Preparing Process of Cerium Acetate and Rare Earth Acetate

JOURNAL OF RARE EARTHSVol. 22, Spec. , Dec. 2004, p. 026Preparing Process of Cerium Acetate and Rare Earth AcetateQiao Jun(乔军)", Ma Ying(马莹), Xu Yanhui (许延辉), Zhang Jun (张军), Chang Shu(常叔), Hao Xianku (郝先库)( Baotou Research Institute of Rare Earth, Baotou 014010, China)Abstract: Preparing process was presented and the influences of concentration of acetic acid, reaction temperature, theratio of cerium carbonate and acetic acid, heat preservation time to the yield of cerium acetate were discussed. The crys-tlline cerium acetate and rare eath acetate such as (La, Ce, Pr, Nd) (Ac), (Ce, Pr, Nd)(Ac),,(Pr, Nd, Er,Y)( Ac), and yttrium acetate were prepared under this condition. The shape ，structure and composition of the crystalswere determined by the methods of SEM, TG-DTA, X-ray diffraction and chemical analysis. The optimum preparedconditions of cerium acetate were described. This prepared process has characteristics such as simple process route, lowcost, high yield, good quality , no pollution to environment, etcKey words: cerium acetate, rare earth acetate, composition; rare earthsCLC number: 0614. 33Document code: AArticle ID: 1002 -0721(2004) -0026 -06Recently, with the development of rare earthwhich means a lot to the development of human benew material applying in the fields of electronic ,ing and the society. Cerium acetate has been studiedchemical industry and environmental protection, theand produced in batch scales in some foreign raredemand of crystalline cerium acetate and rare earthearth enterprises since the early 1980s. There areacetate with high purity and high solubility in watersome product standards of cerium compounds in Ron-in global market is increasing significantly.na Pronc Company in France , the chemist departmentWith the development of the traffic and transpor-of Grace Company in US and Telabah chemist facto-tation, the tail gas emitted by automobiles turned tory in Austria, etc. At that time only Ronna Proncthe atmosphere pollution source that cannot be neg-Company in France had produced cerium compoundlected in the world. At present the automobilessuch as 1000 kg cerium nitrate every batch, 200 kgreached 60 million, and the amount is increasing atcerium sulfate every batch, 500 kg cerium acetate ev-the speed of 5 million every year. These automobilesery batch, etc and the other two companies and Mo-emit 200 million tons of carbon monoxide, 40 mil-lybdenum Company in US, BDH Company in Eng-lion tons of carbon-hydrogen compound and 20 mil-land, EM Company in West Germany have relion tons of nitrides oxygen compound every year ,searched but not formed a scale of batch production.which made up the optical-chemist fume that takeCerium acetate and cerium compounds have been re-form the acid rain and lead to kinds of cancer. Cryssearched in china since 1990s. The preparing processtalline cerium acetate is badly needed by the automo-presented need to be improved because of its low pu-biles tail gas cleansing and its study and producing inrity of product and high cost. The process introducedscale successfully will be contributed to the green en-here firstly uses cerium carbonate with high purity tovironmental protection.prepare cerium acetate，and then condenses it to pro-The oxide-film formed from aluminum has anduce the crytalline cerium acetate. The effects ofexcellent capability of resisting the corrosion. How-concentration of acetic acid, reaction temperature ,ever, in aqueous solution, chromate must be used asthe ratio of cerium carbonate and acetic acid, heata restrainer to avoid corroding in the spots. For manypreservation time are discussed. The optimum prepar-years, people in the profession have endured the tox-ing conditions of cerium acetate and rare earth acetateicity of chromate which is main the factor causingare confirmed. The shape, structure and compositioncancer. Crysalline cerium acetate may completelyof tthe methods oftake the place of chromate to act as a restrainer ,SEM中国煤化工ae ceoemee aTHCNMHGReceived date: 2004 -08 - 10; revised date: 2004 - 10 -28Biography: Qiao Jun (1970 - ), Female , Senior engineerCorresponding author (E一mail: btmaying@ sohu. com)Qiao J et al. Preparing Process of Cerium Acetate and Rare Earth Acetatenalysis. The results show that cerium