Effect of nitric acid modification of montmorillonite clay on synthesis of solketal from glycerol and acetone

[EN]The effect of acid modification of a natural montmorillonite clay (MM) by HNO3 on the catalytic properties of MM from Dash-Salakhlinsk (Kazakhstan) has been investigated in the synthesis of solketal from glycerol and acetone in solvent free and acetonitrile media. HNO3 concentration allowed to control the chemical composition, the surface acidity, the porous structure of the acid-activated MMs and their catalytic performance. The main reaction product was solketal with 86.6–98% selectivity. Conversion of glycerol depended on the Brønsted acidity. The most active sample, namely, MM activated with 0.5 mol/dm3 HNO3, showed good reusability for 3 catalyst cycle

Effect of structure and acidity of acid modified clay materials on synthesis of octahydro-2H-chromen-4-ol from vanillin and isopulegol

The Prins cyclization of (−)-isopulegol with vanillin to form octahydro-2H-chromen-4-ol was studied in the presence of natural layered aluminosilicates modified by 0.5 mol/dm3 HCl, such as montmorillonite, kaolin, and metakaolin obtained by the calcination of kaolin at 650 °C. According to infrared spectroscopy using pyridine as probe molecule, the amount and strength of Brønsted acid sites depend on the type of clay and decrease in the following order HCl-montmorillonite > HCl-kaolin > HCl-metakaolin. The difference in Brønsted acidity and textural properties of clays affected the reaction rate and the selectivity towards octahydro-2H-chromen-4-o

Synthesis of octahydro-2H-chromen-4-ol from vanillin and isopulegol over acid modified montmorillonite clays: Effect of acidity on the Prins cyclization

Two calcium-rich natural layered aluminosilicates containing 90–95 wt.% montmorillonite were chemically activated using 0.125–3.0 M HCl solutions. Structural and textural properties were characterized by X-ray diffraction, elemental analysis and N2-adsorption/desorption analyses. According to infrared spectroscopy using pyridine as probe molecule, the amount of Brønsted acid sites increased when increasing HCl concentration. The catalytic performance of these materials was investigated in the Prins cyclization of (−)-isopulegol with vanillin to form octahydro-2H-chromen-4-ol, carried out in toluene at 35 °C. It was found that the amount of Brønsted acid sites and the microporosity of the catalysts are key factors for the control of the reaction rate and the selectivity towards octahydro-2H-chromen-4-o

Synthetic and natural materials with the brucite-like layers as high active catalyst for synthesis of 1-methoxy-2-propanol from methanol and propylene oxide

The aim of this study was to investigate the correlation between the basic and catalytic properties of brucite and Mg,Al-layered double hydroxides (Mg,Al-LDHs) in the reaction of propylene oxide with methanol. The basic properties of the solids were investigated by FT-IR spectroscopy using CDCl3 as probe molecule and Hammett acidity titration with n-butylamine and benzoic acid. Both the increase in the activation temperature and the decrease in Al content favored the increase in the basicity of Mg,Al-LDH. The nature of “Mn+single bondO2− Lewis acid-base” pairs was a key factor to control the catalytic behavior of the solids. The length of the M-O bond, the basicity of the oxygen ion and the strength of the metal ion on the surface affected the catalytic activity of the solids and their isomer selectivity in the reaction between methanol and propylene oxide to form 1-methoxy-2-propanol. It was demonstrated that brucite(150) can be applied as catalyst for at least four successive cycles without loss of activit

Effect of acid modification of kaolin and metakaolin on Brønsted acidity and catalytic properties in the synthesis of octahydro-2H-chromen-4-ol from vanillin and isopulegol

