【作者】 黄辉；

【导师】 曹贵平；

【作者基本信息】 华东理工大学 ， 化学工程， 2011， 博士

【摘要】 脂肪醇是精细化工的重要基础原料,利用其分子结构中的羟基官能团,与多种化合物进行反应得到的脂肪醇衍生物广泛地应用于表面活性剂、润滑剂等的工业生产。按原料来源来分,脂肪醇可分为合成醇和天然醇。由于受石油价格及消费者偏好的影响,以天然油脂为原料的天然醇生产规模逐渐超过以乙烯为原料的合成醇的生产规模。而脂肪酸甲酯高温高压加氢作为天然醇生产过程中的重要一步,其广泛使用的Cu/Zn催化剂寿命较短,是天然醇产业发展的瓶颈问题。本文研究了脂肪酸甲酯中可能存在的水、含硫化合物、含氯化合物、甘油和甘油酯对Cu/Zn催化剂催化加氢活性的影响,并对部分失活催化剂的二次加氢活性进行了初步探讨。本文的主要研究工作和成果有以下几方面：(1)对不同的脂肪酸甲酯原料进行了筛选,优选了月桂酸甲酯作为适合小试研究的脂肪酸甲酯原料,并在间歇高压釜中对月桂酸甲酯加氢制月桂醇的反应条件进行了优化。结果表明,反应温度为230℃、反应时间为8h、搅拌转速为450rpm、催化剂与月桂酸甲酯的投料质量比为5.5%、反应压力为11MPa是最为适宜的反应条件。(2)在月桂酸甲酯中添加不同质量含量的水,考察了水在月桂酸甲酯加氢制月桂醇的反应初始阶段和结束阶段对Cu/Zn催化剂加氢活性的影响,并通过XRD、BET、H2-TPR、SEM、TEM和ICP-AES对不同水失活程度的Cu/Zn催化剂进行了表征。结果表明,水在加氢反应的初始阶段就已经开始影响Cu/Zn催化剂的加氢活性,且随着水含量的增加,月桂酸甲酯的转化率和月桂醇的选择性随之下降。由于水在油性的反应体系中的溶解度极低,极易积聚在Cu/Zn催化剂表面,覆盖催化活性位,并促使Cu晶粒增长、比表面积降低、催化剂团聚加剧,水热浸出作用同时导致催化剂组分的流失,削弱铜和锌之间的协同效应,导致Cu/Zn催化剂的失活。水失活后的Cu/Zn催化剂的催化加氢活性能够部分恢复。(3)以1,2-二氯乙烷、1,1,2-三氯乙烷、氯代丁烷和氯代十二烷为模型毒物,考察了月桂酸甲酯加氢制月桂醇Cu/Zn催化剂的氯失活过程,并通过XRD、BET、ICP-AES和SEM对不同氯失活程度的Cu/Zn催化剂进行了表征。结果表明,月桂酸甲酯的转化率和月桂醇的选择性均随着不同含氯化合物含量的增加而降低。含氯化合物的存在会改变活性位的价态、降低催化剂的比表面积、促进Cu晶粒的增长、加剧Cu/Zn催化剂的团聚。从含氯化合物中分解出的氯原子能与催化剂中的ZnO结合生成溶于反应体系液相的ZnCl2,这又可以作为路易斯酸促进交酯反应的进行而得到副产物十二酸十二酯。(4)考察了硫醇、二硫醚和其他结构的硫化物对月桂酸甲酯加氢制月桂醇Cu/Zn催化剂的影响,并通过XRD、EDS和XPS对硫失活催化剂进行了表征。结果表明,月桂酸甲酯的转化率和月桂醇的选择性不仅分别随着硫醇和二硫醚的硫含量的增加而降低,且随着硫醇和二硫醚的碳链的增长而降低。在低硫浓度时,硫醇和二硫醚中的硫会与Cu/Zn催化剂中的Zn组分结合生成ZnS；在高硫浓度时,硫醇和二硫醚中的硫在与Zn组分结合外,还会与Cu组分结合生成硫化铜。此外,含硫化合物的毒性大小还与其结构有关,含硫化合物的质子亲合能越大,其对Cu/Zn催化剂的毒性越大。(5)在间歇高压釜中考察了甘油和三乙酸甘油酯对Cu/Zn催化剂上月桂酸甲酯加氢制月桂醇催化活性的影响,并采用XRD、BET、GC-MS和TG-DTA等方法对失活催化剂和反应产物进行了分析。结果表明,月桂酸甲酯的转化率和月桂醇的选择性均随着甘油和三乙酸甘油酯含量的增加而降低。甘油和三乙酸甘油酯并没有改变Cu/Zn催化剂活性中心的价态,且对催化剂晶粒大小变化影响不大。甘油会在Cu/Zn催化剂的作用下分解得到强疏油性物质1,2-丙二醇,并会吸附在催化剂上,导致催化剂活性中心被覆盖,催化剂比表面积减小,进而引起Cu/Zn催化剂的失活。但甘油失活催化剂可以通过甲醇处理再生恢复活性。三乙酸甘油酯会被加氢生成乙醇和甘油,同时经酯交换得到一系列副产物。而生成的部分甘油会再进一步得到丙烯醛,而这种含有双键的物质很容易聚合为难熔且难以溶解于常规溶剂的交联物,并覆盖催化剂的活性中心,降低催化剂的比表面积,也导致Cu/Zn催化剂的严重失活。更多还原

