Cylindrical NiMg/Ce<
sub>
0.6<
/sub>
Zr<
sub>
0.4<
/sub>
O<
sub>
2<
/sub>
pellet catalysts with two different sizes (large: radius = 1.59 mm
and small: radius = 0.75 mm) were produced by extrusion of powder catalysts. The small catalyst pellets had a higher specific surface area, pore volume, average pore size, radial crush strength, and resistance to breakage than the large ones. Tri-reforming tests with surrogate biogas were conducted at 3 bar and 882 �C, with the feed molar ratios of CH<
sub>
4<
/sub>
: CO<
sub>
2<
/sub>
: air fixed at 1.0: 0.7: 0.95 and the H<
sub>
2<
/sub>
O/CH<
sub>
4<
/sub>
molar feed ratio (0.35 ? 1.16) varied. The small catalyst pellets exhibited lower internal mass transfer resistance and higher coking resistance, compared to the large ones. CO<
sub>
2<
/sub>
conversion decreased and H<
sub>
2<
/sub>
/CO molar ratio increased with the increase of H<
sub>
2<
/sub>
O/CH<
sub>
4<
/sub>
molar feed ratio, which are consistent with the trends predicted by thermodynamic equilibrium calculations. Finally, the results indicate that the NiMg/Ce<
sub>
0.6<
/sub>
Zr<
sub>
0.4<
/sub>
O<
sub>
2<
/sub>
catalyst pellets are promising for commercial scale applications.