JPS6247054B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a solid electrolyte membrane capable of separating hydrogen, and a method for separating hydrogen from a hydrogen-containing gas using the solid electrolyte membrane. Conventionally, regarding hydrogen separation using inorganic membranes,
Various metal alloy membranes are known, particularly palladium-silver alloy membranes, which are used for separation and purification of hydrogen produced by petroleum cracking. In hydrogen separation using such an alloy membrane, if other gases contained in the hydrogen-containing gas, such as oxidizing or reducing gases such as oxygen, sulfur, and halogens, are present at high temperatures, the metal surface The hydrogen decomposition ability changes due to the action of such gases, and when used for a long time, it gradually deteriorates and eventually ceases to function. In particular, in the production of hydrogen by thermochemical decomposition of water, which has recently been expected to be put to practical use, it is industrially difficult to use the alloy membrane described above to separate and purify hydrogen from the obtained hydrogen-containing gas at high temperatures. It is. Therefore, if a stable separation membrane that has a high selective hydrogen decomposition ability and can separate by a simple method could be provided, it would have great industrial value. Therefore, the following conditions are required for the material used as this type of separation membrane. That is, (1) high selective hydrogen permeability; (2) No deterioration due to oxidizing gas, etc. (3) Can be used at high temperatures of 800℃ or higher. (4) It can be separated by a simple method. As a result of our search for a substance with such properties, the present inventors discovered that Perot is an oxide containing strontium and cerium as main components and a certain other metal, and forms a skite-type crystal. It was found that oxides have excellent hydrogen gas decomposition ability and have the above-mentioned properties as a separation membrane, and the present invention was achieved. That is, the present invention is based on a perovskite metal oxide formed from an oxide of at least one metal selected from the group consisting of (a) strontium, (b) cerium, and (c) scandium, yttrium, neodymium, and zinc. It is a solid electrolyte membrane that has hydrogen ion and electron conductivity in an atmosphere where at least hydrogen is present, and that hydrogen and other gases are mixed at a temperature of 100 to 1400°C through such a solid electrolyte membrane. This is a method of separating hydrogen from gas. The solid electrolyte membrane of the present invention has the above-mentioned (a)
It is believed that the metal oxides of component (b) and component (c) form a solid solution with each other, thereby providing hydrogen ion and electron conductivity. In other words, in such a solid solution, P-type electronic conductivity appears due to the generation of electron holes, and when hydrogen atoms enter the solid solution as hydrogen ions, the emitted electrons are canceled out by the electron holes. Hydrogen selectively permeates through the solid diaphragm due to the local battery phenomenon, and becomes a so-called mixed conductor in which hydrogen ions can move in the solid solution and electrons can also move through the remaining electron holes. It is considered possible. The phenomenon of selective permeation of specific gases and permeation of hydrogen ions through metal oxides based on such principles is known, for example, in Bi-Mo solid electrolyte membranes and La-Y solid electrolyte membranes, but this is not the case in this study. The solid electrolyte membrane according to the invention has hydrogen permeability that is 10 times higher than that of these known membranes. The solid electrolyte forming the solid electrolyte membrane in the present invention includes (a) strontium, (b) cerium, and
(c) A perovskite-type oxide formed from an oxide of at least one metal selected from the group consisting of scandium, yttrium, neodymium, and zinc. (a) Strontium and (b) cerium contained in the oxide are each contained as metal atoms per total metal atom.
It is 30 to 70 mol%, preferably 40 to 60 mol%. The content of (c) at least one metal selected from the group consisting of scandium, yttrium, neodymium and zinc is 0.5 to 25 mol%, preferably 1 to 20 mol%, based on all metal atoms in the oxide. The oxide can be prepared by various methods. One of the methods is to prepare a compound containing each of (a) strontium, (b) cerium, and (c) at least one metal selected from the group consisting of scandium, yttrium, neodymium, and zinc, especially by firing as described below. Compounds that can be converted into oxides, such as strontium oxide, cerium dioxide, scandium oxide, yttrium oxide, etc., or preferably nitrates, carbonates, but also sulfates, phosphates, etc. There is a method of mixing inorganic acid salts, organic acid salts such as acetates and oxalates, halides such as chlorides, bromides, and iodides, or hydroxides in a desired ratio and firing the mixture. Alternatively, a mixed aqueous solution of each of the metal salts or metal alcoholates described above may be prepared by a so-called coprecipitation method, such as hydrolysis with an alkaline aqueous solution such as aqueous ammonia, and then