and utilizing reduction promoters leads to improved conversion and - PowerPoint PPT Presentation

Fischer-Tropsch synthesis: foregoing calcination and utilizing reduction promoters leads to improved conversion and selectivity with Co/silica Mohammad Mehrbod Mechanical Engineering Program, Mechanical Engineering Dept., UTSA Michela Martinelli, Burtron H. Davis Center for Applied Energy Research, University of Kentucky Donald C. Cronauer, A. Jeremy Kropf, Christopher L. Marshall Advanced Photon Source, Argonne National Laboratory Gary Jacobs Chemical Engineering Program – Dept. of Biomedical Engineering/ Dept. of Mechanical Engineering, UTSA March 18, 2017 LCCP Laboratory of Catalysis and Catalytic Processes LC

2 Introduction Steam Reforming / Partial Oxidation Hydrogen CH 4 + H 2 O → CO + 3H 2 Water-gas Shift / Preferential Oxidation CH 4 + 1/2O 2 → CO + 2H 2 CO + H 2 O → H 2 + CO 2 CO + 1/2O 2 → CO 2 FT Catalyst Natural Gas SYNGAS CO and H 2 Methanol, Ethanol Gasification C + H 2 O → CO + H 2 Oxygenate Synthesis CO + 2H 2 → CH 3 OH PEM Fuel Cells/SOFC Portable Power Coal Diesel Jet Fuel Waxes Lubricants Fischer-Tropsch Synthesis CO + 2H 2 → -[CH 2 ] n - + H 2 O Biomass LCCP Laboratory of Catalysis and Catalytic Processes LC

3 Introduction Catalyst support and promoter :  Cobalt often supported on metal oxide carriers like alumina or titania. Problem: The weak interaction between Co/TiO 2 Co/Al 2 O 3 Co/SiO 2 SiO 2 and cobalt oxides on calcined catalysts leads to agglomerated Co 0 after activation. Productivity is lower. We consider 3 aspect: Activity (CO Product conversion per Stability Selectivity gram of cat.) Past efforts 1,2 showed that direct reduction of cobalt Ru Re nitrate led to small, difficult-to-reduce Co species. Promoter We revisit the possibility of direct cobalt nitrate Ag Pt reduction, but utilize promoters to facilitate activation of the difficult-to-reduce Co species. 1. B.H. Davis, E. Iglesia, DOE Quarterly Report #8, July-September 2000, Technology Development for Iron and Cobalt Fischer-Tropsch Catalysts, Contract DE-FC26-98FT40308, Final Report, June, 30 2004. LC LCCP Laboratory of Catalysis and Catalytic Processes 2. Li, J.; Jacobs, G.; Das, T.K.; Zhang Y.; Davis, B.H., Applied Catalysis A: General 236 (2002) 67-76.

Experimental 4 Catalyst preparation PQ Co. CS- 2133, dried 80˚C to 100˚C 12% wt. Co/SiO 2 Promoted Unpromoted Calcined at 350 ° C Calcined at 350 ° C Uncalcined Uncalciend To prepare 0.5 wt.% (calcined basis) Pt promoted catalysts, tetraamineplatinum (II) nitrate was added by IWI to the dried Co(NO 3 ) 2 /silica parent batch, and the material was dried again in the rotary evaporator. Calcined 12%Co/SiO 2 0.5%Pt- 0.276%Ag- 0.477%Re- 0.259%Ru- 12%Co/SiO 2 12%Co/SiO 2 12%Co/SiO 2 12%Co/SiO 2 Uncalcined 12%Co/SiO 2 0.5%Pt- 0.276%Ag- 0.477%Re- 0.259%Ru- 12%Co/SiO 2 12%Co/SiO 2 12%Co/SiO 2 12%Co/SiO 2 LCCP Laboratory of Catalysis and Catalytic Processes LC

Experimental 5  BET surface area and porosity measurements BET surface area and porosity characteristics were measured using a Micromeritics 3-Flex system.  Temperature programmed reduction TPR profiles of calcined catalysts were recorded using a Zeton- Altamira AMI-200 unit equipped with a thermal conductivity detector (TCD).  Hydrogen chemisorption and percentage reduction by pulse reoxidation Hydrogen chemisorption was conducted by using temperature programmed desorption (TPD), also measured with the Zeton- Altamira AMI-200 instrument  TPR-EXAFS/ TPR-XANES spectroscopies In-situ H2-TPR XAFS studies were performed at the Materials Research Collaborative Access Team (MR-CAT) beamline at the Advanced Photon Source, Argonne National Laboratory  Catalytic activity FTS reaction tests were conducted using a 1 L CSTR equipped with a magnetically driven stirrer with turbine impeller LCCP Laboratory of Catalysis and Catalytic Processes LC

Results BET surface area and porosity measurements If the support is the main contributor to the area, then after adding 12.3 wt. % Co and assuming no pore blocking, the specific surface area should decrease to 291 m 2 /g for the air calcined Co catalyst and 225 m 2 /g for the uncalcined catalyst. BET surface area and BJH porosity measurements. XRD analysis of the catalysts. A s V p Average D p Sample Thermal treatment (BET) (BJH Des) (BJH Des) (m 2 /g) (cm 3 /g) (nm) SiO 2 349 2.68 24.3 uncalcined 163 0.79 14.4 uncalcined 0.5%Pt-12%Co/SiO 2 Intensity (a.u.) (c) reduced 272 1.11 14.2 12%Co/SiO 2 air calcined 278 1.16 14.6 air calcined/reduced 276 1.16 14.8 Uncalcined 139 0.67 13.4 Reduced 256 0.99 13.5 uncalcined 12%Co/SiO 2 0.5%Pt-12%Co/SiO 2 air calcined 275 1.00 13.6 (b) air calcined/reduced 258 1.03 13.9 Uncalcined 151 0.67 13.2 0.236%Ag- Reduced 263 0.96 13.0 air calcined 12%Co/SiO 2 12%Co/SiO 2 (a) Uncalcined 155 0.71 13.7 0.259%Ru- Reduced 277 0.89 13.9 12%Co/SiO 2 Uncalcined 156 0.73 13.9 0.477%Re- 10 20 30 40 50 60 70 80 90 Reduced 273 1.00 13.5 12%Co/SiO 2 2-Theta (°) LCCP Laboratory of Catalysis and Catalytic Processes LC

