Method of preparing catalyst for low-temperature synergistic catalytic purification of NOx and HCN in flue gas, and use thereof

A method of preparing a catalyst for low-temperature synergistic catalytic purification of NOx and HCN in flue gas, comprising the following specific steps:

• (1) dissolving an active metal salt in deionized water to obtain a metal salt solution, wherein the active metal salt is two or more of a lanthanum salt, a cobalt salt, an aluminum salt, a copper salt, an iron salt, a manganese salt, a cerium salt, a nickel salt and a niobium salt;
• (2) dissolving citric acid in ethanol under stirring to obtain a citric acid/ethanol solution;
• then adding tetrabutyl titanate into the citric acid/ethanol solution, mixing uniformly, and reacting for 20-30 min to obtain a tetrabutyl titanate-citric acid/ethanol solution;
• (3) adding glacial acetic acid dropwise into the tetrabutyl titanate-citric acid/ethanol solution of the step (2) under stirring to react for 30-40 min to obtain a solution A;
• (4) adding the metal salt solution of the step (1) dropwise into the solution A of the step (3), mixing uniformly and adding nitric acid, then adding ammonium hydroxide dropwise to adjust the pH value of the system to 3-5 or 9-11, and rising the temperature at a constant speed until the temperature is 70-80° C. to obtain a gel B;
• and
• (5) subjecting the gel B of the step (4) to a constant-temperature treatment under a condition of a temperature of 90-110° C. for 2-3 days, then baking under a condition of a temperature of 300-500° C. for 3-4 h in a furnace, cooling in the furnace, pulverizing, tableting, and sieving to obtain a catalyst M-N/TiO2 for low-temperature synergistic catalytic purification of NOx and HCN in the flue gas, wherein M-N is two or more metal oxides of active metals lanthanum, cobalt, aluminum, copper, iron, manganese, cerium, nickel and niobium.