Home – Home – Jornals – Chemistry for Sustainable Development 2018 number 4

Video fixation of the growth of methane hydrate in three-phase water–oil–methane systems was carried out. Three kinds of crude oil were taken for experiments. The formation of unusual associates of gas hydrate with oil, growing into the volume of the aqueous phase, was found to be possible in two of these oil kinds at the late stages of hydrate growth. Possible mechanisms for the formation of these associates are discussed.

Polystyrene pyrolysis in oil residue was studied within temperature range 360-380 °C at atmospheric pressure. The composition of liquid pyrolysis products was determined by means of gas chromatography - mass spectrometry. The residue from the joint pyrolysis of modified bitumen was studied by means of PMR and FTIR spectroscopy; softening temperature, penetration and pyrobitumen content were determined. It was established that the major products of polystyrene pyrolysis in bitumen are saturated compounds, ethyl benzene, cumene, toluene, and 1,3-diphenylpropane, which are formed as a result of hydrogen transfer from bitumen components to the products of thermal degradation of polystyrene. The maximal rate of polystyrene destruction in bitumen shifts to the region of elevated temperature. Bitumen modification proceeds mainly due to the reactions involving the condensation of its components, initiated by hydrogen transfer. The effect of residual polystyrene on bitumen characteristics is much weaker.

The effect of nonpolar reagent, sulphury aromatic concentrate (SAC) and its composition with potassium butyl xanthogenate (PBX) on the floatation and sorption characteristics of gold-containing pyrite was studied. Mineral fractions -0.074+0.044 and -0.044+0.02 mm in size with the mass fraction of pyrite 91.8 and 92.2 %, with gold content 50.5 and 54.5 g/t, respectively, were used for floatation experiments. Experiments were carried out in the apparatus for micro-floatation in the presence of foam-forming agent Т-80. It was established that SAC possesses the collecting capacity with respect to pyrite samples with different particle sizes, but its activity is lower than that of PBX. It was shown that the floatation activity of pyrite fraction under the action of PBX and SAC decreases with a decrease in the size of mineral grains. The consumption of PBX may be decreased to 50 % without the loss of recovery for the floatation of pyrite with particle size-0.074+0.044 and -0.044+0.02 mm if it is used in composition with SAC. For the floatation of the fine pyrite fraction, PBX/SAC composition (SAC fraction being 25 % of PBX consumption) promotes an increase in the degree of pyrite extraction into the foamy product by 5 %. It was established that the treatment of the mineral with particle size-0.074+0.044 mm in the aqueous emulsion of SAC is accompanied by reagent sorption, which explains its collecting capacity with respect to pyrite. The nature of sorption is most probably physical because SAC passes into water partially during subsequent washing with water. The presence of SAC on the mineral surface hinders the sorption of PBX and thus promotes a decrease in its consumption for floatation.

The sorption activity of carbamide-containing sorbent made of aspen bark was studied with respect to nickel, zinc and lead from aqueous solutions with different metal concentrations. The effect of carbamide content in the aspen bark sorbent on its sorption activity with respect to admixtures under investigation was revealed. It was demonstrated that the adsorption-based deposition of 10.7 mass % of carbamide on the support made of aspen bark causes an increase in the capacity of the sorbent by a factor of 1.9-3.3 depending on metal nature. It was established that the resulting aspen bark sorbent is characterized by the high sorption capacity: the limiting sorption of lead, zinc and nickel is 91.17, 25.78 and 23.34 mg/g, respectively. The data on the kinetics of metal sorption and their analysis with the help of the models of pseudo-first and pseudo-second order are reported. The acidity of aqueous solutions providing efficient sorption of the metals under study was determined: pH 5.5-6.0 for zinc solutions and pH 5.5-7.0 for lead and nickel solutions. It was shown that the carbamide-containing aspen bark sorbent is efficient for the purification of low-concentration metal solutions: purification degree of the solutions containing 10.5 and 1.0 мg/l admixtures is not less than 66.7 and 89.9 %, respectively. The stability of the developed carbamide-containing sorbent to carbamide washing out was revealed in the studies of nickel, zinc and lead sorption. In combination with the high sorption activity, this determines the promising character of the use of this sorbent for additional purification of technical-grade water from metal admixtures.

