Investigation of the Properties of Mo/ZSM-5 Catalysts Based on Zeolites with Microporous and Micro–Mesoporous Structures

The dehydroaromatization of methane (MDA) is of great interest as a promising process for processing natural and associated petroleum gases, the main component of which is methane. The rapid loss of catalyst activity because of coke formation hinders the introduction of the DHA methane process into the industry. Therefore, the aim of this research was to find ways to improve Mo/ZSM-5 catalysts for MDA. The paper presents the results of the synthesis of high-silica zeolites of the ZSM-5 type with microporous and micro–mesoporous structures, the preparation of Mo/ZSM-5 catalysts based on them, and the study of the physicochemical and catalytic properties of the obtained samples during the non-oxidative conversion of methane into aromatic hydrocarbons. Zeolite catalysts were investigated using IR spectroscopy, X-ray diffraction, TPD-NH3, SEM, HR-TEM, and N2 adsorption. It was found that the addition of carbon black in the stage of the synthesis of zeolite type ZSM-5 did not lead to structural changes, and the obtained samples had a crystallinity degree equal to 100%. The creation of the micro–mesoporous structure in Mo/ZSM-5 catalysts led to an increase in their activity and stability in the process of methane dehydroaromatization. The highest conversion of methane was observed on a 4.0%Mo/ZSM-5 catalyst prepared based on zeolite synthesized using 1.0% carbon black and was 13.0% after 20 min of reaction, while the benzene yield reached 7.0%. It was shown using HR-TEM that a more uniform distribution of the active metal component was observed in a zeolite catalyst with a micro–mesoporous structure than in a microporous zeolite

Investigation of non-oxidative methane conversion over granulated Mo/ZSM-5 catalysts

The relevance of the investigation is caused by the need for rational use of natural hydrocarbon gases, containing methane as the main component. Currently, plenty of these gases are burned in flares at oil production sites, that does great damage to the environment in the oil-producing regions of our country. The most promising process that allows obtaining valuable chemical products is the non-oxidative methane conversion into aromatic hydrocarbons over zeolite catalysts modified with transition metal ions. The Mo/ZSM-5 catalysts have high activity in this process. These catalysts are obtained both by impregnation and solid-phase synthesis. Development of the method of preparation of Mo/ZSM-5 catalysts using binder is of great importance for the industrial technology of processing gaseous hydrocarbons. The aim of the work is to study the effect of concentration and method of introducing a binder on physicochemical and catalytic properties of the Mo/ZSM-5 catalyst in non-oxidative methane conversion. Methods of investigation: IR spectroscopy, low-temperature adsorption of nitrogen, temperature-programmed desorption of ammonia (TPD-NH3), gas chromatography. Results. The Mo-containing catalyst based on ZSM-5 zeolite and nanosized molybdenum powder was prepared via solid-phase synthesis. The authors have studied the effect of a binder on physicochemical properties and activity of the Mo/ZSM-5 catalyst in non-oxidative conversion of methane into aromatic hydrocarbons. It was ascertained that the addition of a binder to the Mo/ZSM-5 catalyst results in a change in its texture and acid characteristics. It is shown that the activity of the Mo-containing zeolite during the non-oxidative conversion of methane into aromatic hydrocarbons is determined by the concentration of the binder in the catalyst and does not depend on the method of its introduction

Production of Aromatic Hydrocarbons from C3, C4-alkanes over Zeolite Catalysts

Гидротермальным способом из щелочных алюмокремнегелей синтезированы алюмосиликат и галлоалюмосиликат структурного типа MFI. Исследованы структурные, кислотные и каталитические свойства полученных цеолитов в процессе дегидроциклизации низших алканов. Установлено, что наибольшее количество ароматических углеводородов образуется при превращении бутана на галлоалюмосиликате, а наименьшее – при превращении пропана на алюмосиликате. Показано, что для достижения близкой конверсии пропана и бутана и выхода целевого продукта в присутствии изученных катализаторов температура процесса при превращении пропана должна быть на 50 градусов выше при одинаковых других условиях реакцииAn aluminosilicate and a galloaluminosilicate of MFI structure are synthesized by the hydrothermal method from alkaline aluminosilicates. Structural, acidic, and catalytic properties of synthesized zeolites are investigated in the course of dehydrocyclization of lower alkanes. It is found out that aromatic hydrocarbons are formed in their highest amount when butane is converted over the galloaluminosilicate, while the lowest amount of them is resulted from the conversion of propane over the aluminosilicate. It is shown that to achieve the nigh conversion of propane and butane and the yield of desired product in the presence of the catalysts under study, the process temperature during the propane conversion should be 50 degrees higher under the same other reaction condition

