生物基乳酸催化转化生成2,3-戊二酮研究

发布时间：2018-06-04 08:26

本文选题：2 + 3-戊二酮　；参考：《西华师范大学》2017年硕士论文

【摘要】：2,3-戊二酮为黄绿色油状液体,主要用作食品香精的原料,明胶硬化剂,相片的粘结剂等。其天然品存在于芬兰松等精油中,远不能满足需求。现有的合成方法有:1)在盐酸羟胺存在下,用氮气保护,将甲基丙酮用过量亚硝酸钠和稀盐酸氧化而制得。2)由羟基丙酮与己醛在酸性催化下通过缩合反应得到。但上述两种合成方法均采用了大量的液体酸,生产过程废酸排量较大,对环境存在着较大的危害。因而,2,3-戊二酮的清洁生产在当下具有紧迫性。近年来,生物质及其衍生物由于具有可持续性、可再生性和绿色环保性,因此其开发利用成为重要的研究课题之一,受到国内外的广泛关注。基于此,本论文选择生物基乳酸为原料,通过催化缩合方式合成2,3-戊二酮展开研究,旨在探索一条2,3-戊二酮的清洁生产路线。2,3-戊二酮的合成存在的主要问题在于催化剂的表面酸碱位与缩合反应不匹配,导致反应选择性低;活性组分在反应过程中易于流失,导致稳定性较差。本文从催化剂分子设计思路出发,来构建缩合反应催化剂,结合现代表征手段探明催化剂表面酸碱位与缩合反应活性之间的关系,深入探讨催化剂的制备条件与反应工艺条件对反应的影响,在此基础上,提出了可能的反应机理。本文具体的研究内容如下:催化剂的制备采用浸渍法和沉淀法。催化剂的表征方面,主要采用了X-射线粉末衍射(XRD)、红外(FT-IR)对催化剂结构进行了表征;采用EDX对催化剂的元素组成进行了分析;采用N2-物理吸脱附(BET)、扫描电镜(SEM)等对催化剂的织构、外貌进行了分析;采用化学吸附-脱附(CO2-TPD/NH3-TPD)研究了催化剂表面的酸碱位分布及密度。催化剂活性评价采用固定床微反应装置进行气固催化反应活性评价。本论文主要研究了二氧化硅负载的碱金属硝酸盐,铯掺杂的镁铝复合物和铯掺杂的羟基磷灰石三大体系。催化剂体系1:二氧化硅通过浸渍法将不同碱金属硝酸盐负载其表面,并将该催化剂用于乳酸缩合反应生成2,3-戊二酮的反应中。考察了反应温度、硝酸盐的负载量等对乳酸缩合反应的影响。以4.4%(x,摩尔分数)CsNO3/SiO2为催化剂,在反应温度为300℃条件下,2,3-戊二酮的收率达54.1%。关联催化剂的活性与CO2-TPD表征的碱性发现,碱性位是影响该反应的关键,碱性位越多,活性越好。催化剂体系2:虽然前述催化剂体系对缩合反应的初始活性比较高,但稳定性较差,其原因在于活性组分Cs在催化反应过程中的流失。为了解决催化剂的稳定性,我们采用了原位分子组装手段,将活性组分Cs掺杂到载体结构中去,为此制备出了一系列掺杂型的镁铝复合物催化剂。并考察了镁铝比对催化剂性能的影响。在选用最优选的催化剂,在反应温度为300℃条件下,2,3-戊二酮的收率达30%,收率不高,但其稳定性较前一个体系相比有了较大的提高。催化剂体系3:尽管催化剂体系2的催化剂活性不高,但稳定性较好,表明分子组装手段掺杂活性组分Cs有可行性。在此思路指导下,我们采用分子组装手段制备了Cs掺杂的羟基磷灰石催化剂。考察了煅烧温度和硝酸铯的掺杂量这两个重要影响因素对催化剂的性能的影响。此外,还就反应工艺条件中的反应温度、原料乳酸的进样速率和乳酸浓度也进行了优化。在优选的最佳比例和最佳煅烧温度下,反应温度为290摄氏度条件下,2,3-戊二酮的收率可达65%左右;更为重要的是催化剂的稳定性很好,达40 h。通过对催化剂表征发现,催化剂表面的酸-碱位是影响催化活性的关键,碱位/酸位比为7-8,催化性能好,基于此,提出了乳酸缩合反应的酸碱协同催化反应机理。
[Abstract]:2,3- glutarone is a yellow green oil like liquid, which is mainly used as the raw material of the flavor of food, gelatin sclerosing agent, and the binder of the photo. Its natural products are found in the essential oil of Finland pine and so on. The existing synthetic methods are: 1) in the presence of hydroxylamine hydrochloride, it is protected by nitrogen, and the methyl acetone is oxidized by excessive sodium nitrite and dilute hydrochloric acid. .2) is obtained by the condensation reaction of hydroxyl acetone and acetaldehyde under the acid catalysis. However, the two synthetic methods have adopted a large amount of liquid acid. The production process has a large amount of waste acid and has a great harm to the environment. Therefore, the clean production of 2,3- glutarone is urgent at the moment. In recent years, biomass and its derivatives are from Because of its sustainability, renewable and green environmental protection, its development and utilization has become one of the most important research topics, and is widely concerned at home and abroad. Based on this, this paper chooses biologically based lactic acid as the raw material and syntheses 2,3- glutarone through catalytic condensation. The purpose of this study is to explore a clean production route of 2,3- glutarone.2 The main problem of the synthesis of 3- glutarone is that the surface acid base position of the catalyst is not matched with the condensation reaction, and the reaction selectivity is low. The active component is easily lost during the reaction process and leads to the poor stability. The relationship between the surface acid base position of the chemical agent and the activity of condensation reaction, the influence of the preparation conditions of the catalyst and the reaction process conditions on the reaction are deeply discussed. On this basis, the possible reaction mechanism is put forward. The