【作者】 马利娜；

【导师】 计建炳；

【作者基本信息】 浙江工业大学 ， 化学工程， 2013， 博士

【摘要】 传统化学工业是以石化资源,如石油、煤炭、天然气等为原料,实现物质转换得到所需要的最终产品。随着可再生生物能源的发展,生物柴油正在作为一种柴油机燃料的添加剂、一种极具潜力的车用燃料替代品,推动着以可再生的生物资源替代石化资源作为原料的化工产业迅猛发展。以生物柴油为原料制备出高附加值产品,一方面可以大大提高资源利用率,另一方面对生物柴油的产业化显得异常重要。发展以生物柴油为基础的化工产业链逐步成为现阶段的研究热点。由于醛／酸及其衍生物是制药、化妆品等重要的化工中间体,具有较高的附加值,所以在对双键转化的众多工艺过程中,将较长的不饱和脂肪链氧化裂解得到短链脂肪醛或酸是比较令人感兴趣的。相对于将油酸甲酯氧化裂解得到壬酸和壬二酸氢甲酯来说,将其裂解为壬醛和壬醛酸甲酯研究较少,所以本论文将围绕油酸甲酯氧化裂解制备醛展开工作。从以往的文献中可以看出采用油酸甲酯一步法氧化裂解制醛过程中存在转化率较低或者转化率高了但选择性较低,采用多步法制醛多为有机合成常用方法,不经济,所以本文选用两步法对油酸甲酯进行氧化裂解(即：经环氧化—氧化裂解)。下面对研究的内容进行介绍：1.油酸甲酯的精馏提纯。为得到纯度较高的油酸甲酯供后续反应需要,选择乌桕皮油作为初始原料。首先采用两步法(预酯化-酯交换)将乌桕皮油转化为生物柴油(脂肪酸甲酯,FAME)。其次,自行搭建精馏塔,在塔顶绝压为1mmHg左右将生物柴油分离得到高纯度的棕榈酸甲酯(>99.5%)和油酸甲酯(>85%)。然后,将间歇精馏改为分批进料方式。在分批进料3次后,C18：1(>85%)的收率提高到63.2%,C18:1(>90%)的收率达到了45%,而C18：1(>93%)收率达到了10%。由此可以看出,通过分批进料方式大大的提高了高纯度油酸甲酯的收率。继续增加分批进料次数,最终获得了C18：1(>97%),且收率有25%的高纯度油酸甲酯。2.油酸甲酯的环氧化。这部分本文分两种环氧化方法进行考察。(1)考察了甲酸原位环氧化各工艺条件的影响：反应温度、反应时间、双氧水：油酸甲酯、带水剂：油酸甲酯,采用L16(45)正交试验筛选环氧油酸甲酯工艺条件。从极差值结果看出甲酸的加入量是对油酸甲酯环氧化有较大影响,而溶剂对环氧化的影响相对最小。从方差分析结果看出反应温度和甲酸的添加比例对环氧化效果具有显著意义。提高反应温度,增长反应时间均有利于环氧化反应,但考虑到过高的反应温度会造成双氧水的分解,所以最优反应条件为温度80℃,反应4小时,甲酸和双氧水与油酸甲酯比例均取2,溶剂与油酸甲酯摩尔比为10的。通过试验验证,环氧油酸收率可达94%。(2)近年来众多文献报道了含钛分子筛在烯烃环氧化中取得了较为满意的环氧化效果。本文首次采用冷冻处理后的MCM-41载体,以含水的TiCl4溶液作为钛源,制备含钛分子筛TiO2/MCM-41(C)。同时,以未经冷冻处理的载体MCM-41为载体,采用同样的方法所制备了Ti02/MCM-41(H)。通过电感耦合等离子体质谱(ICP-MS)、X射线衍射(XRD)、BET表征、透射电镜(TEM)等技术对以上所制备的含钛分子筛进行表征。结果发现TiO2/MCM-41(C)具有更高的微孔有序性、氧化钛物种的分布更加均匀并且与载体之间具有更强的相互作用。当钛的负载量达到76.6mg/g时,孔径从3.4nm减少到了2.4nm。油酸甲酯在353K下环氧反应10h后,MO的转化率可达97.6%,环氧油酸甲酯(MES)选择性可达93.1%。TiO2/MCM-41(C)经3次循环使用后,仍可保持最初的优良催化性能。3.环氧油酸甲酯氧化裂解制备壬醛和壬醛酸甲酯。采用原子层沉积法(ALD)法制备出一系列不同WO3含量的WO3/HMS催化剂,通过ICP-MS、XRD、BET、TEM等技术对制备的催化剂进行了详细表征。在以双氧水为氧化剂的环氧油酸甲酯(MES)氧化裂解制壬醛酸甲酯(MAA)反应中考察了催化剂性能,并与以SBA-15和MCM-41为载体制备的含钨催化剂进行了比较。表征结果证实,对于载体HMS,钨含量小于5%时钨物种能均匀的分散在HMS的孔道中,而采用SBA-15和MCM-41为载体时,以5wt.%的比例制备时,钨的实际含量明显低于5wt.%,并且钨物种出现了团聚现象。反应结果表明,以HMS为载体,钨含量小于5wt.%的WO3/HMS表现出较好的选择性,MAA的产率可达80%以上；溶剂对反应选择性影响较大,以t-BuOH和二氧六环作为溶剂有利于反应进行；随着反应温度的升高,MES的转化率明显提高。另外,催化剂2-WO3/HMS重复使用3次后催化活性仍能基本保持。4.环氧油酸甲酯氧化裂解机理及动力学模型的建立。首先是对2-WO3/HMS氧化裂解MES中所产生的中间产物采用核磁,红外等表征手段证实在氧化裂解过程中,一个环氧化物分子首先形成了过氧化物,再经热重排而得到两分子的醛。在排除外扩散的影响下,并考察了内扩散对反应的影响。其次,在此基础上建立本征动力学模型。进行了一系列的本征动力学实验测定。最后,采用非线性最小二乘法对模型参数进行估算,且估算值达到F检验值的要求。更多还原

【Abstract】 Non-renewable fossil, such as oil, coal, natural gas, is used as raw material in the traditional chemical industry. With the development of renewable biological resources, biodiesel was used as an additive of diesel fuel and a potential succedaneum of fuel, which promot the rapid development of chemical industries base on renewable resources. Producing high value-added products from biodiesel as raw material will increase resource utilization rate and is important for biodiesel industrialization. Recently, development chemical industry chain base on biodiesel gradually become a research hotspot.In particular, the oxidative cleavage of long aliphatic chain fatty acid methyl esters, leading to