新型多酸催化剂的设计合成及在乙酰丙酸烷基酯制备中的催化性能研究

发布时间：2018-01-16 12:10

本文关键词：新型多酸催化剂的设计合成及在乙酰丙酸烷基酯制备中的催化性能研究　出处：《东北师范大学》2017年博士论文　论文类型：学位论文

【摘要】：随着化石能源的日益枯竭,生物质能源作为可替代能源之一引起了人们的关注。乙酰丙酸烷基酯是一类重要的生物质基平台化学品,用作柴油和汽油的含氧添加剂,可以提高生物柴油的低温流动性。目前制备乙酰丙酸烷基酯的方法包括乙酰丙酸与醇的酯化、糖类(单糖、二糖或多糖)的醇解、糠醇的醇解等。但这几种合成路线都受制于热力学平衡,需要加入过量的醇来推动反应平衡向产物方向进行,因此产物在醇溶液中的浓度过低,增加了分离纯化产物的成本,并且还存在反应温度高、转化步骤多等缺点,不符合“绿色化学”的要求。Manzer等人和亚琛工业大学Palkovits教授团队以商业固体酸催化剂(Amberlyst-36)在无水无氧条件(Schlenk真空线,N2惰性气体保护)从ɑ-当归内酯出发与醇作用制得乙酰丙酸烷基酯,提出乙酰丙酸烷基酯的新合成路线。但这种苛刻的反应条件不利于此反应在工业上的应用。因此,我们开创性地提出了一种合成乙酰丙酸烷基酯的新策略:即在新型杂多酸的催化作用下,等摩尔量的醇与ɑ-当归内酯加成,生成的中间体(异-乙酰丙酸烷基酯)在强Br?nsted酸性催化下经过酯交换过程得到主产物乙酰丙酸烷基酯。并基于此模型反应,开展了多金属氧酸盐的酸性能与催化活性间关系的研究。(1)筛选了一系列Keggin/Dawson型分子杂多酸,并从中遴选出了Br?nsted酸性最强,对模型反应活性最高的H_6P_2W_(18)O_(62)。以Dawson型分子杂多酸H_6P_2W_(18)O_(62)和氯化铯(CsCl)为前体,通过离子交换法使Cs+交换杂多酸二级结构中的抗衡阳离子H+合成了一系列固体催化剂Cs_nH_(6-n)P_2W_(18)O_(62)(n=1-6)。催化剂结构通过各种表征方法确定,同时考察了系列催化剂在模型反应中的活性。Cs+的引入导致催化剂总酸量下降,Cs_nH_(6-n)P_2W_(18)O_(62)(n=1-6)中Cs+数目越多催化剂的非均相性越强。相反在ɑ-当归内酯与醇的反应中发现催化剂的活性与Cs含量有关,提高Cs含量催化剂的活性降低。综合考虑到系列催化剂Cs_nH_(6-n)P_2W_(18)O_(62)(n=1-6)的总酸量、活性和非均相性三个影响因素,Cs3H3P2W18O62为最佳催化剂。在最佳反应条件下:ɑ-当归内酯(0.625 g,6.375 mmol)、正丁醇(0.473 g,6.375 mmol)、75℃、1.5 h、催化剂Cs3H3P2W18O62用量(15 wt%=93.75mg),可以高效制得乙酰丙酸丁酯(产率为79.6%)。催化剂具有良好的机械稳定性,可以循环使用5次而保持较高活性。(2)以Dawson型分子杂多酸H_6P_2W_(18)O_(62)和氯化胆碱ChCl为前体,通过离子交换法合成了一系列具有温控性能的杂多酸催化剂Ch_nH_(6-n)P_2W_(18)O_(62)(n=1-6),并通过各种表征手段确证其结构。我们考察了催化剂Ch_nH_(6-n)P_2W_(18)O_(62)(n=1-6)在模型反应中的活性,发现Ch的引入一方面影响催化剂的酸性,另一方面控制催化剂的温控性(即在高温反应时催化剂溶解于反应混合物中,在反应结束降温至室温时催化剂自动从反应体系中析)。综合考虑到催化剂的活性与温控性能,Ch2H4P2W18O62是模型反应的最佳催化剂。在最佳反应条件下:ɑ-当归内酯(0.625 g,6.375 mmol)、正丁醇(0.473 g,6.375 mmol)、75℃、1 h、催化剂Ch2H4P2W18O62用量为(20 wt%=125.12 mg),可以高效制得乙酰丙酸丁酯(产率为79.4%)。催化剂易于再生,可以循环使用5次而保持较高活性。(3)第二与第三章中的非均相多酸催化剂是利用调节抗衡离子的形式实现的,但所合成的多酸催化剂仍只具有单一的Br?nsted酸性能且机械稳定性仍然不够强。第四章中利用介孔ZrO_2/Si O_2复合载体(m-SiZr),采用浸渍法将H_6P_2W_(18)O_(62)固载到m-SiZr上制备出Br?nsted酸性/非均相性都很强的D-HPW/m-SiZr复合材料。采用一系列表征方法确定其组成和结构,以ɑ-当归内酯和醇的加成反应为模型反应,充分研究了各物理化学性质对催化活性的影响。在最佳反应条件下:ɑ-当归内酯(0.625 g,6.375 mmol)、正丁醇(0.473 g,6.375 mmol)、75℃、1 h、催化剂D-HPW/m-Si Zr(5 wt%=31.28 mg),可以高效制得乙酰丙酸丁酯(产率为91.1%),催化剂重复使用6次而保持较高活性。(4)为了深入探索双酸中心催化剂对乙酰丙酸烷基酯产率的促进作用,因此第五章评价了一系列双酸中心的杂多酸催化剂HnPW11MO40(M=TiIV、CuII、AlIII、SnIV、FeIII、CrIII、ZrIV、ZnII)在该模型反应中的活性。即研究了不同Lewis酸性金属M的引入对催化剂HnPW11MO40的Br?nsted/Lewis酸性质和催化活性的影响。发现Lewis酸性的掺杂会提高催化剂的总酸量,导致其对ɑ-当归内酯制备乙酰丙酸烷基酯(模型反应)中的酸催化活性提高。H_5PW_(11)TiO_(40)的催化活性最高,经过高温煅烧处理后的H_5PW_(11)TiO_(40)不溶解于反应混合物,展现出了催化剂的非均相性。H_5PW_(11)TiO_(40)超高的酸催化活性可以使ɑ-当归内酯与不同的脂肪醇加成高效制备一系列乙酰丙酸烷基酯,并且H_5PW_(11)TiO_(40)可以高效循环使用5次。在最佳反应条件下:ɑ-当归内酯(0.625 g,6.375 mmol)、正丁醇(0.473g,6.375 mmol)、75℃、10 min、催化剂H_5PW_(11)TiO_(40)(1 wt%=6.256 mg),可以高效制得乙酰丙酸丁酯(产率为96.3%)
[Abstract]:With the increasing depletion of fossil energy, biomass energy as one of the alternative energy has attracted people's attention. Levulinic acid alkyl ester is an important type of biomass based platform chemicals, oxygen additives for diesel and gasoline, can improve the low-temperature fluidity of biodiesel. The method of preparation of levulinic acid esters including acetyl esterification propionic acid and alcohols, sugars (monosaccharides, two sugars or polysaccharides) alcoholysis, furfuryl alcohol alcoholysis. But these synthetic routes are subject to thermodynamic equilibrium, need