【作者】 李辉；

【导师】 汪宝和；

【作者基本信息】 天津大学 ， 化学工艺， 2014， 硕士

【摘要】 羧酸酯是一种重要的精细化工原料及有机合成中间体，广泛应用于涂料，医药，食品，香料以及高分子等领域。传统的酯的合成方法工艺路线长且对生产设备腐蚀严重，醛一步氧化酯化合成羧酸酯的方法具有流程短，反应条件温和，反应后处理简单等诸多优点，具有广阔的应用前景。在一步氧化反应的工艺路线中，高效催化剂的选择是影响该工艺的一个关键因素。首先，本文选用不同疏水程度的载体采用等体积浸渍的方法制备了钯催化剂，并进行评价、表征，结果表明疏水性催化剂具有更高的催化活性。在考察的几种不同的疏水性载体中，SDB(X-5)具有较大的比表面积，且该载体有良好的机械性能，因此是作为催化剂载体的最佳选择。考察了催化剂制备条件对催化剂的影响，确定了最佳还原温度为200℃，还原时间为10h。考察了助组分对催化剂性能的影响,向催化剂Pd3/SDB(X-5)中分别加入Pb、Bi、Fe、Cu等助组分制备了双组份及三组分催化剂，评价结果表明Pb、Bi的加入可以提高反应的转化率及选择性，且催化剂最佳组成为Pd3Pb0.6Bi1.5/SDB(X-5)。TEM表征结果显示助组分的加入使活性组分的粒径减小，在催化剂表面的分布更加均匀。XPS表征结果显示，在多组分催化剂中，出现电子从Pd向Pb和Bi转移的现象。XRD表征结果显示在催化剂中金属组分间存在较强的相互作用，并有合金Pd3Pb及PdBi的生成，这有利于催化剂活性及稳定性的提高。其次，考察了单组分催化剂Pd3/SDB(X-5)用于不同类型的醛和醇的氧化酯化反应，并以苯甲醛的一步氧化酯化反应为例对反应温度，反应时间，反应液中醛醇摩尔比等参数进行了优化，实验结果表明，该催化剂在脂肪醛以及苯环上连接给电子基的芳香醛的氧化酯化反应中有较好的催化性能。最后，采用分子模拟的方法考察了不同疏水程度的催化剂载体对水的吸附性能，通过对饱和吸附量及过程吸附能的计算，从微观层面上研究了催化剂载体的疏水程度对反应活性的影响。更多还原

【Abstract】 Esters, extremely important fine chemical raw materials and organicintermedium, are mainly used for the production of coatings, medicines, foods,flavors and polymers. The traditional esters synthesis routes have the shortages likelong process flow and serious causticity to the equipments and so on. The method thatsingle-step oxidative esterification of aldehydes to esters has a broad applicationprospects with advantages such as short reaction time, mild reaction conditions andsimple posttreatment. In this process, development of catalysts with high efficiency isthe key factor.Firstly, catalysts with different supports were prepared by the incipientimpregnation method; their activities were evaluated and the catalysts werecharacterized. The results indicate that catalysts with hydrophobic carriers have highercatalytic activities. BET results showed that SDB(X-5) has a large surface area, andgood mechanical properties, therefore, SDB(X-5) is the best carrier. The effects ofpreparation conditions on the catalytic reactions were investigated and the resultshowed that reduction temperature200℃, reduction time of10h were the optimum.The effects of co-catalysts on the catalytic performance were studied. The bimetallicand trimetallic catalysts were prepared with Pb, Bi, Fe, Cu as the second (or third)metal. The evaluate result indicated that addition of Pb, Bi to monometallic catalystsimproved the catalytic performance obviously, and the optimum catalyst wasPd3Pb0.6Bi1.5/SDB(X-5).TEM result indicates that the addition of Pb and Biameliorated the metal distribution on the supports. XPS result showed that theelectron of Pd transferred to promoters in this tri-metallic catalyst. XRD resultshowed that a strong interaction between Pd-Pb and Pd-Bi, leading to the formation oftwo binary alloys composed of Pd3Pb and PdBi, which were favorable for improvingthe activity and stability of the catalyst.Secondly, the catalytic activities of Pd3/SDB(X-5) in the oxidative esterificationof different type of aldehydes were studied and benzaldehyde was chosen as a testsubstrate to optimize the reaction conditions of temperature, time and the molar ratioof aldehydes with alcohols. The results indicated that this catalyst has better catalyticactivities in the oxidative esterification of aliphatic aldehydes and the aromaticaldehydes with electron-donating substituents.Finally, adsorptions of water in different catalyst supports have been studied by molecular simulation method. Based on the data of adsorption capacity and isostericheat, we get the information about the relationship between the hydrophobicity ofsupports and catalytic activity on the micro level.更多还原