【作者】 李颖；

【导师】 赵新强；

【作者基本信息】 河北工业大学 ， 化学工艺， 2017， 硕士

【摘要】 辛醇是重要的有机化工原料。正丁醛自缩合是工业生产辛醇工艺中重要的碳链增长反应。本文以可生物降解的天然高分子材料壳聚糖作为催化剂,对正丁醛自缩合反应进行了研究。首先,考察了不同方法改性的壳聚糖对正丁醛自缩合反应的催化性能,发现催化活性相差不大。以未改性壳聚糖为催化剂,考察了反应条件对正丁醛自缩合反应的影响,确定了适宜的反应条件为:催化剂用量为5wt.%,反应温度为80℃,反应时间为8 h。在此条件下,正丁醛转化率为96.0%,辛烯醛的收率和选择性分别为86.0%和89.6%。通过氨水处理的方法,回收的壳聚糖催化剂可重复使用5次,催化活性基本不变。采用GC-MS对壳聚糖催化正丁醛自缩合反应体系进行了定性分析,并推测了反应体系中可能存在的副反应。其次,利用原位红外光谱研究了正丁醛在壳聚糖催化剂表面的吸附和脱附过程,确定壳聚糖催化正丁醛自缩合反应机理为:一分子正丁醛首先与氨基活性中心形成亲核烯胺结构,烯胺再进攻另一分子正丁醛的羰基碳完成缩合反应。利用在线红外分析系统React IR TM IC-10研究了壳聚糖催化正丁醛自缩合反应过程发现正丁醛自缩合反应分两步进行:正丁醛自缩合先生成2-乙基-3-羟基己醛,2-乙基-3-羟基己醛再脱水生成辛烯醛。壳聚糖不但催化第一步反应,也对第二步反应有催化作用,提高反应温度对第二步反应的影响更大。最后,在研究壳聚糖催化正丁醛自缩合反应机理的基础上,建立了壳聚糖催化正丁醛自缩合反应动力学。该反应系自催化反应,动力学反应方程式如下:rB=-dcB/dt=cB1.56[1.547×exp(-13.043×10~4/RT)+260.803×exp(-4.039×10~4/RT)]r2E2H=dc2E2H/dt=260.803×exp(-4.069×10~4/RT)×cB1.56式中:rB,r2E2H 为正丁醛和辛烯醛的反应速率,mol·L-1·min-1 CB为正丁醛的浓度,mol·L-1更多还原

【Abstract】 2-Ethylhexanol(2EHO)is an important organic chemical.n-Butyraldehyde self-condensation is a crucial step of carbon chain extention for industrial manufacture of 2EHO.In the present work n-butyraldehyde self-condensation was investigated in the presence of a biodegradable natural polymer chitosan.First of all,the catalytic performance of different functionalized chitosan samples on n-butyraldehyde self-condensation to 2-ethyl-2-hexenal(2E2H)was evaluated,and the results showed that there were little differences in the catalytic performance before and after chitosan was functionalized.The effect of reaction conditions on the n-butyraldehyde self-condensation catalyzed by non-functionalized chitosan was investigated,and the suitable reaction conditions were obtained as follows:a weight percentage of chitosan = 5%,a reaction temperature = 80℃ and a reaction time = 8 h.Under the above reaction conditions,n-butyraldehyde conversion attained 96.0%,the yield and selectivity of 2E2H were 86.0%and 89.6%,respectively.The recovered chitosan sample could be used for 5 times without a significant deactivation after being treated with ammonium hydroxide.Additionally,the reaction products obtained from chitosan catalyzed n-butyraldehyde self-condensation were indentified by GC-MS and several possible side-reactions were conjectured.Secondly,the adsorption and desorption of n-butyraldehyde on chitosan surface was studied by in-situ FT-IR.The mechanism of n-butyraldehyde self-condensation catalyzed by chitosan was proposed:a n-butyraldehyde molecule was adsorpted on a site of-NH2 to form an enamine and then the nucleophilic enamine attacked the carbonyl carbon of another n-butyraldehyde molecule to complete the aldol condensation reaction.Then the reaction process of n-butyraldehyde self-condensation was investigated by React IR TM IC-10 and the result showed that n-butyraldehyde self-condensation comprises two steps:n-butyraldehyde self-condensation to 2-ethyl-3-hydroxyhexanal followed by dehydration to 2E2H.The chitosan catalyzes not only the first step but also the second step reaction.Futhermore,there was a greater effect on the second step reaction when the reaction temperature was increased.Finally,the reaction kinetic of n-butyraldehyde self-condensation over chitosan catalyst was studied.It was found that the reaction was auto catalytic and the kinetic equations are as follows.rB=-dcB/dt=cB1.56[1.547×exp(-13.043×10~4/RT)+260.803×exp(-4.039×10~4/RT)]r2E2H=dc2E2H/dt=260.803×exp(-4.069×10~4/RT)×CB1.56 rB,r2E2H was the reaction rate of n-butyraldehyde and 2E2H,mol·L.-1·min-1 cB was the concentration of n-butyraldehyde,mol·L-1更多还原