Thermal Decomposition Process Research Articles

The inhibitory combustion reaction performance and tail gas analysis of composite ultra-fine dry powder extinguishing agent containing different additives

For lack of an extinguishing agent with high-efficiency, non-toxic and environmentally friendly, a new type of extinguishing agent was fabricated to solve such an urgent problem. In this study, the zinc borate (ZB) and ferrocene (Fe(Cp)2) were utilized as two additives for extinguishants to suppress combustion reaction and the toxicity of the tail gas was detected. The mass fraction of ZB corresponding to the optimal inhibitory effect was determined to be 0.5–1.5%, by contrast, the optimum interval of Fe(Cp)2 was detected as 0.5–1.0%. Similarly, with the increasing proportion of the two additives, the homologous inhibitory action was gradually weakened. From the perspective of thermogravimetric analysis (TGA), it was indicated that the ZB accelerated the pyrolysis process of the extinguishant, making its thermal decomposition process more thoroughly. Meanwhile, the differential scanning calorimetry (DSC) demonstrated that the decomposition efficiency was markedly improved when the amount of ZB was maintained at 0.5–1.5%. Besides, the tail gas tests were implemented to assess the extent of toxic and harmful properties. In terms of the carbon monoxide (CO) and carbon dioxide (CO2) generated, once the mass fraction of ZB and Fe(Cp)2 was less than 1.5% and 1.0% respectively, the concentration of CO and CO2 was distinctly lower than that without additives. Moreover, the inhibitory ability on nitrogen oxides (NOx) was enhanced when the mass fraction of the two additives was kept below 1.0%. The results confirmed that a more practical extinguishant was proposed and it can provide guidance for the application and development of extinguishants.

Sm Doped ZnO Nanowires@PAN Nanofibrous Membranes for Photocatalytic Degradation of Dye.

Wastewater involving a lot of contaminants like organic dyes from the textile finishing industry causes a greater adverse impact on human beings. There are many patents on nanofibers involved metallic oxides, this paper studies photocatalytic degradation of free-pollution Zinc Oxide (ZnO) nanomaterials on dye decontamination. Polyacrylonitrile (PAN) nanofibrous membranes loaded with Zinc Oxide (ZnO) nanowires were fabricated and evaluated for photocatalytic degradation. In this work, Polyacrylonitrile (PAN) nanofibrous membranes loaded with ZnO seeds were prepared by electrospinning PAN/Zn (Ac)2 solution followed by a thermal decomposition process. ZnO nanowires were hydrothermally grown on the surface of PAN nanofibers. The effects of the ratio of PAN and zinc acetate in a solution, decomposition temperature and ammonia (NH4OH) on the morphologies of ZnO nanowires were observed. ZnO nanowires showed the optimum morphologies when the ratio of PAN/Zn (Ac)2 was 10:1.5. The decomposition temperature was 150oC, and NH4OH was added in the hydrothermal reaction. The photocatalytic degradation of Rhodamine B solution under UV irradiation was used as a model reaction. The photodegradation ability of the ZnO @PAN membrane doped with cerium (Sm) was also investigated. Slight Sm doping increased the photocatalytic degradation rate from 57% to 89% under ultraviolet light irradiation for 2h. After 5 times of cycling under the same conditions, it still maintained the dye decolorization rate that was above 65%. Sm doped ZnO nanowires @PAN nanofibrous membranes were easily produced and could provide a novel process for the degradation of dye decontamination.

Polyurethane/Silane-Functionalized ZrO2 Nanocomposite Powder Coatings: Thermal Degradation Kinetics

A polyurethane (PU)-based powder coating reinforced with vinyltrimethoxysilane (VTMS)-functionalized ZrO2 nanoparticles (V-ZrO2) for thermal stability was developed. Chemical structure, microstructure and thermal degradation kinetics of the prepared coatings were investigated. The peak of aliphatic C–H vibrating bond in the Fourier transform infrared (FTIR) spectrum of V-ZrO2 was a signature of VTMS attachment. Scanning electron microscopy (SEM) images reveled that, by increase of V-ZrO2 content from 0.1 to 0.3 wt.% and then 0.5 wt.%, some agglomerations of nanoparticles are formed in the PU matrix. Thermogravimetric analysis (TGA) of the PU/V-ZrO2 powder coatings was performed at different heating rates nonisothermally to capture alteration of activation energy (Ea) of degradation of PU/V-ZrO2 powder coatings as a function of partial mass loss by using Friedman, Kissinger–Akahira-Sunose (KAS), Ozawa–Wall–Flynn (FWO) and modified Coats–Redfern isoconversional approaches. It was observed that by addition of 1 wt.% V-ZrO2 to PU resin the early state degradation temperature at 5% weight loss increased about 65 °C, suggesting a physical barrier effect limiting the volatility of free radicals and decomposition products. Incorporation of 5 wt.% ZrO2 led to about 16% and 10% increase in Ea and LnA of blank PU, respectively, which was indicative of higher thermal resistance of nanocomposite powder coatings against thermal degradation. There was also obvious agreement between model outputs and experimental data. The results reveal that nanocomposite coating shows superior thermal properties compared to neat PU powder coatings, and the presence of nano ZrO2 in sufficient amount causes retardation of the thermal decomposition process.

