金属改性MCM-48催化剂的制备及其庚烷异构性能研究

发布时间：2018-04-06 20:05

  本文选题：Zn-MCM-48　切入点：分子筛催化剂　出处：《东北石油大学》2017年硕士论文

【摘要】：国六汽油新标即将在全国范围供应,新的汽油标准要求大幅度降低硫、锰以及烯烃含量,而我国高辛烷值汽油资源不足,为了弥补低硫、无锰带来的辛烷值损失,必须大力发展烷烃异构化技术获得高辛烷值汽油调和组分。其中,正庚烷异构化反应是获得高辛烷值汽油的重要手段之一。由于MCM-48介孔分子筛具有高比表面积利于活性组分分散,以及具有三维螺旋孔道结构有利于传输物料,可调变的孔径则具有择形催化作用。但是纯硅MCM-48介孔分子筛缺乏活性中心,热稳定性差。将金属以负载或原位掺杂的方式引入MCM-48分子筛骨架可以增强其热稳定性,增加分子筛中氧化还原活性位或酸碱活性位。因此本文制备了不同金属(Ni、Co、Zn)改性的MCM-48分子筛,并通过X射线衍射分析(XRD)、N2吸附-脱附分析、傅里叶变换红外光谱分析(FT-IR)、扫描电镜(SEM)、NH3程序升温脱附(NH3-TPD)等表征手段考察金属引入对分子筛结构、酸性、稳定性的影响,同时以改性MCM-48为载体,Ni为活性组分,制备Ni/M(Ni、Co、Zn)-MCM-48双功能催化剂,考察其催化正庚烷异构化反应性能。主要内容如下:1.以水热合成法合成原位掺杂镍、钴、锌的MCM-48介孔分子筛,并考察了引入杂原子对MCM-48介孔分子筛结构和性能的影响。表征结果表明:当物质的量配比为0.98 TEOS:0.558 CTAB:0.469 NaOH:57.64 H2O:0.02 M时,成功合成了具有立方相Ia3d结构的M-MCM-48(M=Ni,Co,Zn)分子筛,金属部分进入分子筛骨架并改变了材料的酸性质。2.采用浸渍法将活性组分Ni负载到不同金属改性MCM-48分子筛载体上来制备Ni/M-MCM-48催化剂,并以庚烷异构化为探针反应,考察了金属负载量、还原温度和反应时间、反应温度以及重时空速和氢烃比等对Ni/Zn-MCM-48催化性能的影响。结果表明:在金属负载量为4%,还原温度为400oC,还原时间为4h,反应温度为260oC,WHSV为5.1h-1,氢烃摩尔比为2时,催化剂庚烷异构化性能较好,正庚烷转化率和异庚烷选择性分别达到45%和62%。
[Abstract]:The new gasoline standard will soon be available nationwide. The new gasoline standard requires that the contents of sulfur, manganese and olefins be greatly reduced, while the high octane number gasoline resources in China are insufficient. In order to make up for the loss of octane number caused by low sulfur and no manganese,It is necessary to develop the technology of isomerization of alkanes to obtain high octane gasoline blending components.Among them, n-heptane isomerization is one of the important methods to obtain high octane gasoline.Because MCM-48 mesoporous molecular sieves have high specific surface area to facilitate active component dispersion and three-dimensional helical pore structure to facilitate the transport of materials, adjustable pore size has shape selective catalysis.However, pure silicon MCM-48 mesoporous molecular sieves lack active centers and have poor thermal stability.Introducing metal into MCM-48 molecular sieve skeleton by loading or in situ doping can enhance its thermal stability and increase the redox active sites or acid-base active sites in the molecular sieve.In this paper, MCM-48 molecular sieve modified by different metals NiCoCZN) was prepared, and the adsorption-desorption analysis of N2 was carried out by X-ray diffraction analysis.Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to investigate the effect of metal introduction on the structure, acidity and stability of molecular sieve, and the modified MCM-48 as carrier Ni as active component.The bifunctional catalyst of Ni- / Mg-NiCo-NiCo-ZnO-MCM-48 was prepared and its catalytic activity of n-heptane isomerization was investigated.The main content is as follows: 1.MCM-48 mesoporous molecular sieves doped with nickel, cobalt and zinc in situ were synthesized by hydrothermal synthesis. The effects of heteratoms on the structure and properties of MCM-48 mesoporous molecular sieves were investigated.The characterization results show that M-MCM-48M (MCM-48M) with Ia3d structure is successfully synthesized when the mass ratio of the material is 0.98 TEOS:0.558 CTAB:0.469 NaOH:57.64 H2O:0.02 M. the metal part enters the framework of the molecular sieve and changes the acid property of the material.The active component Ni was loaded on different metal modified MCM-48 molecular sieve carriers by impregnation method to prepare Ni/M-MCM-48 catalyst. The amount of metal loading, reduction temperature and reaction time were investigated by using heptane isomerization as probe reaction.The effects of reaction temperature, heavy space-time velocity and the ratio of hydrogen to hydrocarbon on the catalytic performance of Ni/Zn-MCM-48 were investigated.The results show that when the metal loading is 4, the reduction temperature is 400oC, the reduction time is 4h, the reaction temperature is 260oC, WHSV is 5.1h-1, and the molar ratio of hydrogen to hydrocarbon is 2, the heptane isomerization performance of the catalyst is better. The conversion of n-heptane and the selectivity of isoheptane are 45% and 62%, respectively.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE624.9
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本文编号：1718677