I asked Gemini Plus about the reaction of M200A (M200A, a proprietary amine-based solvent often associated with gas sweetening or industrial cleaning) and Nitric Acid, as has been reported in the media as the two (2) chemicals involved in yesterday’s tragic event in WV. It has been reported that H2S was involved; yet, reading this AI analysis, I do not see how H2S was generated by this reaction, unless the M200A was “sour” (contaminated with sulfur from gas processing), which is possible. Maybe they had H2S on site, and the explosion caused its release. AI states this reaction produces Hydrogen Cyanide (HCN), which is more toxic than H2S. HCN’s IDLH is 50 ppm, and H2S is 100 ppm.
Here is the analysis…
The mixture of M200A, a proprietary amine-based solvent often associated with gas sweetening or industrial cleaning) and Nitric acid resulted in a major industrial accident in West Virginia on April 22, 2026.
The reaction is extremely hazardous, characterized by rapid, violent exothermic decomposition.
The Chemical Reaction
While “M200A” is a trade name, it is primarily composed of methyldiethanolamine (MDEA), a tertiary amine. When a strong oxidizing acid like nitric acid (HNO3) is mixed with a tertiary amine, several dangerous processes occur simultaneously:
Neutralization (Exothermic): The initial contact causes an immediate acid-base neutralization reaction. This releases a significant amount of heat (Q).
CH3N(C2H4OH)2+HNO3→[CH3NH+(C2H4OH)2][NO3−]+Q
Oxidative Decomposition: Because nitric acid is a powerful oxidizer, it begins to break down the organic structure of the MDEA. This secondary reaction is often runaway, meaning the heat from the first reaction accelerates the oxidation.
Gas Evolution: The reaction produces dense, toxic clouds of nitrogen oxides (NOx), specifically nitrogen dioxide (NO2), which appears as a characteristic reddish-brown vapor.
Key Hazards Observed
According to reports from the Kanawha County incident:
Explosion: The rapid generation of gas and heat in a confined space (like a pump area or tank) can lead to a mechanical overpressure explosion.
Toxic Cloud: The reaction releases NOx gases, which are severe respiratory irritants and can cause pulmonary edema. There are also reports suggesting the potential evolution of hydrogen sulfide (H2S) if the M200A was “sour” (contaminated with sulfur from gas processing).
Corrosive Spray: The violence of the reaction can aerosolize the unreacted nitric acid, causing severe chemical burns to anyone nearby.
Safety Note for Process Engineers
As you are involved in process safety, this incident highlights a critical Reactive Chemistry Hazard. It underscores the danger of decommissioning or cleaning operations where “empty” tanks may still contain residual organic solvents (M200A) that are incompatible with common cleaning agents like nitric acid.
Source: Google Gemini Plus