specific content of this paper is as follows: the preparation of the catalyst is made by impregnation and precipitation. The structure of the catalyst was characterized by X- ray powder diffraction (XRD) and infrared (FT-IR); the composition of the catalyst was analyzed with EDX; the texture and appearance of the catalyst were analyzed by N2- physical desorption (BET), scanning electron microscope (SEM) and so on. The acid base of the catalyst surface was studied by chemical adsorption desorption (CO2-TPD/NH3-TPD). A fixed bed microreaction device was used to evaluate the activity of gas solid catalytic reaction. This paper mainly studied three major systems: silica loaded alkali metal nitrate, caesium doped magnesia aluminum complex and cesium doped hydroxyapatite. The catalyst body 1: silica was impregnated with different alkaloids. The metal nitrate is loaded on its surface, and the catalyst is used in the reaction of lactic acid condensation to produce 2,3- glutarone. The effect of reaction temperature, nitrate load and so on on the condensation reaction of lactic acid is investigated. The yield of 2,3- glutarone is 54.1%. with 4.4% (x, mole fraction) CsNO3/SiO2 as the catalyst and the yield of 2,3- glutarone at the reaction temperature of 54.1%. The activity of the catalyst and the alkaline discovery of the CO2-TPD showed that the basic position is the key to the reaction. The more basic position and the better the activity, the catalyst system 2:, although the initial activity of the catalyst system is high, but the stability is poor, the reason is the loss of the active component Cs during the catalytic reaction. The stability of the chemical agent, we used the in situ molecular assembly method, doped the active component Cs into the carrier structure, and prepared a series of doped magnesium aluminum complex catalysts. The effect of magnesium aluminum ratio on the performance of the catalyst was investigated. The optimum catalyst was selected and the 2,3- glutarone was used at the reaction temperature of 300. The yield is 30%, the yield is not high, but the stability of the catalyst system has been greatly improved compared with the previous system. Although the catalyst system 3: is not highly active in the catalyst system 2, the stability is good. It shows that the molecular assembly method is feasible to doping the active component Cs. Under the guidance of this train of thought, we have prepared the Cs doping by molecular assembly. The effect of the two important factors of calcining temperature and the amount of caesium nitrate on the performance of the catalyst was investigated. In addition, the reaction temperature in the reaction conditions, the injection rate and the concentration of lactic acid were also optimized. At optimum proportion and the optimum calcination temperature, the reaction temperature was obtained. Under the condition of 290 degrees Celsius, the yield of 2,3- pentan is about 65%. More importantly, the stability of the catalyst is very good. Up to 40 h. through the characterization of the catalyst, the acid base position on the surface of the catalyst is the key to the catalytic activity, the base / acid ratio is 7-8, and the catalytic activity is good. Based on this, the acid base coordination of lactic acid condensation reaction is put forward. The mechanism of the same catalytic reaction.
【学位授予单位】：西华师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O623.523

【参考文献】