Research On Platinum Group Precious Metal Recovery Of Nitrobenzene Hydrogenation Catalyst

Aniline tar are the by-products in the nitrobenzene hydrogenation reaction,contains a spot of platinum group precious metal catalyst.Currently there is no available recycling programs for the tar,due to recovery difficulty.Not only causes waste of resource,but increases environmental pollution.So the recovery of precious metals has considerable economic value and significant resource utilization.Bases on characteristics of platinum group precious metal,we propose a environment friendly,simple to operate,economize on investment and high yield technical curse for the reclaim of precious metals.The optimal parameters are obtained by the single factor and orthogonal experiment.Main results for this study are as follows:(1)By contrast two methods of separation filtration and centrifugation,determined the best collection method and process conditions of noble metal catalyst.The best conditions with ethyl alcohol as solvent,the ratio of liquid and solid 0.9:1,the temperature of 25 ?,the centrifuga speed of 6500 r/min,the centrifugal time of 4 min.At this time,The recovery rate of the catalyst is 99.69%.(2)Precious metals concentrating by the fire concentration method and the wet leaching method.The optimum incineration conditions are determined.Control the aniline tar in platinum group precious metal catalyst was about 35%,the temperature of 700 ?,the time of 2.5 h.Reduction of incineration ash by formic acid.Aqua regia is applied for leaching of fine ash.At this point,the extraction rate of Pd can reach 96.8% and Pt 95.3% for one timer.The leaching rate of Pt and Pd on two run can come up to 99.5%.(3)Separating base metals by two stage ion exchange method.The optimum adsorption conditions are determined: anion exchange resin of D201,the temperature of 40 ?,the flow rate 1.5 mL/min,the time of 110 min,Pt and Pd adsorption rate are 100%.The optimum desorption conditions are determined: ammonia(5%)are regarded as the best strippant,the flow rate 0.2 mL/min,the temperature of 60?,the time of 140 min.The both Pt and Pd desorption rate is more than 90%.The deuterium content in the desorption solution is 0.04%.(4)The use of ammonium chloride for precipitate the platinum.When the solution is pH=1,the precipitation rate of platinum is 99.24%.We would form precipitates by adding ammonium hydroxide and hydrochlor-ic acid.The precipitation rate of palladium can reach 98.75%.Hydrazine hydrate reduction was presented,the purity of product sponge platinum is 99.07% and sponge palladium is 99.26%.After three purification,the purity of sponge platinum and palladium reached 99.95%.The experimental results show that the recovery rate and purity of precious metal with this method was high.And there are high economic returns.