The application of red mud as a pre-catalyst for the formation of functionalised carbons

Aims of the British Council red mud project:

-Investigate red mud for cracking of CH4 to produce H2 and C

CH4 → C + 2H2

-Apply the C so produced to water purification

-Valorisation - two “waste” products generating two useful products

Elemental composition of red mud samples (wt %)

Major elements Sample

code SiO2 Al2O3 Fe2O3 TiO2 CaO MgO Na2O K2O P2O5 MnO LOI

RM4 16.40 10.44 42.70 6.44 2.85 1.56 3.72 0.05 0.02 - 15.30

RM6 12.40 10.12 36.40 18.70 2.65 2.52 3.85 0.09 0.02 - 12.80

RM 7 14.60 23.51 36.79 0.74 1.18 0.07 6.08 0.02 0.15 0.12 16.47

RM4 & RM7 same site but 24 month interval

ICP analysis

RM4 15 m2g-1, RM6 8 m2g-1 & RM7 14 m2g-1

0

50

100

150

200

250

300

350

400

450

0 20 40 60 80 100 120 140 160 180 200Time on stream/min

10E7

Hyd

roge

n fo

rmat

ion

rate

/ mol

H2g

-1s-

1

RM4

RM6

RM7

Mass normalised hydrogen formation rates at 800°C

CH4:N2 =80:20, 60ml min-1, 0.4g

400 x 10-7 mol/g/s

0

50

100

150

200

250

300

350

0 10 20 30 40 50 60 70 80 90

2θ

Cou

nts

a,c,d,e

c,d

c,d, e

a,c,d,e

c

a,b,c

c,d,e ca a,c,d

c

RM4

RM7

RM6

a: Graphite (C) 23-0064 b: Iron (Fe) 03-1050c: Iron carbide (Fe3C) 03-0989d: Aluminium oxide (Al2O3) 26-0031e: Quartz (α-SiO2), 05-0490

d,e

ddd

e

ad

a,e

b,dccc,d

e

d

d

d

e

de e

ee

Post 800°C reaction XRD analysis

RM 7 in-situ XRD, 72wt%C

-40

-35

-30

-25

-20

-15

-10

-5

0

5

0 100 200 300 400 500 600 700 800Temperature/˚C

Wei

ght/%

RM4

RM6

RM7

Post 800°C reaction TGA in 2%O2/Ar

RM4 47.71 wt%C, RM6 43.49wt %C & RM7 38.06wt%C

SEM of post in-situ XRD RM 7 - 72wt%C

Butane cracking

Adsorption capacity of Cr, Cu and Pb on RM, ARM and CRM

pH Surface area

Cr

Cu

Pb

m2/g

mg/g

mmol/g

mg/g

mmol/g

mg/g

mmol/g

RM

11.5

10-15

1.3

0.025

8.9

0.14

133

0.64

ARM

4.5

45-48

1.7

0.033

3.5

0.055

9.0

0.045

CRM

8.2

70

0

0

25

0.39

94

0.45

CrO42-, Cu2+ & Pb2+

Methanol – CH3OH

Acetonitrile – CH3CN

700°C

800°C

900°C

C (wt%) H (wt%) N (wt%) 700°C 22.35 ± 4.77 - 1.31 ± 0.21800°C 61.40 ± 7.10 - 1.70 ± 0.25900°C 63.10 ± 0.52 - 1.60 ± 0.16

0 200 400 600 800 1000

40

50

60

70

80

90

100

Weig

ht (%

)

Temperature (oC)

700 oC 800 oC 900 oC

10 20 30 40 50 60 70 800

150

300

450

600

750

900

Inten

sity (

a.u.)

2θ

700 oC 800 oC 900 oC

500 1000 1500 2000 2500 3000

150

300

450

600

750

900

1050

1200

1350Int

ensit

y (a.u

.)

Wavenumber (cm-1)

700 oC 800 oC 900 oCD

G

Temp. (°C) C(wt%) H(wt&%) N(wt%)

Ni/ZSM-5 700 10.56 ± 0.12 0.46 ± 0.01 0.95 ± 0.02

Pd/ZSM-5 700 10.22 ± 0.01 0.43 ± 0.01 0.91 ± 0.01

RM7 700 17.50 ± 9.10 - -

Ni/ZSM-5 800 16.24 ± 0.74 - 1.41 ± 0.03

Pd/ZSM-5 800 16.00 ± 0.10 0.21 ± 0.04 1.25 ± 0.01

RM7 800 43.54 ± 7.53 - -

Ni/ZSM-5 900 44.82 ± 0.01 3.02 ± 0.06 -

Pd/ZSM-5 900 35.60 ± 0.10 - 2.16 ± 0.01

RM7 900 48.42 ± 0.71 - 0.57±0.21

C6H6/CH3CN

RM – C is very heterogeneous

Summary:

The efficacy of a variety of red muds for the production of hydrogen and graphitic carbons has been demonstrated.

Different carbon structures containing different degrees of functionality can prepared.

The presence of reduced iron phases in post reaction samples imparts magnetic behaviour which may facilitate envisaged downstream applications.

Acknowledgements:

Abdulrahman Alharthi, Vidya Batra, Malini Balakrishnan, Hannian Gu, Nidhi Gupta, Ian Pulford, Jose Rico Cerda, Snigdha Sushil.

Kim Wilson, Ross Blackley, Wuzong Zhou, David Morgan

British Council, India – UKIERI Grant SA07-19

Chinese Scholarship Council

Saudi Cultural Bureau