本文選題：撞擊流反應器 + 沉淀法��； 參考：《武漢工程大學》2011年碩士論文

【摘要】：稀士元素具有獨特的4f電子結(jié)構(gòu),被譽為新材料的寶庫,在工業(yè)及新材料制備上得到廣泛的應用。氧化鑭超細粉體具有許多獨特的性質(zhì),在許多領(lǐng)域具有廣泛的應用,如在汽車廢氣的處理,氣體催化劑載體,甲烷氧化耦合催化劑,光學玻璃,陶瓷,電極的制備中有著應用。但目前的制備技術(shù)還存在一些未解決的問題,如產(chǎn)品質(zhì)量、純度、粒徑等問題,此外,開發(fā)氧化鑭超細粉體制備技術(shù),可以增加高豐度稀土元素鑭的工業(yè)應用,解決鑭的積壓問題。因此非常有必要對制備氧化鑭超細粉體的工藝進行細致研究。 本論文采用撞擊流反應-沉淀法制備氧化鑭前驅(qū)體,然后將前驅(qū)體進行焙燒得到氧化鑭超細粉體,考察碳酸氫銨、草酸銨、氨水等不同沉淀劑對氧化鑭前驅(qū)體粒徑的影響因素,并對草酸銨制備的氧化鑭前驅(qū)體進行熱分解動力學研究,擬合出動力學模型,并得到相關(guān)動力學參數(shù)。 (1)在浸沒循環(huán)撞擊流反應器中以碳酸氫銨為沉淀劑,以硝酸鑭為鑭源,加入少許表面活性劑作分散劑制備氧化鑭前驅(qū)體,再經(jīng)過焙燒得到氧化鑭超細粉體。通過正交試驗考察了濃度比n(NH4HCO3):nLa(NO3)3·6H2O、反應時問、反應溫度、PEG用量、螺旋槳轉(zhuǎn)速、焙燒時間及焙燒溫度對氧化鑭超細粉體粒徑的影響,方差分析結(jié)果表明,在F值為0.1,0.05,0.01情況F,焙燒溫度、反應時問、濃度比均具有顯著性。結(jié)合正交及單因素試驗,優(yōu)化工藝參數(shù)為：濃度比nNH4HCO3:nLa(NO3)3·6H2O=6:1、反應時間為30 mmin、反應溫度30℃、加入PEG用量為4%、螺旋槳轉(zhuǎn)速1000r/min、焙燒溫度800℃焙燒時間3 h。SEM表明所得產(chǎn)品粒徑為100 nm。 (2)在撞擊流反應器中以草酸銨為沉淀劑制備氧化鑭超細粉體,并通過單因素實驗對制備過程進行優(yōu)化,得到優(yōu)化工藝參數(shù)為：濃度比n(NH4)2C2O4:nLa(NO3)3·6H2O=6:1、反應時間為30 min、反應溫度30℃、加入PEG用量為4%、螺旋槳轉(zhuǎn)速1000r/min、焙燒溫度800℃、焙燒時間3 h。SEM表明所得產(chǎn)品為球狀顆粒,粒徑約為200 nm。 (3)在撞擊流反應器中以氨水為沉淀劑制備氧化鑭超細粉體,通過對制備過程的單因素優(yōu)化,得到優(yōu)化工藝參數(shù)為：氨水加入量為25 mL、反應時間為15 min、反應溫度45℃、加入PEG用量為10%、螺旋槳轉(zhuǎn)速2000 r/min、焙燒溫度800℃、焙燒時間2 h。通過SEM觀察,所得產(chǎn)品為球狀顆粒,粒徑約為100 nm。 (4)對草酸銨沉淀法制備的氧化鑭前驅(qū)體進行熱分解動力學研究,結(jié)合熱重(TG-DSC)及紅外光譜(IR)分析,得到氧化鑭前驅(qū)體為十水草酸鑭,其熱分解主要分為五個階段,第一個階段失去6個結(jié)晶水,第二、三階段分別失去2個結(jié)晶水,第四階段產(chǎn)生中間體La2O2CO3,最后為氧化鑭的生成。通過使用Flynn-Wall-Ozawa (FWO)法和Kissinger-Aksahira-Sunose(KAS)法對十水草酸鑭的熱分解過程進行分析,結(jié)果表明,兩種方法得到的活化能E均隨轉(zhuǎn)換率α的變化而變化,說明十水草酸鑭的熱分解不是簡單的一步反應,而是多步反應。由于model-free的特點,多步反應無法求得動力學模型及相關(guān)參數(shù),此時的活化能一般采用平均值法求得,動力學模型及相關(guān)參數(shù)需使用多元非線性擬合求取。通過FWO法得到草酸鑭的熱分解的五個階段的平均活化能分別為：68.94,116.76,144.31,181.43,179.24kJ/mol。通過KAS法得到草酸鑭的熱分解的五個階段的平均活化能分別為：65.60,114.28,141.49,179.01,171.79 kJ/mol。 (5)采用多元非線性擬合對十水草酸鑭的熱分解機理進行擬合,得到熱分解機理符合g(α)=[1-(1+α)1/3]2模型,五個階段的動力學參數(shù)為第一階段：E=65.47 kJ/mol,lgA=-1.6 S-1；第二階段：E=106.9 kJ/mol,lgA=-0.1 S-1；第三階段：E=120.9 kJ/mol,lgA=-0.183 S-1；第四階段：E=177.68 kJ/mol,lgA=2.27 S-1；第五階段：E=156.4 kJ/mol,lgA=-2.54 S-1。擬合TG曲線能很好的匹配原始TG曲線。
[Abstract]:The dilute element has a unique 4f electronic structure known as the treasure house of new materials. It has been widely used in industry and new material preparation. The ultrafine lanthanum oxide powder has many unique properties and has been widely used in many fields, such as the treatment of automobile exhaust gas, gas catalyst carrier, methane oxidation coupling catalyst, optical glass, There are some applications in the preparation of ceramics and electrodes, but there are still some unsolved problems, such as product quality, purity, particle size and so on. In addition, the development of lanthanum oxide ultrafine powder preparation technology can increase the industrial application of lanthanum rich in rare earth elements and resolve the backlog of lanthanum. Therefore, it is very necessary to prepare lanthanum oxide. The process of ultrafine powder is studied in detail.
Lanthanum oxide precursor was prepared by impinging flow reaction precipitation method, and the precursor was roasted to ultrafine lanthanum oxide powder. The influence factors of ammonium bicarbonate, ammonium oxalate, ammonia and other precipitant on the particle size of lanthanum oxide precursor were investigated, and the thermal decomposition kinetics of lanthanum oxide precursor prepared by ammonium oxalate was studied. The kinetic model is obtained and the related kinetic parameters are obtained.
