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题名:
甲基丙烯醛与甲醇生成酯的催化剂及反应过程研究
作者: 刁琰琰
学位类别: 博士
答辩日期: 2009-06-02
授予单位: 中国科学院过程工程研究所
授予地点: 过程工程研究所
导师: 张锁江
关键词: 甲基丙烯醛 ; 甲基丙烯酸甲酯 ; 负载Pd催化剂 ; 反应机理
其他题名: Studies on Catalyst and Reaction of the Direct Production of Methyl Methacrylate from Methacrolein and Methanol
学位专业: 化学工艺
中文摘要: 甲基丙烯酸甲酯(methyl methacrylate, MMA)是一种重要的聚合单体,主要用作生产有机玻璃、模塑料、腈纶、涂料和医药功能高分子材料等。目前工业化生产MMA的主要工艺为丙酮氰醇法和异丁烯(isobutene, IB)氧化的三步法。丙酮氰醇法,以剧毒的氢氰酸为原料,反应过程中还使用高腐蚀性的硫酸,并副产大量难以处理的硫酸氢铵,整个反应的原子利用率只有47%;异丁烯氧化的三步法反应流程长且经由甲基丙烯酸,对设备要求高。异丁烯经由甲基丙烯醛(methacrolein, MAL)直接反应生产MMA的路线以原子经济性高和工艺流程短的特点,吸引了越来越多的关注。 本文针对此路线的关键—MAL与甲醇(MeOH)在氧气气氛下直接反应生成MMA的负载贵金属Pd催化剂及反应过程的关键科学问题进行了系统的应用基础研究,主要研究工作及创新性成果如下: (1) 采用浸渍法制备出了用于MAL氧化酯化生产MMA的催化剂,并对不同载体、Pd的前躯体、助剂及还原方法制备的催化剂进行表征及反应性能的评价,建立了催化剂的组成-制备方法-结构与反应性能的关系。从XRD、XPS、TEM、和CO-FTIR等分析,助剂Pb与Pd形成活性中心Pd3Pb晶体,催化剂的反应性能提高。碱性载体对Pd3Pb晶体有给电子作用且影响晶体的大小。水合肼还原的催化剂中Pd3Pb晶体比氢气还原的小,且CO在小晶体催化剂上的线式/桥式吸附比高。以弱碱性MgO-Al2O3 为载体、Na2PdCl4 为前驱体、Pb为助剂和水合肼湿法还原制备的催化剂中的Pb3Pb晶体最小,且对CO的吸附在低波数,线式/桥式吸附比例高,催化反应性能最好。 (2) 选用活性高的Pd5Pb5/MgO-Al2O3催化剂,考察了醇醛比、反应温度、压力和氧气流量等工艺参数对反应性能的影响。在消除了反应的内扩散和外扩散的影响后,获得了MAL反应生成MMA的宏观动力学方程。 (3) 运用原位吸附的方法研究,MeOH在催化剂上发生解离吸附生成甲氧基和吸附氢;MAL中的C=O键在催化剂上以1,2-双σ键和σ-π键两种方式吸附,且1,2-双σ键吸附是生成半缩醛的必要吸附形式,也是生成MMA的必要条件。氧气在此反应中的作用是氧化除去反应过程中生成的吸附H。 (4) 间歇式反应中,催化剂出现了活性下降现象,TG和BET分析表明,催化剂的部分失活的主要原因是反应中生成的副产物MAL和MMA的聚合物和其他有机物吸附或部分聚合在催化剂的表面占据了表面的活性位或堵塞了催化剂的孔道。催化剂再生可用甲醇或水合肼洗涤或者高温煅烧的方法。连续式反应中由于新的物料的流动可以避免间歇式反应中发生的催化剂的失活现象。经多次氧化还原活化处理的催化剂在连续式反应釜中反应200小时后,没有出现失活的现象。 (5) 成功的进行了催化剂的公斤级放大,催化剂的反应性能与小试基本一致,并对中试反应进行了准备。
英文摘要: Methyl methacrylate (MMA), which is an important monomer, is widely used in producing acrylic plastics and polymer dispersions for paints, plexiglass, coatings and so on. The main commercial process for the production of MMA contains the traditional acetone cyanohydrine (ACH) process and IB oxidation process. The ACH process uses high toxic hydrocyanic acid (HCN) as the raw materials, uses high caustic sulphuric acid in the process and generates solid waste of ammonium bisulfate. The atom utilization efficiency is only 47%. The process flow of IB direct oxidation is too long and produces methacrylic acid. The process of direct oxidative esterification of MAL to MMA attracts more attention due to its short process flow and high atom utilization efficiency. In this dissertation, catalyst and reaction process of oxidative esterification of MAL with methanol (MeOH) were studied. The main work as follows: (1) The catalysts with different compositions using in oxidative esterification of MAL and MeOH were prepared by wet impregnation method and characterizated by different methods. The influences of preparation variables of promoter, support, impregnation temperature, reducing agent and reduction temperature on catalytic performance of supported Pd nano-crystallite catalyst were studied in detail. The relationship between the composition-preparation condition-structure of catalyst and the catalytic performance was established. The addition of promoter Pb improved the performance of catalyst for Pd and Pb atoms formed new active center of Pd3Pb crystal with face-center cubic structure. From the characterization of XRD, XPS, CO-FTIR and TEM, the support influence the size of Pd3Pb crystals. The increase of alkaline of support, the adsorption of CO moved to low wavenumber, and the ratio of linear adsorption to bridge adsorption decreased. The size of Pd3Pb crystal reduced by hydrazine hydrate was smaller than that reduced by H2. Therefore, catalyst Pd5Pb5/MgO-Al2O3 that using MgO-Al2O3 as the support, Na2PdCl4 as precursor, Pb as promoter and hydrazine hydrate as reducing agent had the best catalytic performance. (2) The influences of molar ratio of MAL to MeOH, reaction temperature, reaction pressure, and the flow of O2 on catalytic performance of Pd5Pb5/MgO-Al2O3 were studied. When internal diffusionand external diffusion were eliminated, the macrodynamic equation was obtained. (3) From the analysis of in situ FTIR, MeOH dissociated to form methoxide species on catalyst. The C=O bond of MAL adsorbed on he catalyst asσ-π bond and 1, 2-bi-σbond that was to form hemiacetal. Hemiacetal might be the intermediate of the reaction. The effect of O2 was to oxide hydrogen on the surface of catalyst produced in the reaction. (4) From the analysis of TG and BET, the catalyst deactivation was ascribed to the accumulation of polymers and some other by-products on the catalyst surface active sites. Washing the deactivated catalyst in MeOH or an aqueous hydrazine solution at the atmosphere of 80 ℃ for 10 h, or calcining in air at the temperature of 500 ℃ could regenerate the activity of catalyst. In continuous-flow process, there was no deactivation of catalyst after 200 h. (5) After laboratory experiment, the preparation of catalyst was enlarged to kilograms level. Activity of catalyst was as good as that of catalyst prepared in laboratory.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ipe.ac.cn/handle/122111/1309
Appears in Collections:研究所(批量导入)_学位论文

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Recommended Citation:
刁琰琰. 甲基丙烯醛与甲醇生成酯的催化剂及反应过程研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2009.
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