The Ni–Cu/Al2O3 catalysts used for the synthesis of carbon nanofibers and hydrogen were prepared by solution combustion synthesis using sucrose, urea, and oxalic acid as fuel. The resulting catalyst was a powder with a specific surface area of 60–128 m2/g. Catalyst samples were tested in a flow reactor at a temperature of 550°C in a methane medium at a pressure of 1 and 5 atm. The influence of organic fuel content on the composition and textural characteristics of resulting catalysts and their efficiency in the synthesis of carbon nanofibers and hydrogen was studied. The methane conversion was revealed to change within 5–17.5
Using chemical vapor deposition (CVD) and the traditional method of incipient wetness impregnation, new Pd–glass fiber catalysts (GFCs) for the oxidation of volatile organic compounds (VOCs) were synthesized. GFC samples were characterized by physicochemical methods (SEM, XPS), and the formation of metal particles on the surface of glass fibers was studied. The process of methane oxidation over the synthesized GFCs was studied, and the specific rates and activation energies of the methane oxidation reaction were determined. The comparative analysis of catalysts prepared by CVD and impregnation was carried out, and the potential of CVD as an efficient GFC synthesis method was demonstrated.
The paper is devoted to studying the process of thermal catalytic biomass processing in a fluidized-bed reactor for useful heat generation. Miscanthus, pine nut shells, and spent coffee were selected as initial biomass. The biomass crushed to a fraction smaller than 0.5 mm (coffee was not ground, as the size of its particles was initially 0.2–0.4 mm) was fed into a fluidized-bed reactor at processing temperatures of 650, 700, and 750°C, respectively. The objective of these experiments was to generate useful heat by burning the supplied biomass and utilize it, e.g., in maintaining an autothermal regime, as well as to investigate the resulting ash residues and analyze the flue gases emitted during the combustion process, followed by process simulation in Aspen Plus. The data of simulation show good agreement with experiment, and the proposed scheme can be used as one of the approaches to evaluating the feasibility of catalytic biomass combustion in a fluidized-bed in autothermal mode.
The results of studying the samples of efficient sorbents based on domestic natural raw materials, namely, ferromanganese nodules (FMNs) are presented. The use of these sorbents has significant potential for solving the pressing problem of environmental protection, such as the purification of gas flows from toxic sulfur compounds. The influence of the calcination temperature of sorbents on their physicochemical and sorption characteristics is studied. It is shown that the calcination temperature of a sorbent significantly affects its sorption capacity with respect to hydrogen sulfide, and optimal sorption characteristics are exhibited by the sorbent calcined at 300°C. SEM elemental mapping and DRIFT study results for spent samples allowed us to propose a temperature-dependent pathway of hydrogen sulfide sorption on the synthesized sorbents.
The studies of acid-catalyzed production of cellulose acetates derived from various types of biomass are reviewed in this work. Conventional acetylation methods in the presence of strong inorganic acids, transition metal salts, iodine or polyoxometalates are considered. Their disadvantages are corrosive activity and poor environmental performance (for example, formation of wastewater that requires disposal). The promising areas for further studies are the development of new regenerable catalysts and the regulation of the degree of substitution during acetylation in their use. Such systems may yield materials for their use in separators for energy storage devices, including supercapacitors.
The results of experimental and theoretical studies on the steam reforming of synthetic diesel fraction (SDF) over industrial methanation catalyst NIAP-07-01 of hydrogen production for fuel cells are reported. SDF (boiling point, 180–290°C) obtained by Fischer–Tropsch synthesis over a zeolite-containing Co/SiO2/ZSM-5/Al2O3 catalyst consists of C11–C18 hydrocarbons (88 g_H_2 /(kgSDF) at 650°C and an H2 concentration of 66.5
The physicochemical properties of supported molybdenum-containing catalysts, the state of the active component, and the activity and selectivity of the catalysts in the ethylene-to-propylene conversion and propylene metathesis reactions were studied. It was shown that the activity of molybdenum-containing catalysts in ethylene and propylene conversion grows with an increase in the number of medium and strong acid sites on their surface. The alumina-supported catalyst is active at temperatures of 100–250°C, whereas the silica gel-based catalyst requires temperatures of up to 500°C. The higher activity of the MoO3/γ-Al2O3 catalyst in metathesis reactions is attributed to the formation of highly dispersed molybdenum species and Brønsted acid sites.