Activity and deactivation of ZSM-5 catalysts in the dimethyl ether synthesis from CO and H2 and methanol dehydration

The increasing demand for producing dimethyl ether from synthesis gas explains the renewed interest in studying the activity and stability of catalysts. In the present work, resource catalytic testing of ZSM-5 zeolites was carried out in the one-step synthesis of dimethyl ether from synthesis gas for 120 hours. Formation of condensation products was observed on zeolite surface after catalytic tests which leads to lower catalytic activity of samples. Condensation products were investigated by thermal analysis in an oxidizing atmosphere. Textural characteristics of zeolites before and after reaction were investigated. It was shown that methanol significantly contribute to formation of condensation products on the catalyst surface in the process of dimethyl ether production

Activity and deactivation of ZSM-5 catalysts in the dimethyl ether synthesis from CO and H2 and methanol dehydration

The increasing demand for producing dimethyl ether from synthesis gas explains the renewed interest in studying the activity and stability of catalysts. In the present work, resource catalytic testing of ZSM-5 zeolites was carried out in the one-step synthesis of dimethyl ether from synthesis gas for 120 hours. Formation of condensation products was observed on zeolite surface after catalytic tests which leads to lower catalytic activity of samples. Condensation products were investigated by thermal analysis in an oxidizing atmosphere. Textural characteristics of zeolites before and after reaction were investigated. It was shown that methanol significantly contribute to formation of condensation products on the catalyst surface in the process of dimethyl ether production

Кинетические особенности процесса превращения пропана в ароматические углеводороды

Kinetic features of the propane conversion into aromatic hydrocarbons over a gallium-containing zeolite catalyst have been investigated. On the basis of the experimentally obtained kinetic dependences and the available literature data, a kinetic model of propane aromatization is proposed, which makes it possible to form various variations of chemical reaction behavior and to calculate the most probable routes of propane conversionПроведено исследование кинетических особенностей процесса превращения пропана в ароматические углеводороды на галлийсодержащем цеолитном катализаторе. На основе экспериментально полученных кинетических зависимостей и имеющихся литературных данных предложена кинетическая модель ароматизации пропана, позволяющая сформировать различные варианты протекания химических реакций, рассчитать наиболее вероятные маршруты превращения пропан

Hydrodesulfurization of DBT with bulk sulphide catalysts. Reaction mechanism

The major problem of modern petroleum refining is the increasing efficiency of hydrogenation for producing high quality distillate fuel. Today hydroprocessing catalysts occupy a leading position among the other catalytic systems. When applying traditional supported catalysts the heavy oil components of petroleum disperse systems with a high molecular weight precipitate on the surface of the support granules and block the working surface of pores. Mesoporous supports with a relatively high pore size is not always effective. So, the annual increase in the proportion of publications relating to the massive (unsupported) sulfide catalysts of hydrogenolysis reflects the changes in the research direction. The relevance of the research is in urgent need to develop new methods and approaches to the synthesis of original, massive domestic sulfide catalyst systems with a high degree of activity and efficiency in hydrotreating of oil fuel fractions, a preparation of which is based on use of energy-saving and hi-tech approaches. The main aim of the research is to synthesize bicomponent bulk sulfide catalysts in a single step by a solid phase method, to investigate their activity in a model hydrogenolysis reaction of dibenzothiophene, to determine the composition of products and the most probable mechanism of the reaction. Methods of research: transmission electron microscopy, UV spectroscopy, X-ray fluorescence analysis, gas chromatography-mass spectrometry. Results. For the first time the authors have obtained in a single step the highly active bicomponent catalysts by direct mechanochemical combination of coarse cobalt (nickel) powders and molybdenum disulfide as promoter and precursors of the active component respectively. The systematic studies were performed to determine the effect of the ratio of initial reagents, duration of mechanoactivation on activity of dibenzothiophene hydrodesulfurization. The authors determined the optimal conditions for preparing Ni- and Co-containing systems providing ultra-low sulfur content (1-3 ppm) in a model dibenzothiophene hydrogenolysis and the composition of the reaction products. It was shown that the dibenzothiophene hydrogenolysis occurs concurrently with cracking and hydrogenation routes

