EXPERIMENTAL STUDY ON SORPTION

Transcription

1 EXPERIMENTAL STUDY ON SORPTION ENHANCED STEAM METHANE REFORMING BY NI-CAO-MAYENITE COMBINED MATERIALS A. Di Giuliano 1,2, J. Girr 1, K. Gallucci 2, C. Courson 1 1 Institut de Chimie et Procédés pour l Energie, l Environnement et la Santé UMR CNRS 7515 ECPM, University of Strasbourg, France. 2 Department of Industrial and Information Engineering and Economics, University of L Aquila, Italy.

2 Context: Hydrogen production Hydrogen is mainly obtained by natural gas reforming process which is very energy intensive. To reduce the environmental footprint of Steam Methane Reforming (SMR) and to increase the hydrogen yield, Sorption Enhanced SMR (SE-SMR) is an innovative route. SORPTION ENHANCED STEAM METHANE REFORMING (SE-SMR) (T = 650 C ; P = 1 atm) Steam Metahne Reforming (SMR) CH 4 + H 2 O CO + 3H 2 ΔH K = J/mol Water Gas Shift (WGS) CO + H 2 O CO 2 + H 2 ΔH K = J/mol Carbonation CaO (s) + CO 2 CaCO 3(s) ΔH K = J/mol H 2 Regenerated solid CALCIUM LOOPING Solid saturated by CO 2 Calcination CaCO 3(s) CaO (s) + CO 2 ΔH K = J/mol REGENERATION (T = C ; P = 1 atm)

3 Combined Sorbent/Catalyst Materials CO 2 SORBENT + SMR CATALYST = Further COMBINED SORBENT-CATALYST application MATERIAL (CSCM) CaO Ni 0 Mayenite (Ca 12 Al 14 O 33 ) CaO sorbents undergo a decay during multiple CO 2 -sorption/regeneration cycles, mainly because of sintering. SUPPORT CAO BINDER Efforts focused on calcium oxide binder, assuring a stabilization of the capture capacity.

4 CSCM synthesis methods 1) Wet mixing [1,2] Mayenite or CaO-Mayenite Calcination of Ca(CH 3 COO) 2 to CaO (4h ; 750 C) CaO + Al(NO 3 ) 3 9H 2 O Stirring in distilled water (70 C; 1h) 2) Wet impregnation [3,4] Ni-Mayenite or Ni-CaO-Mayenite Mayenite or CaO-Mayenite + Ni(CH 3 COO) 2 4H 2 O or Ni(NO 3 ) 2 6H 2 O Stirring in distilled water (70 C ; 1h) Drying (12h ; 120 C) Drying (12h ; 120 C) Calcination 1 (4h ; 750 C) Hydration + Drying (12h ; 120 C) Calcination 2 (1.5h ; 900 C) Calcination (4h ; 900 C) Various CaO content between 15/85 and 54/46 Ni content = 3wt% [1] Z. Li et al, Energy & Fuels 19, 2005, [2] I. Zamboni et al. PREPA11, 33 (2014) [3] A. D Orazio et al, Int. J. Hydr. En. 2013, 38, [4] I. Zamboni, Ph.D. thesis, ICPEES 2013

5 Intensity [a.u.] CSCM characterization X-Ray Diffraction CaO15Ni(N)3 Ca 12 Al 14 O 33 (Mayenite) CaAl 2 O 4 CaO (Lime) NiO (Bunsenite) Phases formed: CaO Mayenite (Ca 12 Al 14 O 33 ) NiO CaO15Ni(Ac)3 CaO θ [degrees] CaO crystallite size decreases after nickel addition = no sintering due to calcination. Mayenite crystallite size slightly increases after nickel addition. NiO crystallite sizes are lower than 20 nm. Similar values for acetate and nitrate precursors. Crystallite sizes Sample Phase D p [nm] CaO15 CaO 30,3 Mayenite 33,3 CaO 27,4 CaO15Ni(Ac)3 Mayenite 37,7 NiO 19,5 CaO 26,8 CaO15Ni(N)3 Mayenite 38,6 NiO 18,9

