不同晶粒尺寸H-ZSM-5催化剂上甲醇芳构化反应性能(英文)
发布时间:2019-01-27 14:26
【摘要】:芳烃是一类重要的有机化工基础原料,通常采用传统的石油路线生产芳烃,包括催化裂化和催化重整等工艺.由于石油资源的紧缺,以可再生资源为原料生产芳烃工艺的发展具有十分重要的意义.甲醇作为一种重要的基础原料,可来源于煤、天然气和生物质等,因此,甲醇制芳烃工艺(MTA)的研究受到日益关注.ZSM-5分子筛具有较大的比表面积、可调节的酸性、优良的择形选择性和很高的水热稳定性,因而在甲醇芳构化中展现出良好的催化性能.研究发现,甲醇转化率和产物分布与ZSM-5分子筛的酸性和多孔性等密切相关.本文通过调控模板剂与水的比例和晶化时间,采用水热法制备了一系列不同晶粒度H-ZSM-5分子筛催化剂,通过X射线衍射(XRD)、扫描电镜(SEM)、N_2物理吸附脱附(BET)和X射线荧光光谱等技术对所得分子筛的理化性质、骨架结构和形貌进行了表征;采用吡啶红外光谱和NH_3程序升温脱附技术对其酸性进行了分析,使用热重(TG)技术对反应后催化剂的积碳含量进行了分析,并将所制备的H-ZSM-5分子筛催化剂分别应用于MTA反应,系统性地探究分子筛晶粒度对其理化性质和MTA催化性能的影响.XRD结果表明,所合成的五种样品均具有典型的ZSM-5分子筛特征衍射峰且无杂晶,且具有不同的晶粒度,分别为4.0±0.3,1.2±0.2μm,614.1±31.9、391.9±32.4和99.1±7.0 nm.N_2物理吸附脱附曲线可以发现,晶粒度为99.1±7.0 nm的ZSM-5分子筛展现出典型的Ⅰ型和Ⅳ型物理吸附曲线且在较高的相对压力(p/p_0=0.8-1.0)处有一个明显的H4型迟滞环,表明此分子筛具有介孔和大孔结构;BJH吸附孔径分布图表明,这些介孔主要分布在2-7和20-50 nm范围内;同时各样品的比表面积和孔体积随着其晶粒度的减小而增大.结果还表明五种不同晶粒度的ZSM-5分子筛具有相似的SiO_2/Al_2O_3摩尔比和酸性质.MTA反应结果表明,随着催化剂晶粒度的降低,甲醇的平均转化率,芳烃选择性和BTX选择性有所提高,在300 min时晶粒度较大的三个催化剂上,甲醇转化率迅速降至90%,而晶粒度较小的两个催化剂上,甲醇转化率始终维持在95%以上,其中晶粒度为99.1±7.0 nm的样品上芳烃选择性最高(平均42%以上),BTX选择性达37%.对失活催化剂积碳含量分析,随着催化剂晶粒度的降低,积碳量降低.晶粒度较低的纳米分子筛催化剂具有更短的孔道,更高效的扩散性能,更高的比表面积和独特的梯级孔结构,因而在甲醇芳构化反应中展现出更长的寿命,更高的活性和更低的积碳量,在甲醇制芳烃工业化生产中具有巨大潜力.
[Abstract]:Aromatics are a kind of important organic chemical raw materials, which usually produce aromatics by traditional petroleum route, including catalytic cracking and catalytic reforming. Because of the shortage of petroleum resources, it is very important to develop the process of producing aromatics from renewable resources. As an important basic raw material, methanol can be derived from coal, natural gas and biomass. Therefore, the study of methanol to aromatics process (MTA) has attracted increasing attention. ZSM-5 molecular sieve has a large specific surface area and adjustable acidity. Because of its excellent shape selectivity and high hydrothermal stability, it exhibits good catalytic performance in methanol aromatization. It was found that methanol conversion and product distribution were closely related to the acidity and porosity of ZSM-5 molecular sieves. In this paper, a series of H-ZSM-5 molecular sieve catalysts with different crystal sizes were prepared by hydrothermal method by adjusting the ratio of template to water and crystallization time. The (SEM), was obtained by (XRD), scanning electron microscope (SEM). The physicochemical properties, skeleton structure and morphology of the molecular sieve were characterized by physical adsorption and desorption of N-2 by (BET) and X-ray fluorescence spectroscopy. The acidity of the catalyst was analyzed by pyridine infrared spectroscopy and NH_3 temperature programmed desorption, and the carbon content of the catalyst was analyzed by thermogravimetric (TG). The H-ZSM-5 molecular sieve catalysts were used in MTA reaction, and the effects of molecular sieve grain size on their physicochemical properties and catalytic properties of MTA were systematically investigated. The results of XRD showed that, The five samples were characterized by typical diffraction peaks of ZSM-5 molecular sieve, no heterocrystals, and different grain sizes, which were 4.0 卤0.3 卤1.2 卤0.2 渭 m, respectively. The physical adsorption and desorption curves of 614.1 卤31.9391.9 卤32.4 and 99.1 卤7.0 nm.N_2 can be found. ZSM-5 molecular sieves with a grain size of 99.1 卤7.0 nm exhibit typical physical adsorption curves of type 鈪,
本文编号:2416351
[Abstract]:Aromatics are a kind of important organic chemical raw materials, which usually produce aromatics by traditional petroleum route, including catalytic cracking and catalytic reforming. Because of the shortage of petroleum resources, it is very important to develop the process of producing aromatics from renewable resources. As an important basic raw material, methanol can be derived from coal, natural gas and biomass. Therefore, the study of methanol to aromatics process (MTA) has attracted increasing attention. ZSM-5 molecular sieve has a large specific surface area and adjustable acidity. Because of its excellent shape selectivity and high hydrothermal stability, it exhibits good catalytic performance in methanol aromatization. It was found that methanol conversion and product distribution were closely related to the acidity and porosity of ZSM-5 molecular sieves. In this paper, a series of H-ZSM-5 molecular sieve catalysts with different crystal sizes were prepared by hydrothermal method by adjusting the ratio of template to water and crystallization time. The (SEM), was obtained by (XRD), scanning electron microscope (SEM). The physicochemical properties, skeleton structure and morphology of the molecular sieve were characterized by physical adsorption and desorption of N-2 by (BET) and X-ray fluorescence spectroscopy. The acidity of the catalyst was analyzed by pyridine infrared spectroscopy and NH_3 temperature programmed desorption, and the carbon content of the catalyst was analyzed by thermogravimetric (TG). The H-ZSM-5 molecular sieve catalysts were used in MTA reaction, and the effects of molecular sieve grain size on their physicochemical properties and catalytic properties of MTA were systematically investigated. The results of XRD showed that, The five samples were characterized by typical diffraction peaks of ZSM-5 molecular sieve, no heterocrystals, and different grain sizes, which were 4.0 卤0.3 卤1.2 卤0.2 渭 m, respectively. The physical adsorption and desorption curves of 614.1 卤31.9391.9 卤32.4 and 99.1 卤7.0 nm.N_2 can be found. ZSM-5 molecular sieves with a grain size of 99.1 卤7.0 nm exhibit typical physical adsorption curves of type 鈪,
本文编号:2416351
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