ExxonMobil joins the Pyromaniax

October 21, 2014 |

Exxon-logoPetroleum giant signs 2-year research project with Iowa State to explore fast pyrolysis as a biofuel technology?

What exactly is going on in the fast pyro reaction — can deep insight lead to biocrude instead of biooil? Can biooil be more stabilized?

The Digest looks behind the news.

One science project that never got done in primeval times was setting up a time-lapse camera somewhere in Texas around 60 million years ago, and accumulating a photographic record of where exactly petroleum actually came from.

Even at a rate of one exposure a year, the resulting film would run for nearly five years, and would be about as interesting as watching paint dry (sort of in reverse, since it’s better described as watching paint form). But it would have solved the mystery.

To make matters worse, we have no dinosaur-in-the-street interview to provide on-the-spot answers:

DINO: There, over there, I saw it!
REPORTER: What did you see?
DINO: Those leaves and muck over there…they’re changing! They’re becoming hydrocarbons! Run for your lives!


So, we’re left to guess, and the general consensus is that the hydrocarbon soup — the stuff we are we are so busy finding, drilling, tracking and pumping — came out of a gigantic collection of muck, fiber and leaves which has gone through an achingly slow pyrolysis.

Back to Pyrolysis Academy

Now, pyrolysis isn’t so hard to understand at a high level. That grade school experiment where you burn sugar and make a lava-like brown flow that rises and bubbles briefly as a liquid stew, then suddenly solidifies into a bunch or desiccated black carbon. That’s pyrolysis — though a highly oxygenated, uncontrolled version of it.

Pyrolysis means simply heating biomass — but not so hot that it begins to combust — and the fast pyrolysis reaction that was discovered around 1980 is thought by many to be the world’s best hope for discovering a machine that can turn biomass into oil so quickly that it becomes an economically viable way of making an oil that is workable in all the ways that petroleum is.

So far, it’s more about vision than reality. There have been a number of fast pyrolysis reactors built — and they really do transform biomass, in a matter of seconds, into a fraction of burnable gas, a fraction of biooil, and a fraction of black residue known as biochar. But then, we try to work with the resulting bio-oil, and its a mess compared to petroleum.

And here’s the problem with bio-oil, vs petroleum. And you wouldn’t think that it’s a problem until you have to do with it.

The lazy kid and the hyperactive one

You see, petroleum is like the laziest kid in the neighborhood. You have to prod it and poke it to get it to do anything for you. So, over the years, we have developed these huge refineries that throw temperature and pressure and catalysts at petroleum, to transform it into the array of fuels, chemicals and materials that we know today.

By contrast, bio-oil is like the hyperactive kid in the neighborhood with ADHD that you want to make sure is taking his Ritalin.

It reacts in a volatile way even when you don’t want it to, and changes from one stew of molecules into another. It has always been viewed typically as a very uncontrollable reaction, a non-selective process that gives you this soup of molecules and doesn’t behave like petroleum.


Enter ExxonMobil

But hang on, help may be on the way. ExxonMobil and Iowa State University just announced a collaboration on pyrolysis. But not a simple process development from what we know today. Rather, a deep investigation into pyro — what is actually going on inside the reactor, and what can be done for stabilization of the bio-oil that is so tantalizingly close to petroleum, but lacks that inert nature that leaves us in control of its transformation.

The Digest spoke this week with Iowa State’s Dr. Robert “The Godfatha of Pyrolysis” Brown, who is one of the two principal investigators at Iowa State for the ExxonMobil collaboration.

“Big Oil has a bad rap on renewables,” Brown sighed. “Some companies have backed out of some commitments, and many of them have had no special interest in the cellulosic fermentation space. But most of the people I have talked with like the promise of biofuels and are genuinely interested in them.”

“We had a first conversation a few years back when they came to visit about pyrolysis. That was it, and I didn’t hear from them again, until about a year ago, when they came back again, interested specifically in pyrolysis, and the conversations led in part to the collaboration you’ve heard about.

