Abstract

We studied the effect of the nature of the structure-forming additive on the physicochemical and catalytic properties of the synthesized zeolites and catalysts prepared on their basis during the nonoxidative conversion of methane to aromatic hydrocarbons. Zeolites were synthesized by hydrothermal crystallization from alkaline alumosilica gels using hexamethylenediamine (HMDA) and ammonium bicarbonate (ABC) as templates. To create a mesoporous structure in zeolites, grade P354 carbon black was added to the reaction mixtures during synthesis. The synthesized zeolites were studied by IR spectroscopy, X-ray diffraction analysis, low-temperature nitrogen adsorption, scanning electron microscopy, and temperature-programmed desorption of ammonia. The catalytic properties of the samples were studied during the nonoxidative conversion of methane to aromatic compounds. All the synthesized samples are ZSM-5 zeolites; the addition of carbon black during their synthesis slightly affects their textural properties, increasing the volume of mesopores. The modification of zeolites with molybdenum results in a lower specific surface area and porosity. Zeolites obtained using HMDA are characterized by greater strength and a lower concentration of high-temperature acid sites compared to samples synthesized with ABC. The addition of molybdenum to zeolites lowers the strength and concentration of both types of acid sites. Mo-containing catalysts obtained from zeolites with a micro-mesoporous structure show higher activity and stability in the reaction of methane dehydroaromatization compared to microporous systems.

中文翻译：

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模板性质对ZSM-5沸石及Mo/ZSM-5催化剂理化及催化性能影响的研究

摘要

我们研究了在甲烷非氧化转化为芳烃过程中，结构形成添加剂的性质对合成沸石和以其为基础制备的催化剂的物理化学和催化性能的影响。以六亚甲基二胺（HMDA）和碳酸氢铵（ABC）为模板，通过水热结晶从碱性硅铝凝胶中合成沸石。为了在沸石中形成介孔结构，在合成过程中将 P354 级炭黑添加到反应混合物中。通过红外光谱、X射线衍射分析、低温氮气吸附、扫描电子显微镜和氨程序升温解吸对合成的沸石进行了研究。研究了甲烷非氧化转化为芳香族化合物过程中样品的催化性能。合成的样品均为ZSM-5沸石；在合成过程中添加炭黑会稍微影响其结构特性，增加中孔的体积。用钼对沸石进行改性会导致较低的比表面积和孔隙率。与使用 ABC 合成的样品相比，使用 HMDA 获得的沸石具有更高的强度和更低浓度的高温酸位点。在沸石中添加钼会降低两种类型酸位点的强度和浓度。