Sorption of carbon dioxide by the composite sorbent “potassium carbonate in porous matrix”

Sorption of CO₂ in the presence of water vapor by the K₂CO₃—-Al₂O₃ composite sorbent was studied by IR spectroscopy in situ, X-ray diffraction analysis, and the differentiating dissolution method and reasons for a decrease in its dynamic capacity are given. The samples containing K₂CO₃·1.5H₂O in pores are characterized by the maximal dynamic capacity. A mechanism for CO₂ sorption was proposed, which qualitatively explains the obtained dependence of the capacity on the water content in the composite sorbent. A high dynamic capacity can be maintained by regeneration of the sorbents by water vapor at 170 °N. The capacity of the sorbents decreases during the first 10 sorption—regeneration cycles due to the formation of an inactive phase of potassium aluminum carbonate.     

Competitive formation of 4-aminoisoxazoles and 5-aminooxazoles in the cyclization reactions of O-alkylated hydroxyimino nitriles

Base-catalyzed cyclization of O-alkylated α-hydroxyimino nitriles gave mixtures of 4-aminoisoxazoles and 5-aminooxazoles, their ratio depending on the substituent structures and the reaction conditions. The formation mechanism of 5-aminooxazoles in this reaction is discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1773–1780, October, 2006.     

Hydroisomerization of benzene-containing gasoline fractions on a Pt/SO 42? -ZrO2-Al2O3 catalyst: II. Effect of chemical composition on acidic and hydrogenating and the occurrence of model isomerization reactions

The acidic and hydrogenating of Pt/SO₄²⁻-ZrO₂-Al₂O₃ samples containing from 18.8 to 67.8 wt % Al₂O₃ as a support constituent were studied by the IR spectroscopy of adsorbed CO and pyridine, and the model reactions of n-heptane and cyclohexane isomerization on these catalysts were examined. The total catalyst activity in the conversion of n-heptane decreased with the concentration of Al₂O₃; this manifested itself in an increase in the temperature of 50% n-heptane conversion from 112 to 266°C and in an increase in the selectivity of isomerization to 94.2%. In this case, the maximum yield of isoheptanes was 47.1 wt %, which was reached on a sample whose support contained 67.8 wt % Al₂O₃. A maximum yield (69.6 wt %) and selectivity (93.7%) for methylcyclopentane formation from cyclohexane were also reached on the above catalyst sample. This can be explained by lower concentrations of Lewis and Br?nsted acid sites in the Pt/SO₄²⁻-ZrO₂-Al₂O₃ system, as compared with those in Pt/SO₄²⁻-ZrO₂. The experimental results allowed us to make a preliminary conclusion that the Pt/SO₄²⁻-ZrO₂-Al₂O₃ catalyst whose support contains 67.8 wt % Al₂O₃ is promising for use in the selective hydroisomerization of benzene-containing gasoline fractions in the thermodynamically favorable process temperature range of 250–300°C.     

Synthesis of sulfonamide derivatives of pyrido-[2,1-<Emphasis Type="Italic">b</Emphasis>]quinazolin-11-one and pyrido[1,2-<Emphasis Type="Italic">a</Emphasis>]quinazolin-6-one

Methods were developed of indirect introduction of sulfonamide group in the structures of pyrido-[2,1-b]quinazolin-11-one and pyrido[1,2-a]quinazolin-6-one underlain by cyclocondensation of 2-halo-5-(Rsulfamoyl) benzoyl chlorides with derivatives of 2-aminopyridine. The fact of thermal rearrangement of 8-(morpholin-4-ylsulfonyl)pyrido[1,2-a]quinazolin-6-one into isomeric 2-(morpholine-4-ylsulfonyl)pyrido[2,1-b]-quinazolin-11-one was experimentally registered.     

Multistep flow-membrane filtration,gel-permeation chromatography,and spectrophotometric determination of polydisperse compounds

To determine the molecular weight distribution of natural polydisperse compounds (peat humic acids) and synthetic substituted polyvinyls, membrane filtration, gel-permeation chromatography, and spectrophotometric determination procedures were developed. The determination limit of polyvinyls was 0.1–0.2 mg/mL. The absorbance of polyvinyl solutions was a linear function of the concentration over the range 0.1–6.0 mg/mL. It was found that the size-fraction distributions of both humic substances and substituted polyvinyls depended not only on the molecular weight, but also the molecular conformation.     

Effect of preparation procedure on the properties of CeO2

The effect of preparation procedure on the physicochemical and catalytic properties of CeO₂ was studied. Differences in the electronic and structural characteristics of CeO₂ depending on preparation procedure and treatment temperature were found using X-ray diffraction analysis, transmission electron microscopy, UV-visible electronic spectroscopy, and X-ray photoelectron spectroscopy. With the use of the temperature-programmed reaction with CO, it was demonstrated that CeO₂ samples with a high concentration of point defects—oxygen vacancies caused by the presence of Ce³⁺—were characterized by an increased mobility of bulk oxygen. The samples of CeO₂ with a high concentration of structural defects—micropores of size 1–2 nm and stepwise vicinal faces in crystallites—exhibited a high catalytic activity in the reaction of CO oxidation.     

The structure of a thiadiazole-containing expanded heteroazaporphyrinoid determined by gas electron diffraction and density functional theory calculations

The molecular structure of a macrocycle with a 24-membered ring, a thiadiazole-containing expanded heteroazaporphyrinoid, has been, for the first time, directly characterised by a synchronous gas electron diffraction and mass spectrometric experiment and DFT calculations; the molecule has the equilibrium structure of C(3h) symmetry with a planar macrocycle.