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题名: C4烯烃绿色合成催化材料的制备及反应机理的研究
作者: 李杨
学位类别: 博士
答辩日期: 2016-06
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 郝郑平
关键词: 绿色化学,节能减排,催化反应,1-丁烯双键异构,异丁烷直接脱氢 ; green chemistry, energy conservation and emission reduction, catalytic reaction, 1-butene double-bond isomerization, isobutane direct dehydrogenation
其他题名: Catalyst Preparation and Reaction Mechanism for Green Catalytic Synthesis of C4 Olefins
学位专业: 环境工程
中文摘要:       传统的金属催化体系在1-丁烯双键异构制备2-丁烯反应中温度高、催化性能差,在异丁烷直接脱氢制备异丁烯反应中也存在稳定性差、污染大、成本高等问题,对催化体系进行优化以实现降低反应温度、提高催化稳定性并降低催化剂本身的毒性和污染性,可以从源头上实现节约能耗和降低污染的目的。
      本论文主要针对1-丁烯双键异构制备2-丁烯反应和异丁烷直接脱氢制备异丁烯反应,分别建立了负载型Pd催化体系和C催化体系,系统考察了催化剂的催化性能,结合多种技术手段分析了催化剂的结构特征和表面特性,揭示1-丁烯双键异构和异丁烷直接脱氢的催化反应过程和催化反应机理。得到的主要研究结果如下:

     (1)1-丁烯双键异构制备2-丁烯反应 研究负载型贵金属(Pd、Pt、Au)催化剂上1-丁烯双键异构反应,发现负载型Pd催化剂在室温下即表现出1-丁烯双键异构的催化活性。进一步研究负载型Pd催化剂,使用二氧化硅纳米球(SNS)、SiO2、TiO2、Al2O3、Hβ分子筛、ZSM-5分子筛、碳纳米管(CNT)、椰壳活性碳(CSAC)等多种载体,发现Pd/SNS催化剂的1-丁烯双键异构反应催化活性最高,室温下2-丁烯产率可以达到57%,产物为反式和顺式的2-丁烯。研究揭示催化剂的活性中心为高分散的金属态Pd纳米粒子,并且催化剂的表面酸性越强,催化性能得到相应提高。采用H2SO4淋洗处理负载型Pd催化剂,Pd/SNS催化剂上2-丁烯的产率显著提高到97%,更有力证明了催化剂的表面酸性对1-丁烯双键异构反应的显著促进作用。
      通过对不同反应温度条件下Pd/SNS催化剂上1-丁烯双键异构反应催化性能的考察,发现反式-2-丁烯和顺式-2-丁烯的比例随着反应温度的升高有所降低,研究揭示了叔丁基碳正离子中间体的构型决定了1-丁烯双键异构反应中产物2-丁烯的反顺比。同时O2通过―half Mars-van Krevelen‖机理将2-丁烯产率显著提高到57%,并且无CO2等副产物生成。
      研究发现H2SO4淋洗处理未经H2还原的Pd*/CNT催化剂在1-丁烯双键异构制备2-丁烯反应中表现出高稳定性的催化作用,反应96 h后2-丁烯的产率仍保持在52%;研究表明强酸淋洗后氧化态Pd纳米粒子也可作为1-丁烯双键异构反应的活性中心,而H2SO4淋洗处理Pd*/CNT催化剂保持高稳定的表面酸性和Pd纳米粒子的良好分散是催化剂具有高稳定性的重要原因。