【Abstract】 Fatty alcohols, as important raw materials for industry of fine chemicals, could be used to produce their derivatives by reacting with many compounds using its hydroxyl group, which have found numerous applications in surfactants and lubricants production. Fatty alcohol could be divided into natural alcohol and synthetic alcohol by the origination of its feedstock. Based on effect of the price fluctuation of crude oil and preference of terminal customers, the importance of nature fatty acids or esters process is steadily growing relative to the alternative petrochemical process during these years. Hydrogenation step of fatty aicd methyl ester to fatty alcohol is of great importance in the commercial production of natural alcohol. However, the Cu/Zn catalyst, widely used in this process, retains certain activity and slectivity for a relative short time scale, which have been the bottleneck for the development of natural alcohol production. In this dissertation, the effect of various impurities on Cu/Zn catalyst, like water, sulfur-containing compounds, chlorine-containing compounds, glycerine and glycerides, which are difficult to be removed from fatty esters, have been investigated. Furthermore, the rehydrogenation ability of deactivated Cu/Zn catalysts was discussed. The main work and results in this dissertation are listed as follows:(1) Several types of fatty aicd methyl esters were used as feedstock for experimental research of Cu/Zn deactivation, and methyl laurate was selected as the most suitable one. The effect of operation conditions on the hydrogenation of methyl laurate to lauryl alcohol was conducted using a stirred autoclave reactor system. The experimental results indicated that the mass transfer resistance could be eliminated with an agitation rate over 450rpm, the best performance of Cu/Zn catalyst could be reached at the reaction temperature of 230℃, hydrogen pressure of 11MPa, reaction time of 8h and catalyst-ester with a weight ration of 0.055.(2) The effect of water on Cu/Zn catalyst prepared by co-precipiation for hydrogenation of methyl laurate in a slurry phase was studied. The catalysts were characterized by means of XRD, BET, H2-TPR, SEM, TEM and ICP-AES. The results indicate that catalytic activity decreases with increased amount of water in methyl laurate at the initial or ending stage. Correalting with the results from the above characterization, it is found that the main causes for the water deactivation of the Cu/Zn catalyst were the water occlusion of active catalyst sites by the low solubility of water in the substrate and the promotion of crystal growth, as well as the Cu/Zn catalyst agglomeration in the presence of water. The catalytic activity of water deactivcated Cu/Zn catalyst could be patially recovered in the rehydrogenation reaction.(3) The mechanism of deactivation of Cu/Zn catalyst poisoned by organic chlorides in’ hydrogenation of methyl laurate to lauryl alcohol was studied in a stirred autoclave. The un-poisoned and poisoned catalysts were characterized using XRD, BET, ICP-AES and SEM, respectively. The results indicated that both of catalytic activity and selectivity decreased with increasing amount of chlorides in methyl laurate. According to the characterization of the catalysts, the main causes for the chlorine deactivation of the Cu/Zn catalyst were that the chlorides could modify the valence state of active sites, decrease the BET surface area, and promote the growth of crystal and catalyst agglomeration. Further investigation showed that chlorine atom decomposed from the chlorides combined with ZnO to produce ZnCl2, which could be dissolved in the liquid and promote ester-exchange reaction to lauryl laurate as Lewis acid.(4) The sulfur deactivation of Cu/Zn catalyst was studied by investigating the effect of different types of sulfur-containing compounds on the hydrogenation of methyl laurate to lauryl alcohol. To the alkyl thiols and dialkyl disulfides, the conversiton of methyl laurate and the selectivityl of lauryl alcohol decresed not only with the increasing sulfur concentration, but also with the increment of the alkyl chain length. The XRD, EDS and XPS results indicated that alkyl thiols and dialkyl disulfides prefer to adsorb on Zn sites of the oxide followed by reacting with supported Cu, without S-C or S-S bond decomposition during the deactivation. Results of other sulfides deactivation further suggest that the poisoning effect of sulfides could be related to their molecular structures and valence bonds.(5) The effect of glycerine and glyceryl triacetate on the hydrogenation of methyl laurate over Cu/Zn catalyst was investigated, respectively. XRD, BET, GC-MS and TG-DTA were used for catalyst characterization or product analysis. Extremely oleophobic 1,2-propanediol and insoluble highly cross-linked solids could be generated from the thermal decomposition of glyceryl triacetate and glycerine, respectively, and block the catalytic sites by physical adsorption, derease the surface area, leading to the catalyst deactivation. The catalytic activity of glycerine deactivated catalyst could be regenerated by methanol washing.更多还原