Studies on the preparation and catalytic action of zeolites in the form of nanosized crystals are reviewed. Examples of successful synthesis of nanosized zeolites of the FAU, MFI, BEA, and MOR ...structural types and their use in such processes of petroleum chemistry and refining as catalytic cracking, hydrocracking, hydroisomerization, oligomerization, transalkylation, conversion of methanol and acetone to olefins, and other processes are given. The progress and prospects of using nanosized zeolites in slurry reactors comprising three-phase systems, in which individual zeolite particles are dispersed in a liquid medium, are considered.
Keywords
: nanosized zeolites, catalytic cracking, hydrocracking, transalkylation, slurry reactor
Layered microporous titanosilicate AM-4 (Aveiro-Manchester-4) is a synthetic analog of microporous lintisite-type minerals. We applied the hydrothermal method to synthesize AM-4 compound from ...different titanium sources, i.e. titanium (III) chloride solution, titanyl-sulfate (titanite ore treatment product) and sodium metasilicate by stepwise cooling of an initial titanium-silicate mixture. In acid solution the crystal structure of AM-4 transformed into a novel layered titanosilicate SL3 (synthetic decationated lintisite) with a unique topology that consists of Ti2Si4O10(OH)4 nano-blocks. It was found that SL3 compound had a tendency for uptake of Ag from the standard test copper-nickel electrolyte. A possibility of repeated use of SL3 as a renewable sorbent was shown on the example of sorption Ca2+ cations. Both AM-4 and SL3 compounds can be considered as new functional materials of renewable and thermally stable nature with potential application for sorption and immobilization of the radioactive iodine isotopes.
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•Hydrothermal synthesis of an analog of the lintisite can be carried out on the basis of a solid technical semi-product of the Khibiny titanite treatment.•The quality of AM-4 can be improved by conducting synthesis with a multi-stage heating and cooling cycle.•The crystal structure of the AM-4 is similar to the nanopuzzle and can be transformed into a new layered compound•The AM-4 can be the basis for obtaining a repeatedly renewable sorbent of ions (for example Ag, Ca or I).
The effect of different binders (aluminum hydroxide (sample K-1), silica gel (sample K-2), pseudoboehmite (sample K-3), a kaolin–silica sol mixture (sample K-4), and a kaolin–aluminum hydroxide ...mixture (sample K-5)) on the set of the textural, acidic, and catalytic properties of catalysts based on nanocrystalline zeolite Beta has been studied. It has been shown that the introduction of aluminum hydroxide, silica gel, and a kaolin–aluminum hydroxide mixture as binders does not lead to the blocking of the pore structure of the zeolite, while the introduction of pseudoboehmite and a kaolin–silica sol mixture into the catalyst composition leads to a decrease in the micropore volume. Using the NH
3
TPD method, it has been found that the use of aluminum hydroxide, pseudoboehmite, and a kaolin–aluminum hydroxide mixture as a binder leads to an increase in the number of acid sites of the catalyst compared with the respective parameter of the original BEA-25 zeolite. The observed changes are attributed to the migration of aluminum from the binder to the zeolite structure to form new acid sites, as evidenced by
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Al MAS NMR data. It has been assumed that an increase in acidity for the K-4 sample is associated with the interaction of silica with the extra-framework aluminum of the Beta zeolite. With respect to activity in the benzene alkylation with propylene, the catalysts can be arranged in the following order: K-1 > K-3 > K-2 > K-5 ≈ BEA > K-4, which correlates with the number of acid sites in the samples. The best process parameters have been achieved in the presence of the K-1 sample exhibiting a stable on-stream behavior for 10 h and providing a selectivity for alkylation products (cumene + DIPB) of 99.7% and a cumene selectivity of 89.7 wt % at 100% propylene conversion.
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•Hydrocracking catalyst activity depends on concentration of Bronsted acid sites (BAS).•Catalyst selectivity depends on BAS concentration in meso- and micropores.•NiMo/small crystals ...BEA has the highest activity and selectivity to naphtha and gas.•NiMo/small crystals Y has the highest selectivity to diesel.
