1. Catalyst Characterization
Synthesis of carbon-supported nickel catalysts for the dry reforming of CH4
B. Fidalgo, L. Zubizarreta, J.M. Bermúdez, A. Arenillas, J.A. Menéndez*
Instituto Nacional del Carbón, CSIC, Apartado 73, 33080, Oviedo, Spain *
OBJECTIVE
The aim of this work was to study the influence of the surface chemistry of activated carbons used as support, method of drying and reduction temperature on the characteristics and the final activity of the prepared catalysts
ACKNOWLEDGEMENTS. B.F., L.Z. and J.M.B. are grateful to the support received from the CSIC I3P Programme co-financed by the European Social Fund (ESF) and the CSIC JAE Programme. Financial support from the PCTI Asturias (Project PEST08-21) is also acknowledged.
INTRODUCTION
Dry reforming
Advantages
Low H2/CO ratio
CO2 consume
Use in CETS
CH4 + CO2
H2 + CO
Catalyst
CH4 feedstock
Synthesis gas
Influenced by selected metal, support and its chemistry surface, stages of preparation…
RESULTS 25 50 75
100
125
150
175
FY5oxNi-MW-500
FY5oxNi-E-500
FY5oxNi-E-300
FY5Ni-E-300
FY5oxNi-MW-300
FY5Ni-MW-300
Ni particle size (A)
Reduction temperature has high influence, producing sintering at 500ºC
MW drying gives rise to smaller particle sizes, so it favors Ni dispersion. The effect of the surface chemistry is reduced using MW heating. 20 40 60 80
Time (min)
Conversion (%)
The catalysts prepared over the non-oxidized carbon and reduced at 300 ºC show the best performance
No significant different of the catalysts prepared at different temperatures were found, maybe due to the sintering during the reaction at 800ºC
The negative effect of the oxidation overcomes the positive effect, in terms of interaction between Ni particles and carbon surface, achieved by using an oxidized support
Ni which has interaction with the support
Ni without interaction with the support
Catalyst prepared over the oxidized AC only show the high temperature peak of Ni with high interaction with the support
Oxidation favors the interaction between the Ni and the support
CONCLUSIONS
The MW drying presents numerous advantages on the preparation of Ni-C catalysts such as smaller particle size are achieved, the influence of surface chemistry is reduced and outstanding reduction of the time required for the preparation.
The surface chemistry and temperature of reduction have also strong influence in the final physical and chemical properties of the catalyst.
For the application in the dry reforming reaction, improvement of Ni particle size or Ni dispersion is not a prime step, due to the sintering of Ni particles which may take place at the reaction temperature (800 ºC).
The oxidation of the carbon support shows strong decrease of the catalytic properties of the catalyst.
EXPERIMENTAL
Activated
Carbon
FY5
Drying
None
(NH4)S2O8 +
H2SO4
FY5ox
FY5oxNi
FY5Ni
Oxidation
Impregnation
Ni(NO3)·6H2O
Pretreatment
Microwave
Oven
Conventional
FY5oxNi-MW
FY5oxNi-E
FY5Ni-MW
FY5Ni-E
300 ºC
500 ºC
Reduction
Catalyst Characterization
Textural Characterization (CO2 and N2 isotherms)
Ni particle size (X-Ray diffraction)
Ni-AC interaction (Temperature programmed reduction and Temperature programmed desorption)
Operation Conditions
Temperature = 800 ºC
Pressure = 1 atm
VHSV = 0.32 L g-1 h-1
CH4:CO2 = 1:1
Gas inlet
Gas outlet
Dry reforming catalytic test in an electric furnace