SWAP Process Makes Cheaper, Cleaner Ammonia

Using a molybdenum-based catalyst with samarium as an electron source, researchers in Japan have created a process that produces ammonia more efficiently than the conventional Haber-Bosch process.

AsianScientist (May 7, 2019) – A team of scientists in Japan has devised a method to produce ammonia more cleanly and efficiently. They published their technique in the journal Nature.

In 1900, the global population was under two billion, whereas in 2019, it is over seven billion. This population explosion was fueled in part by rapid advancements in food production which was contingent on the widespread use of ammonia-based fertilizers.

The Haber-Bosch process is essential for the production of ammonia on an industrial scale, but it only converts ten percent of its source material per cycle. Among the source materials is hydrogen (H2) produced from fossil fuels, which is chemically combined with nitrogen (N2) at temperatures of about 400-600 degrees Celsius and pressures of about 100-200 atmospheres, also at great energy cost.

To improve the efficiency of ammonia production, researchers led by Professor Yoshiaki Nishibayashi at the University of Tokyo, Japan, created a new catalytic method which they called the Samarium-Water Ammonia Production (SWAP) process. SWAP takes in N2 from the air and combines it with protons (H+) from water and electrons (e) from the element samarium (SmI2) using a special molybdenum-based catalyst.

SmI2 is used up in the SWAP process but can be recycled with electricity to replenish its lost electrons. Furthermore, the researchers noted that their special molybdenum-based catalyst produces 4,350 ammonia molecules in about four hours before it expires.

“Our SWAP process creates ammonia at 300-500 times the rate of the Haber-Bosch process and at 90 percent efficiency,” said Nishibayashi. “Factor in the gargantuan energy savings in the process and sourcing of raw materials and the benefits really show.”

Anyone with the proper source materials can perform SWAP on a table-top chemistry lab, whereas the Haber-Bosch process requires large-scale industrial equipment. The smaller and less expensive setup could therefore grant more farmers access to ammonia-based fertilizers.

“A strong motivation was to make the SWAP process possible on a desktop scale. I hope to see this process democratize production of fertilizers,” said Nishibayashi. “So it’s not just about the upfront costs but also the continued cost and energy savings of raw materials. My team offers this idea to improve agricultural practices in places that need it the most.”

The article can be found at: Ashida et al. (2019) Molybdenum-catalyzed Ammonia Production With Smi2 and Alcohols or Water.


Source: University of Tokyo; Photo: Yoshiaki Nishibayashi.
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