The effect of the conditions of mechanochemical activation (initial components and activation time) on the phase and surface composition, texture characteristics of the catalysts based on strontium titanates with layered perovskite structure and their activity in the oxidative condensation of methane (OCM) at a temperature of 800-900 oC was studied. The resulting catalysts were characterized by means of XPA, mercury porosimetry, BET, XPES. The conditions for obtaining single-phase, well crystallized Sr₂TiO₄ were chosen: the use of a mixture of TiO₂ + SrCO₃ as the initial components, activation time 8 min, annealing at 1100 °С for 4 h. It was shown that the catalysts obtained using the mechanochemical method exhibit higher activity in the reaction of OCM (high methane conversion degree, high yield of С₂-hydrocarbons) in comparison with the catalysts prepared through co-precipitation.

The effect of mechanical activation of low-calcium ash of hydroremoval from the Apatity TPS without alkaline and other chemical reagents on its binding characteristics was studied. Mechanical activation was carried out in a centrifugal planetary mill AGO-2 for up to 400 s. Initial and mechanically activated ash was studied by means of X-ray phase analysis, IR spectroscopy, scanning electron microscopy, laser granulometry. Specific surface was determined. The data on aqueous leaching of initial and mechanically activated ash, as well as the data obtained by means of IR spectroscopy and thermogravimetric analysis, show that mechanical activation causes a noticeable increase in ash reactivity with respect to water. During normal solidification, the compression strength of ash-based samples after MA for 60-400 s at the age of 7 and 28 days was 0.7-1.7 and 1.4-2.2 MPa, respectively.

Heating of heptene-1 in the presence of di- and polysulphides of о - tert -butylphenol (TAB stabilizer) at a temperature of 200 °C in the inert atmosphere leads to isomeric S-heptylthiophenols in good yield. When this reaction is carried out in the air, the products of heptene-1 dimerization and trimerization are formed; similarly to initial heptene-1, they are oxidized by atmospheric oxygen with the formation of aliphatic alcohols and esters. The possibility to grafting sulphur-containing fragments to the olefin initiated the experiments with rubber, a polymeric olefin. Thermal treatment of the compositions of butadiene-nitrile rubber in the presence of sulphur-containing compounds obtained on the basis of 2- tert -butylphenol (TAB) is accompanied by thermolysis of the polysulphide components of TAB stabilizer and the formation of 4-mercaptophenols and thermolysis products that cannot be extracted from rubber, which is the evidence of their grafting to it. Technical characteristics of rubber incorporating the fragments of compounds included in TAB stabilizer were studied. The possibility to use this rubber with the grafted antioxidant for manufacturing the products contacting with the solvents was demonstrated.

The composition and thermal behaviour of the ethanol lignins isolated by means of extraction with organic solvents from the wood biomass of the coniferous and deciduous trees were studied by means of nonisothermal thermogravimetric (TG/DTG, DSC) analysis, FTIR spectroscopy, elemental analysis, scanning electron microscopy (SEM). Comparative analysis of the IR spectra of initial lignin and lignin treated thermally at 200 °C provides evidence that they have identical structural and groups composition. The initial temperature of abies lignin decomposition (252 °C) is higher by approximately 10 °C than that for aspen wood. It was established that prevailing decomposition of abies lignin in argon proceeds within the temperature range 337-427 °C: the highest rate of destruction is -2.9 %/min, the maximal decomposition is observed at 400 °C. Aspen lignin undergoes intense decomposition within a lower temperature range (327-400 °С) with the maximal rate of mass loss-3.1 %/min at 378 °C. The data of IR spectra of the products of abies lignin decomposition at 400 °С provide evidence of the substantial degree of lignin polymer decomposition with the possible formation of the derivatives of quaiacol and substitute4d phenol compounds. The completion of lignin thermal destruction at 800 °C is accompanied by the formation of carbon residues with the yield of 34 % from aspen lignin and 37 % from abies lignin. The appearance of carbonized particles in the structure of the material (starting from 240 oC) and further intensification of the formation of carbon matrix with an increase in pyrolysis temperature to 600 oC were confirmed by means of SEM. The maximal rates of aspen lignin decomposition were discovered to be higher than those of abies lignin within all conventional temperature ranges.

