改性磷酸锂催化剂在环氧丙烷异构化中的应用研究

发布时间：2018-04-27 04:03

  本文选题：环氧丙烷异构化 + 烯丙醇　； 参考：《南京理工大学》2017年硕士论文

【摘要】：烯丙醇作为基础化工原料具有广泛的应用,主要原因是其分子结构中同时具有双键和羟基两种官能团,可以参与氧化、还原、醚化、酯化等多种反应。目前工业上常用的制备烯丙醇的方法是气相环氧丙烷异构化法,具有工艺简单,效率高,污染小等优点。碱性磷酸锂催化剂用于环氧丙烷异构化反应,其催化活性和选择性都较高,但是催化剂容易因积碳而失活,给连续生产带来极大的不便。针对以上问题,本文对催化剂分别进行水蒸气预处理和金负载的方法有效抑制了积碳的产生,并提高了催化剂的活性。为了找到更加适合环氧丙烷异构化反应的催化剂,对各类催化剂进行了小范围的筛选。对催化剂进行水蒸气预处理明显抑制了碱性磷酸锂催化剂的表面积碳生成,且其催化活性明显提高。实验结果显示,在300℃下经过水蒸气处理30 min时,催化剂呈现最好的催化活性。而且,经过水蒸气处理的催化剂在反应12小时后的积碳量是15.1%,远远低于未经处理的催化剂上的积碳量(21.5%)。实验证明,经水蒸气处理后,Br(?)nsted酸量的减少可能导致积碳量的减少,而催化剂活性的提高可能是Lewis酸量的增加和强碱强度的增加两者协同作用的结果。金纳米颗粒负载于磷酸锂表面而得到Au/Li_3PO_4催化剂,此方法明显提高了磷酸锂的催化活性。实验结果显示,金的负载量为0.042 wt%,pH值为13,煅烧温度为300 ℃时,催化剂呈现最好的催化活性。实验证明Au/Li_3PO_4催化剂强碱强度的增强导致催化活性提高。通过XPS和密度泛函理论共同证实强碱强度增强是因为电子从磷酸锂的氧原子转移到金粒子表面,导致富电子的金粒子表现为碱性更强的碱。为了找到更高活性的催化剂,本文对各类催化剂进行了小范围的筛选,实验结果显示,Ag和Cu对磷酸锂催化活性并没有明显的提高,反而一定程度上抑制了磷酸锂的催化活性。至于TiO2、X型分子筛、g-C3N4、Au-Pd/TS-1、固体超强酸、纳米Ag、CeO2-TiO2这几种催化剂,虽然环氧丙烷的转化率几乎都在10%以下,但是丙醛的选择性几乎都在50%左右,与磷酸锂催化剂相比较,这些催化剂呈现较高的丙醛选择性。所以,在经过催化剂的改性之后,这些催化剂有待成为环氧丙烷异构化制备丙醛反应的优选催化剂,这部分工作还有待深入研究。
[Abstract]:Allyl alcohol is widely used as a basic chemical raw material. The main reason is that its molecular structure has two functional groups, double bond and hydroxyl group, which can participate in many reactions such as oxidation, reduction, etherification, esterification and so on. At present, gas phase epoxypropane isomerization is the commonly used industrial method to prepare allyl alcohol, which has the advantages of simple process, high efficiency, low pollution and so on. The catalytic activity and selectivity of alkaline lithium phosphate catalyst for the isomerization of propylene oxide is high, but the catalyst is easily deactivated due to carbon deposition, which brings great inconvenience to continuous production. In view of the above problems, the methods of water vapor pretreatment and gold loading can effectively restrain the formation of carbon deposition and improve the activity of the catalyst. In order to find more suitable catalysts for the isomerization of propylene oxide, various catalysts were screened in a small range. The surface area carbon formation of alkaline lithium phosphate catalyst was obviously inhibited by steam pretreatment, and its catalytic activity was improved obviously. The experimental results show that the catalyst exhibits the best catalytic activity after 30 min of water vapor treatment at 300 鈩，

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