New catalyst to convert unpleasant hydrogen sulfide into cash

Engineers and scientists at Rice University have developed a method for petrochemical refineries to turn an unpleasant byproduct into money.

The smell of rotten eggs is unmistakably present in hydrogen sulfide gas. Thousands of tons of the toxic gas are produced annually as a byproduct of processes that remove sulfur from petroleum, natural gas, coal, and other products. It frequently comes from sewers, stockyards, and landfills, but it is especially problematic for refineries, petrochemical plants, and other industries.

Naomi Halas, a Rice engineer, physicist, and chemist, and colleagues present a process that transforms hydrogen sulfide into sulfur and high-demand hydrogen gas in a single step using gold nanoparticles. Even better, the one-step process only needs light as its source of energy. Peter Nordlander of Rice University, Emily Carter of Princeton University, and Hossein Robatjazi of Syzygy Plasmonics are co-authors of the study.

Each hydrogen sulfide gas molecule (H2S) consists of two hydrogen atoms and one sulfur atom. The main component of the hydrogen economy, clean-burning hydrogen gas (H2), has two hydrogen atoms in each of its molecules. In the latest research, Halas’ team placed tiny islands of gold on the surface of silicon dioxide powder grains. Each island was a gold nanoparticle that was 10 billionths of a meter across and had a strong interaction with a particular visible light wavelength. “Hot carriers,” or brief, high-energy electrons, are produced by these plasmonic processes and can power catalysis.

In the work, Halas and co-authors demonstrated how a bank of LED lights could effectively induce hot carrier photocatalysis and convert H2S straight into H2 gas and sulfur using a laboratory setting. Comparing it to the well-established catalytic process refineries employ to break down hydrogen sulfide is striking. It is referred to as the Claus process and instead of producing hydrogen, it transforms sulfur into water. There are several steps in the Claus procedure as well, some of which call for combustion chambers to be heated to a temperature of roughly 1,500 degrees Fahrenheit.

Halas and Nordlander are co-founders of Syzygy Plasmonics, a startup firm with more than 60 people based in Houston that has licensed the plasmonic hydrogen sulfide remediation technology.