Hydrodesulfurization of DBT with bulk sulphide catalysts. Reaction mechanism

The major problem of modern petroleum refining is the increasing efficiency of hydrogenation for producing high quality distillate fuel. Today hydroprocessing catalysts occupy a leading position among the other catalytic systems. When applying traditional supported catalysts the heavy oil components of petroleum disperse systems with a high molecular weight precipitate on the surface of the support granules and block the working surface of pores. Mesoporous supports with a relatively high pore size is not always effective. So, the annual increase in the proportion of publications relating to the massive (unsupported) sulfide catalysts of hydrogenolysis reflects the changes in the research direction. The relevance of the research is in urgent need to develop new methods and approaches to the synthesis of original, massive domestic sulfide catalyst systems with a high degree of activity and efficiency in hydrotreating of oil fuel fractions, a preparation of which is based on use of energy-saving and hi-tech approaches. The main aim of the research is to synthesize bicomponent bulk sulfide catalysts in a single step by a solid phase method, to investigate their activity in a model hydrogenolysis reaction of dibenzothiophene, to determine the composition of products and the most probable mechanism of the reaction. Methods of research: transmission electron microscopy, UV spectroscopy, X-ray fluorescence analysis, gas chromatography-mass spectrometry. Results. For the first time the authors have obtained in a single step the highly active bicomponent catalysts by direct mechanochemical combination of coarse cobalt (nickel) powders and molybdenum disulfide as promoter and precursors of the active component respectively. The systematic studies were performed to determine the effect of the ratio of initial reagents, duration of mechanoactivation on activity of dibenzothiophene hydrodesulfurization. The authors determined the optimal conditions for preparing Ni- and Co-containing systems providing ultra-low sulfur content (1-3 ppm) in a model dibenzothiophene hydrogenolysis and the composition of the reaction products. It was shown that the dibenzothiophene hydrogenolysis occurs concurrently with cracking and hydrogenation routes

The Study of Thermal Conversion of Mechanically Activated Aspen Wood in the Presence of High-Silica Zeolite Catalyst

Исследовано влияние добавок высококремнеземного цеолита в Н-форме с силикатным модулем 60 (НВКЦ-60) и механохимической обработки древесины осины в мельнице-активаторе АГО-2 на ее термические превращения. Установлено, что совместное механохимическое активирование древесины осины и катализатора НВКЦ-60 приводит к резкому уменьшению размера частиц компонентов смеси, разрушению основных структурных компонентов древесины, дисперсному распределению катализатора по поверхности древесины и к увеличению степени конверсии древесины осины в процессе термопревращения в среде сверхкритического этанола. В присутствии катализатора НВКЦ-60 происходит увеличение выхода этанолрастворимых продуктов, выкипающих до 180 °С, в 1,6–2,2 раза и промотирование реакции этерификации кислот, образующихся при деструкции компонентов древесиныThe influence of zeolite catalysts in the H-form with silicate module 60 (HSZ-60) and mechanochemical treatment in the activator mill AGO-2 on the thermal conversion of aspen wood has been studied. It was found that the joint mechanochemical activation of aspen wood and HSZ-60 catalyst results in a drastic decrease in particles size of the mixture components in destruction of the main structural components of wood and increases the homogenity of zeolite catalyst distribution on the wood surface and the degree of aspen wood conversion in supercritical ethanol. Catalyst HSZ-60 increases by 1,6 – 2,2 times the yield of ethanol soluble products with boiling point up to 180 °С and promotes the etherification reactions of acids, obtained during degradation of wood component