“Chemical Looping” – Scientists Find A Way To Turn Toxic Sewage Gas Into Clean Hydrogen Fuel

The study builds on previous work using “chemical loopback”.

Scientists have discovered a new chemical process to turn stinky, poisonous gas into clean-burning fuel.

The process, detailed recently in the journal American Chemical Society ACS Sustainable Chemical Engineering, converts hydrogen sulfide – more commonly known as “sewage gas” – into hydrogen fuel. Hydrogen sulfide is emitted from manure piles and sewer lines and is a key by-product of industrial activities, including oil and gas refining, paper production, and mining.

The process detailed in this study uses relatively little energy and a relatively inexpensive material – chemical iron sulfide with a trace of molybdenum as an additive.

In addition to smelling rotten eggs, hydrogen sulfide is very toxic, corrodes pipes and damages the health of people who encounter it.

“Hydrogen sulfide is one of the most harmful gases for industry and the environment,” said Lang Qin, study co-author and associate researcher in chemical and biomolecular engineering at Ohio State. University. “And because the gas is so harmful, a number of researchers want to turn the hydrogen sulfide into something that is not that harmful, preferably valuable.”

The study builds on previous work by the same research group using a process called chemical loopback, which involves adding metal oxide particles in high pressure reactors to burn fuels without direct contact between air and air. fuel. The team first used the chemical loopback of coal and shale gas to convert fossil fuels into electricity without emitting carbon dioxide into the atmosphere. The initial process used iron oxide to break down fossil fuels.

Researchers then applied the concept to hydrogen sulfide and invented the SULGEN process, which converts hydrogen sulfide into hydrogen. The researchers found that the pure chemical, iron sulfide, did not perform well at the large scales needed for industrial use, Qin said. The research team tried to identify other inexpensive chemicals that could catalyze this transformation in larger quantities. This study shows that the introduction of a trace of molybdenum in iron sulphide could be an interesting option.

This material is relatively inexpensive and easy to acquire, making it an attractive option for larger scale operations.

The transformation of this poisonous gas into hydrogen fuel creates an alternative to oil and gas, which are major contributors to climate change, the researchers said.

“It is too early to say whether our research can replace any of the hydrogen fuel production technologies that exist,” said Kalyani Jangam, lead author of the study and graduate student at the Clean Energy Research Laboratory of the ‘Ohio State. “But what we’re doing is adjusting that decomposition process and making it a valuable product.”

For this most recent study, researchers found that molybdenum improves the degradation of hydrogen sulfide, dividing it into two parts: fuel hydrogen and sulfur.

This work is at the start of the scientific process – researchers have shown that the process works in the laboratory; industrial level tests are coming.

“The big picture is that we want to solve the problem of harmful gases, and we thought our chemical loopback process would allow that,” Qin said. “And here we’ve found a way to do it in the lab that creates this value-added hydrogen fuel. “

Reference: “Mo-doped FeS mediated H₂ Production from H₂S via an In Situ Cyclic Sulfur Looping Scheme ”by Kalyani Jangam, Yu-Yen Chen, Lang Qin and Liang-Shih Fan, August 12, 2021, ACS Sustainable Chemical Engineering.
DOI: 10.1021 / acssuschemeng.1c03410

The main author of this article is Liang-Shih Fan, professor of chemical and biomolecular engineering at Ohio State. Yu-Yen Chen, a former doctoral student in Fan’s lab, also contributed.