【作者】 邓全丽；

【导师】 吴剑；

【作者基本信息】 湘潭大学 ， 化学工艺， 2008， 硕士

【摘要】 以苯为原料己内酰胺生产工艺中,环己酮肟是关键中间体,传统工艺大多采用环己酮-羟胺法。以钛硅分子筛TS-1为催化剂,环己酮、氨和双氧水为原料的液相氨肟化反应,条件温和,选择性高,副产物少,能基本实现“零排放”。1990年前后意大利Enichem公司开发建成TS-1分子筛催化液相氨肟化反应工业化装置,为环己酮肟的工业化生产打开了一个新的篇章。然而,TS-1分子筛催化剂价格昂贵,粒度较小(0.1-0.3μm),催化环己酮氨肟化反应后难以与反应液体系分离,回收困难,流失严重。因此,分离回收TS-1分子筛已成为环己酮氨肟化工艺中迫切需要解决的难题,限制着氨肟化技术的推广应用。本文采用环境友好型“双功能催化剂”——杂多酸(盐)催化环己酮氨肟化反应,成功制备了以P为中心原子,W、Mo、V为配位原子的杂多酸及其盐,经FTIR、XRD、ICP表征,结果表明其具有Keggin型结构。对影响杂多酸(盐)合成收率的主要因素,如反应温度、物料配比、pH值及溶剂量等进行了考察。结果表明:合成保持在近沸状态,物料配比接近化学计量,pH值维持在1.6-1.8,杂多酸收率达82.51%。以环己酮氨肟化催化反应体系对杂多酸(盐)进行评价,结果表明以Keggin型磷钨杂多酸的催化性能最好,具有催化活性高,选择性和稳定性好,催化反应条件温和且无污染等优点。以磷钨杂多酸为催化剂对环己酮氨肟化反应工艺条件进行了优化,考察了催化剂用量、反应温度、反应时间、H2O2用量及溶剂对反应的影响。实验结果表明:以水作溶剂,H3PW12O40用量为19.6g/1mol环己酮,双氧水与酮摩尔比为1.6/1,20℃下反应5.0h,氨肟化反应收率89.41%,选择性高达98.38%。在预实验的基础上,初步探索了环己酮氨肟化的反应机理。水相中Keggin型杂多负离子通过与过氧化氢形成一种高活性过氧化多酸化合物,使过氧化多酸几乎完全转移到有机相,从而将氧原子从过氧化多酸转移到底物,催化环己酮氨肟化反应。此外,杂多酸的酸性可增加羰基的亲电性,有利于亲核试剂的进攻,并使醇胺的羟基质子化,利于肟的生成。实验结果还表明,高浓度的双氧水对肟的选择性无明显影响,由此推测氨肟化反应可能是按羟胺机理进行的。本文通过大量系统性的实验,制备了以SiO2、活性炭、活性Al2O3、水滑石等为载体的负载型催化剂,用BET、FTIR、XRD进行了表征。结果表明,活性组分可不同程度与载体结合,但其结构并未发生变化。首次用负载型杂多酸(盐)催化环己酮氨肟化反应,结果表明,以活性Al2O3为载体的杂多酸(盐)催化剂性能最好,环己酮肟收率达90.23%,选择性高达99.78%,比均相催化剂更高。负载后的催化剂易分离,但由于活性组分(盐)易溶脱,在催化剂回收方面未能达到预期的效果。更多还原

【Abstract】 Cyclohexanone oxime is one of the most important intermediate in the industrial caprolactam technology in which benzene is used to be raw material. Conventionally it is synthesized in the cyclohexanone-hydroxylamine process. Using Titanium Silicate-1(TS-1) as catalyst, cyclohexanone oxime can be prepared from cyclohexanone, ammonia and hydrogen peroxide, which is called liquid phase ammoximation process. It can not only proceed in mild reaction condition, reach high selectivity, but also can avoid byproducts, finally realize“Zero Emission”. In 1990, Enichem of Italy developed and built an industrial equipment of liquid phase ammoximation catalyzed by titanium silicate-1, which opened a new period of cyclohexanone oxime industrial producing. However, TS-1 is very expensive and with small-granularited catalyst, which causes difficulties in industrial production, for example separation and recycle. So, how to separate and reclaim the titanium silicate-1 zeolite is becoming the most urgent problem to be resolved in the research and development of ammoximation of cyclohexanone.In this thesis, environment-friendly heteropoly acid(salts) catalyst are used in the ammoximation reaction of cyclohexanone. In the first part, a series of heteropoly acid(salts) are successfully synthesised, in which P is acted as the central atom and W、Mo、V are acted as coordinating group. They are characterized by FTIR, XRD, ICP and the results reveal that heteropoly acids get the Keggin-type structure. Then, the main factors which affect the yield of heteropoly acids are studied, such as reaction temperature, material ratio, pH value and quantity of solvent. The experiment results show that under condition of boiled and pH 1.6~1.8, the yield of heteropoly acids can reach up to 82.51%.In chapter two, the synthesised heteropoly acids(salts) are estimated by ammoximation of cyclohexanone system. Results show that the heteropoly acids with Keggin structure have the advantages of high catalyse ability, excellent selectivity and stability, mild reaction condition and free of pollution. Using heteropoly acids as catalyst, the ammoximation reaction process are optimized and effects of the dosage of catalyst, reaction temperature, reaction time, the dosage of H2O2 and solvent on reaction are inverstigated. The results indicate that using water as solvent, at 20℃for 5.0h, with H3PW12O40 19.6g/1mol cyclohexanone and ratio of hydroperoxide/acetone 1.6/1, the conversion of cyclohexanone and the selectivity of cyclohexanone oxime can reach 89.41% and 98.38% respectively.On the base of plenty preliminary experiments, the reaction mechanism of ammoximation catalyzed by heteropoly acids(salts) is studied. In the proposed mechanism, the Keggin-type heteropoly negative ion is bonded with H2O2 in aqueous phase, forms the active peroxidized heteropoly compounds and transfers most of the peroxidized polyacid into the organic phase, then oxygen is transfered from peroxidized polyacid to the substrate, which catalyzes the ammoximation. Moreover, the electrophilicity of the carbonyl group can increase the acidity of heteropoly compound. This not only creats a suitable condition for the attack of nucleophilic reagent, but also make the hydroxyl group in alcohols and amine protonation, which benefit the formation of cycohexanoxime. Meanwhile, results indicated that high concentration of hydroperoxide has no significant influence on the selectivity of oxime, which supposes that the mechanism of ammoximation is hydroxylamine approach.At the last part of this thesis, on the basis of systemic research experiments, the immobilized catalysts, which supported on silicon dioxide, active carbon and active alumina, are prepared and characterized by BET, FTIR, XRD. Results proved that the active ingredient is combined with carrier and the characteristic structure is unchanged. The result of ammoximation catalyzed by immobilized heteropoly acids(salts) for the first time shows that the Al2O3-based catalyst exhibits the highest activity with a yield of 90.23% and a selectivity of 99.78%, even better than homogeneous catalyst. Though the immobilized catalyst is easily separated, but active ingredient is also easy off-bonded and the reuse of catalyst can not achieve the prospective results.更多还原