Evaluation of the stability of electroless deposition-derived NiPt

Evaluation of the stability of electroless deposition-derived NiPt

Evaluation of the stability of electroless deposition-derived NiPt bimetallic catalysts for dry reforming of methane AIChE Annual Meeting San Francisco, CA November 17, 2016 Jayson Keels, Khalid Askar, John R. Monnier, John R. Regalbuto University of South Carolina Department of Chemical Engineering Biogas Potential U.S. Methane Emissions, By Source Other; 8.00% Manure Management;

Natural Gas & 8.00% Petroleum System; 33.00% Coal Mining; 9.00% 28% of methane emissions comes from biogas Heating value equal to annual energy production of 40 nuclear power plants Landfills; 20.00% Enteric Fermentation; 22.00% Total = 600 Mt CO2 Equivalent www.epa.gov

2014: EPA allows biogas as viable pathway to meet RFS cellulosic requirements 2 Biogas Potential U.S. Methane Emissions, By Source Other; 8.00% Manure Management; Natural Gas & 8.00% Petroleum Coal Mining; System; 9.00% 33.00% Landfills; 20.00% Enteric Fermentation; 22.00%

Total = 600 Mt CO2 Equivalent www.epa.gov 28% of methane emissions comes from biogas Heating value equal to annual energy production of 40 nuclear power plants 2014: EPA allows biogas as viable pathway to meet RFS cellulosic requirements 2 Biogas Utilization Direct Heat IC Engine Gas

Turbine Flaring Direct Combustion BIOGAS Steam Turbine 3 Biogas Utilization Direct Heat IC Engine Gas Turbine

Flaring Direct Combustion Steam Turbine BIOGAS CH44 Separation NG CNG LNG 3 Biogas Utilization Direct

Heat IC Engine Gas Turbine Flaring Enhanced Combustion Direct Combustion Catalytic Reforming (syngas) Steam Turbine BIOGAS

Fuel Cells CH44 Separation NG CNG Liquid Fuels LNG 3 Biogas Utilization CH2O Assimilation Direct Heat IC Engine

Gas Turbine CH44 Fermentation Flaring Direct Combustion Steam Turbine Enhanced Combustion Catalytic Reforming (syngas) BIOGAS

Fuel Cells CH44 Separation NG CNG Liquid Fuels LNG 3 Dry Reforming Dry Reforming of Methane Side Reactions Reverse Reverse water-gas water-gas shift shift Methane

Methane decomposition decomposition Boudouard reaction Boudouard reaction T.D. Gould, M.M. Montemore, A.M. Lubers, L.D. Ellis, A.W. Weimer, J.L. Falconer, J.W. Medlin, Appl. Catal. A: Gen. 492 (2015) 107-116. 4 Dry Reforming Dry Reforming of Methane Side Reactions Reverse Reverse water-gas water-gas shift shift Methane Methane decomposition decomposition Boudouard reaction Boudouard reaction

Ni-based catalysts are highly active and inexpensive. Catalyst Deactivation 1. Sintering typical operating temperatures: 600 800 oC. 2. Coke Formation 2 primary types of coke: Support Encapsulating Support Filamentous T.D. Gould, M.M. Montemore, A.M. Lubers, L.D. Ellis, A.W. Weimer, J.L. Falconer, J.W. Medlin, Appl. Catal. A: Gen. 492 (2015) 107-116. 4 Dry Reforming Dry Reforming of Methane Side Reactions

Reverse Reverse water-gas water-gas shift shift Methane Methane decomposition decomposition Boudouard reaction Boudouard reaction Ni-based catalysts are highly active and inexpensive. Catalyst Deactivation 1. Sintering typical operating temperatures: 600 800 oC. 2. Coke Formation 2 primary types of coke: Support Encapsulating

Support Filamentous Possible solution: promote with precious metals. Most studies use bulk techniques to synthesize bimetallic catalysts. Gould et al.: NiPt bimetallic catalysts prepared by ALD improve stability. T.D. Gould, M.M. Montemore, A.M. Lubers, L.D. Ellis, A.W. Weimer, J.L. Falconer, J.W. Medlin, Appl. Catal. A: Gen. 492 (2015) 107-116. 4 Project Objectives Utilize electroless deposition (ED) to synthesize Ni core/Pt shell catalysts supported on -Al2O3. Investigate bimetallic interaction of catalysts using temperature programmed reduction (TPR) and x-ray diffraction (XRD). Compare stability of the Ni, Pt, and NiPt catalysts. Characterize coke formation. 5

Electroless Deposition Electroless deposition (ED) is a catalytic process in which a metal is reduced and deposited onto the surface of a pre-existing metal. RA: Reducing Agent A: Primary Base metal B: Secondary metal 6 Catalyst Preparation Ni and Pt monometallic catalysts supported on -Al2O3 Dry impregnation (DI) using Ni(NO3)2 and H2PtCl6 Reduced at 600 oC and 275 oC respectively Pt deposited onto Ni catalyst using ED Developer bath:

Pt precursor: H2PtCl6 Reducing agent: dimethylamine borane (DMAB) Chelating agent: ethylene diamine (EN) DMAB/EN/Pt = 5/4/1 Temperature = 70 oC Dried in air and heat treated at 200 oC in H2 7 Pt ED on Ni Kinetics of Pt deposition All samples reach desired Pt loadings within 30 min. Induction period in plots likely due to in situ reduction of NiO by RA to form Nio. Catalyst Name 3% Pt

5% Ni [email protected] [email protected] [email protected] Ni wt loading (%) 0.00 5.00 4.99 4.91 4.86 Pt wt loading (%) 3.00 0.00 0.20 1.90 2.75

Theoretical monodisperse Bulk Pt/Ni coverage, Pt, atomic on Ni ratios 0.00 0.00 0.07 0.012 0.69 0.12 1.02 0.17 8 TPR Characterization 1. 2. 3.

Catalysts previously reduced in H2 Pre-oxidized at 300 oC in 10% O2 for 2 hr TPR at 10 oC/min in 10% H2/bal Ar Primary Ni reduction peak shifts to lower temperatures. Edges/corners peak disappears. Edges/corners Enhanced reducibility implies strong bimetallic interaction. 9 Evaluation for DRM 10 DRM Stability

Catalyst stability CH4/CO2/He = 1/1/2, T = 700 oC 11 DRM Stability Catalyst stability CH4/CO2/He = 1/1/2, T = 700 oC 11 DRM Stability Catalyst stability CH4/CO2/He = 1/1/2, T = 700 oC 11 Post-Reaction TPO TPO burn-off (after complete deactivation)

10% O2/bal He 10 oC/min Catalyst Total Coke (mmol C/gcat) 3% Pt 7.21 [email protected] 6.99 [email protected] 1.52 [email protected]

4.22 5% Ni 3.54 14 XRD of Ni-Pt Catalysts Fresh (after H2 treatment at 200 oC) Ni-Pt alloy forms with Pt addition. Pt (111) observed at high loadings. Spent (after 20 hr TOS) Pt peaks sharpen. Alloy peaks shift to right. 12 Particle Size Summary

Pt leaves alloy and agglomerates Ni particles are much more resilient than Pt ND: Not Detected 13 Conclusions Alloy shell formed around Ni particle after ED. Strong bimetallic interaction indicated by TPR and XRD. Catalyst lifetime decreases with increasing Pt loading. Catalyst lifetime inversely proportional to extent of coke formation. During DRM, Pt separates from alloy and agglomerates. Further characterization of coke should be performed. Effect of temperature on rate of deactivation should be investigated. 15 Acknowledgements 15

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