Ammonia Production from nitrogen and water microdroplets

Ammonia is an important chemical compound with the formula NH3. It is widely used in industry for various purposes due to its unique properties.  One of the most significant uses of ammonia is as a fertilizer. Ammonia is a primary source of nitrogen, which is an essential nutrient for plant growth. It is used to produce ammonium nitrate, urea, and other nitrogen-rich fertilizers that help boost crop yields. Another important industrial use of ammonia is in the production of chemicals such as plastics, dyes, and pharmaceuticals. Ammonia is used as a raw material in the production of various organic compounds, including amino acids, which are building blocks of proteins. Ammonia is also a crucial component of refrigeration systems. It has a low boiling point and can be easily compressed into a liquid, making it an ideal refrigerant. Ammonia-based refrigeration systems are widely used in industries such as food processing, chemical manufacturing, and pharmaceuticals. Additionally, ammonia is used in the production of cleaning products, such as household cleaners, as well as in the production of explosives.

New ammonia production methods are crucial for several reasons, including increased efficiency, reduced environmental impact, and improved sustainability. Traditionally, ammonia production has been accomplished through the Haber-Bosch process, which uses high-pressure and high-temperature conditions to convert nitrogen and hydrogen gases into ammonia. This process is energy-intensive, requiring significant amounts of fossil fuels, and produces large amounts of greenhouse gas emissions, primarily carbon dioxide. Newer ammonia production methods, such as electrochemical synthesis and biological nitrogen fixation, have the potential to improve the sustainability of ammonia production. For example, electrochemical synthesis uses renewable energy sources, such as solar or wind power, to produce ammonia, reducing greenhouse gas emissions and dependence on fossil fuels. Biological nitrogen fixation is another promising method that uses nitrogen-fixing bacteria to convert nitrogen gas into ammonia. This process is energy-efficient and reduces the need for synthetic nitrogen fertilizers, which can have negative environmental impacts, such as nitrogen runoff and soil degradation. Additionally, new ammonia production methods can increase efficiency and reduce costs. For example, some new methods use lower temperatures and pressures, reducing the energy requirements and costs associated with ammonia production.

In a new research paper published in the peer-reviewed journal, Proceedings of the National Academy of Sciences, Stanford researchers led by Richard Zare, the Marguerite Blake Wilbur Professor have discovered a simple and environmentally sound way to make ammonia with tiny droplets of water and nitrogen from the air. The most common method to produce ammonia is the Haber-Bosch process, a breakthrough that helped revolutionize agriculture and feed a booming human population. But the industrial procedure is energy intensive. To break nitrogen’s strong bonds, the Haber-Bosch process requires roughly 80-300 atmospheres of pressure and temperatures around 572-1000 F (300-500 C). The steam-treating of natural gas involved in the process also releases ample amounts of climate-changing carbon dioxide. All told, to satisfy the current annual worldwide demand for 150 million metric tons of ammonia, the Haber-Bosch process gobbles up more than 2% of global energy and accounts for about 1% of the carbon dioxide emitted into the atmosphere. In contrast, the innovative method debuted by the Stanford researchers requires less specialized circumstances.

The research team used a new chemistry based on the high reactivity of water microdroplets. Previously, the lab demonstrated that caustic hydrogen peroxide spontaneously forms in microdroplets in contact with surfaces. Experiments since have borne out a mechanism of electric charge jumping between the liquid and solid materials and generating molecular fragments, known as reactive oxygen species. Taking those findings further, the authors  used magnetite as the catalyst for the reaction.  When the researchers applied the catalyst to a Graphite mesh that they 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. The authors  analyzed the microdroplets’ characteristics and saw the signature of ammonia in the collected data using mass spectrometry. The new method is remarkable in that it uses three phases of matter: nitrogen as gas, water as liquid, and catalyst as solid. According to the authors, the principle 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.

In summary, the importance of new ammonia production methods lies in their potential to improve the sustainability, efficiency, and cost-effectiveness of ammonia production while reducing the negative environmental impacts associated with traditional methods.  The authors are hopeful their new 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.