Toshihiko Fujimori, Katsumi Kaneko Research Center for Exotic - - PowerPoint PPT Presentation

Toshihiko Fujimori, Katsumi Kaneko

Research Center for Exotic Nanocarbons Shinshu University

March 5th, 2013 SJ-NANO 2013 “Nanotechnologies and New Materials for Environmental Challenges” Epochal Tsukuba International Congress Center, Tsukuba, JAPAN

The Project in SICP

(FY2009 - FY2012)

Nanostructured Carbon Monoliths for Storage and Conversion of Methane

Francisco Rodríguez-Reinoso (Universidad de Alicante) Katsumi Kaneko (Shinshu University)

• Preparation of nanostructured porous

carbons from natural resources

• Characterization of nanostructures
• Adsorption properties of carbons

Major component

• f natural gas

C H H H H

CH4 + 2O2 = CO2 + 2H2O + 890.36 kJ

Methane

Target: Methane

CH4 + 2O2 = CO2 + 2H2O + 890.36 kJ

Advantages

• Efficient (high energy density)
• Clean (low CO2 emission)
• Abundant (for several hundred years use)

Target: Methane

Bottleneck for practical use

• Severe conditions required for storage

(Low temperature / High pressure)

Target: Methane

Low boiling point Tb = 111.5 K Supercritical at

• perating temperature

Tc = 190.5 K

Critical point

CH4 solid CH4 gas

Liquefied natural gas (LNG) Compressed natural gas (CNG)

Towards More Effective Storage Lower energy

Extremely large surface area in a small volume Guest species are adsorbed much more strongly

Larger amount

with

• Adsorption on microporous materials

Adsorbent: Activated Carbons

http://en.wikipedia.org/wiki/File:Activated_Carbon.jpg

Adsorbent: Activated Carbons

Randomly stacked defective graphitic units

• Highly porous with micropores
• Light
• Chemically stable

Guest species

Missions

Methane Storage

characterization

Methane Conversion

Catalytic investigation

Porous Carbons

preparation

Spain Japan

Collaborative Publications

1) "Anomaly of CH4 Molecular Assembly Confined in Single-Wall Carbon Nanohorn Spaces”

• S. Hashimoto et al., J. Am. Chem. Soc. 133, 2022-2024 (2011). IF = 9.907

2) "Ultrahigh CO2 adsorption capacity on carbon molecular sieves at room temperature”

• J. Silvestre-Albero et al., Chem. Commun. 47, 6840-6842 (2011). IF = 6.169

3) “Effect of nanoscale curvature sign and bundle structure on supercritical H2 and CH4 adsorptivity of single wall carbon nanotube.”

• M. Yamamoto et al., Adsorption, 17, 643-651 (2011). IF = 2.000

4) "Well-defined mesoporosity on lignocellulosic-derived activated carbons.”

• A. Silvestre-Albero et al., Carbon 50, 66-72 (2012). IF = 5.378

5) “Formation of COx-Free H2 and Cup-Stacked Carbon Nanotubes over Nano-Ni Dispersed Single Wall Carbon Nanohorns.”

• S. Wang et al., Langmuir 28, 7564-7571 (2012). IF = 4.186

6) "Diffusion-Barrier-Free Porous Carbon Monoliths as a New Form of Activated Carbon.”

• T. Kubo et al., ChemSusChem 5, 2271-2277 (2012). IF = 6.827

Today’s Topics

Diffusion-Barrier-Free Porous Carbon Monoliths as a New Form of Activated Carbon ChemSusChem 5, 2271-2277 (2012). Formation of COx-Free H2 and Cup-Stacked Carbon Nanotubes over Nano-Ni Dispersed Single Wall Carbon Nanohorns Langmuir 28, 7564-7571 (2012) Methane Hydrate Formation in Carbon Nanospaces Ongoing study

Porous Carbon Monolith

Advantages

• Easy handling
• Tightly packed particles
• Enhanced properties

— Inter-particle porosity — Conductivity

Disadvantages

• Binder required for molding
• Diffusion obstacle

Activated carbon powder Activated carbon monolith

Source Ethylene tar/ Vacuum residue Pyrolysis 733 K Under N2 Ball-milled with KOH Mesophase pitch

