CATALYTIC CONVERSION OF BIOGAS TO BIOFUELS - TAP STUDIES

Transcription

1 CATALYTIC CONVERSION OF BIOGAS TO BIOFUELS - TAP STUDIES Dr. Maria Olea School of Science & Technology Teesside University, UK M.Olea@tees.ac.uk

2 Maria Olea 1, Takehiko Sasaki 2, Nobuaki Aoki 3, Andrei Y. Khodakov 4, Veerle Balcaen 5, Wei Wang 1, Stanislas Pietrzyk 4, Adam Adgar 1, Simon N. Hodgson 1, Kazuhiro Mae 3, Guy B. Marin 5 1 University of Teesside, School of Science and Technology, Borough Road, Middlesbrough TS1 3BA, Tees Valley, UK 2 The University of Tokyo, School of Frontier Sciences, Department of Complexity Science and Engineering, Kashiwanoha, Chiba , Japan 3 Kyoto University, Department of Chemical Engineering, Katsura, Kyoto , Japan 4 Université des Sciences et Technologies de Lille, UCCS, F Villeneuve Dascq, France 5 Ghent University, Department of Chemical Engineering, Krijgslaan 281, S5, Ghent 9000, Belgium

3 Temporal Analysis of Products (TAP) reactor:

4 Temporal Analysis of Products (TAP) reactor: TAP mode Scan mode (1) High-speed beam valve, (2) continuous flow valve, (3) zero-volume manifold, (4) catalytic microreactor, (5), (6) cryo shields (all of these being situated in the reactor chamber), (7) differential chamber, (8) detector chamber (MS).

5 Temporal Analysis of Products (TAP) reactor: quite a new but important tool created by J.T. Gleaves in 1986; modified in 1997; designed to operate in milisecond time regime; to investigate gas-solid reactions; on industrial catalysts; applications in many areas of chemical kinetics and chemical engineering; to characterize the chemical activity by determining intrinsic reactivities; to relate these characteristics to catalyst structural characteristics; different strategy: no carrier gas Knudsen diffusion regime.

6 TAP mode: Qualitative information < > reaction mechanism - state-defining TAP experiments - single-pulse - alternating pulse - state-altering TAP experiments - multipulse Semi quantitative information < > estimate number of active sites - quantify the adsorbed amount - integration of response Quantitative information < > kinetics - modelling parameter estimation Scan mode: Evolution of reaction

7 TAP Single-pulse experiment Inlet Outlet Time (s) Time (s) Response Time(s) Mean response

8 TAP Multipulse experiment Inlet Outlet Time (s) Time (s) Response Time (s) Total response

9 Inlet TAP Alternating pulse experiment Outlet Time (s) Time (s) Response Time(s) Mean response

10 Biogas to biofuels conversion of biogas to syngas over a newly-developed mesoporous Ni/SiO 2 catalyst syngas conversion over a Co/SiO 2 catalyst

11 Absorbance Intensity(a.u.) Intensity (a.u.) Catalytic conversion of biogas to syngas over Ni/SiO 2 catalysts CH 4 CO2 CO 2 2 H 2 (100) 2 nd loaded meso-silica Frequency/THz Ni 5% Ni 11% MCM (110) 2 (degrees) (200) 1 meso-silica 2 1 st loaded meso-silica 3 2 nd loaded meso-silica ATR (degrees) Wavenumber/cm -1

12 Flow Diffusion features: Ar pulsing - TAP Single-pulse experiment Non-porous: D ea = Measured Simulated T = 373 K Time [s] Porous: D ea = 0.06 cm 2 s -1 T = 373 K Ar response curves at RT, over g of fresh and re-oxidized catalyst, respectively

13 Non-porous catalyst: Standard Diffusion Curve Porous catalyst: Where D ea porous DeAnon porous p(1 b) (1 ) F A = flow of gas A at reactor outlet (mol/s) N pa = number of molecules of A in inlet pulse D ea = effective Knudsen diffusivity of gas A (cm 2 s -1 ) ε b = porosity of the bed (= 0.23) ε p = porosity of the pellet (= 0.39) L = length of the reactor (cm) t = time (s) b

