Stainless steel microreactors coated with carbon nanofiber...

ICOSCAR-3, Ischia 2009

Stainless steel

microreactors coated with

carbon nanofiber layer:

Impact of temperature and

hydrocarbon

L. Martinez-Latorre, P. Ruiz-Cebollada, A. Monzón, Enrique García-Bordejé

Instituto de Carboquímica (CSIC) Zaragoza, Spain


Carbon nanofibers as catalyst support

• Benefits of CNF attachment to a macroscopic support:

• the catalyst is easier to handle and separate

• no formation of fines and plugging

• low pressure drop

• Properties of carbon nanofibers

high purity

chemical and mechanical resistance

high external surface area: mesopores

low tortuosity

specific interaction with metals

heat and electric conductivity

pore

poresolid

solid

Inorganic tradicional support


Sintered metal fibers

P. Tribolet, L. Kiwi-Minsker, Catal.Tod., 105 (2005) 337.

CNF on several structured reactors

- M. J. Ledoux, C. Pham-Huu, Catal. Tod., 102-103 (2005) 2.

- P. Li, T. Li, J. H. Zhou, et al. Mic.and Mes. Mat, 95 (2006) 1.

Carbon/graphite felt

- N. A. Jarrah, L. Lefferts et al., J. Mater. Chem., 15 (2005) 1946.

- PWAM. Wenmakers, J. C. Schouten et al., J. Mat. Chem., 18 (2008) 2426.

Ni and carbon foams

- N. Jarrah, J. van Ommen, L. Lefferts, Catal.today, 79-80 (2003) 29.

- E. Garcia-Bordeje, I. Kvande, D. Chen et al., Adv. Mat., 18 (2006) 1589.

- K. M. de Lathouder, F. Kapteijn, J. A. Moulijn et al., Catal. Tod., 105 (2005) 443.

Cordierite monoliths


Microreactors

Properties of microreactors

high geometric surface area 5000 y 50,000 m2 m−3

distributed in-situ chemical manufacturing

ability to tailor reactor geometry

improved process control

safe operation

easy to scale up

high mass transfer rate

high heat transfer rate

- N. Ishigami, H. Ago, Y. Motoyama, M. Tsuji et al. Chem. Comm., (2007) 1626.

- I. Janowska, G. Wine, M. J. Ledoux, C. Pham-Huu, J. of Mol. Catal. A-Chem., 267 (2007) 92.

Silica microreactors coated with carbon nanostructures


There is a limitation of coating layer thickness due to:

adherence problems

diffusional limitations for fast gaseous reactions and sluggish

liquid phase reactions

total mass of catalyst per reactor volume too small

Microreactors wall-coated with conventional

microporous catalyst supports:

MOTIVATION


Microreactors wall-coated with CNFs

sufficient catalytic surface area per reactor volume

no internal diffusion limitations

low fluidic resistance

Requirements of the coating

high activity and selectivity

optimum porosity

uniform thickness

durability

Favourable properties


Approach

Growth temperature: 580-650 ºC

Hydrocarbon: CH4 or C2H6

Composition: hydrocarbon/ H2 ratio

1. Calcining platelets in static air at 800 ºC (b)

2. Coating the microchannels with alumina via sol-gel using a syringe

3. Disperse Ni by strong electrostatic adsorption

4. Calcination at 600 ºC with N2 and reduction at 550 ºC in H2 flow

5. Growth of a layer of entangled CNFs (c) during 3 hours varying the

conditions:

a b c

Fe 69.8

Cr 17.77

Ni 11.39

S 0.83

Si 0.22

Fe 68.8

Cr 19.42

Ni 9.37

S 1.24

Si 1.17

As-received Calcined


Alumina coating: impact of Al loading on adhesion

No flushing with

presurized air

0.3 wt % Al

20 m thickness

Flushing with

presurized air

0.1 wt % Al

6 m thickness

weight loss in ultrasonic treatment

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 50 100 150

Time in ultrasonic bath (min)

Alu

min

a l

oad

ing

(%

)


CNF growth: carbon productivity

CH4:H2 gas

C2H6:H2 gas

60:40

40:60

50:50

80:20

90:20

Ca

rbo

n p

er

alu

min

a (

wt%

)

Growth temperature (ºC)

