Transcription audio Généré automatiquement
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Hello, everyone.
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My name is John Lee and I'm I'm s a
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student in chemical and Biomolecular engineering program in HK S.
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T. And I'm doing this presentation as a requirement of
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one of my colleagues, Of course.
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So today I'm going to talk about investigation of Libyan
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based catalyst in catalytic combustion of methane, A low temperature.
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So the catalytic combustion of methane is known as the
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ones process which has lots of benefits compared to conventional
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ones like it does not produce carbon monoxide or ex
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Well, since this is called a catalytic combustion reaction, there
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must be a catalyst involved.
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The catalyst involved in this case is a plating based
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catalyst. Uh, while normally we're using played in oxide, which
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is the most active phase of the palladium catalyst.
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Uh, even this process has so many benefits.
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It still has, like, one big problem, which is the
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catalyst deactivation.
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When the operating temperature is below 400 degrees, 450 degrees
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Celsius below that temperature, the catalyst will deactivate Do two
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hydroxy oil or water accumulation on the oxide support, while
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we also call this phenomenon water, water inhibition, effect or
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water poisoning.
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This is called water inhibition effect is because the presence
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of water would actually inhibit the oxygen exchange between the
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gas phase oxygen and the oxygen from the A support.
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So to better understand this process, uh, I have proposed
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the following hype hypothesis.
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So the rate of oxygen exchange with the support is
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affected by temperature and the type of support we're using.
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And I have conducted, uh, methodology to show to, to
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prove, like whether my hypothesis, right or not.
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So, as you can see from here, so the first
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step is super paired Catalyst.
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The color is prepared by using a precursor which is
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played a nitrate dehydrate and dissolve it into a request.
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Hmm. Three solution and then in pregnant, the precursor onto
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the metal oxide support.
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The material will be dried overnight at room temperature and
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then cocaine in air for like four hours.
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In this case, we're using three types of metal oxide
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support, which are aluminum, magnesium oxide and mm cm 41.
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And after preparing this callous, we will use an incision
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transmission for real transform infrared spectrum meter, operating at 325
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degrees sources to conduct the experiment.
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So the catalyst is placed inside a reactor, and we
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also have a high pressure liquid nitrogen tank connecting with
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the spectral media to allow the continuous void of nitrogen
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flowing into the system to minimize the presence of any
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atmospheric water vapor and carbon dioxide to minimize the interference.
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So the reactant comes from two mixture.
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Gas cylinders, one containing helium and oxygen, and the other
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one containing methane oxygen helium.
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So we first Prezi preheat the system by allowing the
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helium and oxygen mixture flowing through director, director cell.
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And then we do the experiment by adding the other
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mixture of methane, oxygen and helium into the rector and
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ruined for like 20 minutes.
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And we're doing two separate trials, one with consistent operating
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temperature as 325 degrees Celsius and the other one with
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different temperatures.
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So let's look at the first trial.
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These are the results obtained from first trial.
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The first World is using aluminum, and the second one
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is using magnesium oxide, and the third one is using
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M. C.
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M. 41.
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While people have stated that the oxygen mobility on the
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support impacts water inhibition of the Cadillac reaction, Uh, so
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In other words, the greater the support surface oxygen mobility,
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the resistance to what exhibition will be larger.
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So in this case, you can see the mechanism.
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Oxide has the largest oxygen surface of mobility, while the
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X M 41 has the lowest oxygen mobility.
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So we can expect that the M C M 41
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would deactivate much faster than the other two.
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But actually, what we found is that by comparing these
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three, uh, comparing these three figures if we just compare,
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figure one figure two, which is aluminum and magnesium oxide.
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Since aluminum has a lower oxygen mobility than the magnesium
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oxide, uh, we can see that we we can see
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that the alumina would actually be actively much faster than
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the mechanism oxide because the oxygen in alumina no, not
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the oxygen.
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So by comparing a figure 12 as aluminum has a
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lower maximum oxygen mobility than the mechanism oxide.
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The catalyst on magnesium aluminum with the activity faster than
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the catalyst in magnesium oxide.
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Since you can see there's a dick client carbon dioxide
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over time, meaning that the reaction is not happening in
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aluminum well, but if we also consider figures three where
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the M c m 41 has the lowest oxygen mobility.
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But actually you you do not see any decrease in
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oxygen in carbon dioxide and water.
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Actually, there are all increasing mean There is no evidence
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of the activation of this reaction.
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So this disapproved the statement we have made before.
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And then let's look at the, uh, second trial when
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we do the experiment under different reaction temperature.
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Uh, the reaction shows that this this this result shows
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that the mechanism oxide the activists faster than they illuminate
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in this case, because the proportion of carbon dioxide and
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water are decreasing when during the reaction meaning that the
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reaction is not happening properly.
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But this opposite This is the opposite result obtained from
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compared to the results from the previous slide.
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So this actually proves that there is a water no.
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So by comparing figure a m B and figure the
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annual show like opposite result, meaning that, uh, the there
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is like a temperature dependence for the oxygen exchange.
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But it's hard to conclude the same for the type
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of support we're using because that one actually this proof
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what we said before, Well, one possible statement.
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We can make this like the different oxygen exchange activity
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may be related to the difference in the surface area
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of each support.
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For example, for uh, M c.
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M 41 it has a higher surface area than the
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others. So when we did the methane, so we when
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we add nothing into the system, the combustion reaction maybe
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initially hindered due to diffusion limitation associated with a high
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surface area of M C.
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M 41 so that we found and when we talk
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about like water accumulation noted that there is not only
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affects the oxygen exchange between the gas with oxygen and
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the support, but it also affects active catalytic site.
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But if you look at this flow chart, you can
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see that, uh, actually, one big problem in methane combustion
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is we need to activate the strong sage ground in
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methane. So under normal condition, when the temperature is about
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450 degrees Celsius is the method would absorb, uh onto
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a saturated play.
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Them side and the neighboring oxygen side would extract hydrogen
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proton from the methane and forming a hydroxyl group.
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Well, combining two hydroxy group, we will form.
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We will form water, and when the water dissolves from
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the uh from the surface, it will form oxygen vacancies
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and formation of this oxygen one consists will enhance the
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oxygen exchange.
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But when we when we are operating the thing under
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450 degrees Celsius, which means the catalyst is de activated,
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deactivated, we found that the play them unsaturated side and
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the Austrian side are occupied by water instead, and therefore
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instead forming the hydroxy group.
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Instead, they're forming a stable, he said.
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They're forming a stable, uh, palladium hydroxide bound, and this
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will inhibit methane activation on palladium palladium.
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And also, since there is no oxygen vaccine generated in
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this case, it will.
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It will also like inhibit the oxygen immigration from the
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support to the palladium catalyst.