Synthesis of Carbon Nanostructure For Catalysis A. Rinaldi, N. Abdullah, I. S. Mohamad, Sharifah Bee. Abd. Hamid, D.S. Su, R. Schloegl Nanotechnology and Catalysis Research Centre, Institute Of Postgraduate Studies University Malaya, Kuala Lumpur, Malaysia FHI, The Max-Planck Society, Berlin, Germany

Presentation Outline History of Carbon Nanotubes Properties and Applications of Carbon Nanotubes Synthesis of Carbon Nanotubes Concept Application as Catalysis

The Industrial Revolution That Changed The World

Interesting Facts About Carbon Nanotubes Strength to weight ratio 500x for Al, steel, Ti A few nm across Up to 100  m in length Can with- stand repeated buckling and twisting Can conduct electricity higher than Cu, or act as a semiconductor like Si Transports heat better than any known material Maximum strain ~10% much higher than any material Can be functionalized

Synthesis of Carbon Nanotube Mullti-wall and single-wall Nanotube synthesis technique Arc dischargeLaser FurnaceChemical Vapor Deposition (CVD) What are the different methods to synthesis CNTs ?

Development of CNT vs Economy Productivity of commercial techniques: 40 g/day and more Quality: High selectivity–narrow distribution of tube diameters (80%) Purification efficiency: from 1% toward ~ 30% and more development Price drop from $2500/g to $500/g, expecting to be $6/g Development of CVD techniques reduces the cost of the process Reference:

Application in Catalysis

The anisotropy of sp 2 carbon If we can control the kinetic steady state between oxygen functional group formation and the decarboxylation reaction of the substrate then we can mimic an oxide reactivity (redox and acid-base) at a metal-like surface without using a real metal

graphite 168hr dry Catalysis is Controlled by Defects graphite 72 hr dry 168 hr dry 168 hr wet TPRS-MeOH:O2=3, HSV=11700 hr -1 Defects change the ratio of prismatic to basal face area and thus affect the steady state between activation and decarboxylation kinetics: proof of principle Defects change the ratio of prismatic to basal face area and thus affect the steady state between activation and decarboxylation kinetics: proof of principle The selective oxidation of methanol is used as test reaction.

Concept: Tune the C-O bond properties Two quinoid groups By changing the bending of the graphene unit through nanostructuring a continuous modification of the polarity of the C-O bonds will be possible: control redox vs. basic properties. By changing the bending of the graphene unit through nanostructuring a continuous modification of the polarity of the C-O bonds will be possible: control redox vs. basic properties.

Catalytic activity for Oxydehydrogenation reaction (ODH) (ethylbenzyne to styrene)

An Example: The Styrene Synthesis Production: t per year (2000)

Dehydrogenation of Ethylbenzene to Styrene Dehydrogenation of Ethylbenzene to Styrene  H = +124,9 KJ/mol + H 2 Dehydrogenation (non oxidative) + 1/2 O 2 + H 2 O  H = -116 KJ/mol Oxidative dehydrogenation Industrial Process: T reaction = °C Excess of overheated steam H 2 O/EB = 10-15/1 Conversion % Selectivity %

Designing material as a CNT Catalyst Cheap Reproducible Accessible Chemically and mechanically stabile

SupportImpregnated Catalyst Supported CNT CNT

Thermal-CVD Reactor Maximum loading: 20 gram

Images CNT/AC Activated CarbonCNT/AC Multiwalled defective CNT

CNT/AC for ODH catalyst CNT after reaction

Images CNT/Clay clayCNT/clay

Commercial catalyst Commercial: baytubes Loose fluffy powder Used as a comparison to the ODH catalytic ability of the nanotube samples

CNT/clay for ODH catalyst CNT/clay shows superior activity in comparison to the commercial CNTs possibly due to : -open structure of the bentonite support materials and -the amount of defects present in the CNTs on clay (defects=active sites) Reduced clay CNT/clay Commercial CNT

Mechanical stability test for CNT/Clay CNTs are still attached to the clay support!! Mechanically stabile. After

Summary CNT is an important material in nanotechnology CNT with “tunable” electronic property hold catalytic activity sites as metal-like based catalysis. Some geometrical design of the final material are needed to properly utilize CNT as catalyst. Activated carbon and clay material are potential material to immobilize CNTs for ODH reaction Future modifications are needed to optimize the application.

Thank You

Synthesis of Carbon Nanotube Arc discharge The most investigated technique Produces good quality samples Ratio NT/Nanoparticles is around 2:1 in the best cases Yields are low and very sensitive to He pressure Voltage: 20 V (DC) Current: A Helium atmosphere (500 Torr)

Synthesis of Carbon Nanotube Laser Furnace High yield of nanotubes and nanoparticles Highly graphitic and structural perfect Oven temperature: 1200oC Laser to vaporize graphite Gas carrier: Ar, He

Synthesis of Carbon Nanotube Chemical Vapor Deposition (CVD) Mostly developed and applicable produces pure, well alignment CNT large area deposition capability controlled growth of CNT diameter and density right combination of carbon, precursor, matched catalysts, support material and carrier gases

Activation of di-oxygen The selectivity problem in oxidation catalysis arises from different options for the intermediate binding of activated oxygen to the catalyst: electrophilic (oxidising) nucleophilic (basic) carbon offers the unique chance to achieve oxygen activation metal-free

The catalliance rational design approach understanding synthesis application model catalyst technical catalyst new catalyst graphite nanodiamonds activated carbons nanostructured carbons in-situ analysis kinetics concept strategy realization

The model system graphite oxidation behavior

Theoretical Underpinning defectation leads to double bond localization (band gap opening) and drastically changes the energetics of adsorption (H as model) M. Scheffler, J. Carlson

Schematic concept of ODH 1- Adsorption of ethylbenzene 2- Dehydrogenation at basic centres 3- Desorption of styrene 4- Adsorption of oxygen and reaction with OH groups 5- Desorption of water Schematic drawing of the catalytic oxidative dehydrogenation over carbon nanofilaments: Angew. Chem. Intl. Ed. (2001) 40 No.11

Structure-Sensitivity of Carbon Styrene CO CO 2 Benzene Toluene Ethene % yield Styrene yield - 34 % carbon black Ethene CO 2 CO Styrene Toluene Benzene % yield Styrene yield - 52 % CNT Oxidative Dehydrogenation of EB without any water addition at 100 K lower temperature than DH. Metal-free catalysis works well!