Sintering of nickel steam reforming catalysts: effective mass diffusion constant for Ni-OH at nickel surfaces

TY - JOUR

T1 - Sintering of nickel steam reforming catalysts

T2 - effective mass diffusion constant for Ni-OH at nickel surfaces

AU - Sehested, Jens

AU - Larsen, Niels Wessel

AU - Falsig, Hanne

AU - Hinnemann, Berit

N1 - Natural Gas Conversion the Status and Potentials in the Light of NGCS-10

PY - 2014

Y1 - 2014

N2 - The lifetimes of heterogeneous catalysts in many widely used industrial processes are determined by the loss of active surface area. In this context, the underlying physical sintering mechanism and quantitative information about the rate of sintering at industrial conditions are relevant. In this paper, particle migration and coalescence in nickel steam reforming catalysts is studied. Density functional theory calculations indicate that Ni-OH dominate nickel transport at nickel surfaces in the presence of steam and hydrogen as Ni-OH has the lowest combined energies of formation and diffusion compared to other potential nickel transport species. The relation between experimental catalyst sintering data and the effective mass diffusion constant for Ni-OH is established by numerical modelling of the particle migration and coalescence process. Using this relation, the effective mass diffusion constant as a function of temperature is determined from experimental data to D Ni-OHKNi-OH = 7.7 × 10-6 m2 s-1 bar-0.5exp((- 137 kJ/mol)/RT). With this work we are able to bridge the gap between sintering in macroscopic catalysts and microscopic particle diffusion.

AB - The lifetimes of heterogeneous catalysts in many widely used industrial processes are determined by the loss of active surface area. In this context, the underlying physical sintering mechanism and quantitative information about the rate of sintering at industrial conditions are relevant. In this paper, particle migration and coalescence in nickel steam reforming catalysts is studied. Density functional theory calculations indicate that Ni-OH dominate nickel transport at nickel surfaces in the presence of steam and hydrogen as Ni-OH has the lowest combined energies of formation and diffusion compared to other potential nickel transport species. The relation between experimental catalyst sintering data and the effective mass diffusion constant for Ni-OH is established by numerical modelling of the particle migration and coalescence process. Using this relation, the effective mass diffusion constant as a function of temperature is determined from experimental data to D Ni-OHKNi-OH = 7.7 × 10-6 m2 s-1 bar-0.5exp((- 137 kJ/mol)/RT). With this work we are able to bridge the gap between sintering in macroscopic catalysts and microscopic particle diffusion.

KW - Diffusion

KW - Nickel catalysts

KW - Particle migration

KW - Sintering

KW - Steam reforming

U2 - 10.1016/j.cattod.2014.01.009

DO - 10.1016/j.cattod.2014.01.009

M3 - Journal article

AN - SCOPUS:84896993909

SN - 0920-5861

VL - 228

SP - 22

EP - 31

JO - Catalysis Today

JF - Catalysis Today

ER -