In the early 1990s when I was a graduate student in Chemical Engineering at the University of Pennsylvania, I taught a class called Introduction to Chemical Engineering to the freshmen. During my first lecture, I asked the students to guess the highest volume chemical produced in the United States. They made some worthy guesses, but none were correct. The correct answer back then as well as today, a quarter of a century later, was and is sulfuric acid by a landslide. Furthermore, sulfuric acid would have been the correct answer in 1900 or any other year between then and now. Currently, the United States churns out 36 million tons of it every year.
Before I explain why we make so much sulfuric acid, I want to share an encounter I had with the history of the production of sulfuric acid. The first commercial-scale method for producing sulfuric acid, known as the lead chamber process, was invented by John Roebuck in 1746 in Birmingham, England. That method produces sulfuric acid by burning sulfur to make sulfur dioxide gas and then mixing it with steam in a lead-lined chamber. After several chemical reactions occur and the steam condenses, you are left with sulfuric acid in the liquid phase. The chambers had to be lined with lead; otherwise the sulfuric acid would eat right through them. After getting into the iron business and investing in James Watt’s steam engine, Roebuck died in 1794. If he is up there somewhere in inventor heaven, I am sure he was pleased to see that his lead chamber process remained the primary method for making the highest volume chemical in the world for 200 years.
In 2004 I worked on a project at a chemical plant in the town of Usti in the Czech Republic. Usti has been an important center of the central European chemical industry since the early 1800s. The 133 acre plant is enormous, sort of like a small city, and began operations in 1856. One day I asked if I could have a tour. It was fascinating to see the contrasts of the gleaming modern projects like the one I was working on adjacent to older facilities that had been there for many decades. We walked into one of the older buildings and there before me was a row of 10 lead chamber reactors making sulfuric acid exactly the same way that John Roebuck had 248 years earlier. I felt like I had just step through some sort of time travel portal from a science fiction movie.
But I digress. Sulfuric acid has far too many uses for me to provide you with an exhaustive explanation of why we produce so much of it. So I will cover just some of the major ones. First and foremost is fertilizer. The key elements in fertilizer are nitrogen and phosphorous, albeit in the correct chemical forms. As I explained in Yes, This Really is a Column about Phosphorous, phosphorous is mined from the ground as rock particles that contain many impurities, particularly calcium. Despite containing phosphorous, the rock itself is not an effective fertilizer. In order to extract the phosphorous from the rock particles, they are dissolved in sulfuric acid, which converts the phosphorous into phosphoric acid. Once you have phosphoric acid, it can easily be converted into phosphorous-containing fertilizer.
Since sulfuric acid is a strong acid and fairly cheap, it is used in a myriad of other chemical production processes. Many chemical reactions occur either more quickly or more completely in an acidic environment. Examples include papermaking and production of paints and dyes. Sulfuric acid is also used to remove rust in the last step of iron and steel production.
I find it interesting that in what we perceive to be our modern, technologically-advanced world, the highest volume chemical we produce, sulfuric acid, is utilized for the fairly low-tech applications of processing rock, making paper, or polishing scissors. (See what I did there?) Perhaps you think that the U.S. Chemical Industry is kind of a dinosaur itself. However, the United States is the largest producer of chemicals in the world and the industry makes $800 billion worth of products a year.
Now that we know that sulfuric acid, at 36 million tons per year, is the highest volume chemical produced in the U.S., let’s have a quick look at the rest of the top ten and their uses as well.
- Propylene: 14.3 million tons – plastics, foam cushions, carpets;
- Sodium Hydroxide: 14.0 million tons – soaps, detergents;
- Sodium Carbonate: 11 million tons – glass and brick making;
- Ammonia: 8.0 million tons – nitrogen-containing compounds for fertilizer;
- Benzene: 5.8 million tons – precursor for many other chemicals, particularly styrene;
- Acetic Acid: 5.4 million tons – plastics including polyvinyl acetate;
- Ethylene Oxide: 4.0 million tons – antifreeze;
- Formaldehyde: 3.4 million tons – foam insulation, particle board glue;
- Methanol: 2.4 million tons – raw material to make formaldehyde, industrial solvent;
It’s taken me a couple of days to determine how to conclude this column. My concern has been that the sulfuric acid story I have told and the list of chemicals I have shown may tell a different story to me than to you. So let me tell you what I see.
A couple of years ago, my friend Robert Newton made a documentary called Still Standing – The Real Story of the North Carolina Textile Industry. His documentary clearly illustrates that the popular perception that the North Carolina textile industry is dead and gone is simply not correct. We have a number of growing and innovative textile companies here in the Tar Heel State. Heck, we even make Spanks! Writing this column was a reminder for me that the perception that manufacturing in the United States is dead and gone is also incorrect. In fact, not only are we making fancy new chemicals like nanoparticles or advanced photovoltaic polymers, we still lead the world in making old-school chemicals like sulfuric acid and sodium hydroxide. I find that realization to be oddly comforting. Do you?
Jeff Danner discussed this week’s column with Aaron Keck on WCHL.
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