Aqueous-phase reforming a pathway to chemicals and fuels

Transcription

1 Alexey Kirilin Aqueous-phase reforming a pathway to chemicals and fuels Laboratory of Industrial Chemistry and Reaction Engineering Process Chemistry Centre Åbo Akademi

2 Agenda 2 Short Introduction, biomass, what is APR? Main tasks of the doctoral research Experimental methods Choice of catalytic systems Catalytic results Summary

3 Introduction - Biomass 3

4 Catalytic transformation of biomass 4 Hydrolysis Cellulose Hemicellulose Hydrolysis Oxidation Oligomers Aldoses Hydrogenation Sugar acids Chemicals Sugar alcohols Esterification Aqueous reforming Fuels Lubricants

5 Aqueous phase reforming (APR) 5 Biomass RR=11/5

6 Aqueous phase reforming (APR) 5 Biomass RR=11/5

7 The main tasks of the research 6 Task 1. Investigation of reaction products and intermediates Task 2. Synthesis and characterization of catalysts Task 3. Catalyst stability studies Task 4. Investigation of reactant structure on process properties Task 5. Influence of a second metal (Re) Task 6. Modelling of reaction kinetics

8 Experimental setup 7 Reaction conditions: 0.5 g of a catalyst 225 C 30 bar Carrier gas N 2 (30 ml/min) Continuous fixed-bed reactor 10 wt.% of xylitol used as a feed Reagents in the liquid phase

9 Reactor s scheme 8 H 2 (for reduction) MFC MFC HPLC pump N 2 (1% He) mass flow controller catalyst furnace MFC GC sampling collector P safety valve pressure controller effluent

10 Product analysis 9 APR of Polyols Gas phase Liquid phase Micro-GC HPLC TOC On-line sampling Volatile compounds were identified by means of Solid-phase microextraction (SPME) + GC-MS TOC total organic carbon analysis Mass balance % (by carbon analysis)

11 Important parameters in APR 10 G L H 2, CO 2, alkanes Oxygenates 100% Catalyst activity, stability and selectivity to H 2 Product distribution between phases Ratio H 2 /CO 2 v ( H ) 2 v( C ) Selectivity to H 2 (%) = 1/ RR 100% in gas RR reforming H 2 /CO 2 ratio (11/5 fo xylitol)

12 Choice of active metal and support 11 Based on catalytic activity in the APR of ethylene glycol Ni Pt Al 2 O 3 TiO 2 Ru Pd C MgO

13 Choice of active metal and support 11 Based on catalytic activity in the APR of ethylene glycol Ni Pt Al 2 O 3 TiO 2 Ru Pd C MgO C-C cleavage WGS activity Pt/Al 2 O 3, Pt/TiO 2, Pt/C and bimetallic catalyst PtRe/TiO 2

14 Catalyst stability Bildningshastighet Formation rate [x ], mol/min Time on stream, h Catalyst showed stable performance within more than 120 h time on stream Time. h CO 2 [ 10 4 ]. mol (X C x H y )[ 10 5 ]. mol C x H y /CO

15 Distribution of carbon Carbon content, % 13 benchmark catalyst Pt/Al 2 O 3 G H 2, CO 2, alkanes 100% L Oxygenates 100 Liquid Gas WHSV, MVKV, h -1 t -1 WHSV weight hourly space velocity g subs /g cat /hour [h 1 ]

16 Distribution of carbon Carbon content, % 13 benchmark catalyst Pt/Al 2 O 3 G H 2, CO 2, alkanes 100% L Oxygenates 100 Liquid Gas WHSV, WHSV, h -1 h -1 WHSV weight hourly space velocity g subs /g cat /hour [h 1 ]

17 Distribution of carbon Carbon content, % 13 benchmark catalyst Pt/Al 2 O 3 G H 2, CO 2, alkanes 100% L Oxygenates 100 Liquid Gas WHSV, WHSV, h -1 h -1 WHSV weight hourly space velocity g subs /g cat /hour [h 1 ]

18 Gas phase composition Yield, % Yield, % Yield, % 14 Studied by micro-gc and GC-MS, benchmark catalyst Pt/Al 2 O CO propane etane n-butane 15 H СО WHSV, h WHSV, MKMV, ht n-hexane iso-butane n-pentane WHSV, h -1-1

19 Liquid phase 15 Studied by HPLC and SPME benchmark catalyst Pt/Al 2 O 3 изосорбид isosorbid Carbon in liquid. % Product distribution. % Alcohols Diols Triols Ketons Acids Other Total amount detected. %

20 Influence of reactant structure Yield of H 2, % Alkane selectivity, % Reforming of xyltiol Reforming of sorbitol 10 5 Reforming of xyltiol Reforming of sorbitol WHSV, h -1 Higher yields of hydrogen for xylitol substrate with shorter carbon chain WHSV, h -1 Higher selectivity to alkanes at lower space velocities Conditions: 225 С, 30 atm., N 2 30 ml/min, 10 wt.% solution, Pt/Al 2 O 3

