Abstract

The effect of the method for the introduction of zirconium in the 4Mo/ZSM-5 catalyst and of its amount on the physicochemical and catalytic properties of the catalyst during the nonoxidative conversion of methane into aromatic hydrocarbons (benzene and naphthalene) has been studied. The catalyst was modified with zirconium by impregnation and solid phase mixing. The resulting zeolite catalysts were studied by IR spectroscopy, X-ray diffraction analysis, low-temperature nitrogen adsorption, temperature-programmed ammonia desorption, scanning and transmission electron microscopy, and simultaneous thermal analysis. With an increase in the zirconium concentration introduced in the 4Mo/ZSM-5 catalyst, the strength and concentration of its strong acid sites that are responsible for methane aromatization decrease regardless of the method of modification. The particle size and morphology of the catalyst, the distribution of Mo and Zr in them, and the presence of coke deposits on their surface were determined by scanning and transmission electron microscopy. The catalytic tests and subsequent thermal analysis of the samples showed that the addition of zirconium to the 4Mo/ZSM-5 catalyst leads not only to an increase in its catalytic activity, but also to operational stability due to the lower rate of coke formation. It was established that 4Mo/ZSM-5 modified with 1 wt % Zr by solid-phase synthesis is the most effective catalyst in methane dehydroaromatization (DHA).

中文翻译：

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Mo-Zr/ZSM-5 甲烷脱氢芳构化催化剂的物化及催化性能

摘要

研究了4Mo/ZSM-5催化剂中锆的引入方法及其用量对甲烷非氧化转化芳烃（苯和萘）过程中催化剂物理化学和催化性能的影响。通过浸渍和固相混合对催化剂进行锆改性。通过红外光谱、X射线衍射分析、低温氮气吸附、程序升温氨解吸、扫描和透射电子显微镜以及同时热分析对所得沸石催化剂进行了研究。随着4Mo/ZSM-5催化剂中锆浓度的增加，无论采用何种改性方法，负责甲烷芳构化的强酸位点的强度和浓度都会降低。通过扫描和透射电子显微镜测定了催化剂的粒径和形貌、其中Mo和Zr的分布以及其表面焦炭沉积的存在。催化测试和随后的样品热分析表明，在4Mo/ZSM-5催化剂中添加锆不仅可以提高其催化活性，而且由于结焦率较低，因此可以提高操作稳定性。结果表明，通过固相合成用 1 wt% Zr 改性的 4Mo/ZSM-5 是甲烷脱氢芳构化 (DHA) 中最有效的催化剂。