This invention provides a multinary solid solution fine particle represented by Pd.sub.xRu.sub.yM.sub.z (M is at least one member selected from the group consisting of Rh, Pt, Cu, Ag, Au and Ir. x+y+z=1, x+y=0.01 to 0.99, z=0.99 to 0.01, x:y=0.1:0.9 to 0.9:0.1), a method for producing the same, and a supported catalyst.

The invention relates to a noxious gas purificant and its preparation and purification method for removing nitrogen oxides from gas streams thereof. The preparing method is characterized in that: mixing, according to a predetermined ratio and a process, a salt of iron, manganese, cobalt, or copper, and a related derivative thereof, an alkali or alkaline substance and a related derivative thereof, water and a forming agent, so as to obtain a solid compound or mixture; drying and activating the solid compound or mixture to produce a solid product as the purificant; and introducing the purificant into a gas-solid reactor, and removing noxious gases in a gas stream by performing, in a preconfigured temperature and using the purificant, a gas-solid reaction on the harmful gases in the gas stream. The purificant can be recycled and reused.

A flue-gas purification system includes a flue-gas cycling system, a reactor, and an absorbent adding system having at least a catalytic absorbent, wherein the catalytic absorbent is being gasified for reacting with the flue-gas in the reactor in a homogenous gas-gas phase reacting manner. Therefore, the purification system has fast reaction rate between the pollutants of the flue-gas and the catalytic absorbent, which is preferably ammonia, to efficiently remove pollutants, so as to effectively purify the flue-gas.

The invention relates to a noxious gas purificant and its preparation and purification method for removing nitrogen oxides from gas streams thereof. The preparing method is characterized in that: mixing, according to a predetermined ratio and a process, a salt of iron, manganese, cobalt, or copper, and a related derivative thereof, an alkali or alkaline substance and a related derivative thereof, water and a forming agent, so as to obtain a solid compound or mixture; drying and activating the solid compound or mixture to produce a solid product as the purificant; and introducing the purificant into a gas-solid reactor, and removing noxious gases in a gas stream by performing, in a preconfigured temperature and using the purificant, a gas-solid reaction on the harmful gases in the gas stream. The purificant can be recycled and reused.