21 Influence of reactant structure Yield of H 2, % Alkane selectivity, % Reforming of xyltiol Reforming of sorbitol 10 5 Reforming of xyltiol Reforming of sorbitol WHSV, h -1 Higher yields of hydrogen for xylitol substrate with shorter carbon chain WHSV, h -1 Higher selectivity to alkanes at lower space velocities Conditions: 225 С, 30 atm., N 2 30 ml/min, 10 wt.% solution, Pt/Al 2 O 3

22 Influence of reactant structure Yield of H 2, % Alkane selectivity, % Reforming of xyltiol xylitol Reforming of sorbitol 10 5 Reforming of xyltiol xylitol Reforming of sorbitol WHSV, h -1 Higher yields of hydrogen for xylitol substrate with shorter carbon chain WHSV, h -1 Higher selectivity to alkanes at lower space velocities Conditions: 225 С, 30 atm., N 2 30 ml/min, 10 wt.% solution, Pt/Al 2 O 3

23 Catalysts Effect of a second metal: series Pt/TiO 2, Pt-Re/TiO 2 Re/TiO 2 Prepared by incipient wetness impregnation, from HReO 4 and or (NH 3 ) 4 Pt(NO 3 ) 2 2. Effect of a support material and support structure one commercial Pt/C (Degussa) four prepared and characterized materials 5% Pt/C (Degussa) 2.5% Pt/TiC-CDC (CDC carbide-derived carbon) 5% Pt/Sibunit from (NH 3 ) 4 Pt (HCO 3 ) 2 5% Pt/Sibunit H 2 PtCl 6 5% Pt/BAC (Birch active carbon)

24 Catalysts Effect of a second metal: series Pt/TiO 2, Pt-Re/TiO 2 Re/TiO 2 To enhance selectivity to hydrocarbons 2. Effect of a support material and support structure one commercial Pt/C (Degussa) four prepared and characterized materials 5% Pt/C (Degussa) 2.5% Pt/TiC-CDC (CDC carbide-derived carbon) 5% Pt/Sibunit from (NH 3 ) 4 Pt (HCO 3 ) 2 5% Pt/Sibunit H 2 PtCl 6 5% Pt/BAC (Birch active carbon)

25 Example: APR of xylitol over Pt-Re/TiO 2 18 Yield of H 2, % Pt-Re/TiO 2 Pt/Al 2 O 3 Higher yields of hydrogen for monometallic Pt catalyst Higher selectivity to alkanes in the presence of bimetallic Pt-Re catalyst 10 Pt/TiO WHSV, h -1 Conditions: 225 С, 30 atm., N 2 30 ml/min, 10 wt.% solution In cooperation with prof. C. Hardacre from Queen s University, Belfast

26 Yield of H 2, % Selectivity to alkanes, % Example: APR of xylitol over Pt-Re/TiO Pt-Re/TiO Pt/TiO Pt-Re/TiO 2 Pt/Al 2 O Pt/TiO 2 10 Pt/Al 2 O WHSV, h -1 Higher yields of hydrogen for monometallic Pt catalyst WHSV, h -1 Slightly higher selectivity to alkanes in the presence of bimetallic Pt-Re catalyst Conditions: 225 С, 30 atm., N 2 30 ml/min, 10 wt.% solution In cooperation with prof. C. Hardacre from Queen s University, Belfast

27 Characterization Uptake of H 2, a.u. Frequency, % Concentration of NH 3, % 20 Transmission electron microscopy Particle size distribution Pt/BAC Pt/BAC ~2 nm 5 20 nm d, nm Temperature programmed reduction (H 2 ) Temperature programmed desorption (NH 3 ) Pt/Al 2 O 3 Pt/Al 2 O C K 75 C 180 C K 20 K min K 15 K min K min K 5 K min 349 K -1 3 K min Temperature, C Temperature, K

28 APR of xylitol over Pt/C Rate of alkanes formation [x10 5 ], mol min Effect of acidity H 2 /CO NH 3 desorbed, mol g Supervised visiting PhD student Benjamine Hasse for 2 months In cooperation with prof. B. Etzold from University of Erlangen-Nürnberg

29 APR of xylitol over Pt/C Rate of alkanes formation [x10 5 ], mol min Effect of acidity H 2 /CO NH 3 desorbed, mol g Supervised visiting PhD student Benjamine Hasse for 2 months In cooperation with prof. B. Etzold from University of Erlangen-Nürnberg

30 APR of xylitol over Pt/C Rate of alkanes formation [x10 5 ], mol min Effect of acidity H 2 /CO NH 3 desorbed, mol g Supervised visiting PhD student Benjamine Hasse for 2 months In cooperation with prof. B. Etzold from University of Erlangen-Nürnberg