short aliphatic chain aldehydes and acids is interesting among so many possible carbon double bond functionalizations, because acids, aldehydes and their derivations is important chemical intermediates for lubricants, plastictizers, adhesives, cosmetics and pharmaceuticals with high value-added. The research on oxidative cleavage to aldehydes is less relative to the research on oxidative cleavage to acid. From the previous literatures, we can find low conversion or high conversion with low selectivity using one-step oxidative cleavage of methyl oleate to aldehydes. And multi-steps methods are always applied in organic synthesis, diseconomic. Therefore, a process for the production of nonanal and methyl azelaaldehydate by oxidative cleavage of the methyl oleate (MO) in two reaction steps (epoxidation and oxidative cleavage) was studied in this paper. The details in this work are summarized as follows.1. MO purification. In order to get high purified MO for the following process requiring, tallow oil was chosed as the raw material. First, biodiesel was preparaed by two steps, esterification and interesterification, from tallow oil. Second, a vacuum rectification tower was built. And the high purify MO (90%) and methyl palmitate (>99.8%) were obtained by vacuum rectification (about1mmHg). Then, the operation process was changed to batch feeder. After3times feeder, the yield of C18:1was improved to63.2%(>85%),45%(>90%), as well as10%(>93%). The results show that, the batch-feeded process has improved the yield of high purity C18:1. Last but most, the yield of C18:1(>97%) was25%by using muti batch-feed process.2. The epoxidation of MO. Two kinds of epoxidation process were investivaged. (1) The influences of process condition, temperature, reaction time, molar ratio of H2O2/MO and molar ration of solvent/MO, were investigated for the epoxidation of MO with performic acid generated in situ. And the L16(45) orthogonal experimental design was used to optimize the conditions of the epoxidation of MO. The maxmium results show that the moler ratio of formic acid/MO significantly affected the epoxidation yield, and influence of molar ratio of solvent/MO is relatively small. Besides, the results of variance analysis shows that temperature and addition amount of formic acid significantly affected the epoxidation. Improving temperature and extending reaction time are of benefit of the epoxidation. Considering the decomposition of hydrogen peroxide at high temperature, the optimum condition is the mole ratio of formic acid/MO=2, H2O2/MO=2, solvent/MO=10,80℃and reaction for4hours. At last, the yield of epoxide can reach94%at optimum condition.