The technology is proposed for deep catalytic purification of gases formed in the combustion of pyroxylin powder, the filling of substandard ammunition of small arms. The technology involves dosing ammonium carbonate directly into the furnace with ammunition, gas processing in the apparatus for wet purification to remove catalytic poisons (lead and antimony compounds) and tar substances, selective catalytic reduction (SCR DeNOx) of nitrogen oxides by ammonia vapour and the catalytic oxidation of СО into harmless products.

Cracking of vacuum residue from the Novokuybyshevsk oil refinery was studied. The yields of gaseous, liquid and solid products at a temperature of 500 °C and process duration 10-30 min were determined. The hydrocarbon composition of liquid products was studied. It is shown that the addition of WC/Ni-Cr nanosized powder (NSP) promotes an increase in the yield of the fraction with boiloing temperature up to 360 oC by 66.4 mass % in comparison with initial vacuum residue and by 40.4 mass % in comparison with cracking without NSP. The effect of WC/Ni-Cr NSP on the changes in the molecular structures of high-molecular heteroatomic compounds (resins, asphaltenes) was studied.

Oil refining products are traditionally used as reagents for floatation coal cleaning. To enhance floatation efficiency, oxidative modification of nonpolar hydrocarbon reagents is used. In the present work ozone is considered as the oxidative reagent, and kerosene fraction is the nonpolar agent. The effect of ozonation on the component composition and technological characteristics of kerosene was studied. It is shown that ozonolysis of kerosene results in a decrease in the relative content of aliphatic СН₂-bonds in the -position to the aromatic core, and the fraction of methyl, methoxyl, alkyl ether and alicyclic structures increases; the fraction of polycyclic arenes decreases, while the fraction of monocyclic arenes increases; the content of aliphatic carboxylic acids, linear and cyclic ethers and esters, lactones and anhydrides increases. Due to an increase in the fraction of heteropolar oxygenated compounds in ozonated kerosene, it may serve as the basis for obtaining floatation reagent with the integrated properties of foam-former and collector, which promotes an increase in the efficiency of floatation of coal sludge.

Development of biocompatible coatings on implant surface is an essential and urgent problem. Coatings based on titanium oxynitride formed by means of reactive magnetron sputtering are used as the biologically inert material for surgical products. Oxynitride coatings are suitable for use under the conditions of long-term contact with biological liquids. The characteristics (corrosion stability, film solubility) of Ti-O-N coatings deposited on the substrates by means of reactive magnetron sputtering were investigated. The coatings and the compositions of model liquids formed as a result of the dissolution of titanium oxynitride films in physiological liquids were studied by means of infrared and gas spectroscopy, atomic emission analysis. It was established that the samples of Ti-N-O biocoating contain nitrogen, and the solutions contain nitrogen oxide NO, the molecule which is vitally necessary for living organisms.

Cu-Mo/ZSM-5 catalysts with Мо content 4.0 mass % and Сu 0.05 to 1.0 mass % were prepared by dry mechanical mixing of ZSM-5 zeolite with nanosized powders (NSP) of molybdenum and copper. To carry out comparative tests, Cu-Mo/ZSM-5 systems were prepared from 4.0 % Мо/ZSM-5 catalyst by impregnation with Cu(NO₃)₂ solution and mechanical mixing with copper oxide (CuO). The acid characteristics of thus prepared samples were investigated by means of temperature-programmed desorption of ammonia. The concentration and strength of the acid sites of the catalysts were measured. It was established that the addition of 0.1 % copper NSP to the 4.0 % Mo/ZSM-5 catalyst promotes a decrease in the concentration of strong acid sites to 140 mmol/g, while further increase in the fraction of copper NSP causes an increase in their concentration (to 153 mmol/g). The activity of the catalysts in methane conversion decreases in comparison with the sample containing 0.1 % Cu NSP. Methane conversion degree after reaction for 20 min with 4.0 % Мо/ZSM-5 and 0.1 % Сu-4.0 % Мо/ZSM-5 catalysts was 16.1 and 18.9 %, respectively. The effect of the temperature of methane conversion on its conversion degree in the presence of the 0.1 % Сu-4.0 % Мо/ZSM-5 catalyst was studied. It was demonstrated that temperature rise from 650 to 750 °С is accompanied by an increase in methane conversion. For instance, within the first 20 minutes of reaction at a temperature of 750 °C and 650 °C is 18.9% and 7.9% respectively. It was shown that the optimal feed space velocity of methane during its conversion over the 1.0% Cu-Mo/ZSM-5 catalyst is 1000 h^-1.