching for innovative ways of reducing greenhouse gas emissions associated with the production of ammonia. To address this need, research and development is under way around the world to replace the century-old Haber-Bosch process for manufacturing ammonia from N2 and H2, powered by renewable electricity. This involves replacing H2 obtained from steam-reformed CH4 to H2 that is instead obtained from electrolyzed H2O. This transition will enable the changeover from the Haber-Bosch production of NH3 to electrochemical, plasma chemical, thermochemical, and photochemical generation of NH3. If ammonia can eventually be produced directly from N2 and H2O powered by just sunlight, at a technologically significant scale, efficiency, and cost, in a “solar ammonia refinery,” green ammonia can change the world! It is well known that the century-old Haber-Bosch process, N2 + 3H2 → 2NH3, is thermally powered by fossil energy, resulting in a greenhouse gas intensive process, which needs to be replaced by one driven instead by renewable energy. To address this issue, we need to replace the energy-intensive synthesis process of ammonia from N2 and H2 by one powered instead by renewable electricity. This involves replacing H2 obtained from steam-reformed CH4 to H2 that is instead obtained from electrolyzed H2O. Consequently, the required energy is dramatically decreased, and the conversion no longer requires CH4 derived from natural gas because the H2 comes directly from H2O. Herein, we present a critical overview of past and current research on ammonia synthesis that is envisioned to evolve to the “solar ammonia refinery” of the future. A high-level analysis of the energy requirements of the proposed greening ammonia strategies further supports the “solar ammonia refinery.” An overview of current research theme of catalytic ammonia synthesis and potential candidates for “solar ammonia refinery.” A high-level analysis of the energy requirements for different ammonia synthesis strategies is shown.

Original languageEnglish (US)
Pages (from-to)1055-1074
Number of pages20
JournalJoule
Volume2
Issue number6
DOIs
StatePublished - Jun 20 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Energy(all)

Keywords

  • energy analysis
  • nitrogen fixation
  • nitrogen reduction
  • renewable ammonia
  • solar ammonia

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