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Activated carbon is a form of carbon processed to be riddled with small, low-volume pores that increase the surface area available for adsorption or chemical reactions.

• The porosity within activated carbon imparts their characteristics of adsorption.

• Activated carbons made from hardwoods, coconut shells, fruit stones, coals, peat, petroleum coke, and synthetic macromolecular systems.

• All activated carbons are assemblies of defective graphene layers.

SEM images of AC.

Activated Carbon

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2Properties The carbon structure is resistant to acidic or basic media. The structure is stable at high temperature (even above 1000K),

in the absent of air. A gram of activated carbon can have a surface area in excess of

500 , with 1500 being readily achievable. Activated carbon binds materials by Van der Waals force

or London dispersion force physically. Activated carbon adsorbs iodine very well. Carbon monoxide is not well adsorbed by activated carbon. Cost of the carbon supports is usually lower than conventional

supports such as alumina and silica.

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3Applications

The applications can be classified into two categories: gas and liquid phase.  

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4Applications (Liquid Phase):

Food and Beverages : Bear and wineChili and spicesSugar, starch, sweeteners and maple syrupCaffeineVegetable Oils

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5Applications (Liquid Phase)

Water treatment:Treatment of both industrial and municipal waste water By using activated carbon as a filter in the filtration industry.

Chemical and Pharmaceutical

Other Usage:Use it as filters for the dialysis of poisons and drugsFelts for wounds

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6Other Applications (Liquid Phase):

Industrial dry cleaning Cleaning of electroplating solutions Mineral recovery (Gold recovery)

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7Applications (Gas Phase): Gas purification:To produce pure gases in the chemical industry and reduce pollutant gases to a very low concentrations in the single stage, in protection against poison gases, activated carbon is being used.

Separation of Gas Mixture (SGM)Are designed to separate gases in a mixture by sieving.

Methane storage:Using natural gas hydrate (NGH) as the adsorbate in AC.

Solvent recovery:Recover the solvent vapors from air streams to adsorb by AC.

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8Carbon Nanotubes Carbon nanotubes (CNTs) take the form of cylindrical carbon

molecules and their novel properties make them potentially useful in a wide variety of applications.

They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat.

Multi-walled nanotube Singled-walled nanotube

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9Why CNT may be suitable to be used as a catalyst support?

Before answering this question, it is important to analyze the CNT properties.

1. Electronic properties:Very high current carrying capacity. 2. Adsorption properties:They present specific adsorption properties compared to AC.3. Thermal properties:All nanotubes are expected to be magnificent thermal conductors along the tube. And they have thermal stability under reaction condition.

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10Continued:4. Hardness:Greater than diamond, which is considered the hardest material.5. Strength:Carbon nanotubes are the strongest, flexible materials yet discovered in terms of tensile strength and elastic modulus respectively.

To conclude, it appears that the combination of these properties makes CNT attractive and competitive catalyst supports by comparison with activated carbons.

They could replace activated carbons in liquid-phase reactions as long as the properties of activated carbons of AC are still difficult to control and their microporosity has often slow down catalyst development.

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11Advantages of CNT:1. Extremely small and lightweight. 2.They have plentiful resources to produce them, and many can be made with only a small amount of material. 3. Are resistant to temperature changes, meaning they function almost just as well in extreme cold as they do in extreme heat. 4. The high purity of the material can avoid self-poisoning.5. The mesoporous nature of these supports can be of interest for liquid-phase reaction, thus limiting the mass transfer.

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12Disadvantages of CNT

1. Extremely small, so are difficult to work with. 2. Currently, the process to produce the nanotubes are relatively expensive. 3. Would be expensive to implement this new technology in and replace the older technology in all the places that we could. 4. The full potential of nanotubes for applications will not be realized until the growth of nanotubes can be further optimized and controlled.5. There are many challenges exist in both the micromechanical characterization of nanotubes, and the modeling of the elastic and fracture behavior at the nanoscale.

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13

QUESTIONS?

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14References

Harry Marsh, F. R.-R. (2006). Activated carbon, Elsevier. Serp, P., et al. (2003). "Carbon nanotubes and nanofibers in catalysis."

Applied Catalysis A: General 253(2): 337-358. Scida, K., et al. (2011). "Recent applications of carbon-based

nanomaterials in analytical chemistry: Critical review." Analytica Chimica Acta 691(1–2): 6-17.

Zeng, Q., et al. (2006). "Synthesis and Application of Carbon Nanotubes." Journal of Natural Gas Chemistry 15(3): 235-246.

Grobert, N. (2007). "Carbon nanotubes – becoming clean." Materials Today 10(1–2): 28-35.

Dai, H. (2002). "Carbon nanotubes: opportunities and challenges." Surface Science 500(1–3): 218-241.

Popov, V. N. (2004). "Carbon nanotubes: properties and application." Materials Science and Engineering: R: Reports 43(3): 61-102.

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15Adsorption

The adsorption process is when an adsorbate enters into the porosity of the adsorbate.

It is primarily a physical process. ( substances do not make a chemical reactions with the adsorbent).

Van der Waals and London dispersion intermolecular forces are important in the adsorption phenomenon.

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16Classifications of Activated Carbons

Some broad classification is made for general purpose based on their physical characteristics.

Powdered activated carbon (PAC) Granular activated carbon (GAC) Extruded activated carbon (EAC) Bead activated carbon (BAC) Impregnated carbon Polymer coated carbon Other Uncategorized

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17Nanotubes classification:

1. single-walled nanotubes (SWNTs)2. multi-walled nanotubes (MWNTs)

SWNT (graphical representation)

MWNT (graphical representation)