6 H 2 consumption [TCD signal, a.u.] H 2 consumption [TCD signal, a.u.] Catalyst properties Temperature Programmed Reduction CaO15Ni(Ac)3 CaO15Ni(N)3 T reforming = 650 C CaO54Ni(Ac)3 CaO54Ni(N)3 T reforming = 650 C Temperature [ C] Temperature [ C] Reducibility Figure CSCM Reducibility before 650 C (%) Reducibility max (%) Left Right CaO15Ni(Ac)3 CaO54Ni(Ac) CaO15Ni(N)3 CaO54Ni(N) Nickel sintering?

7 Sorption capacity [g CO 2 / 100 g sorbent] CaO conversion [%] BET specific surface [m 2 g -1 ] Sorbent properties Sorption capacity and BET 100 Parent sorbent 80 Ni-acetate Ni-nitrate No specific link Parent sorbent Ni-acetate Ni-nitrate Parent sorbent's CaO nominal fraction [wt%] Parent sorbent's CaO nominal fraction [wt%] Stability of the sorption capacity (thermogravimetry) Sorption/regeneration cycles 800 C 800 C cycles of sorption/regeneration 30 min 30 min 100% N C 30 min 15% CO 2 85% N 2 Calcination CO 2 Sorption 100% N 2 Calcination 650 C x 50 cycles CaO30 CaO30Ni(N)3 8,5 gco 2 /100 gcscm min CSCM sorption capacity Number of cycles CaO30Ni(Ac)3 Sorption capacity loss after 50 cycles CaO30 27,8% CaO54 31,8%

8 Concentration [% v dry-diluent-free basis ] Breakthrough CSCM activity in SE-SMR and SMR 100 SE-SMR CaO15Ni(N)3 80 CH 4 conversion H 2 at the thermodynamic equilibrium of SMR 60 SE- SMR SMR H 2 Pre-breakthrough: SE-SMR thanks to CO 2 capture CO 2 CO Post-breakthrough: SMR after CaO saturation Time [min] CH 4 CO 2 capture permits to overtake the SMR thermodynamic equilibrium. After CaO saturation, the SMR thermodynamic equilibrium is maintained at least for 3h.

9 Concentration [% v dry-diluent-free basis ] CSCM activity in SE-SMR and SMR 100 SE-SMR CaO15Ni(N)3 and CaO54Ni(N)3 80 CH 4 conversion 60 H 2 The lower CaO content leads to the more active and stable CSCM, as expected. 40 H 2 CaO54Ni(N)3 20 CO 2 CaO54Ni(N)3 CO 2 CO Time [min] CH 4 SE-SMR with CaO15Ni(Ac)3: initial activity that rapidly rises very low level at 20 min. SE-SMR with CaO54Ni(Ac)3: no activity.

10 CSCM after test characterization Why CSCM from acetate CSCM from nitrate whereas their catalytic properties are similar! After test crystallite sizes Sample Phase D p [nm] Before test After test CaO 27,4 34,4 Mayenite 37,7 38,2 CaO15Ni(Ac)3 NiO 19,5 - CaCO Ni 0-22,9 CaO15Ni(Ac)3: NiO reduction / no sorption. Mayenite crystallite size slightly increases. CaO 26,8 - Mayenite 38,6 36,4 CaO15Ni(N)3 After NiO test 18,9 - CaCO 3-31,4 Ni 0-24,1 CaO15Ni(N)3: NiO reduction + CO 2 sorption. Mayenite crystallite size decreases.

11 Conclusion TEM before test CaO15Ni(Ac)3 20 nm CaO15Ni(N)3 After test 20 nm NiAl 2 O 4 core shell around Ni crystallites in CSCM (N)? Further characterizations by HR-TEM

12 Thank you for your attention! The research leading to these results has received funding from the European Union s Seventh Framework Program ASCENT grant agreement n [608512].