31 Reaction pathways Based on experimental data 22

32 Reaction pathways Based on experimental data Pathway to hydrogen 22

33 Reaction pathways Based on experimental data Pathway to hydrogen 22

34 Reaction pathways Based on experimental data 22 Pathway to alkanes

35 Reaction pathways Based on experimental data 22 Pathway to alkanes

36 Reaction pathways Based on experimental data Pathway to hydrogen 22 Pathway to alkanes Modelling of kinetics was performed at ÅA A.V. Kirilin, J. Wärnå, T. Salmi, D. Yu. Murzin, Kinetic Modeling of Sorbitol Aqueous-Phase Reforming over Pt/Al 2 O 3, Ind. Eng. Chem. Res., 2014, 53,

37 Modeling Two main pathways are selected 23

38 Modeling 24

39 Modeling Weisz-Prater modulus robsr cd eff 2 for 1-st order reaction Φ < 1, for 0 order reaction Φ < 6 for 2 order reaction Φ < 0.3 r obs maximal initial reaction rate R mean radius of the catalyst particle c substrate concentration. In our case R = m (125 µm) 25 effective diffusion coefficient (D eff ) of substrate (sorbitol) in water Wilke-Chang: 8 o ( M porosity ( ) D ef D D AB tortuosity (2-5) 0. 6 B Vb ( A) = 2.6 (water), M B is molecular weight of solvent, B = cp is solvent dynamic viscosity, T (K) = 498K, P=30 bar), V b(a) = cm 3 mol -1 is liquid molar volume at solute s normal boiling point. B ) 1 2 T [cm 2 /s] Assuming / = 1/10 the diffusion coefficient of sorbitol is calculated to be D ef = m 2 /s (498 K and 30 bar). The concentration of the substrate in the solvent is equal to mol l -1. r max = mol l -1 s -1 at 2.7 h -1 Φ=0.005 substrate diffusion inside the catalyst pores does not affect the reaction rate

40 P=S+W-I, where S is the number of steps, W is the number of balance (link) equations, and I is the number of intermediates 26 P= =8 basic routes (no intermediates are there) N (1) : C N (2) : C N (3) : C O H 6 O H 5 O H Reaction pathways C5O5 H12 H2 C4O4H10 H2 C3O3 H8 H2 CO CO CO N (4) : C 3 O H 3 8 C2O2H 6 H2 CO N (5) : CO H2O CO2 H2 N (6) : N (7) : N (8) : C4O4H10 4H2 C4H10 4H2O C3O3 H8 3H2 C3H8 3H2O C2O2H 6 2H2 C2H6 2H2O D. Murzin & J. Wärnå

41 on metal sites: C O H K C C6O6H 14 on acid sites: V K C ' C ' 4O4H10 12 C4O4H10 V C O H K C C5O5H 12 V 27 and so on for each component Total coverage: V 1 V ' 1 K 1 K 1CC O H K CC O H K CC O H K CC O H K CC O H K C H 2 O 12 C C Rate for basic route 1: r (1) k 2 C O H C O H K 1 C K 4O4H10 14 C3O3H 8 16 k K C C O H C O H V k2k1cc 6O6H14 1 K C K C K C K C K C K C O H Generation rate for compound: C 7 dc C 2 O 2 C O H 3 3 H 8 C O H r d (1) C O H C H O 2 D. Murzin & J. Wärnå

42 Modeling C6OH 28 r (1) k 2 C O H 6 C O H k K C C O H C O H V k2k1cc 6O6H14 1 K C K C K C K C K C C O H C O H C O H K 10 C H O 2 Simplification of the model because of overparametrization 3.5 x 10-4 (1) ' r k2c C O H dc (9) r k ' 18C C O H C 6 O 6 H 14 (1) (9) r r d % WHSVh D. Murzin & J. Wärnå

43 Summary Aqueous-phase reforming of two most abundant polyols has been studied over stable catalysts 2. Effect of reactants structure on selectivity to main product formation reveals that higher selectivities to hydrogen can be achieved in APR of xyltiol compared to sorbitol (up to 85%) 3. Addition of Re as a second metal component leads to enhanced alkane formation 4. Advanced reaction scheme was proposed on the basis of experimental data 5. For the first time reaction sensitivity in APR of xylitol was studied over Pt/C 6. The reaction kinetics was modeled based on kinetic data and mechanistic considerations for sorbitol transformation during APR. APR is a powerfull method for hydrogen production from renewables Kinetic model proposed can be further developed and applied to description of APR data for other substrates as well as for APD/H process

44 Financial support 30 Graduate School in Chemical Engineering (GSCE, ) Fortum Foundation ( ) Academy of Finland in cooperation with North European Innovative Energy Research Programme (N-Inner, ) Haldor Topsøe Scholarship Programme ( ) COST Action CM0903 (UbioChem, )

45 Alexey Kirilin Aqueous-phase reforming a pathway to chemicals and fuels Laboratory of Industrial Chemistry and Reaction Engineering Process Chemistry Centre Åbo Akademi