acetate crystal1.3Synthetic processand rare earth acetate prepared by this process havehigh purity, high rare earth content, big solubility inCertain quantity of cerium carbonate is dissolvedwater along with its big crystal particles and pure col-with nitric acid. The impurities are filtrated before ceri-or. The advantages of low cost and no pollutionum nitrate is precipitated in ammonium bicartbonate tomake this process have potential application in indus-prepare cerium carbonate with high purity. Finally, thetrycerium carbonate is added into acetic acid under certainconcentration of acetic acid and temperature and pre-1 Experimentalserved for some time. Certain quantity of cerium acetatecrystal is separated out after condensed. The first crystal1.1 Raw materials and reagentsis gained after filtrated and the residuum continues be-Cerium carbonate: CeO2/REO≥99. 95%. Lan-ing condensed. The second crystal is gained. Nine crys-thanum oxide，praseodymium oxide, neodymium ox-tals will be gained in tum and the cerium acetate withide，erbium oxide, yttrium oxide: purity ≥99.95% .high purity is prepared after these crystals are filtratedAcetic acid, nitric acid, ammonium bicarbonate, 2" :and aerated for drying. Table 1 shows the chemicalA. R.composition of cerium carbonate of raw materials. Thesynthetic processes are shown in Fig. 1.1.2Methods of analysis2 Results and DiscussionThe concentrations of rare earths are determinedby EDTA titration, the acidities of solutions are titra-2.1 Efects of reaction conditionted by sodium hydroxide neutralization method, theimpurities such as calcium, iron and manganese are2.1.1 Effects of concentration of acetic aciddetermined by AAS, the impurities of rare earths arFig.2 (a) shows the relationship between the concen-analyzed by ICP-MS， the cerium acetate crystaltration of acetic acid and the soluble yield of ceriumshape is figured out by S360 scanning electron micro-carbonate. The cerium carbonate crystal can be dis-scope ( Leica Cambridge, England), TG-DTA testssolved in the dilute acetic acid easily and the solubleare carried out on DT-2A thermal analyzer and its ac-yield is high under the dilute acetic acid with certaincessory TB-2 thermal balance ( Shimadzu, Japan;temperature. The soluble yield increases slowly with theair, 278 K●min~', Al2O3) and X-ray diffractionconcentration. The yield reaches as high as 92% whentests are on PW-1700 automatic powder diffractionhe concentration is 0.5 mol .L '. The optimum con-meter (Philip, Hlland).centration of acetic acid is 1.5~2.5 mol●L-'.Table 1 Chemical composition of cerium carbonate as raw material( % )REOCaOMnO2FeO3SiO2Na2OAL2O3SO2Cl-1048. 80<0. 0050<0.0010 <0050<0.0050 <0. 0050<0.0050<0.0500<0. 0500Eerium carbonate- tissolved with nirate acid-→remove the impurities- 十Filtration→cerium nitrite solution- +[ recipitated with ammonium bicarbonate-十impurities -十abandonedEiltration→pure cerium carbonate disoved with acetic acid ] + erium acetate fee一+ Ccondense and crystal]- firtion p the first crystal (erium acetatathe first mother liguiag十[ condense and crystal - +hiltration t the scond crstal Cerum acetatel中国煤化工. the seor→[ condense and crystal- +iltration- τ the third cHCNMHG_the third mother liquid-◆mix the crystals-回- +btrystaline cerum acetate producFig. 1 Synthetic processes of cerium acetate28JOURNAL OF RARE EARTHS, Vol. 22, Spec. , Dec. 2004100109(9、 [(b)8C706050204060801000.511.522.5Reaction temperaturer cConcentrtion of acetic acid/( mol'L )009080651.3 1.5 1.7 1.9 2.1 2.35 10152025 30Cerium carbonate:acetic acidHeat presevation time/minFig.2 Effects of reaction conditions on preparing process(a) Relationship betweenconcentration of acetic acid and soluble yield; (b) Relationship between reaction temperature and solubleyield; (c) Relationship between raio of cerium carbonate and acetic acid and soluble yicld; (d) Relationship between heat preser-vation time and soluble yield2.1.2 Effects of temperatureFig.2 (b) showstime and the soluble yield. Soluble reaction of ceriumthe relationship between the reaction temperature andcarbonate goes on very quickly in proper condition.the soluble yield. The density of acetic acid in waterThe yield is about 100% in 5 min and then will go a-will decrease with the increasing of reaction tempera-gainst with the increase of the reaction time. Theture. It is favorable to dissolve cerium carbonate.yield will reach to 100% when the reaction lasts forUnder room temperature and the ratio of cerium car15 min. The best heat preservation time is about 10bonate and acetic acid: 1. 