Purification And Oxidative Cleavage Of Methyl Oleate

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.