Natural kaolin and the metakaolin obtained by calcination of kaolin at 650 °C were chemically activated using 0.25–3.0 mol/dm3 HCl solutions. Structural and textural properties of samples were characterized by X-ray diffraction, elemental analysis and N2-adsorption/desorption analyses. The amount of Brønsted acid sites (BAS) was determined by infrared spectroscopy using pyridine as probe molecule. The amount of BAS for kaolin rose with increasing HCl concentration up to 1.0 M, and decreased for higher concentrations, that is related with the leaching of Al from the solid. Effect of HCl concentration on amount of BAS was negligible for metakaolin. The catalytic performance of these materials was investigated in the Prins cyclization of (−)-isopulegol with vanillin to form octahydro-2H-chromen-4-ol, carried out in toluene at 50 °C. The reaction rate and the selectivity toward octahydro-2H-chromen-4-ol depended on the Bronsted acidity, structural and textural properties of the catalysts. The reaction rate in the presence of kaolin modified by HCl correlated with the amount of BAS. HCl-kaolin samples were more active compared with HCl-metakaolin, while selectivity reaction toward octahydro-2H-chromen-4-ol was larger in the presence of HCl-metakaoli

ZEOLITE-CONTAINING TRIPOLI OF KHOTYNETS DEPOSIT (OREL REGION): MINERAL COMPOSITION, SORPTION PROPERTIES AND FORMATION CONDITIONS

Link for citation: Belousov P.E., Karelina N.D., Morozov I.A., Rudmin M.A., Milyutin V.V., Nekrasova N.A.,  Rumyantseva  A.O., Zakusina O.V., Krupskaya  V.V. Zeolite-containing tripoli of Khotynets deposit (Orel region): mineral composition, sorption properties and formation conditions. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.70-84.In Rus. The relevance of the work is caused by the need to develop the mineral resource base of high-quality sorption materials in Russia, as well as to study the properties of natural sorbents with a view to their further application in practice. The aim of the work is to study the features of the geological structure, conditions of formation, mineral composition and sorption properties of zeolite-containing tripoli from the Khotynets deposit. The object of the study is the Khotynets deposit of zeolite-containing tripoli, studied by the field team of the Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry of Sciences RAS in 2019–2020. Methods: XRD, XRF, FTIR, optical and scanning electron microscopy, determination of SSA and pore size distribution, CEC, experiments on the sorption of cesium, strontium and copper. The paleotectonic reconstruction was carried out as well. Results. The productive strata of the Khotynets deposit consists of three benches, the main useful components of which are minerals of the zeolite, opal-cristobalite and smectite group. Their total content reaches 80 %. The formation of the deposit occurred in three stages and is associated with the primary accumulation of biochemogenic silica in coastal sea waters, the removal of terrigenous clay material from the nearby land, their further compaction, and processing of the accumulated material at the diagenesis stage. The formation of clinoptillolite is associated with an increase in pH and the dissolution of the opal-cristobalite and clay material as a result of the secondary impact of low-temperature deep solutions. The performed experiments showed that this mineral material has high sorption characteristics with respect to cesium and copper and can be used as a component of sorption mixtures for the purification of polluted waters

Carboniferous bentonites from 10th Khutor deposit (Russia): composition, properties and features of genesis

Summarization: This article studies the geological structure, mineralogical composition, genesis and industrial properties of bentonite of the 10th Khutor deposit (Republic of Khakassia, Russia). The deposit is confined to the coal-bearing formation of Carboniferous age and is one of the main sources of bentonite for the metallurgical and foundry industries in Russia. The samples were collected during several field seasons and were studied with XRD, SEM, DTA, XRF, FTIR, BET and CEC analysis. The deposit consists of 6 productive layers with montmorillonite of alkaline-earth type varying in content from 38 to 72%. The formation of bentonites is associated with the alteration of volcanic ash of rhyodacite and dacite composition in zones of shallow sea water - bays and lagoons. The specific conditions of the formation, like an evaporitic depositional environment with high concentrations of soluble salts and burial diagenesis, as evidenced by seams and packs of hard coal, affected the textural and surface properties of the bentonite and caused the observed low microporosity and limited illitization.Presented on: Applied Clay Scienc

First geophysical and shallow ice core investigation of the Kazbek plateau glacier, Caucasus Mountains

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