A technology for producing hydrogen and carbon nanofibers from natural gas is considered. A catalyst that actively and stably operated at temperatures of 700–750°C was developed to achieve high ...conversions of methane. The genesis of its phase composition was investigated using electron microscopy and X-ray diffraction analysis. The modification of a 75%Ni–12%Cu/Al
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catalyst with iron oxide led to the formation of a ternary Ni–Cu–Fe alloy. The method developed for producing hydrogen effectively worked with the use of not only methane but also natural gas as a feedstock. An installation with a rotating reactor for producing hydrogen and carbon nanofibers from natural gas made it possible to carry out the process on a 70%Ni–10%Cu–10%Fe/Al
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catalyst for 20–30 h. The hydrogen concentration at the reactor outlet was higher than 70 mol %. The yield of hydrogen reached 590 L per gram of the catalyst.
In order to improve the metrological characteristics of a standard nozzle under actual operating conditions, an improved model of a steady-state gas flow in the varying-cross-section channels was ...used to refi ne the estimates of two methodological errors when reproducing a volumetric flow rate of gas. The first methodological error is caused by the selection of a gas flow model, accounting for the initial kinetic energy of the flow at the nozzle inlet, and the second – by the variation in humidity of the process air. It is shown that these methodological errors should be considered when operating standard volumetric air flow rate measuring devices, containing critical nozzles.
This study was devoted to the processing of vacuum residue to produce lighter oil fractions, such as gasoline and diesel fuel. The hydrocracking and catalytic hydrocracking of vacuum residue in the ...presence of formic acid (FA) were performed in the temperature range of 250–550 °C. Carbon nanofibers (CNFs) were used as catalytic additives. In contrast to conventional hydrocracking, an important stage in the catalytic hydrocracking of vacuum residue is the decomposition of formic acid. Experimental studies on the effect of CNFs on the decomposition of FA demonstrated that CNFs pre-treated in a NaOH solution (CNF (NaOH)s) had the highest activity and selectivity for the production of H2 and CO2. The maximum yield of liquid products in the catalytic hydrocracking process, equal to 34 wt.%, was observed at 300 °C in the presence of CNF (NaOH)s. The characterization of the fractional compositions of the liquid products showed that the ratios of the fractions changed with an increase in the reaction temperature. The maximum concentrations of the light fractions (gasoline and diesel) in the liquid products of the catalytic hydrocracking of vacuum residue were observed at 300–350 °C in the presence of CNF (NaOH)s.
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•Three catalysts were used in different autoclave zones during the tar carbonization.•The carbonization efficiency and coke properties were improved by using 3 catalysts.•The coke ...yield during carbonization increased nearly twice.•The sulfur concentration in the solid reaction products decreased 2–3 times.
The tar carbonization was studied in the temperature range of 350−500 °C. Gaseous products formed during the tar carbonization at 450 °C were analyzed for the concentration of sulfur-containing compounds. H2S and COS were observed in the reaction products. An increase of the carbonization temperature from 450 to 550 °C led to the decrease of the coke yield due to deeper cracking of the tar components. The temperature increases also resulted in the decrease of the sulfur concentration in the coke from 1.28 % to 1.18 %.
The efficiency of the carbonization process and the properties of the obtained coke were further improved by placing three different catalysts Ni-Mo/Sibunit, Cu/Sibunit and Ni/Sibunit in different zones of the autoclave where the tar carbonization was performed. In zone 1 the tar was subjected to hydrocracking and desulfurization over the 8%Ni-2,5%Mo/Sibunit catalyst. In zone 2 sulfur was trapped by the Cu/Sibunit catalyst in the form of copper sulfide. In zone 3 coke was formed over the Ni/Sibunit catalyst predominantly from gases formed by the tar cracking.
Such organization of the carbonization process increased the coke yield to 45 wt.%. The three-zone catalyst arrangement during the tar carbonization also resulted in a substantial decrease of the sulfur concentration in gaseous products, which led to lower sulfur concentration in the solid reaction products in zone 3.
A new method for the synthesis of boron-doped carbon nanomaterial (B-carbon nanomaterial) has been developed. First, graphene was synthesized using the template method. Magnesium oxide was used as ...the template that was dissolved with hydrochloric acid after the graphene deposition on its surface. The specific surface area of the synthesized graphene was equal to 1300 m
/g. The suggested method includes the graphene synthesis via the template method, followed by the deposition of an additional graphene layer doped with boron in an autoclave at 650 °C, using a mixture of phenylboronic acid, acetone, and ethanol. After this carbonization procedure, the mass of the graphene sample increased by 70%. The properties of B-carbon nanomaterial were studied using X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and adsorption-desorption techniques. The deposition of an additional graphene layer doped with boron led to an increase of the graphene layer thickness from 2-4 to 3-8 monolayers, and a decrease of the specific surface area from 1300 to 800 m
/g. The boron concentration in B-carbon nanomaterial determined by different physical methods was about 4 wt.%.