0

100

200

300

400

500

600

700

800

560 580 600 620 640 660


Impact of growth temperature for ethane

580 ºC

625 ºC

600 ºC

650 ºC

Well attached uniform CNF diameter


Temperature-mediated control of CNF primary structure

Methane

Low temperature, 580 ºC High temperature, 650 ºC


Ethane

Low temperature, 580 ºC High temperature, 650 ºC

Temperature-mediated control of CNF primary structure

45 º

25 º


Thick CNF (80-200 nm) for the growth with ethane

b a

Fe 73.91

Ni 22.18

Cr 3.92

element normalized

composition (wt%)

625 ºC 650 ºC


Carbon protrusions for the growth with ethane

625 ºC 650 ºC


580 ºC

b c d

growth temperature (ºC)

-alumina layer Microreactor wall Carbon products

Influence of temperature using ethane

650 ºC

a


0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

10 100 1000

Average Diameter (Å)

Po

re V

olu

me (

cm

³/g

)

0.015

0.02

0.025

0.03

0.035

0.04

BJH adsorption pore size distribution

Ni-alumina coated microreactor CNF-coated microreactor


Adhesion tests of CNF coating

Drop test

Backscattered

SEM image

R. Zapf, G. Kolb, H. Pennemann, V. Hessel, Chem.

Eng.& Tech., 29 (2006) 1509.

Weight loss smaller than 5 wt% of initial coating

Complete coverage


Conclusions

- alumina coating ensured the growth of CNFs with uniform

and thin diameter smaller than 50 nm

-alumina layer is well attached to microreactor surface and

CNFs are strongly anchored within the pores of the -alumina

the CNF coated microreactors prepared with methane at

high temperature (600-650 ºC) and with ethane at low

temperature (580-600 ºC) have good perspectives to be used

in catalytic applications

the primary structure of CNFs can be controlled by the

choice of the temperature and hydrocarbon


Possible target reactions

supporting V catalyst: selective dehydrogenation of

hydrocarbons (as e.g. propane to propene)

Microreactor platelets coated with alumina

supporting Pt, Pd catalyst: NO oxidation for automotive

applications, previously to reduction catalyst (NSR, urea )

supporting Pt: preferential CO oxidation

Schwarz O, Duong PQ, Schäfer G, Schomäcker R. Chemical Engineering Journal

2009;145(3):420-8.

Kaneeda M, Iizuka H, Hiratsuka T, Shinotsuka N, Arai M.. Applied Catalysis B:

Environmental 2009;90(3-4):564-9.

Jain SK, Crabb EM, Smart LE, Thompsett D, Steele AM. Applied Catalysis B:

Environmental 2009;89(3-4):349-55..


Possible target reactions

metal-free: dehydrogenation of hydrocarbons (as e.g. butane

to butane)

Microreactor platelets coated with carbon

nanofibers or nanotubes

supporting Pd catalyst: selective hydrogenation of acetylene

supporting Ru: ammonia decomposition for in-situ H2

generation

Zhang J, Liu X, Blume R, Zhang AH, Schlogl R, Su DS. Science 2008;322(5898):73-7.

Ruta M, Semagina N, Kiwi-Minsker L. J Phys Chem C 2008;112(35):13635-41.

Sorensen RZ, Klerke A, Quaade U, Jensen S, Hansen O, Christensen CH. Catalysis

Letters 2006;112(1-2):77-81.


Personnel in the group

Enrique Garcia-Bordeje: staff scientific researcher

Sabino Armenise: PhD student

Ana Mateo: administrative support

David Villellas: Laboratory engineer

Marcos Nebra: Laboratory engineer

Recent research of the group is the preparation of monoliths coated

with activated carbon or CNF and using of the former as catalyst

support for Selective catalytic reduction of NO with NH3 al low

temperatures.


Description of the “Instituto de

Carboquímica (CSIC)”

Instituto de Carboquímica (Zaragoza, Spain) is formed by 26

scientific staff members plus 35 supporting members. The

Institute belongs to the Spanish National Research Council

(CSIC), which is the largest public research Institution in Spain.

ICB has a high level reputation on research areas with high

social impact (climate change, air pollution, waste recovery and

valorisation, etc.), strategic areas (hydrogen production,

renewal fuels, advanced materials, etc.), as well as other fields

of considerable social demand and research opportunities

(nanoscience and nanotechnology, new molecular sensors,

etc.).

www.icb.csic.es

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