【作者】 刘晓军；

【导师】 毕诗文；

【作者基本信息】 东北大学 ， 有色金属冶金， 2009， 博士

【摘要】 活性氧化铝作催化剂载体在国内外被广泛在高温下用作汽车尾气催化剂,石油炼制催化剂,加氢和加氢脱硫催化剂等的载体。氧化铝是化学键力很强的离子键化合物,根据其晶体结构类型有δ-,χ-,κ-,η-,β-,γ-和α-Al2O3等多种同质异晶体,其中主要的,也是在实际工业中得到重要应用的是γ-Al2O3,β-Al2O3和α-Al2O3三种晶型。γ-Al2O3是目前应用最为广泛,扩大表面积效果较好的涂层材料。γ-Al2O3一般通过灼烧氧化铝的水合物(Al2O3·nH2O)而获得。然而,通常构成活化涂层的γ-Al2O3在800℃以上会转变成α-Al2O3,使密度增加,表面积减少,造成孔隙结构坍塌。并且在1200℃以上活化涂层会从载体上脱落,使气体阻力增大,催化活性降低。加入La203能稳定γ-Al2O3晶体结构,使活化涂层在高温下保持稳定,抑制活性损失。本文针对活性氧化铝载体存在的上述问题,对耐高温高比表面积活性氧化铝的制备及性能进行了系统研究。在热稳定剂的研究过程中,发现La3+改性效果最佳,Ce4+次之,而Pr3+,Nd3+, Sm3+效果不佳,Er3+,Y3+最差。这次序与添加的稀土元素离子半径大小次序La3+> Ce3+>Pr3+>Nd3+>Sm3+>Er3+>Y3+正好相同,表明离子半径越大稳定作用越好。同时,离子的价态也会影响它的稳定效果,这主要是由于离子半径大和价态高会降低离子的移动性,从而在高温下能够固定在氧化铝的表面以阻止氧化铝的烧结。由于La203的影响较为突出。同时其价格(每公斤30元人民币)相对较低廉,因此应用前景较为看好。本人确定把氧化镧作为氧化铝载体的最佳热稳定剂。在活性氧化铝的制备方法中,主要考察了AlCl3,Al2(SO4)3,Al(NO3)3溶胶法与(NH4)Al(SO4)2,(NH4)Al(CO3)2分解法。在其他条件相同的情况下,即热稳定剂为La2O3,扩孔剂分别为PEG,活性炭,EDTA,制备的氧化铝粒子在1200℃煅烧1h。然后从DAT,SEM来分析氧化铝粒子的活性,研究发现AlCl3,Al2(SO4)3与Al(NO3)3由于都采用了溶胶法,所以生产的氧化铝粒子粒度大,比表面积不高；(NH4)Al(CO3)2作为一种新型的无污染原料已经成为近期研究的热点,在(NH4)Al(CO3)2分解法中由于CO32-比SO42-分解温度低,煅烧时虽然能生成小颗粒氧化铝,但不能形成泡沫状氧化铝,所以(NH4)Al(CO3)2分解法形成的高温氧化铝的活性比溶胶法稍高；而(NH4)Al(SO4)2分解法在高温处理过程中形成了泡沫状的氧化铝结构,相比其他制备方法,(NH4)Al(SO4)2分解法制备的高温氧化铝颗粒最小,活性最高,比表面积最大,因此确定硫酸铝铵为最佳制备耐高温高比表面积活性氧化铝的试剂。在低温活性氧化铝的制备过程中,添加剂磷酸盐与硅酸盐能有效地提高氧化铝的活性。因此,在制备耐高温高比表面积活性氧化铝的过程中,加入添加剂磷酸盐与硅酸盐,通过DAT, SEM来分析氧化铝粒子的活性。实验结果表明通过加入添加剂磷酸盐和硅酸盐后,虽然提高了氧化铝的比表面积,但提高的幅度很小,没有达到活性氧化铝应有的比表面积。因此,使用添加剂的方法不适用于耐高温活性氧化铝的制备。常用的扩孔剂如(NH4) 2CO3, PEG,活性炭,EDTA等,虽然能有效地提高活性氧化铝的活性,但在制备耐高温高比表面积活性氧化铝的过程中,作用不大,最主要原因在于扩孔剂的分解温度太低。本实验通过合成含有[La(EDTA)]的固体为扩孔剂,通过对扩孔硫酸铝铵的实验中,经过DAT, SEM分析得出以下结论：合成出含有[La(EDTA)]的固体的高温扩孔剂,采用固体与固体混合的方法,所有实验样品的大孔结构增加,导致它们在1200℃的高温下同样有着较大的比表面积。扫描电镜显示在高温下氧化铝为具有10-30um大孔径的多孔网状结构。合成出在1200℃煅烧1h四个试样的比表面积都在120m2/g以上,其中x([La(EDTA)]-)=l%的样品的比表面积达150.36 m2/g,与相同的文献资料相比高出很多。耐高温高比表面积活性氧化铝的制备采用硫酸铝铵热解的方法。热稳定剂为La2o3,La2O3与A1203的摩尔分数为1：100；扩孔剂为EDTA与热稳定剂合成的化合物H[La(EDTA)]·6H2O晶体,其与热稳定剂的摩尔分数为1：1。更多还原

