Alumina is an important metal oxide used in a wide range of applications. It is a challenge to synthesize stable γ-alumina nanoparticles because, γ-phase of alumina is not as stable as α phase of alumina. But γ-alumina owns a higher surface area making it a good candidate for many industrial applications such as catalyst, catalytic support for petroleum refining, absorbent, alcohol dehydration, catalytic reduction of automotive pollutants like NOx, CO and hydrocarbons. This research focuses on synthesis, characterization and study of phase identification of pure γ-alumina nanoparticles.
Modified “Pechini method”(Danks, Hall, and Schnepp (2016); Huízar-Félix, Hernández, de la Parra, Ibarra, & Kharisov, 2012; Naskar, 2010; Zaki, Kabel, & Hassan, 2012)was used for the synthesis. Transesterification of citrate and ethylene glycol makes a covalent polymer network with trapped Al atoms. Continuous stirring of the reaction mixture while maintaining an optimum temperature is an important factor affecting this reaction. Calcination was carried out at different temperatures to identify phase transitions of alumina nanoparticles. In order to further reduce the particle size and increase the surface area, reactant ratio of citric acid: aluminum acetate was modified to 1:1, volume of ethylene glycol was increased up to 90% of volume of the solution and Triton X was used as a surfactant.
PXRD confirmed the pure γ-alumina phase (JCPDS No. 00-010-0425) in samples calcined at 900 °C. At 1000 °C γ-alumina is converted to α-alumina (JCPDS No. 00-083-2080). After the modifications, γ-alumina was identified at 700 °C. FTIR-ATR analysis shows peaks around 1127 cm-1 indicating the presence of Al-O-Al asymmetric bending modes and the peaks around 500 cm-1-750 cm-1 correspond to γ-AlO6 octahedral sites and 800 cm-1 correspond to AlO4 tetrahedral sites in γ alumina spinel structure. Resulted product of low temperature, pure γ-alumina nanoparticles will facilitate the industrial development in various applications.
氧化铝是一种重要的金属氧化物，有着广泛的应用。由于氧化铝的γ相不像氧化铝的α相那样稳定，因此合成稳定的γ-氧化铝纳米颗粒是一个挑战。但γ-氧化铝具有更高的表面积，使其成为许多工业应用的良好候选者，如催化剂，石油精炼的催化载体，吸收剂，酒精脱水，催化还原氮氧化物，一氧化碳和碳氢化合物等汽车污染物。本文主要研究了纯γ-氧化铝纳米颗粒的合成、表征和物相鉴定。改进的“Pechini方法”(Danks, Hall, and Schnepp (2016));Huízar-Félix, Hernández, de la Parra, Ibarra， &Kharisov, 2012;Naskar, 2010;Zaki, Kabel， &Hassan, 2012)用于合成。柠檬酸盐与乙二醇的酯交换反应生成了含有捕获Al原子的共价聚合物网络。在保持最佳温度的情况下持续搅拌反应混合物是影响该反应的重要因素。在不同温度下进行煅烧，以确定氧化铝纳米颗粒的相变。为了进一步减小粒径，增加比表面积，将柠檬酸与醋酸铝的反应物比改性为1:1，将乙二醇的体积增加到溶液体积的90%，并使用Triton X作为表面活性剂。PXRD证实在900℃煅烧的样品中存在纯γ-氧化铝相(JCPDS No. 00-010-0425)。在1000℃时，γ-氧化铝转化为α-氧化铝(JCPDS No. 00-083-2080)。改性后的γ-氧化铝在700℃下被鉴定。FTIR-ATR分析表明，在1127 cm-1附近的峰表明存在Al-O-Al不对称弯曲模式，500 cm-1 ~ 750 cm-1附近的峰对应γ-氧化铝尖晶石结构中的γ- alo6八面体位点，800 cm-1对应AlO4四面体位点。所得的低温、纯γ-氧化铝纳米颗粒将促进工业发展，在各种应用领域。
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