One-step Direct Preparation Of Samarium Acetate Process Research

Rare earth acetate is a kind of organic acid rare earth metal salt,which can dissolve not only in polar water,but also in non-polar benzene,and can be transformed between organic and inorganic compounds.it is the reaction bridge between organic and inorganic compounds.Rare earth acetate with high purity,easy storage and non-agglomeration is more and more widely used,and its importance is more and more irreplaceable.As one of the rare earth compounds,samarium acetate has important applications in organic catalysis,organic initiator,medicine and so on.It is almost non-toxic and can be added to drugs to improve drug properties,treat difficult and complicated diseases,coupled with the unique physical and chemical properties of rare earth elements,its application prospect will be better and better,but the existing preparation process has some deficiencies.Need to be further improved in all aspects.With the development of science and technology,samarium acetate is deeply used in various fields of science and technology,and the preparation process with low cost,high purity and more environmental protection is becoming more and more important.The relevant literature shows that there are many methods for the preparation of samarium acetate,most of which are prepared under laboratory conditions,the product quality stability and production cost limit the feasibility of large-scale preparation.Samarium acetate crystal is prepared by the existing process,and the crystal mother liquor is heated and concentrated,precipitated and filtered out samarium acetate crystal,which causes a lot of energy consumption and environmental pollution.therefore,the key to the preparation of samarium acetate is how to treat and utilize the crystal mother liquor.Proper treatment of crystallization mother liquor can reduce the discharge of pollution,make full use of raw materials such as acetic acid,and improve the stability and uniformity of product quality.The one-step process for the preparation of samarium acetate studied in this thesis is based on the existing two-step process,which completes the reaction of dissolving samarium carbonate with acetic acid and the crystallization and precipitation of acetic acid in one step and returns the mother liquor after the first reaction to the corresponding reaction process to instead of deionized water to adjust the samarium carbonate.The method makes the recycling of mother liquor,improves the utilization rate of acetic acid,reduces the process steps of concentration and evaporation,reduces energy consumption,saves cost,and makes the product quality more stable,more low-carbon and environmental protection.In this thesis,the feasibility of the process is explored by thermodynamic calculation and establishing kinetic equation.According to the thermodynamic data of the materials in the reaction process,the reaction enthalpy change,equilibrium constant,reaction entropy change and reaction Gibbs free energy change were calculated.According to the characteristics of solid reaction of samarium carbonate solid particles and glacial acetic acid liquid,the reaction rate model was determined,and the corresponding experiments were completed.Through the analysis of the actual results and data,the relationship between the rate constant of the reaction and conversion process and the conversion function was obtained.The activation energy and pre-exponential parameters of Arrhenius reaction were obtained,and the kinetic equation was determined as lnk=2.11-17746.15/RT.In this thesis,through the condition test,the process conditions that may affect the conversion rate of samarium carbonate,such as the mass ratio of glacial acetic acid and samarium carbonate（material-liquid mass ratio）,the mass ratio of deionized water and samarium carbonate（slurry mixing mass ratio）,stirring speed,reaction temperature and reaction time were studied,and the optimal conditions for the preparation of samarium acetate from samarium carbonate were determined:the mass ratio of material to liquid was0.8,the mass ratio of slurry mixing was 2.0,the reaction temperature was 60°C,the reaction time was 60 minutes,and the stirring speed was 250 r/min.Under these conditions,the continuous cycle of crystallization mother liquor to prepare samarium acetate process test was carried out.Through experimental research on the number of mother liquor cycles,it was found that the crystallization mother liquor could be recycled more than nine times,the total amount of rare earth and the impurity content of the samarium acetate crystals crystallized nine times can meet the market’s quality requirements for samarium acetate.Thermogravimetric and differential thermal analysis was used to characterize the product,and the thermal decomposition mechanism of the product was determined by weight loss analysis.The composition of the product was Sm（CH₃COO）₃·4H₂O by comparing the XRD pattern of the product with the standard card.Through the infrared absorption spectrum detection of the product,the characteristic functional groups of the product were analyzed according to the peak position,and the product structure was determined.In addition,the morphology of each crystallization product was analyzed by SEM.Compared with the existing preparation process,the one-step cyclic crystallization mother liquor preparation process of samarium acetate is simpler,with lower energy consumption,more stable quality,and more prominent economic benefits.It can be continuously and large-scale production and has a good market application prospect.