Preparation Of Nano Cerium Oxide By Impingement Streamrotating Packed Bed And Its Catalytic Performance

Nano cerium oxide is a rare earth oxide with unique physical and chemical properties,which is widely used in catalysts,catalyst supports,polishing,etc.The industrial preparation of nano cerium oxide mainly uses stirred tank reactors,since the micro-mixing time of the stirred tank reactor is much longer than the nucleation induction time of the precipitation reaction,the nucleation and growth of the precipitation are in an extremely uneven environment,resulting in the prepared the particle size distribution of the product is not uniform.Impinging stream-rotating packed bed（IS-RPB）combines the advantages of impinging stream reactor and rotating packed bed.The contact mixing and mass transfer of the two liquids are fast and uniform,and the micro-mixing time is much shorter than the precipitation nucleation induction time.Nucleation and growth are in a uniform microenvironment,which is beneficial to the preparation of nanomaterials with small particle size,narrow particle size distribution and good dispersion.Rhodamine B is a kind of refractory dye wastewater,but its degradation efficiency is not high by using ferric tetroxide to catalyze persulfate degradation.To improve catalyst efficiency,two or three catalysts can be compounded to synergistically catalyze.Therefore,in this paper,impinging stream-rotating packed bed was used to strengthen the preparation of nano cerium oxide,and by adjusting the reaction conditions,the controllable preparation of nano cerium oxide with small particle size,narrow distribution and not easy to agglomerate can be achieved.A new method was explored for the industrial production of nano cerium oxide.And in view of the poor effect of ferric oxide catalyzing persulfate to degrade rhodamine B wastewater,preparation of Fe₃O₄/Ce O₂ catalyst with improved catalytic efficiency.Firstly,the effects of ammonium bicarbonate concentration,precipitation temperat-ure,liquid flow rate,high gravity factor,aging temperature and aging time on product particle size during the preparation of precursor were investigated.The experimental results show that the lower the concentration of ammonium bicarbonate is,the smaller the particle size and the narrower the particle size distribution of nano cerium oxide.With the increase of precipitation temperature,liquid flow rate,high gravity factor,aging time and aging temperature,the particle size of nano cerium oxide first decreases and then increases,and the particle size distribution first narrates and then widens.The optimum technological conditions are as follows:sodium bicarbonate concentration 50 g/L,precipitation temperature 90℃,liquid flow 20 L/h,high gravity factor 92,aging temperature 30℃,aging time 1 h.The average particle size of nano cerium oxide is 68 nm,and the particle size is uniform.Secondly,the effects of calcination temperature and calcination time on the particle size and morphology of the product during the calcination process of the precursor were explored.It is found that with the increase of calcination temperature and calcination time,the particle size of the product first decreased and then increased.When the calcination temperature is 650℃and the calcination time is 1.5h,the particle size of the prepared products is small and uniform,the average particle size is 68 nm,and the morphology is spherical.Compared with agitated reactor,impinging stream reactor and high gravity reactor,the nano cerium oxide prepared by impinging stream-rotating packed bed has small particle size,uniform particle size distribution,and is not easy to agglomerate.Finally,the Fe₃O₄/Ce O₂ catalyst was prepared with nano cerium oxide as the carrier,and its performance in catalyzing the degradation of rhodamine B wastewater by persulfate was investigated.The results show that compared with Fe₃O₄ catalyst,the catalytic efficiency of Fe₃O₄/Ce O₂ increases from 87.13%to 99.97%,and the catalytic effect increases by 12.84%.At the same time,the cycle experiments show that the Fe₃O₄/Ce O₂ catalyst has high stability and reusability.