Amazing Zeolites and their new role in natural gas purification | Michael Zhu Chen | TEDxMileHigh


Translator: Denise RQ
Reviewer: Helena Bowen It was 2009, and I was visiting
my grandfather in Beijing, China. One morning, I looked out the window
and saw something that looked like this. It was shocking to see
how bad the pollution was. I could barely even see
the building right across the street. You couldn’t go outside
without putting a mask on, and I started to wonder,
why did it have to be this way? As with most things relating
to energy and the environment, it comes down to one thing: carbon. Carbon is an amazing element. It’s what gives us life and energy,
but it’s also just as dangerous. Carbon dioxide is
one of the major greenhouse gases, and carbon soot is a major air pollutant. So I dug a little deeper, and it turns out
that the smog I saw that morning was in large part caused
by the burning of coal to generate electricity. China and many other countries,
including the U.S., rely on coal to produce power. The problem with coal
is that it is an incredibly dirty fuel. It produces lots of CO2 when you burn it, and not only that,
it releases toxic pollutants, like nitrogen oxides and sulfur oxides. These can contribute to smog. Clearly, coal is an unsustainable fuel,
and we need to look for alternatives. (Applause) Of course, we can turn to renewables,
like photovoltaics and biofuels, but the problem with those technologies
is that they’re very expensive. They cost around $800 just to prevent
one ton of CO2 emissions. A promising solution that we can use
as we transition fully into renewables is the combined cycle power plant. A combined cycle power plant
is a power plant that uses natural gas, and it produces energy
in a two stage process, to make it much more efficient
than a traditional coal power plant. Natural gas has
enormous advantages over coal. It has half the CO2 emissions, and it doesn’t come with
the toxic byproducts that are found in coal. Naturally, natural gas has begun to take up a larger chunk
of the energy pie. Production is expected
to increase 20%, by 2035, and a large portion of that increase is due to the increase
in shale gas production, shown in green. Shale is a sedimentary rock, and it often contains
natural gas trapped inside. It is especially relevant
to us here in Colorado, because we have one of the largest
reserves of shale gas in the country. In fact, we are ranked fifth
in top natural gas producing states, and we’re likely to move
even farther up that list as natural gas production increases. So, natural gas seems like
a great fuel, it seems natural. Why aren’t we using it? It turns out natural gas
is starting to get expensive. Before you can use natural gas to heat
your house or to turn on your stove, it actually needs to be purified. When natural gas is mined out of the well,
it comes as a mixture of different gases. It can contain up to 50% carbon dioxide,
small amounts of other gases, such as nitrogen, water, and helium, and about 50% methane,
the stuff we can actually burn. It’s especially important
to remove CO2 for two reasons. First, it decreases
the energy content of the gas, and second, CO2 can form carbonic acid
in the presence of water, and that can destroy our pipelines. So what’s the solution? It’s detergent. It turns out you can do this at home. You take detergent, add natural gas,
and stick it in your washer. (Laughter) Just kidding. (Laughter) The actual solution– (Laughter) is something that’s an ingredient
in natural gas called zeolites. Zeolites are a type of mineral composed of aluminum,
silicon, and oxygen. They form crystals, and from the outside,
they just look like ordinary rocks. They’re something you might see
on the side of a hiking trail. But when we take a closer look
at zeolites, they become so much more interesting. Zeolites actually have pores
on the nano scale, the same size as
an individual gas molecule. There’s over 200 different types
of zeolite structures, and all of them
are so incredibly beautiful. At the University of Colorado at Boulder, we’ve been working
with one type of zeolite called Sapo-34. Sapo-34 has very small pores:
0.38 nanometers in size, and that’s the same as the diameter
of a single methane molecule. That’s incredibly small. Sapo-34 is very stable. It can function under
a wide range of pressures, and it can take temperatures
up to 700 degrees Celsius, which, for you non-conformists
out there, is 1300 degrees Fahrenheit. (Laughter) So we discovered we can
actually synthesize Sapo-34 as a very thin layer
of interlocking crystals, and this layer is
only 1 micron to 5 microns thick. That’s incredibly small, because
1 micron is 1/1000th of a millimeter. This very thin layer of crystals
can actually act as a membrane. This is an example
of one of the membranes we’ve created, next to a pencil, for comparison. What you’re seeing here
isn’t the membrane itself, but rather the supporting tube
that holds it together. The membrane is actually grown as a very thin layer
on the inside of that tube, and it’s too small to see
with the naked eye. We’re able to test our membranes
by placing them in a gas flow-chamber, so you can simulate
an actual natural gas well by feeding mixtures of carbon dioxide
and methane from the left side. Because CO2 is actually
a lot smaller than methane, it has a very easy time passing through
the tiny little pores in the membrane, and it can actually permeate
through the membrane, exiting at the bottom
in what is called the permeate flow. Whereas the methane, being very large,
has a hard time getting into the membrane. It is retained in the original gas mixture
in what is called the retentate gas flow, and that exits to the right. So what we found in testing our membranes is that we can actually convert
a 50:50 mixture of CO2 to methane into a 1:99 mixture of CO2 to methane, or better, and that’s remarkable, especially when you consider
the advantages of a membrane. (Applause) The current techniques
for removing CO2 from natural gas involve the use of a liquid chemical
which absorbs the CO2 and captures it, but the problem is
it is very energy intensive because you have to apply heat
or create a vacuum in order to pull off the CO2
and reuse the liquid. On the other hand, with a membrane,
you can simply put it in to a gas mixture and it will continuously separate gases,
with no need for energy input. So it’s much more environmentally friendly
and cost-effective. We’ve discovered other applications
for these membranes too, including hydrogen gas purification
for hydrogen gas fuel cells, and helium purification, and we’re working
with Fortune 500 companies to implement this technology. (Applause) The next step in our research
is to increase the size of our membranes. The membrane you saw earlier had a surface area
of about 5 square centimeters, and we’re looking to increase that
by 2,000 times to about one square meter. We’re going to do this by increasing
the length of our membranes and adding in multiple channels. This will allow us to separate gases at even higher pressures
and higher fluorides, which are necessary
for commercial applications. We’re taking what we’ve developed
on the nano level and applying it to the macro. Nano technology is all
about seeing things up close and applying them in a new way. And indeed, small things
can solve big problems. (Applause) It’s truly remarkable what nature
can accomplish on the small scale. Indeed, it’s the little things in life
that really matter. It’s amazing how the things we can’t see
can have such a big impact on our lives in the present and in the future. Something I’ve learned
from this experience is that anyone can do science;
it doesn’t take a genius. (Laughter) I was just a curious
little 12-year-old boy when I looked out the window and saw this. So I encourage you
to go look out your window. Try to discover
the emerging ideas and solutions that will make our world a better place, because sometimes, the most beautiful
things are right in front of our eyes, and we don’t even notice, because we’re either too busy
or too afraid to take a closer look. (Applause)

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