Could we make cars out of petroleum residue?
A new method could turn refinery byproducts into high-value, ultralight structural materials for cars, aircraft, and spacecraft

Date:
March 18, 2022
Source:
Massachusetts Institute of Technology
Summary:
Researchers have developed a way to make lightweight fibers, for
possible use in the bodies of cars, out of an ultracheap feedstock:
the waste material from the refining of petroleum.



FULL STORY ==========================================================================
As the world struggles to improve the efficiency of cars and other
vehicles in order to curb greenhouse gas emissions and improve the range
of electric vehicles, the search is on for ever-lighter materials that
are strong enough to be used in the bodies of cars.


========================================================================== Lightweight materials made from carbon fiber, similar to the material used
for some tennis rackets and bicycles, combine exceptional strength with
low weight, but these have been more expensive to produce than comparable structural elements made of steel or aluminum. Now, researchers at MIT and elsewhere have come up with a way of making these lightweight fibers out
of an ultracheap feedstock: the heavy, gloppy waste material left over
from the refining of petroleum, material that refineries today supply
for low-value applications such as asphalt, or eventually treat as waste.

Not only is the new carbon fiber cheap to make, but it offers advantages
over the traditional carbon fiber materials because it can have
compressional strength, meaning it could be used for load-bearing
applications. The new process is described in the journal Science
Advances, in a paper by graduate student Asmita Jana, research scientist
Nicola Ferralis, professor Jeffrey Grossman, and five others at MIT,
Western Research Institute in Wyoming, and Oak Ridge National Laboratory
in Tennessee.

The research began about four years ago in response to a request from the Department of Energy, which was seeking ways to make cars more efficient
and reduce fuel consumption by lowering their overall weight. "If you look
at the same model car now, compared to 30 years ago, it's significantly heavier," Ferralis says. "The weight of cars has increased more than
15 percent within the same category." A heavier car requires a bigger
engine, stronger brakes, and so on, so the reducing the weight of the
body or other components has a ripple effect that produces additional
weight savings. The DOE is pushing for the development of lightweight structural materials that match the safety of today's conventional steel
panels but also can be made cheaply enough to potentially replace steel altogether in standard vehicles.

Composites made from carbon fibers are not a new idea, but so far in
the automotive world they have only been used in a few very expensive
models. The new research aims to turn that around by providing a low-cost starting material and relatively simple processing methods.



========================================================================== Carbon fibers of the quality needed for automotive use cost at least $10
to $12 per pound currently, Ferralis says, and "can be way more," up to hundreds of dollars a pound for specialized application like spacecraft components. That compares to about 75 cents a pound for steel, or $2 for aluminum, though these prices fluctuate widely, and the materials often
rely on foreign sources. At those prices, he says, making a pickup truck
out of carbon fiber instead of steel would roughly double the cost.

These fibers are typically made from polymers (such as polyacrilonitrile) derived petroleum, but using a costly intermediate step of polymerizing
the carbon compounds. The cost of the polymer can account for more than
60 percent of the total cost of the final fiber, Ferralis says. Instead
of using a refined and processed petroleum product to start with, the
team's new approach uses what is essentially the dregs left after the
refining process, a material known as petroleum pitch. "It's what we
sometimes call the bottom of the barrel," Ferralis says.

"Pitch is incredibly messy," he says. It's a hodgepodge of mixed heavy hydrocarbons, and "that's actually what makes it beautiful in a way,
because there's so much chemistry that can be exploited. That makes it
a fascinating material to start with." It's useless for combustion --
although it can burn, it's too dirty a fuel be practical, and this is especially true with tightening environmental regulations. "There's
so much of it," he says, "the inherent value of these products is very
low, so then it is often landfilled." An alternative source of pitch,
which the team also tested, is coal pitch, a similar material that is
a byproduct of coking coal, used for example for steel production. That
process yields about 80 percent coke and 20 percent coal pitch, "which
is basically a waste," he says.

Working in collaboration with researchers at Oak Ridge National
Laboratory, who had the expertise in manufacturing carbon fibers under
a variety of conditions, from lab scale all the way up to pilot-plant
scale, the team set about finding ways to predict the performance in
order to guide the choice of conditions for those fabrication experiments.



==========================================================================
"The process that you need to actually make a carbon fiber [from pitch]
is actually extremely minimal, both in terms of energy requirements and
in terms of actual processing that you need to do," Ferralis says.

Jana explains that pitch is "made of these heterogeneous set of molecules, where you would expect that if you change the shape or size you would
expect the properties to change dramatically," whereas an industrial
material needs to have very consistent properties.

By carefully modeling the ways bonds form and crosslink between the
constituent molecules, Jana was able to develop a way of predicting how
a given set of processing conditions would affect the resulting fiber properties. "We were able to reproduce the results with such startling accuracy," she says, "to the point where companies could take those
graphs and be able to predict" characteristics such as density and
elastic modulus of the fibers.

The work produced results showing by adjusting the starting conditions,
carbon fibers could be made that were not only strong in tension, as
most such fibers are, but also strong in compression, meaning they could potentially be used in load-bearing applications. This opens up entirely
new possibilities for the usefulness of these materials, they say.

DOE's call was for projects to bring the cost of lightweight materials
down below $5 a pound, but the MIT team estimates that their method can
to do better than that, reaching something like $3 a pound, though they
haven't yet done a detailed economic analysis.

"The new route we're developing is not just a cost effect," Ferralis
says. "It might open up new applications, and it doesn't have to
be vehicles." Part of the complication of making conventional fiber
composites is that the fibers have to be made into a cloth and laid
out in precise, detailed patterns. The reason for that, he says,
"is to compensate for the lack of compressive strength." It's a matter
of engineering to overcome the deficiencies of the material, he says,
but with the new process all that extra complexity would not be needed.

The research team included Taishan Zhu and Yanming Wang at MIT,
Jeramie Adams at Western Reserve University, and Logan Kearney and Amit
Naskar at Oak Ridge National Laboratory. The work was supported by the
U.S. Department of Energy.


========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by David
L. Chandler. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Asmita Jana, Taishan Zhu, Yanming Wang, Jeramie J. Adams, Logan T.

Kearney, Amit K. Naskar, Jeffrey C. Grossman and Nicola
Ferralis. Atoms to fibers: Identifying novel processing methods
in the synthesis of pitch-based carbon fibers. Science Advances,
2022 DOI: 10.1126/ sciadv.abn1905 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220318161434.htm

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