【Abstract】 As the catalyst carrier, activity alumina has the characteristic of thermo stability and ant oxidation. In domestic and foreign, it widely serves as the carrier of automobile exhaust catalyst, petroleum refining catalyst, hydrogenation and hydrodesulfurizing catalyst and so on. Alumina is a ionic bond compound with strong chemical bond. It can divide into quality different various crystal such as delta-, chi-, kappa-, eta-, beta-, gamma- and alpha-alumina according to different crystal texture. Gamma-alumina, beta-alumina and alpha-alumina are mainly and obtain the important application in the actual industry.At present the application of gamma-alumina is the most widely as a coating material, and the effect of it to expand the surface is good. Gamma-alumina is often obtained through burning hydrate of alumina. However, gamma-alumina which usually constitutes the activation coating will chang into alpha-alumina in above of 800℃, it can cause density increase, suface area reduced and pore structure collapsed. And in above of 1200℃, the activation coating will expoliated from the vector, and will caused gas resistance and activity decreased. Adds lanthanum can stabilize the crystal structure of alumina, causes the activation coating keep stable under high temperature, and suppresses the active lost.In this paper, for the above-mentioned the existence of activated alumina problem, research of preparation for high temperature high surface area activated alumina was system carry on.In the course of heat stabilizer he study, La3+ was found that have the best the modified effect, Ce4+ lies the second, and, Pr3+, Nd3+, Sm3+ perform poor and performance of Er3+, Y3+is the worst. This order is the same to the added the size order of ionic radius of rare earth elements La3+> Ce3+> Pr3+> Nd3+> Sm3+>Er3+> Y3+, which indicating that the greater of ionic radius, the better the stability. At the same time, valence of ions also have affect on the stability results, this was mainly due to large ionic radius and the valence state would reduce ion mobility, which can prevent the sintering of alumina at the surface of alumina at a fixed high temperature.As a prominent impact of La2O3, at the same time, its price are relatively low (30 yuan per kg), so the application prospects will be more promising. The author confirm that the lanthanum carrier as the best heat oxide alumina stabilizer.As to the preparation methods of activated alumina, study mainly on the AICl3, A12(SO4)3, Al(NO3)3 sol method and (NH4)Al(SO4)2,(NH4)Al(CO3)2 decomposition method. Under the same conditions, that is,heat stabilizer for La2O3,pore-expanding agent were PEG, activated carbon,EDTA,the preparation of alumina particles calcined at 1200℃for 1 hour. And then use DAT, SEM to analyze the activity of alumina particles, the study found that using the sol method with AICl3, Al2(SO4)3 and Al(NO3)3,the size, pore volume,pore size and surface area of production alumina particle is more or less the same; as a new type of pollution-free raw materials (NH4)Al(CO3)2 has become a recent research hotspot,in the (NH4)Al(CO3)2 decomposition method, as a result of low decomposition temperature of CO32+ than SO42-,although small particles of alumina generate in calcined, but bubble-like alumina could not generated,so high-temperature decomposition of the activity of alumina the formation by the (NH4)Al(CO3)2 decomposition method is of slightly higher than the sol method;and during (NH4)Al(SO4)2 decomposition process at high temperature formed a bubble-like structure of the alumina,compared with other preparation methods,the high-temperature alumina prepared by (NH4)Al(SO4)2 decomposition method has the smallest particles size,the highest activity, the largest surface area,so to determine ammonium aluminum sulfate as the best preparation agents of high temperature high surface area activated alumina.During the preparation process of activity alumina at low temperatures,phosphate and silicate additives can effectively improve the activity of alumina.Therefore,in the preparation process of high temperature of high surface area activated alumina,adding phosphate and silicate additives through DAT,SEM to analyze the activity of alumina particles.The experimental results show that after the adding of phosphate and silicate additives,although increased alumina surface area, but the level of increase is very small, did not meet the specific surface area activated alumina it should have.Therefore,the method of use of additives does not suit for preparation process of high temperature activated alumina.Although commonly used pore-expanding agent such as (NH4)2CO3,PEG,activated carbon,EDTA,etc.can effectively raise the activity of activated alumina,but have very little influence on the process of preparation the high temperature high surface area activated alumina,which mainly because that most pore-expanding agent’s decomposition temperature is too low.Through this experiment the synthesis solid contains [La(EDTA)]- used as the pore-expanding agent,by reaming ammonium aluminum sulfate experiment and the following DAT,SEM analysis,we draw such conclusions:synthesis containing high-temperature solid containing [La(EDTA)]-pore-expanding agent,using a method of solids-solid mixture,the large pore structure of all the experimental samples increase,resulting in the same larger specific surface area a high temperature of 1200℃. Scanning electron microscopy showed that under high temperature alumina has a large diameter 10-30nm porous network structure.,the four samples synthesized which calcined at 1200℃for 1h have 120m2/g or more specific surface area, in which the sample of x([La(EDTA)]-)=1% have surface area of 150.36 m2/g, much higher compared to the literature information under same condition.Method for preparation for activated alumina with high specific surface area. Heat stabilizer is La2O3 and molar ratio of La2O3 and Al2O3 is 1:100; pore-expanding agent is H[La(EDTA)]·16H2O crystals which synthesis by EDTA and heat stabilizer with the molar ratio of 1:1.更多还原