含Sn催化剂的合成、表征及其催化环己酮Baeyer-Villiger氧化

发布时间：2019-03-01 13:26

【摘要】：ε-己内酯是合成众多化工产品的有机中间体和聚合物单体,有着极其广泛的应用。目前,工业上生产ε-己内酯主要是以过氧酸氧化环己酮的Baeyer-Villiger氧化反应,该工艺存在高爆炸性和副产羧酸等缺点。因此,采用环境友好的低浓度H2O_2(30%)代替传统的过氧酸作为氧化剂,更符合绿色化学的发展理念,开发高效的催化剂成为环己酮Baeyer-Villiger氧化反应制备ε-己内酯的关键性技术。本论文首先以NaY分子筛为载体,以SnCl_4?5H_2O为锡源,采用离子交换法制备了Sn-NaY,考察了锡源加入量、温度和时间对催化剂结构及活性的影响。采用FT-IR、UV-Vis、XRD和N_2物理吸附等手段进行了表征。结果表明,随着锡源加入量的增加,生成了更多的骨架外SnO_2,且酸度增加造成了NaY分子筛结构的破坏。随着交换时间的延长,形成更多四配位Sn4+,当交换时间超过8h时,交换达到平衡,Sn的含量不会增加。通过环己酮的Baeyer-Villiger氧化反应对催化剂活性进行评价,得出较优的离子交换条件为:载体与锡源之比为3:1,交换温度为80℃,交换时间为8h。其次,采用CVD法对NaY分子筛负载金属Sn,考察了盐酸脱铝、水热脱铝和(NH_4)__2SiF_6液相同晶取代法脱铝三种方式对NaY分子筛脱铝改性结构及CVD法负载金属Sn后催化剂性能的影响。通过各种手段对催化剂样品的比表面积、孔容和孔径、孔骨架结构等进行了测定,通过以H2O_2为氧源的环己酮的Baeyer-Villiger氧化反应对催化剂的催化性能进行了评价。结果表明,水热法脱铝改性NaY效果最好,CVD负载金属Sn后环己酮的转化率为43.7%,己内酯的选择性为41.5%。最后,选用无定型介孔二氧化硅为载体,SnCl4为锡源,通过化学气相沉积法制备了Sn/Si O_2。系统考察了CVD过程中前处理、温度和时间及焙烧氛围和焙烧温度对催化剂的影响,通过FT-IR、UV-Vis、N2物理吸附、ICP和NH_3-TPD对催化剂的结构进行了表征。结果表明,对载体进行水热处理,可以增加Si-OH的数量,有利于CVD负载过程生成更多的骨架Sn;在N_2氛围中进行焙烧处理,可以防止骨架外的Sn组分被氧化生成SnO_2。进一步通过以H2O_2为氧源的环己酮的Baeyer-Villiger氧化反应评价催化剂的催化性能,得出较优的CVD法制备Sn/SiO_2的条件为:对载体进行焙烧处理,CVD温度540℃,时间1.5h,在N_2氛围中焙烧,焙烧温度为300℃。
[Abstract]:蔚-caprolactone (蔚-caprolactone) is an organic intermediate and polymer monomer for the synthesis of many chemical products. At present, the industrial production of 蔚-caprolactone is mainly due to the Baeyer-Villiger oxidation of cyclohexanone with peroxic acid, which has the disadvantages of high explosive and by-product carboxylic acid. Therefore, the use of environmentally friendly low concentration H2O_2 (30%) instead of the traditional peroxic acid as an oxidant, is more in line with the concept of green chemistry development. The development of efficient catalysts has become the key technology for the preparation of 蔚-caprolactone by Baeyer-Villiger oxidation of cyclohexanone. Firstly, using NaY as carrier and SnCl_4?5H_2O as tin source, Sn-NaY, was prepared by ion exchange method. The effects of the amount of tin source, temperature and time on the structure and activity of the catalyst were investigated. The results were characterized by FT-IR,UV-Vis,XRD and N _ (2) O _ (2) physisorption. The results show that with the increase of the amount of tin source, more extra-skeleton SnO_2, is formed and the structure of NaY molecular sieve is destroyed by the increase of acidity. With the prolongation of the exchange time, more four-coordinated Sn4 was formed. When the exchange time was longer than 8 hours, the exchange reached equilibrium, and the content of Sn did not increase. The activity of the catalyst was evaluated by Baeyer-Villiger oxidation of cyclohexanone. The optimum ion exchange conditions were as follows: the ratio of carrier to tin source was 3? 1, the exchange temperature was 80 鈩，

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