Dry reforming of methane (DRM) is an attractive technology for utilizing the greenhouse gases (CO

2

and CH

4

) to produce syngas. However

the catalyst pellets for DRM are heavily plagued by deactivation by coking

which prevents this technology from commercialization. In this work

a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al

2

O

3

catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature

pressure

and CH

4

/CO

2

molar ratio

but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter

narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking

as the pores in this pellet are more difficult to be plugged or inaccessible. The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity

as the number of inaccessible pores is lower. Besides

the catalyst pellet radius only slightly affects the coke content

a

lthough the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.