calcined. Furthermore, methods such as oxidizing and firing a mixture or alloy of each metal can be mentioned. In either method, when obtaining the solid electrolyte membrane of the present invention, the firing temperature is usually in the range of 500 to 1500°C, preferably 600 to 1450°C in an oxidizing atmosphere. The solid electrolyte of the present invention may contain metals other than (a) strontium, (b) cerium, (c) scandium, yttrium, neodymium, and zinc, as long as they do not impair the hydrogen ion-electron mixed conductivity of the solid electrolyte. It is acceptable even if it contains impurities. In the present invention, the solid electrolyte membrane may be formed by forming an oxide obtained by the preparation method described above, or by a method that combines the preparation of the oxide and the formation of the film. As a method for forming such a film, for example, a solid material such as a pellet or sheet may be formed by mechanical processing such as cutting or polishing, or a powder may be formed by pressure molding or made into a paste. It may be coated on a porous support and sintered. Furthermore, film forming methods such as a vacuum evaporation method, a reactive sputtering method, a chemical vapor phase evaporation method (CVD method), a chemical spray method, and oxidation of alloy plating can be mentioned. Furthermore, during molding, a filler, a reinforcing material, etc. may be used as necessary, and when the solid electrolyte membrane is used as a gas separation membrane, it may be used alone, or as necessary. It can also be used as a composite membrane using a porous support. Examples of the porous support include porous metal plates or sintered bodies such as stainless steel and bronze, and composites thereof; porous oxide sintered bodies such as porous silica alumina, porous alumina, and porous magnesia;
Examples include sintered nitrides such as boron nitride, sintered carbides such as silicon carbide, and the like. The thickness of the solid electrolyte membrane obtained by the molding method described above is usually
A range of 10 ^-3 to 10 ⁴ μ, preferably 10 ^-3 to ^{10 3} μ is appropriate, and when the solid electrolyte membrane is used as a membrane for hydrogen decomposition, the separated hydrogen must be of particularly high purity. If not required, some ventilation holes may be provided. Since the solid electrolyte membrane of the present invention has hydrogen ion conductivity and electronic conductivity, it can be used as a gas separation membrane that selectively separates hydrogen in a hydrogen-containing gas mixture. For example, airtight chambers are provided on both sides of the solid electrolyte membrane, a gas mixture containing hydrogen gas is supplied to one chamber, and the conditions in both chambers are set such that the hydrogen partial pressure in the other chamber is lower than the hydrogen partial pressure. High purity hydrogen gas can be easily obtained by setting . The temperature at which the solid electrolyte membrane is used as a hydrogen separation membrane is usually 100 to 1400°C, preferably 200 to 1200°C, particularly preferably 400 to 1000°C. The hydrogen separation method of the present invention is effective not only in the process of refining petroleum cracking hydrogen, but also in the purification and separation of hydrogen produced by various thermochemical water splitting processes. Moreover, the solid electrolyte membrane of the present invention was found to have good stability and extremely high hydrogen decomposition ability at high temperatures. The present invention will be described below with reference to Examples, but is not limited thereto. In addition, “part” in the examples
"parts by weight" means "parts by weight". Example 1 3.691 parts of strontium carbonate, cerium dioxide
4.088 parts of scandium oxide and 0.086 parts of scandium oxide were mixed and pulverized and fired at 1430°C for 5 hours.The obtained thin pieces with a diameter of 13 mm and a thickness of 0.1 mm were used as a diaphragm. By introducing a hydrogen-steam mixture gas into one chamber and suctioning the other chamber at 10 torr, it was possible to obtain pure hydrogen gas at a rate of 31 m/hr. Examples 2 to 4 A diaphragm was prepared in the same manner as in Example 1 using a predetermined amount of the compound (c) shown in Table 1 instead of scandium oxide in Example 1, and the amount of hydrogen permeation was measured. are shown in Table 1.

[Table] In Examples 2 and 3 in the table, the amount of cerium dioxide used was 3.873 parts.

Claims (1)

[Claims] 1. A perovskite metal oxide formed from an oxide of at least one metal selected from the group consisting of (a) strontium, (b) cerium, and (c) scandium, yttrium, neodymium, and zinc. A solid electrolyte membrane that is mainly composed of solid materials and has hydrogen ion and electronic conductivity at least in an atmosphere where hydrogen is present. 2. Mainly composed of a perovskite metal oxide formed from an oxide of at least one metal selected from the group consisting of (a) strontium, (b) cerium, and (c) scandium, yttrium, neodymium, and zinc; A method for separating hydrogen from a mixture of hydrogen and other gases at a temperature of 100 to 1400°C via a solid electrolyte membrane having hydrogen ion and electronic conductivity in an atmosphere in which at least hydrogen is present.