(2) Since titanium-containing molecular sieves have shown to be efficient catalysts for the epoxidation of olefins, titanium-containing mesoporous silica TiO2/MCM-41(C) was first prepared by impregnating MCM-41, pretreated by refrigeration at278K, with aqueous TiCl4solution as titanium precursor. In addition, TiO2/MCM-41(H) was produced by same method but the support MCM-41without refrigeration in order to investigate the influence of unrefrigerated pretreatment on the structure of TiO2/MCM-41. The dispersion and nature of titanium species were characterized by inductively coupled plasma mass spectrometry (ICP-MS), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-visible diffuse reflectance spectra (UV-vis DRS), standard Brunauer Emmnett Teller (BET), X-ray photoelectron spectra (XPS), scanning electron micrographs (SEM), transmission electron microscopy (TEM). The results indicate that TiO2/MCM-41(C) showed better mesoscopic order, higher dispersion of titanium oxide species, stronger interaction with the MCM-41support. But the pore size decreases from3.4nm to2.4nm when the titanium content increases to76.6mg/g. TiO2/MCM-41(C2) exhibits more excellent catalytic performance than others, and the97.6%conversion of methyl oleate (MO) and93.1%selectivity to epoxidation methyl oleate (MES) can be obtained at353K for10h.3. The oxidative cleavage of MES. A series of WO3/HMS catalysts were prepared by atomic layer deposition (ALD) method and characterized by ICP-MS, XRD, BET, and TEM. The application to oxidative cleavage of methyl9,10-epoxystearate (MES) to methyl azelaaldehydate (MAA) with H2O2as oxidant under mild condition was studied. And the effect of catalyst support (SBA-15, MCM-41), reaction temperature and solvents was investigated. The characterization results showed that tungsten species was highly dispersed on the HMS surface as the WO3content of catalyst below5wt.%. However, the contents of tungsten is5wt.%in theory, but lower than5wt.%by ICP-MS for the catalysts supported on SBA-15and MCM-41. And tungsten species partially congregate and form low-crystalline metal oxide species on the surface of supporter. As a consequence, the catalysts WO3/HMS of tungsten content below5%give higher MES conversion and excellent MAA selectivity. On the other hand, elevating reaction temperature and using t-BuOH or dioxane as solvent will favor the oxidation cleavage of MES reaction. In addition,2-WO3/HMS catalyst has good regeneration and can be reused for three times in the oxidation system.4. The mechanism and dynamic model of oxidative cleavage of MES was studied. First, the intermediate of the oxidative cleavage was invesitaged by NMR and FT-IR. The results proved that the intermediate is a kind of peroxide and thermal rearranged to aldehydes under heated condition. And the dynamic model was built base on the above results. Then the dynamic experiments were carried under the elimination the influence of internal and external diffusion. Last, the dynamic parameters were determinated by least square method base on the experimental data and the result achieves the requirement of the F test value.更多还原