(Anisotropic area = Mesophase)

Preparation

Activation 1073K under N2 flow Molding AC monolith AC powder Wash

Preparation 2

E-powder V-powder E-monolith V-monolith

Binder-free monoliths

200 400 600 800 1000 1200 0.0 0.2 0.4 0.6 0.8 1.0 Amount / mg g-

1

Relative Pressure, P/ P0

Pore Properties

Surface area Micropore volume DR micropore volume [m2 g-1] [mL g-1] [mL g-1] E-powder 2370 0.96 0.82 E-monolith 2530 0.98 0.86 V-powder 2600 1.0 0.89 V-monolith 2820 1.1 0.97

Nitrogen adsorption isotherms at 77 K

E-powder V-powder E-monolith V-monolith

Enhancement of surface area and micropore volume

Methane Storage Ability

E-powder V-powder E-monolith V-monolith

Methane adsorption isotherms at 303 K

Enhancement of methane storage capacity

Adsorption Kinetics

E-powder V-powder E-monolith V-monolith

Adsorption Desorption Adsorption Desorption Adsorption Desorption Adsorption Desorption

Time course of adsorption amount on sudden pressure chanege1 Mpa−2 MPa

Monoliths have practically acceptable diffusion rates

293 K 298 K 303 K 293 K 298 K 303 K 293 K 298 K 303 K 293 K 298 K 303 K 293 K 298 K 293 K 298 K 293 K 298 K 293 K 298 K

Summary

Advantages

• Tightly packed particles
• Enhanced properties

— Inter-particle porosity — Conductivity

• Easy handling

Disadvantages

• Binder required for molding
• Diffusion obstacle

“Binder-free” porous carbon monolith

LNG Adsorption

Temperature [K] Pressure [MPa]

111 191 298 0.1 3.5 20

“Efficient methane storage at milder conditions”

Milder Condition

CNG 600 v/v ~250 v/v ~200 v/v

More Efficient Methane Storage

• Methane hydrate
• Nano-confinement effect

• CH4 confined in the cages of H2O framework
• Composition: CH4·5.75H2O
• Storage capacity: 164 v/v

Methane Hydrate

In nanospaces, high pressure phases formed at low pressure conditions.

• Quasi-high pressure factor: ∼19,000

Nano-confinement Effect

KI B2 phase formation

0.1 MPa in SWCNH

(1.9 GPa in bulk state)

• K. Urita et al.,
• J. Am. Chem. Soc. 133, 10344–10347 (2011)

Phase diagram of bulk methane hydrate (solid)

50 MPa (300 K) 2.6 MPa (273 K) 2.5 kPa (300 K) 0.13 kPa (273 K)

“Confined” formation

“Bulk” formation

Assuming MH formation with the factor of “20,000”…

Sloan and Koh “Clathrate Hydrates of Natural Gases, Third Edition”

Much milder condition!!!

Methane Hydrate Formation

Porous Material (dry) Porous Material (wet) MH in pore

“H2O pre-adsorption−CH4 introduction” method

H2O CH4

Methane adsorption isotherm

Strategy

20 40 60 80 100 10 20 30 40 50 nCH4, wt% Peq (bar)

Rw:1.5_adsorp Rw:1.5_desorp Rw:0_adsorp Rw:0_desorp

VR93-5:1-800

2

VR93-2:1-800

20 40 60 80 100 5 10 15 20 25 n CH4, wt% Peq (bar)

Rw:0.7_adsorp Rw:0.7_desorp Rw:0_adsorp Rw:0_desorp

1

VR93-6:1-800

3

20 40 60 80 100 10 20 30 40 50 60

Rw:1.8_adsorp Rw:1.8_desorp Rw:0_adsorp Rw:0_desorp

nCH4, %wt Peq (bar)

Rw*= 0.7 Rw*= 1.5 Rw*= 1.8 Measured at 275 K

• Sudden uptake at 40~60 bar
• Similar amount uptake
• Hysteresis only for wet samples
• Methane hydrate formation?