7/1, the yield increases~ 15 min.obviously with the increase of the temperature. WhenIt is shown from the resultsx that the ratio of ce-the temperature is 60 C，the yield reaches 95%. .rium carbonate and acetic acid and the reaction tem-The acetic acid is decomposed because of low boilingperature have significant influences on preparingpoint (118.1 C) and this influence will go againstprocess of cerium acetate while the concentration ofthe increasing of dssolve cerium carbonate. The op-acetic acid and the heat preservation time have lightertimum reaction temperature is 60 ~80 C.ones.2.1.3Effects of the ratio of cerium carbonate and2.2 Chemical composition of cerium ace-acetic acidFig.2 (c) shows the relationship be-tate crystaltween the ratio of cerium carbonate and acetic acidand soluble yield. The theoretical calculation quantityThe cerium acetate prepared under the optimumof the ratio is 2.1/1, but the soluble yield is low un-synthesizing, conditions was condensed and for nineder this condition. The yield increases with the de-times中国煤化工nd 3 show theircrease of the ratio. High soluble yield is gained whenchemictMHCNMHGcerium acetatethe ratio is 1. 7/1. It shows that cerium carbonate isentirely dissolved by superfluous acetic acid. Thecrystal with high purity prepared by this syntheticbest ratio is about 1.3/1 ~1.7/1.process has good crystal shape and pure color along2.1.4 Effects of heat preservation timeFig. 2with high rare earth content, high purity, high purity(d) shgye hrelation between the heat preservationof cerium and less impurities of non-rare earths. TheQiaoJ et al.Preparing Process of Cerium Acetate and Rare Earth Acetate29high purity cerium acetate crystal is analyzed by massTable 2 Mass spectrum analysis results of impurities ofspectrum and AAS , and presents the determinate var-rare earths/ %iability: the impurities of non- rare earth decreasesNo. La2O,Pr。OnNd2O3Sm,O3 Y2O3 .with the increasing of crystal time for mother solutionsublimated. The impurities of non-rare earths of the071 0.02000 0.00728 0.01780 0. 002500. 00426upper crystal will increase because of enrichment. Itsquality meets the demand of the international market.Table 3 Analysis of diversified cerium acetate cerystals/%Crystals EREO Fe2O3CaONa2OSiO,C1~_SO:2- Color Shape44.7000.0024 0.00220.0021 0. 00500.010 0.016 White Clubbed46.90 0.00038 0. 0030.0027 0. 00500.010 0.056 White Clubbed46.610.00034 0.00300.0025 0. 00500.010 0.042White Clubbed48.39 0.00023 0. 002050.0018 0. 00500.013 0.045 White Cubbed47.390.00021 0.00420.0034 0. 00500.013 0.04845.91 0.00034 0.00660.0030 0.0050 0.042 0.040 White Clubbed0.00055 0.0110.0031<0.0050 0.068 0. 04243.26 0. 00470. 0300.0036 0.0050 0.054 0.050 White Chbbed42.610.0029 0. 098). 0040.00500.062 0.057Ce(CH,C0O), 1.5HO +Ce(CH,C0O)3+ 1.5H2O↑2.3 Analysis of cerium acetate(1)2.3.1 Scanning electron microscope observationCe( CH,COO), +6. 2502↑-→CeO2 + 6CO2↑+Fig.3 is the SEM photo of cerium acetate. The4. 5H2O↑(2)crystal particles shown clearly are clubbed, symmet-The composition of cerium acetate calculated onrical and regular granule with length of 136 ~ 319the basis of the changes of samples weight is shownμum.in Table 4.2.3.2 TG-DTA analysisThe TG-DTA result ofTable4 Composition of cerium acetate( % )cerium acetate prepared under optimum syntheticconditions is shown in Fig. 4. The DTA curve hasCompositionH20 H2O+CO2 CeO2two heat-adsorbing peaks corresponding two losses ofDetermination results7.60 40.0052. 40weight at TG curve. The first occurs between 150 to200 C that is the temperature of dewatering when ce-Theretical calculation resuts 7.85 42. 1550.00rium acetate starts to break down. The second heat-adsorbing peak is between 275 to 400 C that is theAs shown in Table 4, the weight lost ratios oftemperature of H2O and CO2 escaping. The reactioncerium acetate determined by TG curve are almost i-needs to absorb definite amount of oxygen. DTA anddentical with the theoretical calculation results and itTG curves parallel to the temperature coordinate axisproves that the chemical molecular formula of thisafter the second peak and it means that the decompo-crystal is Ce( CH,COO),●1. 