Study On RutheniumRecoveryfrom Spent Ruthenium Catalysts

Ruthenium is widely used in various catalytic reactions due to its special chemical properties and low price compared with other platinum group metals.Also,Ruthenium is one of the least abundant metals in the earth’s crust,making it extremely difficult to extract ruthenium from mineral resources.Therefore,it is of great significance to study the recovery of ruthenium from the spent catalysts.Compared with other platinum group metals,platinum and palladium,ruthenium is insoluble in aqua regia and its valence state is complex and variable,so it is more difficult to recover ruthenium from the spent catalysts.Based on the analysis of thermodynamics,this paper uses the alkali melt and the alkali melt oxidation distillation process,and the preparation of ruthenium trichloride from the spent catalysts was studied.The following conclusions were obtained:(1)The effects of the choice of alkali flux,alkali melting temperature and alkali melting time on the ruthenium leaching rate in the process of alkaline melting the spent catalysts containing ruthenium after calcination were systematically studied.It was found that the choice of alkali flux had the most significant effect,followed by alkali melting temperature and alkali melting time.The optimal technological parameters of alkali melting Ruthenium were obtained as follows:KOH/KClO3 was used as alkali-flusion reagent,and the optimal dosage of alkali-flusion was 10 times of theoretical dosage.The alkali-flusion reaction temperature was 700℃,and the alkali fusion reaction time was 2.5h.Under that condition,the primary alkali-flusion rate of ruthenium can reach 91%.(2)The process of preparing ruthenium trichloride from alkaline slag leaching solution by precipitation reduction and evaporation crystallization was studied.Through the thermodynamic analysis of the E-pH diagram of Ru-H2O,it was found that under alkaline conditions,RuO4-and RuO42-are easily reduced to Ru(OH)4 precipitation with anhydrous ethanol as reducing agent.When the reaction temperature is normal temperature,the reaction time is 60 min,and the amount of anhydrous ethanol is 12 times of the theoretical amount,the ruthenium precipitation rate is higher.The mass fraction of Ruthenium in the evaporative crystallized RuCl3·xH2O crystalt is 30.3%,which is lower than the theoretical value,and there are other impurities.(3)Using H2SO4-NaCl3 system to carry out oxidation distillation of aqueous solution of alkaline molten slag,the effects of oxidation distillation temperature,oxidation distillation time and dosage of oxidant on the recovery of ruthenium were studied.The results showed that the optimum conditions were as follows:distillation temperature was 95℃,distillation time was 5 h,the dosage of NaClO3 solution was 30 mL.The recovery of ruthenium can reach 93%under these conditions.In the preparation of the RuCl3·xH2O,the ruthenionic quality score was 36.1%,which was consistent with the theoretical value and the amount of impurities was less.The recovery of spent catalyst containing ruthenium by alkali fusion-precipitation reduction and alkali fusion-oxidation distillation was compared comprehensively.It was found that the primary recovery of ruthenium of the former was 81.9%.The RuCl 3·xH 2 O prepared contains Ca,K,A1 and other impurities.The ruthenium primary recovery of the latter was 93.2%,and the impurity content of the prepared RuCl3·xH2O was low.