to add excess alcohol to promote the equilibrium reaction to product direction, so the product of low concentration in the alcohol solution, increase the separation and purification of products the cost, and also has high reaction temperature, transformation steps and other shortcomings, does not conform to.Manzer et al and Professor Palkovits of Rheinisch Westfaelische Technische Hochschule Aachen University team of green chemistry to commercial solid Acid catalyst (Amberlyst-36) in anhydrous conditions (Schlenk vacuum line, inert gas protection from N2) - alpha Angelica lactone and alcohols of levulinic acid is prepared from alkyl ester, a new synthetic route of levulinic acid alkyl ester. But this is not conducive to the harsh reaction conditions of this reaction in industrial applications. Therefore, we put forward a new strategy for the synthesis of levulinic acid alkyl ester: heteropoly acid catalysis in the model, alcohol and alpha - equimolar amounts of Angelica lactone addition, generated intermediates (ISO levulinic acid alkyl ester) in Br? Nsted Acid catalyzed transesterification process after production levulinic acid alkyl ester compounds. And based on this model, carried out the research of the relationship between catalytic activity and acid polyoxometalates. (1) screening of a series of Keggin/Dawson type heteropoly acid molecules, and from the selection of the Br? Nsted Acid The strongest, the highest model reaction activity of H_6P_2W_ (18) O_ (62). The H_6P_2W_ Dawson type molecular heteropoly acid (18) O_ (62) and cesium chloride (CsCl) as the precursor to Cs+, a series of solid catalyst to synthesize Cs_nH_ counter cation H+ exchange two level structure of heteropoly acid by ion exchange method (6-n P_2W_) (18) O_ (62) (n=1-6). The catalyst structure was determined by various characterization methods, also studied the introduction of active.Cs+ series catalyst in the model reaction to the total acidity of catalyst decreased, Cs_nH_ (6-n) P_2W_ (18) O_ (62) (n= 1-6) in the number of non catalyst Cs+ are the stronger. In contrast to alpha - Angelica lactone reaction with alcohol found in the activity of the catalyst is related to the content of Cs, increase the content of Cs catalyst activity decreased. Considering the series of catalyst Cs_nH_ (6-n) P_2W_ (18) O_ (62) (n= 1-6) of the total acidity, activity and heterogeneous of the three factors, Cs3H3P2W 18O62 is the best catalyst. Under the optimum reaction conditions: alpha - Angelica lactone (0.625 g, 6.375 mmol), n-butanol (0.473 g, 6.375 mmol), 75 C, 1.5 h, catalyst dosage of Cs3H3P2W18O62 (15 wt%=93.75mg), can efficiently produce acetyl butyl propionate (yield 79.6%). The catalyst has mechanical stability good, can be recycled 5 times and kept high activity. (2) to H_6P_2W_ Dawson (18) O_ type heteropoly acid molecules (62) and choline chloride as the precursor of ChCl, synthesis of a series of temperature properties of heteropoly acid catalyst by ion exchange Ch_nH_ (6-n) P_2W_ (18) O_ (62) (n=1-6), and its structure was confirmed by various characterization methods. We investigated the catalyst Ch_nH_ (6-n) P_2W_ (18) O_ (62) (n=1-6) in the model reaction activity, found