(1) the lanthanum oxide precursor was prepared with lanthanum nitrate as the lanthanum source in the immersion cycle impingement reactor with lanthanum nitrate as the lanthanum source. The lanthanum oxide precursor was prepared by a few surface active agents and then roasted. The concentration ratio n (NH4HCO3), nLa (NO3) 3. 6H2O, reaction temperature, PEG dosage, snails were investigated through orthogonal test. The effect of rotating speed, roasting time and calcination temperature on the particle size of lanthanum oxide superfine powder. The analysis of variance analysis showed that the F value of 0.1,0.05,0.01 F, roasting temperature, reaction time, concentration ratio were all significant. Combined orthogonal and single factor test, the optimization process parameters were as follows: concentration ratio nNH4HCO3:nLa (NO3) 3. 6H2O=6:1, reaction time was 3 0 mmin, reaction temperature 30 centigrade, adding PEG dosage 4%, propeller speed 1000r/min, calcination temperature 800 centigrade roasting time 3 h.SEM showed that the product diameter was 100 nm.
(2) the ultrafine lanthanum oxide powder was prepared in the impingement reactor with ammonium oxalate as precipitant and optimized by single factor experiment. The optimized process parameters were as follows: concentration ratio n (NH4) 2C2O4:nLa (NO3) 3. 6H2O=6:1, reaction time 30 min, reaction temperature 30, PEG dosage 4%, propeller speed 1000r/min, calcination temperature The product was spherical at 800 degrees C and calcined at 3 h.SEM. The particle size was about 200 nm..
(3) the ultrafine lanthanum oxide powder was prepared in the impinging flow reactor with ammonia as precipitant. Through the single factor optimization of the preparation process, the optimized process parameters were obtained: the ammonia water addition amount was 25 mL, the reaction time was 15 min, the reaction temperature was 45, the dosage of PEG was 10%, the rotation speed of the screw propeller was 2000 r/min, the roasting temperature was 800, and the calcination time 2 h. passed. SEM observation showed that the product was spherical particles with a particle size of about 100 nm..
(4) the thermal decomposition kinetics of lanthanum oxide precursor prepared by ammonium oxalate precipitation method was studied. The lanthanum oxide precursor was ten lanthanum oxalate with TG-DSC and IR analysis. The thermal decomposition of lanthanum oxalate precursor was divided into five stages, the first stage lost 6 crystalline water, and the second, third stage lost 2 crystalline water and fourth stages respectively. The intermediate La2O2CO3 was produced and finally the generation of lanthanum oxide. The thermal decomposition process of lanthanum ten water lanthanum was analyzed by using the Flynn-Wall-Ozawa (FWO) method and Kissinger-Aksahira-Sunose (KAS) method. The results showed that the activation energy E obtained by the two methods all changed with the conversion of conversion rate alpha, indicating that the thermal decomposition of lanthanum oxalate ten was not simple. The one step reaction is a multistep reaction. Because of the characteristics of model-free, the dynamic model and the related parameters can not be obtained by the multistep reaction. The activation energy is generally obtained by mean value method. The dynamic model and the related parameters need to be obtained by multivariate nonlinear fitting. The average activity of the five stages of the thermal decomposition of lanthanum oxalate is obtained by the FWO method. The average activation energy of the five stages of thermal decomposition of lanthanum oxalate by KAS method, respectively, is 65.60114.28141.49179.01171.79 kJ/mol., respectively, by the 68.94116.76144.31181.43179.24kJ/mol. method.
(5) using multivariate nonlinear fitting to fit the thermal decomposition mechanism of lanthanum oxalate ten, the thermal decomposition mechanism conforms to the G (alpha) =[1- (1+ alpha) 1/3]2 model. The kinetic parameters of the five stages are the first stage: E=65.47 kJ/mol, lgA=-1.6 S-1, and the second stage: E=106.9 kJ/ mol, lgA=-0.1 lgA=-0.1; third stage: Third 1; fourth stage: E=177.68 kJ/mol, lgA=2.27 S-1; fifth stage: E=156.4 kJ/mol, lgA=-2.54 S-1. fitting TG curve can very well match the original TG curve.

【學位授予單位】：武漢工程大學
【學位級別】：碩士
【學位授予年份】：2011
【分類號】：TB383.3

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