Hydrocracking of vacuum gas oil has been studied over NiMo/zeolite-Al2O3 catalysts. Three different zeolites have been used for catalysts preparation: zeolites Beta (BEA) and Y (FAU) having small crystal size and zeolite Y modified by recrystallization (RFAU). HRTEM, low-temperature N2 adsorption, FTIR of adsorbed CO and TPD-NH3 showed that zeolites had different crystal sizes, mesopore volume, strength and concentration of acid sites. Sulfide active component particles have been revealed to be similar in all catalysts by HRTEM and XPS. NiMo/BEA catalyst having zeolite with the smallest average particle size and the highest concentration of Brønsted acid sites (BAS) demonstrated the highest hydrocracking activity. Selectivity to middle distillates decreased in the following order: NiMo/FAU > NiMo/RFAU > NiMo/BEA. This effect is accounted for by optimal zeolite acidity and improved availability of the acid sites for bulky molecules of the heavy feedstock.
Characteristics of zeolite ZSM-12 crystallization using methyltriethylammonium chloride and
N,N
-dimethyl-
N
-ethyl(monoethanol)ammonium bromide as templates have been studied. The materials have ...been characterized by X-ray diffraction analysis, scanning electron microscopy, X-ray fluorescence analysis, low-temperature nitrogen adsorption–desorption, temperature-programmed desorption of ammonia, and solid-state
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Al nuclear magnetic resonance spectroscopy. It has been shown that dimethylethylethanolammonium bromide inhibits crystal growth along the
a
and
c
planes and thereby contributes to crystal growth only in the direction of the
b
axis, which, in turn, leads to lower surface area and acidity of the sample than the respective parameters of the zeolite synthesized using methyltriethylammonium chloride.
Changes in the phase, morphological, and textural properties of silicoaluminophosphates with the AEI structure during crystallization at 150, 170, and 190°С are studied. Using a combination of ...physicochemical methods, evolution of the solid phase extracted at different steps of synthesis is shown. It is established that at 150°С the microporous phase containing silicon in tetrahedral positions of the framework appears already at the initial stages of crystallization and further nanostructuring of the solid phase is associated with the incorporation of silicon via the SM3 mechanism. At 170°С, crystallization proceeds through formation of the aluminophosphate and aluminosilicate mixed mesoporous composite. The transformation of mixed composite into the microporous crystalline material is accompanied by the incorporation of SiO
4
isolated tetrahedra into the forming crystalline framework according to the SM2 mechanism; this provides a strong acidity of the material. The intermediate mesoporous semiproduct extracted at the initial stages of synthesis at 190°С is a mixture of disordered aluminophosphate and coarse mesoporous agglomerates; their transformation into silicoaluminophosphate with the AEI structure occurs only upon silica transfer to the liquid phase, and the incorporation of silicon into the AEI crystalline framework proceeds via the SM3 mechanism with the subsequent formation of silicon islands.
This paper presents the results of analyzing the state and dynamics of damaged vegetation from satellite images of high and ultrahigh spatial resolution. This study was conducted based on the example ...of the site of coniferous forests in the Lower Angara region (Krasnoyarsk krai), where a large outbreak of the Siberian moth took place in 1944–1995. The remote assessment of the state of dark coniferous forests revealed the trends of the SWVI (or NDMI) and NDVI indices that characterize long-term changes in the vegetation cover over the period 2000–2018. The SWVI index is the most informative indicator: a sharp decrease in average values and increase in the coefficient of variation of the index are noted for dead and severely damaged wood stands (crown defoliation of more than 75%). The area of dead forests was calculated according to the difference images of the indices (ΔSWVI) with the threshold criterion lσ (the standard deviation). In 2000, the area of forests that died under the impact of the Siberian moth was approximately 19 200 ha. Alter two major fires in 2004 and 2011 and as a result of destructive factors combination, the area of dead forests increased up to 20 400 ha by 2017–2018. Reforestation within the boundaries of dead stands was estimated from the classification of Landsat images (June 20, 2017; June 23, 2018) by the Random Forest algorithm using the selection of templates from detailed Resurs-P images with a spatial resolution of 1 m (Geoton-LI—July 22, 2015 and December 3, 2018), which were taken during different seasons. The classification proved to be highly reliable (Kappa index is more than 0.9). The areas of classified deciduous and coniferous stands, deciduous and mixed stands with mainly coniferous regrowth, grass–shrub vegetation, and barren soil were calculated. Natural regeneration of mainly coniferous undergrowth occurred in 17% of the damaged area, and deciduous regrowth occurred in approximately 10% of the area 23 years after damage by pests. The area damaged by the moth affected reforestation: the larger the area of the outbreak, the higher the share of open lands with grass and shrub vegetation (it accounts for more than half of the area for the large outbreak and approximately 45% for smaller outbreaks). Regrowth was found in proximity of patches of stands and deadwood in the sites unaffected by large fires. Frequent fires in the territory of moth infestation limit the process of reforestation; therefore, most of the vegetation was at the initial stage of the succession cycle.