14 CH 4 pulsing - TAP Single-pulse experiment Diffusion & adsorption/reaction features: CH 4 response curves against Ar curve at increasing temperatures from RT to 600 C over g of fresh catalyst slow decomposition reaction over the catalyst through an irreversible adsorption

15 O 2 pulsing - TAP Single-pulse experiment Reaction features: Oxygen response curves to increased number of O 2 pulses sent at 600 C over g catalyst prior treated with CH 4 multipulses reduction-reoxidation is a reversible process

16 Diffusion & adsorption/reaction features: H 2 pulsing - TAP Single-pulse experiment H 2 response curves against Ar curve at increasing temperatures from RT to 600 C over g catalyst catalyst surface can be reduced by sending H 2 at temperatures higher than 450 C (activated irreversible adsorption)

17 Reaction features/intermediates: TAP alternating pulse experiments CH 4 and CO 2 responses at 550 C with 500 ms delay between the two pulses CH 4 seems to be adsorbed on two different active sites

18 Reaction features/intermediates: TAP alternating pulse experiments CO 2 (probe molecule) responses at different time intervals and 600 C over g catalyst CH 4 species on the surface have a limited lifetime of about 2000 ms

19 TAP alternating pulse experiments CH 4 (probe molecule) responses at different time intervals and 600 C over g catalyst unconverted CH 4 leaving the reactor increasing by increasing the time interval - because the pre-adsorbed CO 2 seems to have a very short lifetime on the catalyst s surface CO 2 adsorption on an oxidized surface of this catalyst is weak and reversible

20 Conclusions t pellet = t bed overall Knudsen diffusion coefficient was determined; CH 4 and H 2 seemed to have an irreversible adsorption with reaction on the surface; CO 2 show only a weak and reversible adsorption; lifetime of CH 4 surface species was about 2000 ms.

21 Height normalized intensity Catalytic conversion of syngas over Co/SiO 2 catalysts H 2 pulsing - TAP Single-pulse experiment 1.0 Kr H2 on reduced catalyst H2 on passivated catalyst Time (s) Height-normalized H 2 and Kr responses from H 2 /Kr single-pulse at 473K on 0.1 g of the passivated and reduced Co/SiO 2 catalysts.

22 Intensity CO pulsing - TAP Single-pulse experiment 10 8 CO response Kr response Time (s) Area-normalized CO and Kr responses from CO/Kr single-pulse at 473K on 0.1 g of reduced catalyst. The responses were normalized to the area of Kr and CO incoming to the reactor.

23 (a) (b) (b) TAP alternating pulse experiments (a) (b) Alternating pulse experiments at T = 473K on 0.1 g of reduced catalyst: (a) Pump molecule CO (blue), probe H 2 (red); (b) pump H 2 (red), probe CO (blue).

24 COMSOL- Optimized parameters of CO and H 2 adsorption from TAP experiments Adsorbing Gas Temperature, K k a k d n s2 *ρ b /H CO CO H E H E H E-8 8.5

25 Flow, mol/(m².s) Flow, mol/(m².s) Experimental and computed TAP responses 12 x Experimental curve Fitting curve a Time, s 10 x Experimental curve Fitting curve b Time, s Experimental and computed TAP responses : (a) H 2, (b) CO on 0.1 g Co/SiO 2 reduced catalyst at 473 K. Two types of adsorption were considered.

26 Acknowledgments This document is an output from the PMI2 Project funded by the UK Department for Innovation, Universities and Skills (DIUS) for the benefit of the Japan Higher Education Sector and the UK Higher Education Sector. The views expressed are not necessarily those of DIUS, nor British Council. The authors thank to Dr. David Reece and TeraView Limited for the TeraHertz measurements.

27 Thank you all for your kind attention!