Research On Comprehensive Recovery Process Of Spent Platinum Catalyst

In recent years,with the development of China's petroleum and chemical industry,the use of platinum catalyst has been increasing year by year.In the process of use,the catalyst will gradually lose its catalytic activity due to carbon deposition,sintering and other reasons,so it needs to be replaced regularly.The abandoned catalyst is rich in platinum resources,which is much higher than the content of platinum in China's associated minerals.The spent catalyst has a high recovery value.In view of the disadvantages of the traditional wet recycling process,such as the high toxicity of oxidants,the complex preparation of platinum,and the low degree of comprehensive utilization,this thesis takes the spent platinum catalyst to be landfilled by a hazardous waste disposal company as the research object and carries out the roasting and decarbonization of the waste catalyst,Oxidative leaching,extraction,electrodeposition to prepare platinum experimental research,the specific research content and results are as follows:(1)The carbon in waste catalyst surface area was removed by air roasting.The influence of raw material size,roasting temperature and roasting time on weight loss rate was investigated by single factor experiment.The optimal roasting conditions were as follows:natural particle size,roasting temperature at 650?,roasting time at 1.5 h.The weight loss rate of raw materials is 14.9%.(2)Platinum was extracted by hydrochloric acid leaching.The optimum extraction conditions were hydrochloric acid concentration of 3mol/L,NaClO₃ addition amount of 6 ml,liquid-solid ratio of 8:1,reaction temperature of 90?,reaction time of 90 min,the leaching rate of Ptis 99.5%(3)TOA was used to extract PtCl₆^2-,and the effects of different process parameters on extraction and reverse extraction were investigated by single factor experiment.The results showed that?-branched primary alcohol as the modifier could effectively eliminate the third phase in the extraction process.The optimal extraction conditions were as follows:solid liquid[H⁺]=0.5 mol/L,TOA volume fraction of 10%,?-branched primary alcohol volume fraction of5%,extraction ratio(V_O:V_A)of 1:1,Ptand Ni extraction rates of 99.6%and 0.2%.The platinum carrying organic phase was washed by dilute HCl and stripped with 0.2mol/L Na OH solution for 3 times.The Ptstripping rate up to 99.8%.After acidification and concentration,the main components of the stripping solution are Na₂PtCl₆ and NaCl,and the impurity content is low.It can be used for electrodeposition to produce platinum electrolyte.(4)P507 was used to separate Al³⁺,and the influence of different process parameters on extraction and stripping was investigated by single factor experiment.The optimal extraction conditions were pH=1.5,saponification rate of P507 of 50%,extraction ratio(V_O:V_A)of 1:1,the extraction rates of Al³⁺,Mg²⁺and Ni²⁺were 99.3%,1.2%and 0.5%,The aluminum-carrying organic phase is back-extracted with 5 mol/L H₂SO₄,and the back-extraction rate of Al³⁺reaches 98.5%.After the stripping liquid is evaporated and crystallized,the product obtained is Al₂(SO₄)₃·14H₂O,and the quality meets the requirements ofClass I products in HG/T 2225—2010.(5)The electrodeposition process of PtCl₆^2-was studied by linear sweep voltammetry.The research results show that the apparent activation energy of PtCl₆^2-electrodeposition is greater than 16 k J/mol,which is mainly controlled by electrochemical reaction.Using the purified Na₂PtCl₆ solution as the electrolyte,the metal platinum was prepared by the constant voltage deposition method,and the influence of stirring,voltage,and electrolyte temperature on the platinum recovery rate was investigated through single factor experiments.The best electrodeposition process conditions are low speed stirring,voltage of 2.0 V,electrolyte temperature of 50?,platinum recovery rate can reach 99.5%.The electrodeposited product is smooth,and the purity of Ptis 99.98%.Through cost-benefit estimation,the direct production profit can reach 1,100 yuan with the complete process developed to treat 1 kg of spent platinum catalyst.The recovery of platinum from spent catalysts is a key factor for producing better economic benefits.