NOVELTY - Catalytically reforming a reactant gas mixture involves providing reactant gas mixture containing hydrocarbons and an oxidant; providing pyrochlore material catalyst comprised of at least one pyrochlore having specific composition; contacting the reactant gas mixture with the pyrochlore material catalyst; and maintaining the reactant gas mixture and the pyrochlore material catalyst at conditions of temperature, pressure and gas flow rate during the contacting to promote catalytic reforming process and produce gaseous mixture comprised of at least hydrogen and carbon monoxide.    USE - For catalytically reforming a reactant gas mixture (claimed).    ADVANTAGE - The method greatly reduces the metal sintering that typically occurs on supported catalysts used in reforming reactions, and reduces deactivation by sulfur and carbon. Also the method enhances oxygen mobility by elemental exchange of promoters at sites in the pyrochlore; minimizes catalytically active metal migration to the surface, leading to the formation of a supported metal catalyst; and improves the lattice oxygen mobility. The pyrochlore catalyst material is utilized in catalytic reforming reactions for the conversion of hydrocarbon fuels into synthesis gas (H2+CO) for fuel cells. By using the pyrochlore material catalyst the method exhibits stable performance under the reaction conditions utilized for catalytic partial oxidation (CPOX), steam reforming (SR), dry reforming (DR), and oxidative steam reforming (OSR).    DETAILED DESCRIPTION - Catalytically reforming a reactant gas mixture, involves providing reactant gas mixture containing hydrocarbons and an oxidant; providing pyrochlore material catalyst comprised of at least one pyrochlore having the composition A'2-w-x(A1)w(A2)xB'2-y-z(B1)y(B2)zO7-d; contacting the reactant gas mixture with the pyrochlore material catalyst; and maintaining the reactant gas mixture and the pyrochlore material catalyst at conditions of temperature, pressure and gas flow rate during the contacting to promote catalytic reforming process and produce gaseous mixture comprised of at least hydrogen and carbon monoxide.    A'=trivalent ion of an element selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, Lu, Bi, Sc, Y, In, or Tl;    A1=trivalent ion of an element selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, Lu, Bi, Sc, Y, In, or Tl;    w, x, y and z=0-1;    A2=divalent ion selected from Mg, Ca, Sr, or Ba;    x=0-1;    B'=tetravalent ion of an element selected from Ti, Cr, Mn, Zr, Mo, Tc, Rh, Pd, Hf, Os, Ir, Pt, Si, Ge, Sn, or Pb;    B1=trivalent ion or tetravalent ion of an element selected from Mo, Fe, Os, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Re or V;    B3=divalent ion, trivalent ion, or tetravalent ion of an element selected from Mg, Ca, Sr, Ba, Y, Ce, Re, Cr, Ti, Zr, Hf, Ni, Co, V, or Mo;or    y+z=less than 1;and    d=number that renders the composition charge neutral.    The average ionic radius ratio of ions in A', A1 and A2-site holding 8-fold coordination with oxygen to ions in B', B1 and B2-site holding 6-fold coordination with oxygen, is 1.46-1.80.