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Yttrium-doped calcined hydrotalcite acetone Preparation and catalytic synthesis of isophorone copper

Author: LiuYan
Tutor: LiuZiLi
School: Guangzhou University
Course: Chemical processes
Keywords: Acetone condensation Isophorone Coprecipitation method MgAl-LDH Lanthanon doped
CLC: O621.36
Type: Master's thesis
Year: 2011
Downloads: 48
Quote: 0
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Abstract


Isophorone is an important fine chemical which is widely used in plastics, pesticides, paint and other fields. Researching on the efficient production technique for isophorone not only has theoretical value but also practical requirements. In the wide research on the preparation of isophorone by condensation of acetone, the key issue is to develop a solid base catalyst with high catalytic activity, high selectivity and good stability.Solid bases are different with variable structures and properties. Hydrotalcite has widely researched owing to its unique structural characteristics, adjustable composition and pore structure and excellent catalytic performance. Our paper employ coprecipitation method to prepare the MgAl-LDO catalysts and MgAlM-LDO(M=Y, La, Ce) catalysts via introducing various lanthanons. The effect of preparation conditions on the catalytic properties and structure of MgAl-LDO catalysts and MgAlM-LDO catalysts is evaluated during the preparation of isophorone by condensation of acetone. In addition, the catalysts are characterized by XRD、FT-IR、TG-DTA、BET、CO2-TPD、SEM, and so on. The results reveal the effect on the role of Y 4f electronic structure in changing hydrotalcite’s structure and improving its catalytic properties.The results show that the reaction conditions have important effect on the performance of MgAl-LDO catalyst, and the main factors are Mg-Al molar radio, the amount of precipitating agent, drying method and shaker. The condition on the best preparation is acquired as follows: Mg-Al molar radio is 1, the amount of precipitating agent is 1.5 times of total materials, microwave drying for 1.5 h at 100℃, calcining for 3 h at 550℃. Under the condition, MgAl-LDO acquires best crystallinity and catalytic properties, where the acetone conversion ratio is 23.46% and isophorone selectivity is 55.95%. The modification of lanthanon to MgAl-LDO catalysts is very obvious, and the modification of Y is best. The results show that the best ratio for doping is 1% and the optimum calcination temperature is determined to be 550℃, which result in that acetone conversion ratio is improved to be 37.53% and isophorone selectivity is improved to be 58.66%.The conditions on preparation of isophorone by condensation of acetone via MgAlY-LDO catalyst are studied. The results show that the optimum reaction temperature is 300℃, and the best WHSV of acetone is 6.3 h-1. In the condition, MgAlY-LDO catalyst obtains the best stability. After continuously using 225 h, MgAlY-LDO catalytic activity begins to decline. However, compared with undoped catalyst, the stability is greatly improved. Experimental results show that inactivation is mainly due to carbon deposition caused by attachment and polymer.Characterization results on MgAlY-LDO catalyst show that Y doping leads to the change of interaction between laminate with the metal ions and hydroxyl. And shelf dehydroxylation process is divided into two phases, where the small range of weight loss is attributed to the hydroxide Y decomposition. Material pore size is in the mesoporous range, and the pore size and shape are uniform distributed and cylindrical, respectively. Y doping results in the decrease of surface area of metal composite oxide, increase on the average pore diameter and pore volume. Meanwhile, different strength of alkali appears on the MgAlY-LDO catalyst surface with the strangest alkali in the center, where the alkali uniform distributed and the alkaline is stronger. Moreover, the increased number of strong base center provides more catalytic center. SEM graph shows that the lamellar structure of MgAlY-LDO, and its microscopic structure is benefit for the exposure of catalytic activity. Thus the raw material is fully contacted with the catalyst surface and play its catalytic properties.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Synthetic organic chemistry > Heavy organic synthesis or catalytic organic synthesis
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