Result Cobalt Reducibility : TPR profiles of uncalcined and calcined catalysts Figure reveals that the air calcined catalyst reduced at a relatively low 0.477%Re-12%Co/SiO 2 uncalcined temperature 0.259%Ru-12%Co/SiO 2 uncalcined Co 3 O 4 + H 2 = 3CoO + H 2 O 0.276%Ag-12%Co/SiO 2 3CoO + 3H 2 = 3Co 0 + 3H 2 O calcined 0.5%Pt-12%Co/SiO 2 uncalcined For uncalcined, promoter addition 12%Co/SiO 2 uncalcined did not shift the peak for nitrate decomposition (black) but did shift 0.5%Pt-12%Co/SiO 2 the peaks for reduction of cobalt calcined oxides (red) derived from nitrate 12%Co/SiO 2 calcined decomposition. LCCP Laboratory of Catalysis and Catalytic Processes LC

Results 8 Cobalt Reducibility : H 2 -TPR Mass Spectrometry  The hydrogen has two consumption peaks, associated with H 2 O production for the calcined sample These peaks are due to the two reduction steps from Co 3 O 4 to Co involving CoO as an intermediate, as previously discussed There is a small peak on H 2 O profile at temperatures lower than 100°C. This is probably due to some 0.5%Pt-12%Co/SiO 2 calcined adsorbed water on the catalyst . LCCP Laboratory of Catalysis and Catalytic Processes LC

Results 9 Cobalt Reducibility : 4 TPR Mass Spectrometry 5 6 3 1 2 At temperatures lower than 180 °C, there are at least six major events, whereby: 3- between 180 ° C and 230 ° C, 4- Between 200 ° C and 250 ° C, 2- Cobalt nitrate thermal 1- The water signal increases 6- Between 300 °C and 750 °C, 5- Between 230 °C and 300 °C, reductive decomposition of formation of NO indicates decomposition without from ambient temperature until there is a series of hydrogen there is an uptake of hydrogen cobalt nitrate occurs, with oxidation of CoO x species involvement of H 2 occurs a maximum, which is reached at uptakes with corresponding and H 2 O evolution without NO X between 110 and 180 ° C continuing evolution of NO 2 110 ° C formed from the decomposition evolution of H 2 O peaks, these formation due to reduction of and H 2 O, including uptake by of cobalt nitrate by the liberated are assigned to reduction of the suggested spinel (e.g., hydrogen NO 2 to the spinel structure CoO species Co 3 O 4 ) to CoO Co 3 O 4 12%Co/SiO 2 uncalcined LCCP Laboratory of Catalysis and Catalytic Processes LC

Results 10 0.477%Re-12%Co/SiO 2 0.5%Pt-12%Co/SiO 2 uncalcined ucalcined 0.276%Ag-12%Co/SiO 2 0.259%Ru-12%Co/SiO 2 uncalcined uncalcined The ranking of promoter effectiveness for CoO reduction from TPR-MS is: Pt > Re > Ru > Ag > unpromoted LC LCCP Laboratory of Catalysis and Catalytic Processes

Results 11 TPR XANES This calcined catalyst starts with a line shape resembling the cobalt oxide spinel structure of Co 3 O 4 , with conversion to CoO being achieved below 250 °C. Next, because of the larger weakly interacting Co clusters, Co 0 metal is rapidly formed by ~300 °C (final dark blue spectrum to first green spectrum for CoO to Co 0 ) LCCP Laboratory of Catalysis and Catalytic Processes LC

Results 12 TPR XANES With the uncalcined catalysts, Co(NO 3 ) 2 slowly converts to CoO X decomposition products that are oxidized to a spinel (e.g., Co 3 O 4 ) – final light blue spectrum. Afterwards, a typical two step reduction of Co 3 O 4 was observed, with CoO as the intermediate (final dark blue spectrum). Relative to the calcined catalyst, reduction of cobalt oxides occurs over a wider range, indicating smaller, interacting Co oxide species. LCCP Laboratory of Catalysis and Catalytic Processes LC

Results 13 TPR XANES CoO converted to Co 0 Conversion of the cobalt The temperature range for (final dark blue spectrum to oxide spectra representing spinel to CoO occurred by 315 °C for all green spectra) with vastly maximum cobalt oxide uncalcined catalysts, and different final extents of spinel content was narrow ( D = 44 °C) for all reduction by 500 °C the temperature range for depending on the presence spectra representing CoO uncalcined catalysts, was narrow ( D = 66 °C), including uncalcined (180 or absence of promoter, as well as the promoter with the temperature of °C), and catalysts containing Pt (197 °C), Ag identity maximum CoO content (206 °C), Re (215 °C), and being: uncalcined and Ru (171 °C). Pt > Re, Ru > Ag catalysts containing Pt, Ag, Re, and Ru. LCCP Laboratory of Catalysis and Catalytic Processes LC