To study the non-oxidative conversion of natural gas into valuable hydrocarbons and hydrogen, a digital model was developed for the reactor, in which laser radiation acts on a two-phase reaction medium consisting of a gas with suspended solid catalytic nanoparticles. The countercurrent flows of this gas-dust medium in the axially symmetric reactor tube absorb radiation in the area of their collision. Heat exchange with the wall along the length of a reactor with laser radiation during endothermic methane conversion was investigated. Laser radiation introduced into the medium locally increases its temperature at the outlet of resulting products from the reactor and shifts their composition towards aromatic compounds. The wall temperature of 1173 K and radiation provided the conversion of methane to hydrocarbons and hydrogen at a level of 65
In this study, bulk copper catalysts and copper catalysts supported on α- and γ-Al2O3 were synthesized. A copper–ammonia–carbonate solution (CACS) was used as a copper precursor. The structure and textural properties of the synthesized catalytic systems were investigated, including their specific surface area, pore volume, and coherent scattering region size. The optimal catalyst reduction temperature in a hydrogen flow, which ensures maximum activity in the D-glucose hydrogenation process, was experimentally determined. It was established that γ-Al2O3 inhibits the thermal decomposition of basic copper carbonate. The catalyst activity in in liquid-phase reduction of D-glucose was estimated by the average reaction rate, as the reaction orders were close to zero. The optimal supported copper content was estimated to be 5.5–5.8 wt cm_H_2^3 s–1 kg_Cu^ - 1 , while the conversion reached 5
In this review, we summarize and systematize our own data on the key regularities in the liquid-phase hydrogenation of carbocyclic alkenes and dienes of norbornene series using the examples of norbornadiene, dicyclopentadiene, and 5-vinyl-2-norbornene over heterogeneous palladium catalysts. The hydrogenation conditions that ensure the preservation of the norbornane framework, as well as the most probable mechanisms of its occurrence, are considered. Based on kinetic and quantum chemical studies, the reactivity during hydrogenation of multiple bonds of various types was assessed, taking into account their adsorption characteristics.
Catalytic ethylene dimerization is the basis of modern technologies for the production of high-purity 1-butene as a valuable semi-finished product of petrochemical synthesis, which is demanded primarily in the production of polymers for various purposes. The paper summarizes current information on the application areas of 1-butene in the chemical industry and the technologies for its catalytic synthesis from ethylene, and identifies trends and approaches in the development of selective ethylene dimerization catalysts.
The synthesis of an active, selective, and stable catalytic coating is a difficult task for the semihydrogenation of alkenols in a continuous-flow microreactor, being a potentially efficient strategy for the production of alkenols in fine organic synthesis. In this study, catalytic PdMe/TiO2 films (Me = Zn, Ag) were synthesized by the simple and efficient template sol-gel method and used in 2-methyl-3-butyn-2-ol semihydrogenation. The prepared bimetallic catalytic PdMe/TiO2 films (Me = Zn, Ag) demonstrated high catalytic selectivity due to the formation of PdZn and PdAg alloy nanoparticles (NPs). The surface of an active PdAg site is transformed under reaction conditions. The PdZn film demonstrated a better catalytic activity. Doping the support with zinc increases the selectivity and stability of the films. The analysis of X-ray photoelectron spectra shows that the zinc doped PdZn/Ti0.8Zn0.2O1.8 film has a higher concentration of active PdZn sites and a better oxidative stability as compared to PdZn/TiO2. The catalytic PdAg/TiO2 and PdZn/Ti0.8Zn0.2O1.8 demonstrated high stability in long-term experiments.
This study was focused on the problem of removing trace amounts of oxygen from hydrocarbon gas mixtures using a Ni-based solid sorbent supported on γ-Al2O3. The studied sorbents were synthesized by the incipient wetness impregnation of alumina supports with a solution containing nickel precursor compounds. The parameters varied during the study were the following: the active component content in the samples (4–8 wt
Methods for synthesizing pelletized ZSM-5 zeolites in the H-form with a high degree of crystallinity and a micro–meso–macroporous structure using synthetic amorphous aluminosilicates synthesized by precipitation from aqueous solutions of sodium silicate and aluminum sulfate or by sol–gel synthesis using tetraethyl orthosilicate and aluminum nitrate have been described. It has been shown that the nature of amorphous aluminosilicate affects the crystallization conditions for the pelletized zeolite and the morphology and degree of dispersion for the resulting ZSM-5 zeolite crystals.
The possibility of using the developed structured monolithic catalysts 0.24 wt
The results of studying Fischer–Tropsch synthesis in the presence of cobalt catalysts based on pelletized HZSM-5, HMOR, and HY zeolites with a micro–meso–macroporous structure were described. Physicochemical and catalytic properties were studied for samples with a cobalt content of 6 and 12 wt
The ability to undergo reversible electron addition while preserving structural stability makes vanadium-containing polyoxometalates attractive objects for research in various fields of chemistry, in particular, the development of modern “green” processes. An efficient Pd-containing catalyst system based on Pd(OAc)2 and a NaH10P4Mo18V7O87 high-vanadium heteropoly acid for the two-stage oxidation of C5–C10 linear α-olefins to respective 2-ketones with a yield of over 93
The effect produced by the degree of hydrotreatment and the content of heteroatoms in an initial cracking feedstock on its conversion, the distribution of cracking products, and the composition of regeneration gases was studied. The four types of feedstocks, such as a hydrocracking residue, hydrotreated vacuum gas oil, nonhydrotreated vacuum gas oil, and a mixed feedstock containing 20
