Study On Recovery Of Ru And Zr From Catalysts For Selective Hvdrogenation Of Benzene

As the high selectivity of ruthenium catalysts was discovered, the process of selective hydrogenation of benzene to cyclohexene over ruthenium catalyst is the new industrial method to obtain cyclohexene owing to its atomic economy and clean production of green chemistry. Due to the scarcity of resources, it is very significant to study on the recovery of valuable metals ruthenium and zirconium from deactivated catalysts in industrial application an in theory field. However, the recovery of deactivated catalysts is only aiming at reclaiming the precious ruthenium, and the method of alkali fusion-oxidation distillation is very dangerous. In view of the problems, a novel recycling process of Ru and Zr is proposed in the present paper for comprehensive recovery and utilization of Ru and Zr. The major research content and conclusions are as follows.By thermodynamic calculation, the possible products and theirs transformation were investigated in the decomposition process of zirconium dioxide with sodium bisulfate, and the equilibrium compositions of the reactions were calculated by HSC thermodynamic calculation software. The primary thermodynamic calculation indicated that the rise of temperature is favorable for the reactions of NaHSO4 and ZrO2 at 100℃-650℃, which equilibrium products are zirconium sulfate and sodium sulphocompound. The existing form of sodium sulphocompound is related to the raw materials ratio of zirconium dioxide and sodium bisulfate and reaction temperature. Effects of reaction temperature, zirconium dioxide to sodium bisulfate molar ratio and time were studied to determine the best technological conditions:temperature at 300℃-600℃ NaHSO4/ZrO2 molar ratio of 5-7, time of 40min. All zirconium dioxide could be decomposed under this conditions. The process of the leaching of zirconium was studied by comparing the effects of stirring intensity, liquid to solid ratio, leaching temperature and time. The results show the optimum leaching conditions:stirring speed 100rpm, liquid to solid ratio 4:1, leaching temperature 40℃, time of 6 min. The zirconium product conforms to Chinese standard of zirconium oxychloride for industrial use.Two processes of alkali fusion and reduction precipitation of ruthenium ion were studied. Effects of the types of alkali fusion reagents, reaction temperature and time were studied, and the optimum conditions were:Na2O2 as alkali-fusion agent, reaction temperature 650 ℃, time of 3 h. One fused rate of ruthenium is able to achieve 83.5% under the optimum conditions. In view of chemical property that the ruthenium contained alkaline solution will availably convert into dark brown precipitate and achieve easily the recovery of ruthenium to Ru(OH)4, the process of the reduction precipitation of ruthenium ion was studied. The results showed that:when the amount of ethanol for reducing agent is 8 times of theoretical amount, the reaction temperature of 30 ℃, the time of 90min, the ruthenium ion was almost completely precipitated. The ruthenium product conforms to Chinese standard of ruthenium chloride for industrial use.