CVD-Synthesis of N-CNT Using Propane and Ammonia.

N-CNT is a promising material for various applications, including catalysis, electronics, etc., whose widespread use is limited by the significant cost of production. CVD-synthesis using a propane-ammonia mixture is one of the cost-effective processes for obtaining carbon nanomaterials. In this work, the CVD-synthesis of N-CNT was conducted in a traditional bed reactor using catalyst: (Al0,4Fe0,48Co0,12)2O3 + 3% MoO3. The synthesized material was characterized by XPS spectroscopy, ASAP, TEM and SEM-microscopy. It is shown that the carbon material contains various morphological structures, including multiwalled carbon nanotubes (MWCNT), bamboo-like structures, spherical and irregular sections. The content of structures (bamboo-like and spherical structure) caused by the incorporation of nitrogen into the carbon nanotube structure depends on the synthesis temperature and the ammonia content in the reaction mixture. The optimal conditions for CVD-synthesis were determined: the temperature range (650-700 °C), the composition (C3H8/NH3 = 50/50%) and flow rate of the ammonia-propane mixture (200 mL/min).

Intensification of Dry Reforming of Methane on Membrane Catalyst: Confirmation and Development of the Hypothesis.

This article presents an analysis of kinetic studies of dry methane reforming (DRM) in a reactor with a membrane catalyst (RMC) in the modes of a contactor with "diffusion" and "forced" mass transfer. Comparison of the specific rate constants of the methane dissociation reaction in membrane and traditional reactors confirmed the phenomenon of intensification of dry methane reforming in a membrane catalyst (MC). It has been experimentally established that during DRM, a temperature gradient arises in the channels of the pore structure of the membrane catalyst, characterized by a decrease in temperature towards the inner volume of the MC, and initiates the phenomenon of thermal slip. The features of this phenomenon are highlighted and must be considered in the analysis of kinetic data. The main provisions of the hypothesis explaining the effect of intensification by the occurrence of thermal slip in the channels of the pore structure of the MC are formulated. The proposed hypothesis, based on thermal slip, explains the difference in rate constants of traditional and membrane catalysts, and substantiates the phenomenological scheme of DRM stages in a reactor with a membrane catalyst.

Transport Reagents through the Pore Structure of a Membrane Catalyst under Isothermal and Non-Isothermal Conditions.

The article presents the results of an experimental comparison of methane transport in the pore structure of a membrane catalyst under isothermal and non-isothermal Knudsen diffusion conditions. It is shown that under the conditions of non-isothermal Knudsen diffusion in the pore structure of the membrane catalyst, there is a coupling of dry reforming of the methane (DRM) and gas transport, which leads to the intensification of this process. The reasons for the intensification are changes in the mechanism of gas transport, an increase in the rate of mass transfer, and changes in the mechanism of some stages of the DRM. The specific rate constant of the methane dissociation reaction on a membrane catalyst turned out to be an order of magnitude (40 times) higher than this value on a traditional (powder) catalyst.

Simple Synthesis of Molybdenum Carbides from Molybdenum Blue Nanoparticles.

In recent years, much attention has been paid to the development of a new flexible and variable method for molybdenum carbide (Mo2C) synthesis. This work reports the applicability of nano-size clusters of molybdenum blue to molybdenum carbide production by thermal treatment of molybdenum blue xerogels in an inert atmosphere. The method developed made it possible to vary the type (glucose, hydroquinone) and content of the organic reducing agent (molar ratio R/Mo). The effect of these parameters on the phase composition and specific surface area of molybdenum carbides and their catalytic activity was investigated. TEM, UV-VIS spectroscopy, DTA, SEM, XRD, and nitrogen adsorption were performed to characterize nanoparticles and molybdenum carbide. The results showed that, depending on the synthesis conditions, variants of molybdenum carbide can be formed: α-Mo2C, η-MoC, or γ-MoC. The synthesized samples had a high specific surface area (7.1-203.0 m2/g) and meso- and microporosity. The samples also showed high catalytic activity during the dry reforming of methane. The proposed synthesis method is simple and variable and can be successfully used to obtain both Mo2C-based powder and supports catalysts.

Synthesis of Microporous Mo2C-W2C Binary Carbides by Thermal Decomposition of Molybdenum-Tungsten Blues.

Molybdenum and tungsten carbides are perspective catalytic systems. Their activity in many reactions is comparable to the activity of platinum group metals. The development of the synthesis method for of highly dispersed binary molybdenum and tungsten carbides is an important task. Dispersions of molybdenum-tungsten blue were used as a precursor for synthesis of binary molybdenum and tungsten carbides. The synthesis of carbides was carried out by thermal decomposition of molybdenum-tungsten blue xerogels in an inert atmosphere. The binary carbides were characterized by XRD, TGA, SEM and nitrogen adsorption. The influence of the molar ratio reducing agent/Me [R]/[ΣMe], molar ratio molybdenum/tungsten [Mo]/[W] on phase composition, and morphology and porous structure of binary carbides was investigated. Samples of binary molybdenum and tungsten carbides with a highly developed porous structure and a specific surface area were synthesized.

Synthesis of Mo2C by Thermal Decomposition of Molybdenum Blue Nanoparticles.

In recent years, the development of methods for the synthesis of Mo2C for catalytic application has become especially important. In this work a series of Mo2C samples was synthesized by thermal decomposition of molybdenum blue xerogels obtained using ascorbic acid. The influence of the molar ratio reducing agent/Mo [R]/[Mo] on morphology, phase composition and characteristics of the porous structure of Mo2C has been established. The developed synthesis method allows the synthesis to be carried out in an inert atmosphere and does not require a carburization step. The resulting molybdenum carbide has a mesoporous structure with a narrow pore size distribution and a predominant pore size of 4 nm.