Method for preparing solid ruthenium nitrosyl nitrate

A method for preparing solid ruthenium nitrosyl nitrate, the method comprising the following steps:

• 1) drying a ruthenium-containing spent catalyst, calcining the spent catalyst at a temperature of between 300 and 500° C. for between 2 and 4 hours, and cooling to room temperature, whereby yielding a calcined ruthenium-containing solid;
• 2) grinding the calcined ruthenium-containing solid obtained in step 1) to yield a powder, introducing the powder to a fluidized bed reactor, aerating the fluidized bed reactor with nitrogen or an inert gas for between 0.5 and 2 hours, charging hydrogen, heating the fluidized bed reactor to a temperature of between 100 and 600° C. for a reduction reaction, whereby yielding ruthenium metal;
• 3) contacting a mixed gas of ozone and air with the ruthenium metal obtained in step 2), allowing the mixed gas and the ruthenium metal to react at a temperature of between 600 and 650° C., whereby yielding gaseous ruthenium tetroxide;
• 4) introducing the gaseous ruthenium tetroxide obtained in step 3) into a three-stage absorption plant comprising a nitrite acid solution, whereby yielding an acid solution comprising ruthenium nitrate;
• 5) adding a solid of sodium nitrite to the acid solution comprising ruthenium nitrate obtained in step 4), stirring, and heating a resulting solution in the state of micro-boiling reflux, whereby yielding a solution of ruthenium nitrosyl nitrate;
• and
• 6) extracting the solution of ruthenium nitrosyl nitrate obtained in step 5) with anhydrous ether, collecting and evaporating an extraction solution for removal of ether, whereby yielding a solid ruthenium nitrosyl nitrate.