One-Step Controllable Preparation Of Lanthanum Acetate Crystal

Rare earth acetate is an important carboxylic acid rare earth compound formed by the combination of rare earth ions and acetic acid molecules.Rare earth acetate,which has good water solubility,complete crystal morphology and high purity,involves more and more fields and plays an increasingly important role.Rare earth acetate,represented by lanthanum acetate,is an important pharmaceutical component and intermediate in medicine,an important catalyst in petroleum industry,an important additive in the field of high-tech materials,and an important component of medicine and fertilizer in agriculture.Because of its low toxicity,easy to remove by heating,high water solubility and special physical and chemical properties of rare earth elements,it has a better application prospect,but the preparation process needs to be improved in all aspects.Therefore,it is very important to prepare rare earth acetate crystals in accordance with various requirements.Under laboratory conditions,a variety of methods can be used to prepare high-quality rare earth acetate compounds.However,most of the preparation methods are not practical considering the factors such as the production and quality of expanded products,the feasibility,stability,production cost and technical and economic benefits Conditions of production.The treatment and utilization of crystallization mother liquor is an important step in the preparation of lanthanum acetate.The treatment of crystallization mother liquor can reduce environmental pollution and improve the utilization rate of raw materials.Most of the existing preparation processes use multiple crystallization and oxalic acid precipitation to treat the mother liquor,which consumes a lot of energy and precipitant,and affects the purity of the product.Based on the existing two-step process for the preparation of lanthanum acetate,the dissolution process of lanthanum carbonate and the crystallization process of lanthanum acetate are combined in one step to directly transform into lanthanum acetate crystal.The crystallized mother liquor is returned to the mixing process of lanthanum carbonate,which is recycled for many times to improve the utilization rate of raw materials,avoid waste,and reduce industrial water and industrial waste water.The thesis takes thermodynamic calculation and kinetic derivation as the starting point for research,and develops a one-step process for preparing lanthanum acetate.By referring to the basic thermodynamic data of the material and using the basic thermodynamic principle formula,the enthalpy change and the entropy change at different temperatures are calculated,and the heat absorption and release of the reaction process are analyzed.Analyze the reaction principle of lanthanum carbonate and glacial acetic acid,make theoretical assumptions and find a matching kinetic model.The kinetic experiments at different temperatures were performed.The data was linearly fitted by the model equation,showing a good linear correlation,indicating that the reaction process of lanthanum carbonate and glacial acetic acid conforms to our hypothetical model equation,and the reaction rate constant was calculated by graphing.And the apparent activation energy,we finally obtained the macro-kinetic equation for the preparation of lanthanum acetate by the reaction of lanthanum carbonate with glacial acetic acid.The thesis researched the process conditions such as material-liquid ratio,slurry ratio,reaction time,reaction temperature and stirring speed in the preparation process through conditional experiments.The best process conditions were obtained from single-factor experiment results:the material-liquid ratio was 1.1,the slurry ratio was 2,the reaction temperature was 75°C,the reaction time was 120 min,and the stirring speed was 200 r/min.Under this process condition,the mother liquor circulation experiment was conducted to study the mother liquor circulation times.The mother liquor was not circulated,and the yield of lanthanum acetate was about 72.62%;as the mother liquor began to circulate,the yield of lanthanum acetate reached 99.24%.It shows that the mother liquor recycling is feasible,and the mother liquor can be circulated more than 9 times.The total rare earth and impurity content of each crystalline product are stable.The content of non-rare earth impurities obtained in 9 cycles meets the requirements of the product quality standard of lanthanum acetate.In order to better optimize the one-step process for preparing lanthanum acetate crystals,we made scanning electron micrographs of the lanthanum acetate crystals prepared at different temperatures to analyze the effect of temperature on the morphology,and found that the acetate crystals were stacked from square flakes into square rods,and As the temperature increases,it becomes longer and thicker.The aging process is a key step in crystal growth.The morphology of the aging crystals was analyzed by scanning electron microscopy.It was found that the lanthanum acetate crystals after aging were of uniform size,larger volume,more complete morphology,fewer defects,and aging time.More than 24 hours is preferred.Through thermogravimetric-differential thermal detection of lanthanum acetate products,the weight loss rate is analyzed to determine the thermal decomposition mechanism and the molecular structure of lanthanum acetate.Inspect the infrared absorption spectrum of the product,analyze the vibration frequency of the functional group of the spectrum,and compare it with the infrared spectrum data reported in the literature to determine the product structure.The product was detected by X-ray powder diffractometer,the measured XRD pattern was analyzed,and by comparison with a standard card,we further determined that the crystal structure of lanthanum acetate prepared by the experiment was La?CH₃COO?₃·H₂O.This paper proposes a one-step process for directly preparing lanthanum acetate crystals.Compared with previous preparation methods,the steps are more simplified,the conditions are easier to control,the mother liquor treatment is more efficient,the preparation cost is more economical,the production efficiency is higher,and the industrial water consumption is smaller.Therefore,this process method achieves low emission,low energy consumption,low cost,continuous and clean preparation of lanthanum acetate.This process research is based on high-efficiency production,environmental protection,and strong feasibility of process application.It can provide some theoretical guidance for actual production,and also provide some theoretical help for the expansion to the preparation of other rare earth element acetates.