Chemicals I Have Made – Hydrogen Peroxide

It’s such a cute, cuddly chemical. Found in its brown plastic container in medicine cabinets across the world, it is poured on cuts and scrapes where it foams up in bubbles. Safe enough to be used as a mouth rinse. Good old 3% hydrogen peroxide! But let me assure you, what is safe at 3% strength, is not safe at 35% concentration. Or at 70% strength. Hydrogen peroxide, or H₂0₂ , is a chemical that must be given a great deal of respect. In my career, I worked in a process that made H₂0₂ for several years, and I’ve seen examples of its power.

When tank cars were loaded with H₂0₂, the hoses would still contain some of the liquid in the lines. There was an attitude that since this was not an organic material, and since the decomposition products were water and oxygen, it was not worthwhile to ensure that the last drops were purged out of the line. So a metal box was filled with steel scraps, metal shavings, and other pieces of metal with a high surface area. This box was used to decompose the peroxide before it ran into our cypress-lined trench system. On one occasion, significantly more peroxide ran down into the box than was intended, and not all of the peroxide decomposed before it entered the tar-covered cypress trench. Decomposition continued, and the heat released along with the enriched oxygen environment inside the trench, actually caused the trench to begin smoldering. The fire alarm was sounded, and the investigation showed that the fire was essentially caused – by water. That is the power inherent in industrial strength H₂0₂.

Before I worked at the plant, they had a specialized still that concentrated peroxide to 90% purity. That strength was used as a rocket fuel, and as a propellant for torpedoes. I never heard of any stories about accidents with that grade, but it would take very little in order to release the energy found in that strong of a chemical. After I left the Memphis Plant, I heard about something that happened to a tank car outside of the plant. Tank cars for peroxide were made of about 1/2″ thick aluminum. One night, a tank car essentially exploded, opening up the top like a pop can. The thought is that someone playing with a rifle, shot the tank car. There is a little organic material that sits atop commercial grade H₂0₂, which reacted to form organic peroxides. The energy from a rifle shot caused the organic peroxide to detonate, which triggered the release of the oxygen from the decomposing peroxide. I saw the car on a trip back to the plant. It clearly showed that there is a lot of energy available with 70% H₂0₂. I have searched diligently on the internet but I can find no on-line evidence of this incident.  One can only imagine what would have happened if this incident occurred after 9/11.

The process for making H₂0₂ is complex. An organic solution called working solution is the key to creating the H₂0₂ molecule, which then recycles to begin the process again. The working solution first enters the hydrogenators, where hydrogen gas contacts a catalyst of palladium chloride coated out as palladium metal on alumina particles. The palladium chloride comes in a solution form in 5 gallon pails, costing multiple thousands of dollars per pail. After the catalyst is filtered out, the working solution goes into the oxidizers, where air is blown through the solution. Hydrogen grabs onto the oxygen, and forms H₂0₂, which then is extracted with water, and concentrated in distillation stills. The working solution then returns and is ready to run through the loop once more.

That is a highly simplified version of the process. In practice, there is art involved. The active chemicals in the working solution can degrade over time. Therefore it is necessary to divert a side stream of working solution to flow through alumina, where the impurities that form in the hydrogenation step absorb onto the alumina. The whole process with the catalyst and the hydrogenation step is labor intensive, and it is always necessary to withdraw a portion of the catalyst and replace with fresh catalyst. To prevent that expense, and to achieve higher yield, the plant I worked at had invested in what is called a fixed bed hydrogenation system. This had shown impressive results in lab-scale testing, and in pilot plant testing, where 5-gallon sized vessels were used to prove the effectiveness before you built a 1000-gallon facility for commercial production. The new commercial facility was commissioned, and put in service.

But problems developed very rapidly. Even though the pilot plant testing did not show it, the commercial scale facility developed some hot spots inside the hydrogenator. This caused the active compound in the working solution to degrade much more rapidly than inside of the fluid bed hydrogenators. Since the investment in the working solution was several million dollars, it became imperative to find some way to reverse the damage. Lab work was expedited, and a solution was identified. They needed some engineer to manage the project and get the equipment ordered, installed, and functioning. I was plucked from the cyanide unit(see  Chemicals I have made – Hydrogen Cyanide ) and put in charge of the project.

It was a true baptism into project management. I got to travel to see the vessel that we were buying in the fabrication shop, up in the extreme northwest corner of New Jersey. There you were more likely to see a black bear than to see a Joisey girl. But the best part of the project was that I got to install and program a Programmable Logic Controller (PLC). Now this was back in 1980, and these were brand new toys  tools that used all of the advances in semi-conductors that were available. You could replace a whole rack of single-function logic switches, with a single unit that could do nearly unlimited functions. I had a lot of fun learning the ladder logic that went with this, and getting the system to work as intended. We started up our treatment unit – and it didn’t solve the problem. The working solution was still getting degraded, even when the fixed bed unit was operated at only a fraction of its intended production rate. The equipment I installed was abandoned, and the large fixed bed unit was shut down and eventually dismantled. But I had learned valuable skills and had managed a significant project by myself.

The manufacture of H₂0₂ is not different by chemical manufacturers. At the time I worked to make H₂0₂, all manufacturers used the process I described. Eventually, the unit I worked at was sold to another company in exchange for one of the other companies processes. I left H₂0₂ when I got a promotion to be a process supervisor for the manufacture of acrylonitrile. But that’s another story for another time.