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Research

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15 pages, 6917 KiB

Open AccessArticle

Study of Soot Deposits during Continuous Methane Pyrolysis in a Corundum Tube

by Matvey S. Galtsov-Tsientsiala, Aleksandr O. Dudoladov, Anatoly V. Grigorenko and Mikhail S. Vlaskin

Appl. Sci. 2023, 13(19), 10817; https://doi.org/10.3390/app131910817 - 29 Sep 2023

Cited by 3 | Viewed by 900

Abstract

Methane pyrolysis is one of the promising methods for producing low-carbon hydrogen, while one of the main problems of methane pyrolysis technology is soot clogging of the reactor space. In this work, soot deposits were studied during continuous methane pyrolysis in a corundum tube with an inner diameter of 50 mm. Experiments were carried out at temperatures of 1000 °C, 1050 °C, 1100 °C, 1200 °C and 1400 °C with methane flow rates of 1 L/min and 5 L/min. Each experiment lasted 1 h. The formed soot accumulated inside the reactor (corundum tube) and the connected filter, where the gaseous product of methane pyrolysis was separated from the soot. The gaseous product was studied by gas chromatography. The soot was studied by SEM, BET and ICP-MS. With an increase in the temperature of the pyrolysis process from 1000 to 1200 °C, the hydrogen yield increased from 28.64 to 92.74% and from 1.10% to 72.09% at a methane flow rate of 1 and 5 L/min, respectively. The yield of soot increased from 1.28 g at 1000 °C to 43.9 g at 1400 °C (at a methane flow rate of 1 L/min). With an increase in the flow rate of methane from 1 to 5 l/min, the yield of soot at 1200 °C increased by almost two times to 75.65 g. It was established that in the region of the reactor where maximum heating occurs, the accumulated soot sinters and forms dense growths. At 1050 °C, the particle size of soot varies from 155 to 650 nm, at 1200 °C—from 157 to 896 nm, and at 1400 °C—from 77 to 532 nm. The specific surface of soot was 3.5 m²/g at 1000 °C and 8.0 m²/g at 1400 °C. The purity of the produced carbon black was about 99.95%. This study is useful in the selection of materials and technical solutions for a pilot plant for methane pyrolysis. Full article

(This article belongs to the Special Issue New Insights into Green Chemistry)

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17 pages, 5406 KiB

Open AccessArticle

Hydrothermal Oxidation of Coarse Aluminum Granules with Hydrogen and Aluminum Hydroxide Production: The Influence of Aluminum Purity

by Grayr N. Ambaryan, Olesya A. Buryakovskaya, Vinod Kumar, Georgii E. Valyano, Elena A. Kiseleva, Anatoly V. Grigorenko and Mikhail S. Vlaskin

Appl. Sci. 2023, 13(13), 7793; https://doi.org/10.3390/app13137793 - 01 Jul 2023

Cited by 2 | Viewed by 994

Abstract

This study is devoted to the hydrothermal oxidation of aluminum—the exothermic process in which hydrogen and aluminum oxide (or hydroxide) are produced. In this work, the influence of the chemical purity of aluminum on the conversion degree of coarse aluminum at hydrothermal oxidation was studied. Distilled water and coarse granules of aluminum with an average size of ~7–10 mm and three different aluminum purities—99.7, 99.9, and 99.99%—were used in the experiments. The oxidation experiments were carried out inside a 5 liter autoclave in an isothermal mode at temperatures from 200 to 280 °C, with a step of 20 °C. The holding time at the set temperature varied from 4 to 10 h. It was shown that the chemical purity of aluminum considerably influences the oxidation kinetics. More chemically pure aluminum oxidizes much faster, e.g., at a temperature of 280 °C and a holding time of 10 h, the conversion degree of granules with a chemical purity of 99.9% and 99.7% was less than 2%, while 99.99% aluminum was almost fully oxidized. The conversion degree of 99.99% aluminum decreased with the reduction in temperature and holding time, to 66–68% at 280 °C, 4 h, and 2–3% at 200 °C, 10 h. Full article

(This article belongs to the Special Issue New Insights into Green Chemistry)

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Review

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16 pages, 1917 KiB

Open AccessReview

Amidoalkyl Naphthols as Important Bioactive Substances and Building Blocks: A Review on the Current Catalytic Mannich-Type Synthetic Approaches

by Hristo Petkov and Svilen P. Simeonov

Appl. Sci. 2023, 13(11), 6616; https://doi.org/10.3390/app13116616 - 29 May 2023

Viewed by 1359

Abstract

Currently, 1-amidoalkyl-2-naphthol derivatives are of increasing interest due to their biological activities and further use in the preparation of other important bioactive molecules, such as aminoalkyl naphthols and oxazines. The synthesis of 1-amidoalkyl-2-naphthol moiety is usually achieved by employing one-pot multicomponent Mannich reactions. This review covers the recent reports on 1-amidoalkyl-2-naphthols’ preparation with the use of different catalysts and summarizes the available published data for the period of the last 3 years. It also puts emphasis on the structure, synthetic transformation and biological importance of this class of products. Full article

(This article belongs to the Special Issue New Insights into Green Chemistry)

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