Ammonia is a colorless, pungent fuel with the chemical system NH3. It is a naturally occurring compound that performs an essential position within the nitrogen cycle and is used as a constructing block within the manufacturing of fertilizers, plastics, and different chemical compounds. It can also be used as a refrigerant and cleansing agent.
Stanford researchers have discovered an environmentally pleasant technique of manufacturing ammonia utilizing small droplets of water and nitrogen sourced from the air.
Ammonia (NH3) serves as the inspiration for the creation of chemical fertilizers used for agricultural crops. For over 100 years, the worldwide manufacturing of ammonia in massive portions has relied on the Haber-Bosch course of. This industrial breakthrough has had a serious influence on agriculture, enabling the feeding of a quickly rising human inhabitants. However, the Haber-Bosch course of is extraordinarily energy-intensive, requiring excessive strain ranges of 80-300 atmospheres and temperatures starting from 572-1000 F (300-500 C) to interrupt nitrogen’s robust bonds. Additionally, the steam-treatment of pure fuel concerned within the course of contributes considerably to the discharge of carbon dioxide, a key contributor to local weather change.
All instructed, to fulfill the present annual worldwide demand for 150 million metric tons of ammonia, the Haber-Bosch course of gobbles up greater than 2% of worldwide vitality and accounts for about 1% of the carbon dioxide emitted into the ambiance.
In distinction, the progressive technique debuted by the Stanford researchers requires much less specialised circumstances.
“We were shocked to see that we could generate ammonia in benign, everyday temperature-and-pressure environments with just air and water and using something as basic as a sprayer,” mentioned examine senior creator Richard Zare, the Marguerite Blake Wilbur Professor in Natural Science and a professor of chemistry within the Stanford School of Humanities and Sciences. “If this process can be scaled up, it would represent an eco-friendly new way of making ammonia, which is one of the most important chemical processes that takes place in the world.”
The new technique additionally makes use of little vitality and at a low value, thus pointing a manner ahead to probably producing the precious chemical in a sustainable method. Xiaowei Song, a postdoctoral scholar in chemistry at Stanford, is the lead creator of the examine, which was not too long ago revealed within the Proceedings of the National Academy of Sciences.
New chemistry from blue-sky examine
The new chemistry found follows within the footsteps of pioneering work by Zare’s lab lately analyzing the long-overlooked and surprisingly excessive reactivity of water microdroplets. In a 2019 examine, Zare and colleagues novelly demonstrated that caustic hydrogen peroxide spontaneously types in microdroplets involved with surfaces. Experiments since have borne out a mechanism of electrical cost leaping between the liquid and strong supplies and producing molecular fragments, referred to as reactive oxygen species.
Taking those findings further, Song and Zare began a collaboration with study co-author Basheer Chanbasha, a professor of chemistry at King Fahd University of Petroleum and Minerals in Saudi Arabia. Chanbasha specializes in nanomaterials for energy, petrochemical, and environment applications and came to Stanford as a visiting scholar last summer.
The research team zeroed in on a catalyst – the term for any substance that boosts the rate of a chemical reaction but is not itself degraded or changed by the reaction – that they suspected could help blaze a chemical pathway toward ammonia. The catalyst consists of an iron oxide, called magnetite, and a synthetic membrane invented in the 1960s that is composed of repeating chains of two large molecules.
The researchers applied the catalyst to a Graphite mesh that Song incorporated into a gas-powered sprayer. The sprayer blasted out microdroplets in which pumped water (H2O) and compressed molecular nitrogen (N2) reacted together in the presence of the catalyst. Using a device called a mass spectrometer, Song analyzed the microdroplets’ characteristics and saw the signature of ammonia in the collected data.
Low-tech, low-energy ammonia synthesis
Zare and colleagues were very pleased with this result, especially in light of the relatively low-tech approach. “Our method does not require the application of any electrical voltage or form of radiation,” said Zare.
From a broader chemistry perspective, the method is remarkable in that it uses three phases of matter: nitrogen as gas, water as liquid, and catalyst as solid. “To our knowledge, the idea of using gas, liquid, and solid all at the same time to cause a chemical transformation is a first of its kind and has a huge potential for advancing other chemical transformations,” said Zare.
While promising, the ammonia production method revealed by Zare, Song, and Chanbasha for now is only at the demonstration stage. The researchers plan to explore how to concentrate the produced ammonia as well as gauge how the process could potentially be scaled up to commercially viable levels. While Haber-Bosch is only efficient when pursued at huge facilities, the new ammonia-making method could be portable and done on-site or even on-demand at farms. That, in turn, would slash the greenhouse gas emissions related to the transportation of ammonia from far-off factories.
“With further development, we’re hoping our ammonia generation method could help address the two major looming problems of continuing to feed Earth’s growing population of billions of people, while still mitigating climate change,” said Zare. “We are hopeful and excited to continue this line of research.”
Reference: “Making ammonia from nitrogen and water microdroplets” by Xiaowei Song, Chanbasha Basheer and Richard N. Zare, 10 April 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2301206120
The study was funded in part by the U.S. Air Force Office of Scientific Research through the Multidisciplinary University Research Initiative.
