NOVELTY - Organized assembly based on superposed layers of materials of similar chemical nature comprises a dense layer (CD1) (porosity less than 5 vol.%), a porous layer (CP1) (porosity 20-80 vol.%) and a catalytic layer (CC1) to form assembly having successive layers (CC1), (CD1) and (CP1) and optionally a second porous layer (CP2) (porosity 20-80 vol.%) between (CC1) and (CD1). At least two of the chemical elements of adjacent layers are identical and one element is different.    USE - In reactor for the production of synthesis gas by the oxidation of natural gas (claimed).    ADVANTAGE - The assembly improves the catalytic process by providing continuity of the thermomechanical and thermochemical properties over the entire perovskite catalytic membrane reactor (PCMR); reduces the risk of debonding or cracking at the interfaces or within a layer is reduced; limits forming operations, as the expansion coefficients and the shrinkage at sintering of the various materials are similar, thus reducing the manufacturing cost of the PCMR.    DETAILED DESCRIPTION - Organized assembly based on superposed layers of materials of similar chemical nature comprises either:    (a) a dense layer (CD1) with a thickness (ED1), and having porosity less than 5 vol.%;    (b) a porous layer (CP1) with a thickness of (EP1), and volume porosity of 20-80%, adjacent to the dense layer (CD1); and    (c) a catalytic layer (CC1) capable of promoting the reaction of partial oxidation of methane by gaseous oxygen to carbon monoxide and hydrogen so as to constitute an assembly (E1) having three successive layers (CC1), (CD1), (CP1); or (CD1), (CP1), (CC1), and a second porous layer (CP2) having volume porosity of 20-80% inserted between (CC1) and (CD1).    At least two of the chemical elements of adjacent layers are identical and one element is different. The dense layer (CD1) comprises a material (AD1) having (in vol.%):    (i) a compound (C1) (75-100) selected from doped ceramic oxides which, at the use temperature, are in the form of a crystal lattice with oxide ion vacancies of perovskite phase, of formula (Ma)1-x-u(Ma1)x(Ma2)u(Mb)1-y-v(Mb1)y(Mb2)vO3-w (I);    (ii) a compound (C2) (0-25), which differs from compound (C1), selected from either oxide-type materials such as boron oxide, aluminum oxide, gallium oxide, cerium oxide, silicon oxide, titanium oxide, zirconium oxide, zinc oxide, magnesium oxide or calcium oxide (preferably magnesium oxide, calcium oxide, aluminum oxide, zirconium oxide, titanium oxide or ceria); strontium-aluminum mixed oxides (SrAl2O4 or Sr3Al2O6); barium-titanium mixed oxide (BaTiO3); calcium-titanium mixed oxide (CaTiO3); aluminum and/or magnesium silicates, such as mullite (2SiO2.3Al2O3), cordierite (Mg2Al4Si5O18) or the spinel phase MgAl2O4; calcium phosphates and their derivatives, such as hydroxylapatite Ca10(PO4)6(OH)2 or tricalcium phosphate Ca3(PO4)2; or materials of the perovskite type, such as La0.5Sr0.5Fe0.9Ti0.1Od, La0.6Sr0.4Fe0.9Ga0.1Od, La0.5Sr0.5Fe0.9Ga0.1Od or La0.6Sr0.4Fe0.9Ti0.1Od; or materials of the non-oxide type, preferably selected from carbides or nitrides such as silicon carbide (SiC), boron nitride (BN), aluminum nitride (AlN) or silicon nitride, sialons (SiAlON), or from nickel, platinum, palladium and/or rhodium; metal alloys; and    (iii) a compound (C12) (0-2.5) produced from at least one chemical reaction of formula (Ia).    The porous layer (CP1) comprises a material (AP1) having (in %) (ia) a compound (C3) (75-100) selected from doped ceramic oxides which, at the use temperature, are in the form of a crystal lattice having oxide ion vacancies of perovskite phase, of formula (Mc)1-x-u(Mc1)x(Mc2)u(Md)1-y-v(Md1)y(Md2)vO3-w (II); (iia) a compound (C4) (0-25) which differs from compound (C3), and selected from (ii); and (iiia) a compound (C34) (0-2.5) produced from at least one chemical reaction represented by the equation (IIa).    The catalytic layer (CC1) comprises a material (AC1) having (vol.%): (ic) a compound (C5) (10-100) selected from doped ceramic oxides which, at the use temperature, are in the form of a crystal lattice having oxide ion vacancies of perovskite phase, of formula (Me)1-x-u(Me1)x(Me2)u(Mf)1-y-v(Mf1)y(My2)vO3-w (II); (iic) a compound (C6) (0-90), which differs from compound (C5), selected from nickel, iron, cobalt, palladium, platinum, rhodium and/or ruthenium, optionally deposited on an oxide or non-oxide ceramic support in an amount of 0.1-60 wt.% of the metal. The ceramic supports are selected from (ii) (other than gallium oxide, strontium-aluminum mixed oxides (SrAl2O4 or Sr3Al2O6), barium-titanium mixed oxide (BaTiO3)) and calcium-aluminum mixed oxide; (and iiic) a compound (C56) (2.5) produced from at least one chemical reaction represented by the equation (IIIa).    The (CP2) comprises material (AP2) having (vol.%) (id) a compound (C7) (75-100) selected from doped ceramic oxides which, at the use temperature, are in the form of a crystal lattice having oxide ion vacancies of perovskite phase, of formula (Mg)1-x-u(Mg1)x(Mg2)u(Mh)1-y-v(Mh1)y(Mh2)vO3-w (IV); (iid) a compound (C8) (0-25), which differ from (C7) and selected from (ii); and (iiid) a compound (C78) (0-2.5) produced from at least one chemical reaction of equation (IVa). Ma-Ma2, Mb-Mb2, Mc-Mc2, Md-Md2, Me-Me2, Mf-Mf2, Mg-Mg2 and Mh-Mh2 each respectively differs from one another.    Ma, Ma1, Mc, Mc1, Me, Me1, Mg and Mg1 = scandium, yttrium, lanthanides, actinides or alkaline-earth metals;    Ma2, Mc2, Me2 and Mg2 = aluminum, gallium, indium, thallium or alkaline-earth metals;    Mb, Md, Mf and Mh = transition metals;    Mb1, Md1, Mf1 and Mh1 = transition metals, aluminum, indium, gallium, germanium, antimony, bismuth, tin, lead or titanium;    Mb2, Md2, Mf2 and Mh2 = transition metals, alkaline-earth metals, aluminum, indium, gallium, germanium, antimony, bismuth, tin, lead or titanium;    x and u = 0-0.5;    x+u = less than or equal to0.5;    y, v and y+v = 0-0.9;    w = value selected so that the structure is electrically neutral;    Fc1 = raw formula of compound (C1);    Fc2 = raw formula of compound (C2);    Fc12 = raw formula of compound (C12);    x1, y1 and z1 = greater than or equal to0;    d = 3-delta;    F3 = raw formula of compound (C3);    Fc4 = raw formula of compound (C4);    Fc34 = raw formula of compound (C34);    F5 = raw formula of compound (C5);    Fc6 = raw formula of compound (C6);    Fc56 = raw formula of compound (C56);    F7 = raw formula of compound (C7);    Fc8 = raw formula of compound (C8); and    Fc78 = raw formula of compound (C56).    An INDEPENDENT CLAIM is also included for a reactor.