Greening Ammonia toward the Solar Ammonia Refinery

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 N 2 and H 2 , powered by renewable electricity. This involves replacing H 2 obtained from steam-reformed CH 4 to H 2 that is instead obtained from electrolyzed H 2 O. This transition will enable the changeover from the Haber-Bosch production of NH 3 to electrochemical, plasma chemical, thermochemical, and photochemical generation of NH 3 . If ammonia can eventually be produced directly from N 2 and H 2 O powered by just sunlight, at a technologically significant scale, efficiency, and cost, in a ''solar ammonia refinery,'' green ammonia can change the world! Ammonia Background Fritz Haber, a German chemist, Nobel Laureate in chemistry 1918, invented a way to make the nitrogen in air available to plants by converting it, together with hydrogen, into ammonia. Working with Carl Bosch at BASF in Ludwigshafen, Germany, he developed the heterogeneous catalytic Haber-Bosch process, 1-5 which first operated on an industrial scale for the production of ammonia in 1913. For developing this process, Carl Bosch received the Nobel Prize in Chemistry 1931. Surprisingly, the best catalyst for the production of ammonia, discovered by Alwin Mittasch, was found to have a composition similar to ''Gallivare'' magnetite, a multi-component iron ore from northern Sweden with a composition composed of Fe 3 O 4 , CaO, Al 2 O 3 , MgO, and Cr 2 O 3 component metal oxides.

Unveiling the Activity Origin of a Copper‐based Electrocatalyst for Selective Nitrate Reduction to Ammonia

“…The production, purification, and compression of hydrogen and nitrogen are highly energy‐intensive . Moreover, the preparation of hydrogen via the reforming of natural gas is accompanied by the emission of huge amounts of greenhouse gas . Thus, using water as a hydrogen source to prepare ammonia through electrocatalytic and photo(electro)catalytic nitrogen reduction has attracted increasing attention .…”

Ambient Electrosynthesis of Ammonia on a Core–Shell‐Structured Au@CeO2 Catalyst: Contribution of Oxygen Vacancies in CeO2

“…In recent years, the electrocatalytic N 2 reduction reaction (NRR) to NH 3 by using water as the hydrogen source and operating under ambient conditions has exhibited great potential as a promising substitute for the energy‐ and capital‐intensive Haber–Bosch process . To date, metal‐based materials have been the most widely investigated electrocatalysts for the NRR, exhibiting acceptable NH 3 yields and faradaic efficiencies (FEs) in aqueous electrolytes and significantly improved FEs in ionic‐liquid electrolytes .…”

“…It is well known that ammonia (NH 3 )p lays as ignificant role in the production of nitrogen fertilizers, industrial organic synthesis, and NH 3 fuel cells (with an energyd ensity of 4.32 kWh L À1 ). [1][2][3][4] AlthoughN 2 is very abundant in the atmosphere, accountingf or about 78 %, it is very inert, with ah igh triple-bond energy of 940.95 kJ mol À1 and no permanent dipole;t hus artificially fixing N 2 to NH 3 is extremely challenging. [5][6][7] Currently,t he century-old Haber-Bosch process is still dominant for the production of NH 3 on an industrial scale.…”

Atomic Modulation, Structural Design, and Systematic Optimization for Efficient Electrochemical Nitrogen Reduction

“…Fixation of atmospheric dinitrogen (N 2 ) to ammonia (NH 3 ) is a vital chemical process for the environment and human life, considering that ammonia is a carbon‐free energy carrier and pivotal precursor for the production of various commodity chemicals such as fertilizers . An annual ammonia production exceeding 150 million tons is crucial to meet the demands in production for the booming world population .…”

“…Overall, ammonia production from the H–B process is unsustainable and harmful to the environment. Apprehensive of its adverse impact, researchers have continuously experimented with other sustainable approaches to ammonia synthesis, and preferentially those with minimal infrastructural needs and operability under ambient conditions …”