Interactions between the endoplasmic reticulum (ER) and mitochondria have received insufficient attention until recently. However, distorted contacts between the ER and mitochondria were identified ...as an important factor in the etiopathogenesis of neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis. In view of these new data, the mechanisms of ER–mitochondrial interactions are necessary to study in detail in order to develop new diagnostic and therapeutic approaches to neurodegenerative diseases and to extend basic knowledge of the physiology of the eukaryotic cell. The review focuses on the functions of mitochondria-associated ER membranes (MAMs). Structural elements of the MAM system, their contributions to the vital cell functions (calcium and lipid homeostasis, autophagy, fusion and division of mitochondria, and the regulation of their number), and the role of MAM dysfunctions in the pathogenesis of various neurodegenerative diseases are considered.
Currently, researchers show considerable interest in the link between gut microbiota and idiopathic recurrent miscarriage (IRM). This study aimed to analyze taxonomic changes of gut microbiota and ...assess its relationship with plasma levels of cortisol, melatonin, TNFa and IL17 in women with IRM. We invited 55 women with IRM and 60 women with normal pregnancy, studied their gut microbiota, and registered serum concentrations of cortisol, melatonin, TNFa and IL17. Women with IRM had changed gut microbiota: significantly decreased — diversity (Chao1 p = 0.014), significantly decreased abundance of Bifidobacterium (p < 0.001), Lachnospira (p = 0.032), Roseburia (p = 0.003), Coprococcus (p = 0.012), and significantly increased abundance of Ruminococcus (p < 0.001) and Klebsiella (p = 0.002). We have shown a statistically significant relationship between cortisol level and abundance of Lachnospira (r = –0.51; p = 0.002), melatonin level and abundance of Coprococcus (r = –0.49; p = 0.012), and identified connections between TNF and IL17 concentrations and Chao1 index (r = –0.51; p = 0.002, r = –0.54; p = 0.001, respectively), TNF concentration and abundance of Ruminococcus (r = 0.51; p = 0.002), IL17 concentration and abundance of Bifidobacterium (r = –0.52; p = 0.001). Modulation of gut microbiota may have preventive and therapeutic effects in women with IRM.
Pharmacoencephalography (pharmaco-EEG) is a prominent instrument for the pharmacological screening of new psychoactive molecules. This experimental approach has not remained a vestige of ...neurobiological studies, and can be used successfully to complete today’s research objectives. The development and rise to universal use of machine learning techniques opens up novel prospects for the use of pharmaco-EEG data to solve the problems of classification and prognosis. We have previously shown that naïve Bayes classifier (NBC) combined with principal component analysis (PCA) can be used to differentiate between antipsychotic and sedative drug effects as well as to distinguish among the antipsychotics’ effects. In the present study, we evaluated the possibility to employ this method to assess the dose-dependency of antipsychotic effects. The experiments were carried out in white outbred male rats with chronically implanted electrocorticographic electrodes. As the agents of interest, we chose two drugs with antipsychotic activity, chlorpromazine and promethazine, in three doses each (0.1, 1, 10 mg/kg and 0.5, 5 and 20 mg/kg, respectively). The training set, used as a reference to determine the pharmacological effects of the agents of interest, included the D
2
-dopamine receptor blocker haloperidol, M-cholinergic receptor blocker tropicamide, H
1
-histamine receptor blocker chloropyramine, the sedative dexmedetomidine, and the anxiolytic phenazepam. We have shown that the lowest chlorpromazine dose (0.1 mg/kg) can be characterized as antipsychotic with a marked histaminolytic effect, while the highest one (10 mg/kg) exhibits predominantly antipsychotic activity with a cataleptogenic effect. All three doses demonstrated anticholinergic activity, which increased with the dose. For promethazine, we observed a clear dose-dependent shift from antipsychotic action to cataleptogenic, alongside a notable antimuscarinic effect of all doses. None of promethazine doses showed any resemblance to chloropyramine, which probably indicates its anti-dopaminergic and antimuscarinic effects being able to mask its H
1
-antihistamine effect in the used dose range. In summary, our results demonstrate that NBC combined with PCA can be used to determine the dose-dependency of antipsychotic agents’ effects based on their impact on electrocorticogram parameters. Further development of this method as well as expansion of psychotropic agent electropharmacogram library would allow for more precise prediction of pharmacological activity of the agents of interest.