The research was aimed at deriving an equation for calculating the degree of moisture filling of pore spaces of centrifuged sediments with capillary fringe filtrate. The previously derived analytical ...equation does not take the gas pressure in the centrifuge into account. To take account of the gas pressure, a modification of the equation for calculating the limiting pore diameter determined from the limiting force equilibrium between the fringe capillary forces and the sum of inertial centrifugal forces in combination with forces of gas pressure is proposed. In the example of calculation, cases of formation of a two-layer capillary fringe (with a base layer saturated with the filtrate and an unsaturated fringe layer) and a single-layer capillary fringe were considered. The calculation results showed agreement between the calculated moisture content curves and the experimental data. The obtained data are required for purposeful changes in the parameters of mechanical drying for reducing or increasing the degree of moisture filling of the sediment.
Specific features of the catalytic tar cracking in the presence of formic acid, BEA zeolite and 8% Ni-2.5% Mo/Sibunit catalyst were studied at 350 °C and 1.0 MPa pressure. The obtained results ...evidenced that formic acid can be used as a hydrogen donor during catalytic reactions. The formic acid addition made it possible to perform efficient hydrocracking of heavy feed such as tar. It was found that both the tar conversion and selectivity to light (gasoline-diesel) fractions grew in the sequence: tar < (tar - formic acid) < (tar - formic acid - BEA zeolite) < (tar - formic acid - BEA zeolite - 8% Ni-2.5% Mo/Sibunit catalyst). Furthermore, significantly lower concentrations of impurities containing sulfur and nitrogen were observed for the (tar - formic acid - BEA zeolite - 8% Ni-2.5% Mo/Sibunit catalyst) system. For example, the sulfur and nitrogen concentrations in the tar precursor were 1.50% and 0.86%, respectively. Meanwhile, their concentrations in the liquid products after the catalytic cracking were 0.73% and 0.18%, respectively.
The problem of calculating the moisture content of pore space of sediment after its mechanical drying in a centrifuge with a peripheral filtering surface is studied. An analytical equation was ...derived along the radius of moisture filling of the sediment by filtrate of the capillary fringe, taking account of lognormal distribution of pore sizes. The proportion of moisture imported into the pores by the bound filtrate is determined. The presence of a basal layer of the capillary fringe is illustrated. The possibility of limiting determination of the smallest pore diameter toward larger size for constructing histograms and calculating the moisture content of the sediment is confirmed. The agreement of the results with the known experimental data received for suspensions of chemical and oil refining industries in filtering centrifuges is confirmed by an example of calculation. The main variable design and technological parameters for calculations based on effective mechanical drying of sediment in the filtering centrifuge rotor are the radius of the circumference of its filtering surface, the angular velocity, and the maximum size of pores in the sediment.
A comparative study of the reactivity and transformation and degradation pathways under conditions of the oxidative acetoxylation was carried out for various palladium complexes. The implementation ...was confirmed for the NHC-connected mechanism of catalysis. Effects of the process of pyridine coligand elimination on catalysis were investigated. It was found that free pyridine inhibits the catalysis of oxidative acetoxylation of 2-phenylpyridine. Mono- and diacetoxyphenylpyridines were obtained regioselectively in 84–94% yields using Pd/NHC complexes of various structures.
The study involved a series of experiments on the coking of vacuum residue (VR) and of a mixture of carbon nanotubes (CNTs) and VR in an autoclave at 400–550°C. Using XRD, TEM, and electrical ...resistivity measurements, the properties of petroleum coke (petcoke) and CNT/petcoke composite were investigated and compared with those after calcination in an inert atmosphere at 1000–1100°C. It was found that the coking of a 2.5% CNT/VR mixture reinforces the petcoke with the CNTs. The CNT/petcoke composite exhibits a slightly higher crystallinity than the petcoke. However, the resistivity of the CNT/petcoke composite was found to be more than an order of magnitude lower than that of the petcoke. After high-temperature (1000–1100°C) calcination, the difference in resistivity between the petcoke and the 2.5% CNT/petcoke composite becomes substantially lower. This is associated with a resistivity drop in the petcoke itself, which approximates the resistivity of the carbon nanotubes. It was also identified that the high-temperature calcination reduces the sulfur content in the CNT/petcoke composite, and this reduction is more dramatic than that for the petroleum coke.
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