    (2)异丁烷直接脱氢制备异丁烯反应 通过对CSAC、煤质活性碳(CAC)、CNT、超分散金刚石(UDD)、石墨(G)、酚醛碳分子筛(RF-1)等C材料催化异丁烷直接脱氢反应性能的研究,发现无氧化性气体条件下即可实现异丁烷直接脱氢制备异丁烯。其中CSAC催化性能最高,在625°C下,异丁烷的转化率和异丁烯的选择性分别为70%和78%,反应72 h后异丁烷转化率降低到34%,选择性始终保持在76%左右。与传统的Cr-K/Al2O3催化剂相比,CSAC催化剂的稳定性显著提高。研究表明CSAC较大的比表面积是其高催化性能的主要原因,无需有机官能团,CSAC乃至反应过程中形成的积碳都能有效催化异丁烷直接脱氢反应进行。
      综上所述,实现了室温下负载型Pd催化剂上1-丁烯双键异构制备2-丁烯反应,催化反应温度有效降低,催化活性得到提高;同时使用C催化剂取代传统金属催化体系应用于异丁烷直接脱氢制备异丁烯反应,在提高催化稳定性的同时降低催化剂本身的环境污染或生产成本。论文在催化材料的制备,反应过程和反应机理的研究方面形成了系统的工作和规律性认识,可为丁烯异构和丁烷脱氢反应提供材料基础和理论支撑。
英文摘要:       The traditional metal oxides catalyst systems, cause high energy consumption and low catalytic performance for 1-butene isomerization for 2-butene, and also exist the shortcomings of serious pollution, high cost and low stability for isobutane direct dehydrogenation for isobutene. Opitimizing those catalytic systems could reduce reaction temperature, improve catalytic stability and avoid pollution caused by catalysts themselves, and so as to achieve the objective of energy saving and emission reduction from the sources.
      In this thesis work, environmental friendly supported noble metal catalysts and carbon catalysts were applied in 1-butene double-bond isomerization for 2-butene and isobutane direct dehydrogenation for isobutene, respectively and investigated the catalytic performance. By combining the structural properties of materials extensively characterized and elucidated using various technologies, the reaction processes and mechanisms of 1-butene double-bond isomerization and isobutane dehydrogenation were thoroughly discussed. The main research results are listed as follows:

 (1) 1-Butene double-bond isomerization for 2-butene
      Supported nobel metals (Pd, Pt and Au) catalysts were studied for 1-butene double-bond isomerization, and supported Pd catalysts showed high catalytic performances at room temperature. Silica nanospheres (SNS), SiO2, TiO2, Al2O3, Hβ zeolite, ZSM-5 zeolites, carbon nanotube (CNT) and coconut shell activated carbon (CSAC) were used as supports, and Pd/SNS catalyst showed high catalytic activities at room temperature with a yield efficiency of 48% and the products were only trans-2-butene and cis-2-butene. The research revealed the catalytic active center was the metal Pd nanoparticls and the catalyst surface acidity affected the catalytic performance. The 2-butene yield over H2SO4 acid leached Pd/SNS catalyst was significantly increased to 97%, this result strongly proved the promotion effect of catalyst surface acidity on catalytic performance for 1-butene double-bond isomerization.
      The catalytic performance for 1-butene double-bond isomerization over Pd/SNS catalyst was extensively explored under various reaction condition. It was found that the ratio of trans-2-butene to cis-2-butene decreased with the increase of reaction temperature. It revealed that the ratio of trans:cis ratio of 2-butene in the final product was determined by the type of butenylcarbenium ion intermediate. Moreover, the addition of O2 could significantly improve the 2-butene yield efficiency to 57% without the formation of by-product CO2 through a ―half Mars-van Krevelen‖ mechanism.
      The Pd/CNT catalyst without H2 reduction was further treated with H2SO4, and the obtained Pd*/CNT-H2SO4 catalyst showed high stablity with the 2-butene yield of 52% after reaction for 96 h. The results showed that the oxidation state Pd nanoparticles could also be catalytic active center, and the stability of the acidity and the size of Pd nanoparticles were the main reactions for the high stablity of Pd*/CNT-H2SO4 catalyst.

(2) Isobutane direct dehydrogenation for isobutene
       Coconut shell activated carbon (CSAC), coal activated carbon (CAC), CNT, ultra dispersed diamond (UDD), graphite (G) and RF-1 were studied for isobutane direct dehydrogenation, and those carbon materials showed catalytic performances without the addition of oxidizing gases. CSAC catalyst showed high activities leading an isobutane conversion and isobutene selectivity of 70% and 78%, respectively. Moreover, the isobutane conversion decreased to 34% with the isobutene selectivity maintaining around 76%, which was superior to that of conventional Cr-K/Al2O3 catalyst. The study showed that the main reason for the high catalytic performance of CSAC catalyst was its large specific surface area, and carbon materials (including the deposited coke) without any functional groups were shown to be effective catalysts for isobutane direct dehydrogenation.
      Overall, supported noble metal catalysts successfully realized the 1-butene double-bond isomerization at room temperature so as to effectively decreased the reaction temperature and improve the catalytic performance. And carbon catalysts were used to replace traditional metal oxides catalyst systems for isobutane direct dehydrogenation, which obtained the higher stability and reduced the environmental pollution and production costs caused by catalysts themselves. The atalyst preparation as well as the reaction process and mechanism were systematically studied, which could provide the material and theoretical basis for butene isomerization and butane dehydrogenation.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36882
Appears in Collections:环境纳米材料研究室_学位论文

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Recommended Citation:
李杨. C4烯烃绿色合成催化材料的制备及反应机理的研究[D]. 北京. 中国科学院研究生院. 2016.
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