5H2O.sition has completed. The decomposition of ceriumCacetate includes two steps :-1(-20-30T(-40室-50-60DTA中国煤化工MHCN M H ......n150 200 300 435 600I/CFig.3 SEM Photo of cerium acetate crystalFig. 4 TG-DTA curves of cerium acetate30JOURNAL OF RARE EARTHS, Vol. 22, Spec. , Dec. 20042.3.3 X-ray diffraction analysisThe XRD pat-Nd)(Ac)3，(Pr, Nd, Er, Y)(Ac)3 and Y(Ac)3.lerm of cerium acetate is shown in Fig.5. It is identi-Their chemical composition is shown in Table 5.cal with the standard in database. The sharp peaksTheir SEM photos are shown in Fig. 6. Their XRDnean good crystal property and that there are no im-patterns are shown in Fig. 7.purity peaks means the crystal has high purity.Table 5 shows the rare earth acetate prepared un-der optimum synthetic conditions has high purity,.5high rare earth content, big solubility in water along.5|with its big crystal particles and pure color. Its quali-2.5↓ty meets the demand of the intermational market..5.Fig. 6(a) shows the clubbed with length ofo.sulMMwwwwwh handi46.5116 μm. Fig.6 (b) shows the flat and clubbed2040506(with length of 68. 9275 μm. Fig. 6(c) shows that20/°)the crystal of mixed rare earth acetate (Pr, Nd, Er,Y) is hexagon column particle, and reunite witheach other. The length range is 19. 8 ~ 58.6 μm.Fig.5 XRD pattern of cerium acetateThe crystal of yttrium acetate is short column particle2.4 Preparation of rare earth acetate andand also reunites with each other. The length of it is42.2 ~ 176 μm.yttrium acetateThe sharp peaks mean good crystal property andLanthanum oxide，praseodymium oxide, neody-that there are no impurity peaks means the crystalsmium oxide， erbium oxide, yttrium oxide is dishave high purity.solved with nitric acid. The impurities are filtrated3 Conclusionsbefore the corresponding nitrate rare earth solution isprepared. They will be mixed together in proportion1. The optimum preparing conditions of ceriumand precipitated with ammonium bicarbonate to pre-acetate are described as follows: Concentration ofpare rare earth carbonate after deposited for a night.acetic acid: 1.5 ~2.5 mol●L-'. Reaction tempera-The acetic acid prepared is added into rare earth car-ture: 60 ~80 C. Ratio of cerium carbonate and ace-bonate to prepare rare earth acetate with high puritytic acid: 1.3/1 ~1.7/1. Heat preservation time: 10and yttrium acetate under the optimum synthesizing~ 15 min.conditions. High purity rare earth acetate and yttrium2. This preparing process has characteristicsacetate is separated out after condensed. The prod-such as simple process route, low cost, high yield,ucts are prepared after filtrated and aerated for dr-good quality, no pollution to environment, etc. andying. They are (La, Ce, Pr, Nd)(Ac), (Ce, Pr,it is suitable for being applied in industry.Fig. 6 SEM photos of rare earth acetate and yttrium acetate(a) Rare earth acetate crystal (La, Ce, Pr, Nd); (b) Rare earth acetate crystal (Ce, Pr, Nd); (c) Rare earth acetatecrystal (Pr, Nd, Er, Y); (d) Yttrium acetate crystalTable 5 Chemical composition of rare earth acetate and yttrium acetate中国煤化工_NameNo. TREO La2O, CeO2 Pr。O Nd2O3C1"(La, Ce, Pr, Nd) Acetate 9'41.41 15.66 51.63 15.72 17.00MHCNMH(042<0.0050(Ce, Pr, Nd) Acetate8'46.75.53.5621.34 25. 100.00018 0.0009(Pr, Nd, Er, Y) Acetate10' 36.7930.30 33.36 3. 3032. 550.00058 0.00140. 0040Yttrium Acetate30. 20>99.99 0.00095 0. 00200. 0021Qiao J et al.Preparing Process of Cerium Acetate and Rare Earth Acetate310.0 11 (a)201°)昌8. Mwwww.www..20305070802日1(° )白:8」(c4(S201(° )望482.(d)2(40602θ(°)Fig.7 XRD pattern of rare earth acetate and ytriuim acetate(a) XRD pattern of rare earth acetate crystal (La, Ce, Pr, Nd); (b) XRD pattern of rare earth acetate crystal (Ce, Pr, Nd);(c) XRD patterm of rare earth acetate crystal (Pr, Nd, Er, Y); (d) XRD pattemn of ytrium acetate crystal[3] Qian Yitai. Guide Theory of Crystal Chemistry-2 [M].References :中国煤化工’Uivesi Pobi[1] Yang Yuchun. Rare Earth Meander [ M]. Bejing: .[4]THCNMHGaterals [M]. BeiChem-ical Industry Publishing House, 1999. 46.House, 1997. 54.[2] State Department Rare Earth Leading Group Office.[5] Gu Qingchao. New-Edited Chemical Tables [M]. Nan-State Rare Earth Information Net [ M]. Collection ofjing: Jiangsu Education Publishing House, 1998. 424.Rare Earth Products Overseas, 1989. 133.