that the introduction of Ch influences the acidity of the catalyst, the temperature of the other hand control catalyst in high temperature reaction (i.e. when the catalyst Dissolved in the reaction mixture, at the end of the reaction temperature to room temperature when the catalyst from the reaction system of automatic temperature control performance and comprehensive activity). Considering the catalyst, Ch2H4P2W18O62 is the best catalyst reaction model. Under the optimum reaction conditions: alpha - Angelica lactone (0.625 g, 6.375 mmol), n-butanol (0.473 G. 6.375 mmol), 75 C, 1 h, Ch2H4P2W18O62 catalyst dosage (20 wt%=125.12 mg), can efficiently produce acetyl butyl propionate (yield 79.4%). The catalyst can be easily recycled, can be recycled 5 times and kept high activity. (3) the second and third chapter in the heterogeneous multi acid catalyst is used regulation of counterions in the form, but more acid catalyst still has only a single Br? Nsted acidity and the mechanical stability is not strong enough. The mesoporous ZrO_2/Si O_2 composite carrier in Chapter fourth (m-SiZr), H_6P_2W_ (1 by impregnation method 8) O_ (62) supported on m-SiZr prepared Br? Nsted Acid / heterogeneous is strong D-HPW/m-SiZr composites. A series of characterization methods to determine its composition and structure, with the alpha - Angelica lactone and alcohol addition reaction as a model, to fully investigate the influence of physical chemistry the nature of the catalytic activity. Under the optimum reaction conditions: alpha - Angelica lactone (0.625 g, 6.375 mmol), n-butanol (0.473 g, 6.375 mmol), 75 C, 1 h, D-HPW/m-Si (Zr wt%=31.28 mg 5 catalyst), can efficiently produce acetyl butyl propionate (yield 91.1%), catalyst agent 6 times of repeated use and maintain a high activity. (4) in order to explore the role of double acid catalyst on the yield of levulinic acid alkyl ester, so the fifth chapter evaluates a series of heteropoly acid catalyst HnPW11MO40 double acid sites (M=TiIV, CuII, AlIII, SnIV, FeIII, CrIII, ZrIV, ZnII) in the model in the reaction activity. That is to study the introduction of different Lewis M acidic metal on the catalyst of HnPW11MO40 Br? Nsted/Lewis acid properties and catalytic activity. Lewis acid doping can improve the total acidity of the catalyst, the alpha Angelica lactone - Preparation of levulinic acid alkyl ester (model) acid catalytic activity increased in.H_5PW_ (11) TiO_ (40) the highest catalytic activity, calcined after H_5PW_ (11) TiO_ (40) is not dissolved in the reaction mixture, showing a heterogeneous.H_5PW_ (11) TiO_ (40) acid catalytic activity can make high - alpha Angelica lactone with different fatty alcohol and into a series of efficient preparation of levulinic acid alkyl ester, and H_5PW_ (11) TiO_ (40) can be efficiently recycled 5 times. Under the optimum reaction conditions: alpha - Angelica lactone (0.625 g, 6.375 mmol), n-butanol (0.473g, 6.375 mmol), 75 C, 10 min (11 H_5PW_, catalyst (1) TiO_ (40) wt% =6.256 mg), the yield of butyl levulinate (96.3%) can be produced efficiently.

【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;TQ225.24

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