James Highfield 1 , Yook Si Loo 1 , Ziyi Zhong 1 , Ruijiang Li 1 & Benjamin Grushko 2

1. James Highfield1, Yook Si Loo1, Ziyi Zhong1, Ruijiang Li1 & Benjamin Grushko2 1 Applied Catalysis Technology, Institute of Chemical & Engineering Sciences, 1 Pesek Road, Jurong Island, SINGAPORE S627833. 2 Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 GERMANY CARBON NANOFIBRE GROWTH FROM LOW TEMPERATURE METHANE DECOMPOSITION OVER SKELETAL TRANSITION METAL CATALYSTS • CH4 C + 2 H2H298 K = + 74.5 kJ mol-1 • Direct eco-friendly route to “CO-free” H2 and speciality carbons. • Single-metal & multinary (alloy ?) skeletal catalysts from quasicrystals (QC) • Route:Al65-75(TM/Cu)35-25arc melt/annealXRD ideally single-phase QC [Selective leach of Al 5 M NaOH under N2] Al = 5-10 wt.% Na < 1 wt.% Surface area = 30–160 m2 g-1 BET XRF In-situ washed, dried, “passivated” catalyst characterization XRD TEM Amorphous (except Ni) catalytic testing [TG-FTIR/MS] custom leaching rig TEM micrograph offresh skeletal Co (ex Al13Co4) TG% Typical TG curve for CH4 decompositon (skeletal Co) 1. abrupt onset of weight gain (blue curve) above 350 C; 2. rapid establishment of fixed rate (10% per h @ 400 C) 400 C 3.0 on carburization Co “needles” broken into fine “teardrops” TEM micrographs of carbon nanofibres on skeletal cobalt deposited at 400 C(up to 50 wt. % as carbon) metal dusting corrosion? 2.0 350 C more proof of irreversible change 300 C 1.0 250 C new activity below 300C ! 0.0 1.0 2.0 3.0 4.0 Time/h 330 C Eapp = 129 +/- 6 kJ mol-1 TG analysis of CH4 decomposition: in-situ pre-reduced samples & controls 300 C 280 C ‡ CH4+ 2 % H2 [12 ml/min; 1:1N2] Red:start at 400 C, then T [new low-T activity] Blue: as for Red, then switch to CH4/N2 at 250 C & T [dramatic inhibition by H2!] Green: mean of increasing rate (Fe-containing samples) [long induction phase?] 250 C Proof of unimolecular decompn: CH4 C + 2 H2 Rate of C deposition vs. H2 level [T = 450 C; cat. Fe19Ni9; CH4: 80 ml min-1] • Summary • Skeletal metals made from quasicrystalline precursors are “triggered” into CH4conversionat T > 350 C, yielding nanofibrous carbons & H2 in the ratio C:H2 = 1:2; • Pre-carburization leads to irreversible metal decrepitation, akin to “metal dusting corrosion”, creating particles in the range 20-50 nm well suited for filament growth; • 1st-row TMs Co, Ni, Fe, & their combinations most active, while Cu moderates activity; • Despite remarkable low-T activity, CH4 conversion is still quite low (< 2% at 400 C); • Process operation would need high recycle ratios and rapid (in-situ?)removal of product H2, a powerful inhibitor.  0.40 mg min-1 C or 33 g at. min-1 1.6 ml min-1 H2  71 mol. min-1 Stoichiometry H2 : C = 2.15 : 1