Solid acid catalysts of cellulose hydrolysis in aqueous media attract considerable research interest because of the ease of their separation from the reaction products. The nature of interaction between the two solids is a relevant topic of ongoing research. One aspect of behavior of solid acids in water was not previously discussed in literature with regard to hydrolysis of cellulose: electrolytic dissociation and formation of electric double layers. In this work, on theoretical level, we consider the role of the double layer created by the solid acid when cellulose hydrolysis takes place. The diffuse layer of protons is regarded as the medium where the hydrolysis reaction occurs. Protonation of cellulose by these protons imparts positive charge onto its surface, and cellulose is electrostatically attracted to the polyanion of the catalyst. Thus, the two solid surfaces stay close to each other despite Brownian motion; this allows explaining the high activity of solid catalysts even when chemisorption of carbohydrates on a catalyst is not favorable.

Nonmagnetic fine narrow fractions of particles with mean diameters of 2, 3, 6, and 10 μm were for the first time separated from fly ash produced by pulverized combustion of Ekibastuz coal using aerodynamic classification with subsequent magnetic separation. These fractions were characterized by the size distribution, bulk density, and chemical and phase compositions. The particle size distributions correspond to d 50 values of 1.9, 2.3, 5.1, and 9.2 μm. As the fraction particle size increases, the bulk density was found to rise gradually from 0.90 to 1.07 g/cm3. The main components of the chemical composition were SiO2 (65–70 wt %) and Al2O3 (23–28 wt %). The phase composition was represented by the glass phase (64–69 wt %), mullite (17–21 wt %), and quartz (10–18 wt %). The main morphological particle types were microspheres with a nonporous smooth surface and microspheres with a porous shell. With an increase in the fraction particle size, the percentage of microspheres with a porous shell increases. The largest fraction contains particles with a network structure. Single-particle scanning electron microscopy–energy dispersive X-ray spectroscopy analysis of nonporous microspheres with a diameter of 1–2 μm, approximate in composition to the internal coal minerals, indicated that, depending on the content of SiO2, Al2O3, and FeO, they form several groups differing in mineral precursors. Thus, for microspheres of group 1 (SiO2 + Al2O3 > 95 wt %), the mineral precursors are NH4-illite and montmorillonite; group 2 (SiO2 + Al2O3 = 90–95, FeO ≤ 4 wt %)minerals of the isomorphic montmorillonite-illite series, including phases with a low level of iron cation substitution; group 3 (SiO2 + Al2O3 = 90–95, 4 < FeO ≤ 6 wt %) and group 4 (SiO2 + Al2O3 < 90, 3 < FeO ≤ 9 wt %)minerals of the illite-montmorillonite series, with a high level of iron cation substitution and with Fe3+ in interlayer sites.

Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to analyze individual microspheres, 1−2 μm in size, located in coal char particles of Inertoid and Fusinoid/Solid morphological types. It was shown that PM 1−2 (where PM = inorganic particulate matter) is formed in the porous structure of the carbon matrix, which controls the microsphere size, from authigenic minerals that determine their composition. Depending on the contents of SiO 2 , Al 2 O 3 , and FeO, the studied microspheres fall into various groups differing in mineral precursors. The precursor of the Group 1 microspheres with the specific composition of SiO 2 + Al 2 O 3 > 95 wt % and FeO ≤ 1.5 wt % is NH 4 −illite. Microspheres containing SiO 2 + Al 2 O 3 < 95 wt % and FeO in increasing content amounts up to 4, 6, and 10 wt %, included in Group 2, Group 3, and Group 4, respectively, are formed from mixed-layer K−illite−montmorillonite minerals subjected to cationic substitution with iron, followed by the entry of Fe 3+ in interlayer sites. Calcite, dolomite, gypsum, magnesite, rutile, and siderite are involved in the formation of Group 5 microspheres with a high content of Ca, Mg, Ti, or Fe. The significant part of PM 1−2 is represented by microspheres of Groups 2, 3, and 4 regardless of the type of coal char particles (62% for Inertoid ones and 75% for Fusinoid/Solid ones). About one-third of the microspheres for both char morphotypes refer to Group 5. Microspheres of Group 1 (8%) are located only in the Inertoid char particles, which results from the characteristic effect of the maceral−mineral composition of original coal. It has been suggested that Inertoid and Fusinoid/Solid char particles are formed from various macerals, semifusinite and fusinite, respectively. Due to the closed-cell structure, semifusinite contains noncation-exchanged NH 4 −illite, the mineral precursor of microspheres with low contents of Fe, K, Na, and Mg. The fusinite structure allows cationic substitution in NH 4 −illite with the formation of mixed-layer K−illite and montmorillonite, the mineral precursors of a significant part of PM 1−2 .

No abstract

The modeling of various modes of formation of microporous silica using high-pressure helium was carried out by the methods of molecular dynamics. It is shown that by controlling the helium pressure in the process of quenching the silica melt, the structure of the obtained glasses can be changed continuously and within wide limits. The density of the obtained glasses varies in the range from 2.2 to 1.5 g / cm3 and the Ostwald solubility coefficients for helium and neon are more than an order of magnitude