CH4 adsorption on dry/wet carbons

Details under investigation...

Use of Stored Methane

Porous carbon monolith

• Handling
• Capacity

Methane storage techniques

Methane hydrate in pores

• Milder condition

Uses

• Fuel
• Source of other chemicals
• Hydrogen
• Nanocarbons
• C1-chemistry

Steam reforming CH4 + 2H2O  4H2 + CO2 CO2 reforming CH4 + CO2  2H2 + 2CO Partial oxidation CH4 + O2  2H2 + CO Methane decomposition CH4  C + 2H2

H2 Generation Reactions from CH4

Merits

• No gaseous COx impurity
• Solid carbon product

— Nanotube production

Methane decomposition

All the reactions require metal catalysts

Catalyst for Methane Decomposition

Metal species

Precious metals: Pd, Pt Problem: Expensive

Support

Oxides: TiO2, Al2O3 , SiO2 , MgO... Non-Oxides: carbon fiber, carbon black... Problem: Impurity or deactivation

Oxide

O O O O O

H2 CO CO2

M M M M M

CH4

Non-Oxide

M M M M

CH4

M Carbon product covers the metal particles, which deactivates the catalytic metal. O

H2

Reaction with oxygen of oxide affords CO and CO2 as impurities Carbon

Strategy Metal species

Cheaper metals: Fe, Co, Ni, Cu

Support

Single-walled carbon nanohorns (SWCNH)

• Dahlia-like assembly structure

— Suitable morphology for deposition

• Large surface area

— Large deposition amount

• Reducing agent for metal salts

— Easier preparation without H2

• Non-Oxide

— No CO/CO2 evolution

Catalyst Preparation (Ni-SWCNH)

Incipient wetness impregnation method

Metal nitrate (MII/III(NO3)m･nH2O) SWCNH Mixed in EtOH (Impregnation) MII/III (NO3)m/SWCNH Heat at 673 K in He flow (Reduction)

M0/SWCNH

Ni nanoparticles (M = Fe, Co, Ni, Cu)

CH4 Decomposition Reaction

He (carrier) CH4 (reactant)

Mass spectrometer

m/z 2 (H2) 16 (CH4) 28 (CO) 44 (CO2) M/SWCNH (catalyst) T

303 K→1200 K 3 K min-1

10% 90%

CO/CO2 Evolution

CO (m/z = 28) CO2 (m/z = 44) Different reduction conditions

a: in He at 673 K for 1 h b: in H2(20%)/He(80%) at 673 K for 40 min c: in He at 873 K for 40 min

No CO/CO2 evolution

Metal type dependency

Co Ni Cu Fe

Good catalytic activity kept at 723 K Durability

723 K 773 K 673 K 823 K 873 K 1173 K

Carbon Product Cup-stacked Carbon Nanotubes Possibility for a nanocarbon growth substrate

Summary

Porous carbon monolith

• Handling
• Capacity

Methane storage techniques

Methane hydrate in pores

• Milder condition

Use of methane

Catalytic decomposition

• H2, Nanocarbon production

Acknoledgement

Universidad de Alicante

Francisco Rodoríguez-Reinoso Manuel Martnez-Escandel Jose M. Ramos-Fernndez Joaquín Silvestre-Albero Ana Maria Silvestre-Albero Mateus Carvalho Monteiro de Castro Mirian Elizabeth Casco

Shinshu University

Morinobu Endo Tsutomu Itoh Hirotoshi Sakamoto Shuwen Wang

Chiba University

Hirofumi Kanoh Tomonori Ohba Takashi Kubo

Nagasaki University

Isamu Moriguchi Koki Urita

メソフェーズピッチ

• ピッチ：

原油やコールタールなどを蒸溜した後に残る黒い滓のこと。 しばしばピッチとタールが混同されるが、タールは液体であり、ピッチは固体に近い性質を 持つ点で異なる。 メソフェーズ： pyrolysisにより、成分が一旦液体になったあと に固化すると、何かしらの規則構造 （芳香族部分の平行な配列）をとる。 構造の異方性→光学的に異方性の部分が 偏光顕微鏡下でみられる。 a)青いスポット b)モザイク状に全体的に拡がっている c)白、オレンジの部分 d)全体的に拡がっている

