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高活性和高稳定性过渡金属磷化物加氢催化剂的制备及性能研究
其他题名Efficient, highly selective and stable transition metal phosphide catalysts for hydrogenation of heavy aromatics
MUHAMMAD USMAN
学位类型博士
导师张锁江
2014-04
学位授予单位中国科学院研究生院
学位专业化学工程
关键词煤焦油   加氢   萘   磷化物   mop
摘要富煤贫油是我国能源结构特点,近年来随着煤化工产业的迅速发展,煤焦油作为转化过程如焦化、热解等必不可少的副产物其清洁提质具有重要意义。煤焦油加氢获得清洁燃料油不仅可提高煤炭利用效率,也可作为新的替代能源来缓解日趋紧张的石油供应具有重要的战略意义。本论文主要围绕煤焦油加氢过程,开发了新型过渡金属磷化物催化剂。以煤焦油中的典型组分萘为模型化合物研究了其加氢机理、加氢动力学等。制备了负载型和非负载型过渡金属磷化物,进行了系统表征和应用。制备合成了过渡金属磷化物Ni2P、MoP、 Co2P和Fe2P,对于系列的磷化物进行了表征。通过加氢活性和选择性研究发现,MoP的还原温度最低,因此具有较小的粒径和较大的比表面积,MoP表面具有的弱酸、中强酸和Lewis酸位使其在固定床反应器中反应100个小时后任能保持较高的反应活性和选择性。 制备了不同过渡金属磷化物的负载催化剂,载体考虑了Hbeta沸石、HZSM-5分子筛、HY分子筛和活性炭。对于负载后的催化剂,通过XRD、TPR、SEM、TEM、BET、 EPMA、NH3-TPD、CO-uptake、FTIR、TG / DTA、XPS等手段对催化剂进行了表征。原位的FTIR、NH3-TPD结合CO-uptake 研究了催化剂的酸性和催化活性位;采用XRD,XPS和TG / DTA方法对反应前后的催化剂进行分析,研究了催化剂的稳定性;通过FTIR、EPMA和CO-uptake研究该催化剂在萘加氢反应过程中影响催化活性和选择性的机理;同时进行了催化剂表面酸性、粒径和孔隙率的测定,并很好的解释了选择性和转化率。结果表明MoP/HY催化剂上四氢萘的选择性最高,并优化了反应温度和空速。提高活性组分MoP的分散性、减小其孔径以及载体HY表面的弱酸性有利于增强萘转化成四氢萘的催化活性和选择性。虽然MoP/HY的催化活性和选择性较高,但是在100小时的反应过程中表现出较低的稳定性。 以萘加氢生产四氢萘为模型反应,评价了活性炭负载的过渡金属磷化物催化剂(MoP, Ni2P, Co2P and Fe2P)的加氢活性、选择性和稳定性。反应压力为4MPa、反应温度为300oC,空速为3.0h-1,结果表明,催化剂的活性有以下顺序:Ni2P ≈ Co2P > MoP >>> Fe2P,但是MoP的选择性最高。通过对反应温度、空速和传质效果对生成四氢萘的影响,最终发现,MoP催化剂在固定床反应器中稳定性最好。
其他摘要This dissertation describes preparation and characterization of bulk and supported transition metal phosphides and their application in deep and selective hydrogenation (HYD) of naphthalene. This topic is of great importance in addressing the highly active, selective and stable hydrogenation of heavy aromatic-naphthalene to tetralin. The work carried out includes synthesis of bulk MoP, Ni2P and Co2P and Fe2P and supported over different zeolites, Hbeta, HZSM-5, HY and Activated carbon (AC). It also includes characterization of these catalytic materials using X-ray diffraction (XRD), Temperature-programmed reduction (TPR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), Electron probe micro analysis (EPMA), Temperature-programmed desorption (TPD) of ammonia, CO uptake, Fourier transform infrared (FTIR) spectroscopy, Thermogravimetry and Differential thermal analysis (TG/DTA), and X-ray photoelectron spectroscopy (XPS) spectroscopy. In situ FTIR and NH3-TPD was employed to study the acidity and probe the catalytic sites by CO uptake. The XRD, XPS and TG/DTA were used to study stability of the catalysts before and after activity analysis. Investigation of the reaction mechanism of naphthalene HYD with in situ FTIR, EPMA and CO uptake was conducted to understand how these material effect activity and selectivity. The use of these techniques allowed for better understanding of the surface acidity, particle size, porosity and nature of the active sites involved in HYD. In this work the first approach for highly selective production of tetralin was tried by bulk transition metal phosphides (MoP, Ni2P, Co2P, and Fe2P). Among all transition metal phosphides MoP was formed at lower reduction temperature resulting in smaller particle size enhancing the overall surface area of the catalyst. The existence of weak, moderate and Lewis acidic sites over MoP were responsible for its high activity, selectivity and stability during the 100 h reaction on-stream in a fixed bed reactor. To search for the highly selective and inexpensive material for the production of tetralin, MoP catalyst supported on Hbeta, HZSM-5 and HY were prepared. Catalytic tests revealed the highest selectivity to tetralin was observed over MoP/HY. The optimum temperature and liquid hourly space velocity (LHSV) was also studied. Well dispersed and small particles of MoP, reduced pore size and weak acidity of HY contribute to enhanced catalytic activity and selectivity in conversion of naphthalene to tetralin. Although the activity and selectivity over MoP/HY was high but this material shows low stability in 100 h reaction on stream. Third approach for the highly active, selective and stable hydrogenation of naphthalene to tetralin was studied by evaluating different catalysts (Ni2P, Co2P, Fe2P and MoP), supported over AC. The tests performed at 4.0 MPa, 300 °C and 3.0/h liquid hour space velocity (LHSV) showed enhanced activity, exhibiting the following order Ni2P ≈ Co2P > MoP >>> Fe2P, however the high selectivity to tetralin was obtained by MoP/AC. Further, the effect of temperature, LHSV and mass transfer effect was also checked for tetralin. Finally the stability of the MoP/AC was tested in the fixed bed reactor for 100 h reaction on stream, which is the highest stability achieved compare to the known literature.
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/15556
专题研究所(批量导入)
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MUHAMMAD USMAN. 高活性和高稳定性过渡金属磷化物加氢催化剂的制备及性能研究[D]. 中国科学院研究生院,2014.
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