“There are two theories going around about what is happening in the reactor. One, that pyrolysis is taking solids and transforming them into other molecules that we condense and capture as liquids, as they are thermally ejected out of the system.

If true, that leaves us with a problem with lignin, which in the fast pyrolysis reaction becomes pyrolytic lignin, which is a kind name for it, because what you get is a sort of goo that comes out of the reactor and there’s nothing economic that really anyone has come up with for it.”

“If fast pyrolysis is based on thermal ejection than it is spitting out goo and that’s about all you are ever going to have,” Brown said.

“But there’s another theory, and that is that pyrolysis is breaking the solids down into small enough pieces that the vapor pressure begins to play a role, and it is an evaporative process. In that theory, what you are seeing in the reactor is that valuable monomers are being formed, but then are rapidly recombining into polymers. And what we see in pyrolytic lignin is the result of recombination.”

“So that what you have is a primary reaction with solid biomass, and then a set of secondary reactions that cause the recombination.”

“That’s interesting, because if we can keep them from recombining, if we can begin to control and quench those secondary reactions, then we can deploymerize cellulose thermally. It could be a mix of the two but I suspect it is preponderantly evaporative.

“One vision is that you can take the three plant polymers – cellulose, hemicellulose and lignin – and make stable intermediates, such as monosaccharides. If we can heat it fast enough and get it out of the reactor before it burns, we can ultimately get these molecules into the BTX or fuel range with an upgrade. But to do so, we have to go beyond the chemistry and look simultaneously at the physical phenomena. That’s part of what the ExxonMobil project is all about.”

“We also need to understand what is catalyzing the secondary reactions. For example, one of the things we have to do is understand what’s causing bad things in the reaction, such as alkali and alkaline metals.”

Combining and recombining

If you’ve used gladwrap recently, you might wonder what it is made of: that’s polyethylene, and we spend quite a bit of industrial resources on distilling off fraction of petroleum known as naphtha, transforming that into ethylene — which is known as a monomer — and then transforming that into a polymer, and that’s polyethylene. People spend their whole lives improving that process.

The thing is, you can throw just about anything you like at ethylene, and it won’t polymerize. Think arguing with a state trooper over a speeding ticket when he’s having a bad day and behind quota. People make good money, and deserve it, for designing catalysts that cause ethylene to polymerize.

By contrast, what may be going on in pyrolysis is that it may be repolymerizing — spontaneously. But, like the unruly teen it is, never in the way you want, or the time you want. A pyrolytic bio-oil is oil’s Rebel Without a Cause.

Looking at commercial companies in the field

“KiOR or Cool Planet?” Brown sighed. “They might come up with unique names for the process because of commercial considerations, but it is pyrolysis ultimately.”

With catalytic pyrolysis, Brown was skeptical that the answer was a magic catalyst. “The problem is that they get all this coke on the catalyst, from the high reactivity and because there is not enough hydrogen. But another problem goes back to the way that petroleum refining works.”

“With petroleum, you fraction through distillation, and you have a specific catalyst for every fraction. So they pull out the fractions and separate them from each other.”

I asked Brown about Cool Planet, which hasn’t gone into a fantastic amount of detail about its pyrolysis, but one of the fundamental approaches that founder Mike Cheiky spoke about was fractionating the streams as they came out of the reactor, and pulling off materials along the line.

“He may have had an insight into petroleum refining, and it would be a very interesting insight. it could be that his process is based on some analogy with petroleum.”

So, how much time for the ExxonMobil-Iowa State project?

It’s a two-year program, with two aspects. One, fundamentally understanding what its happening – is it thermal ejection or evaporative -is there something beyond pyrolytic lignin? Two, stabilization, can we do something that makes a stable bio-oil vs the corrosive active liquid we have today?

The Bottom Line

If pyrolysis is a time machine, right now it can take you all the way back to around 60,000,000 BC — but can only bring you forward to around 1850, when it was felt there was real potential in what was known then as “rock oil”, but no one had actually figured out how to extract stable products from it.

That’s where we are with fast pyrolysis today. When it’s stable – oh, the interest you’ll see.

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