Condensed phase available above Tc of methane (190.5 K)

Dense storage at higher temp./lower pressure

CH4 gas + H2O solid/liquid

CH4 solid MH solid

CH4 gas

Critical point

Condensed phase available above Tc of methane (190.5 K)

Dense storage at higher temp./lower pressure

CH4 gas + H2O solid/liquid

CH4 solid MH solid

CH4 gas

Critical point

Objective Expectation

• Efficient usage of methane
• Reduction of CO2 emission
• Efficient production of H2 and SWCNTs
• Preparation of nanostructured

carbon monoliths from natural resources

• Characterization of the

nanostructures

• Sorption properties for methane
• Catalytic investigation for methane conversion

Development of thermal conductive, nanostructured carbon materials at practical use for

• Methane storage
• Methane conversion (to SWCNT and hydrogen)

Ethylene tar/ Vacuum residue Pyrolysis Ball-milled with KOH Activated under N2 flow Mesophase pitch

(Anisotropic area = Mesophase)

Molding AC monolith AC powder Wash

方針

• 割り当て時間20分
• 15分talk、5分questionくらい。
• スライド数Maxで20枚。
• 細かいデータ見せてると時間なくなる。

Discs preparation for thermal/electrical conductivity measurements

10% wt NaCMC* + few drops of water 15% wt Graphite Flakes Press Discs diameter 10mm 10% wt NaCMC* + few drops of water 15% wt MWCNT Press Discs diameter 10mm 10% wt NaCMC* + few drops of water Press Discs diameter 10mm

Activated carbons

+

* NaCMC (Binder): Carboxymethylcellulose, sodium salt

MWCNT + Graphite Flakes +

SEM images

0.11 0.18 0.13 0.12

Correlation between thermal conductivity and particle size

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 a b c d Thermal conductivity/ W m-1 K-1

Apparently high

3.21 Å 3.51 Å Channel

O2 array in CPL-1 at 130 K, 80 kPa Raman shift of O2 vibration corresponding to 2 GPa

Kitaura, Kitagawa, Science 2002, 298, 2358 Urita, Kaneko, JACS 2011, 133, 10344

Bulk KI B2 phase formation at 1.9 GPa B2 phase of KI in SWCNH at ambient pressure

In nanospaces, high pressure phases formed at lower pressure conditions.

• Quasi-high pressure factor: ∼20,000

LNG Adsorption MH

Temperature [K] Pressure [MPa]

111 191 298 0.1 3.5 20

MH confined in pores ?

“Efficient methane storage at milder conditions”

• Metahne hydrate
• Nano-confinement effect

Milder Condition

CNG 600 v/v ~250 v/v ~200 v/v 164 v/v

More Efficient Methane Storage

Water pre-adsorption

Dry carbon sample was placed in a controlled humidity (85-90%) till weight equilibrium reached. (5~10 days)

Ratio of H2O: Rw = weight of adsorbed water weight of dry carbon

Microporous Materials

Extremely large surface area in a small volume

Overlappe d potential

Surface potential

Adsorbent: Activated Carbons

Wide pore Narrow pore Guest species are bound much more strongly.

Target: Methane

TEM images SEM images

Microscopic Images

V-powder V-monolith V-powder V-monolith 0.11 0.18 0.11 0.18 0.13 0.12 0.13 0.12 E-powder E-monolith E-powder E-monolith

Steam reforming CH4 + 2H2O → 4H2 + CO2 (⊗ H =165 kJ/mol) CO2 reforming CH4 + CO2 → 2H2 + 2CO (⊗ H =248 kJ/mol) Partial oxidation CH4 + O2 → 2H2 + CO (⊗ H =-36 kJ/mol) Methane decomposition CH4 → C + 2H2 (⊗ H = 75.3 kJ/mol)

H2 Generation Reactions from CH4