Catalyst for methanation of carbon oxides, preparation method of the catalyst and process for the methanation
Disclosed is a catalyst for methanation reaction producing methane with high conversion by reaction of hydrogen with carbon dioxide, or a gas mixture of carbon dioxide and carbon monoxide, or a gas mixture containing these compounds as the main components. The catalyst is prepared by the steps of mixing (A) aqueous zirconia sol with salts of (B) stabilizing element(s), which is selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca and Mg, and (C) iron group element(s), drying and calcining the mixture to obtain a catalyst precursor, and subsequent reduction of the precursor. The catalyst comprises, by atomic %, A: 18-70%, B: 1-20% and C: 25-80% based on the elemental states of the metals. The catalyst is characterized by multiple oxide of tetragonal zirconia structure, in which not only the stabilizing element(s) but also a part of the iron group element(s) is incorporated, and on which the iron group element(s) in the metallic state is supported.
1. A catalyst for methanation reaction producing methane by hydrogenating carbon dioxide, carbon monoxide or a mixed gas containing at least one of them as the main components, consisting of, based on the metals in the elemental state:
A) Zr for providing tetragonal zirconia supporter: 18-70 atomic %,
B) one or more of tetragonal zirconia-stabilizing element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca and Mg (in case of two or more are used, in total): 1-20 atomic %, and
C) at least one of the iron group elements being supported on the tetragonal zirconia supporter and acting as the active site: 25-80 atomic %;
wherein the catalyst is made by mixing aqueous zirconia sol, aqueous solution of the stabilizing element or elements, and aqueous solution of the iron group element or elements in a ratio such that the atomic % requirements for Zr, the zicronia-stabilizing element, and the iron group element are satisfied; concentrating the mixture to dry and calcining; and then subjecting to reducing treatment to form the catalyst;
wherein the stabilizing element or elements and a portion of the iron group element or elements are incorporated in the tetragonal zirconia supporter; and
wherein the iron group element or elements not incorporated in the supporter are supported on the supporter in the metallic state.
2. The catalyst for methanation reaction according to claim 1 , wherein the iron group element acting as the active site is Ni.
3. The catalyst for methanation reaction according to claim 1 , wherein the iron group elements acting as the active site are Ni and one or both of Co and Fe, provided that Ni shares 0.6 or more based on the atomic ratio.