The mathematical description of process of heat exchange particles of oil shale and ash the coolant in the semi-coking conditions in a rotating drum reactor installation with solid heat carrier

The article deals with the modeling of heat transfer process in a drum reactor of a semi-coking unit of oil shale with a solid coolant between ash and shale particles in the conditions of constant separation of vapor-gas products. The dominant role of the convective component of the process is revealed and the curves of heating of shale particles are obtained taking into account the endothermic effect.It is established that the smallest fraction of fuel warms up within 30-60 seconds and further serves as a source of heat for other fractions. In the interval of 400-600 seconds, the heating of the largest fraction is completed. The further stay of the shale mixture in the reactor is caused by the lagging rate of the thermal decomposition process from heat exchange, and the temperature decrease by 20-250C by the presence of the endothermic effect of the decomposition of organic matter.

Comparative study on electrospun magnesium silicate ceramic fibers fabricated through two synthesis routes

We report two routes for the electrospinning of magnesium silicate ceramic fibers (MSCFs) using different precursor solutions involving different magnesium sources and synthesis procedures. The thermal decomposition processes and microstructure of the MSCFs were comparatively studied. X-ray diffraction results confirmed the crystalline MgSiO3 phase in the heat-treated fibers. Magnesium sol contained precursor supplied long and straight MSCFs with homogeneous microstructure. Magnesium chloride contained precursor produced coiled or spring-like MSCFs with core–shell structure. The formation mechanism of the unique structure of C2-1000 was briefly analyzed. In addition, true density and specific surface area of MSCFs, and thermal conductivity of fiber tablets were measured. The reported methods can be extended as a general approach to prepare other silicate ceramic fibers.

Spectral and thermal investigation of novel biologically active (N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl-amino)-2-oxo-cetimidic acid) ligand and its metal complexes

Novel Schiff base ligand (N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl-amino)-2-oxo-cetimidic acid) was synthesized from 4-aminoantipyrine and diethyloxalate, but with small yield. The stable chelates with different metal ions (Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Fe(III) and Ru(III)) were formed by template reaction. Their structures were confirmed via elemental microanalyses, spectral techniques and thermal studies. The molar conductance values indicated that the complexes derived from Mn(II), Ni(II), Zn(II), Pd(II) chloride and Cu(II) bromide have nonelectrolytic nature, whereas, those derived from Co(II), Cu(II), Fe(III) and Ru(III) chloride have electrolytic nature. IR spectra indicated that the ligand acted as a neutral ONNO tetradentate moiety in all complexes except in Pd(II) complex, it behaved as a neutral bidentate moiety. All complexes exhibited octahedral geometry, while Pd(II) complex possess square planar structure. The thermal decomposition process of all metal complexes ended with formation of metal except in case of Fe(III) and Ru(III) complexes, it ended with metal oxides. X-ray diffraction supported the nanometer size of Fe2O3 oxide that resulted from thermal decomposition of Fe(III) complex. The ESR spectra for Cu(II) complexes demonstrated this trend, g‖>g⊥>2.0023 revealing the axially symmetric system with the unpaired electron residing in (dx2-y2) orbital. The biological measurements showed that the tested metal complexes have antimicrobial and cytotoxic activities in comparison to the free ligand.

Characterization and comparison of Ti/TiO2-NT/SnO2–SbBi, Ti/SnO2–SbBi and BDD anode for the removal of persistent iodinated contrast media (ICM)

In this study, we investigated the impact of a TiO2 nanotube (NT) interlayer on the electrochemical performance and service life of Sb and Bi-doped SnO2-coatings synthesized on a titanium mesh. Ti/SnO2–SbBi electrode was synthetized by a thermal decomposition method using ionic liquid as a precursor solvent. Ti/TiO2-NT/SnO2–SbBi electrode was obtained by a two-step electrochemical anodization, followed by the same process of thermal decomposition. The synthesized electrodes were electrochemically characterized and analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Terephthalic acid (TA) experiments showed that Ti/SnO2–SbBi and Ti/TiO2-NT/SnO2–SbBi electrodes formed somewhat higher amounts of hydroxyl radicals (HO) compared with the mesh boron doped diamond (BDD) anode. Electrochemical oxidation experiments were performed using iodinated contrast media (ICM) as model organic contaminants persistent to oxidation. At current density of 50 A m−2, BDD clearly outperformed the synthesized mixed metal oxide (MMO) electrodes, with 2 to 3-fold higher oxidation rates observed for ICM. However, at 100 and 150 A m−2, Ti/SnO2–SbBi had similar performance to BDD, whereas Ti/TiO2-NT/SnO2–SbBi yielded even higher oxidation rates. Disappearance of the target ICM was followed by up to 80% removal of adsorbable organic iodide (AOI) for all three materials, further demonstrating iodine cleavage and thus oxidative degradation of ICM mediated by HO. The presence of a TiO2 NT interlayer yielded nearly 4-fold increase in anode stability and dislocated the oxygen evolution reaction by +0.2 V. Thus, TiO2 NT interlayer enhanced electrode stability and service life, and the electrocatalytic activity for the degradation of persistent organic contaminants.

Thermogravimetric and kinetic study of new bis(iminophosphorane)ethane solvates

Thermal and crystallographic characterization of one solvent-free bis(iminophosphorane)ethane (BIPE) form and three solvates with acetonitrile (ACN), dimethyl sulfoxide (DMSO) and toluene is presented. Thermal behaviors of new compounds indicate that the solvent is removed differently from the BIPE structure, accordingly with the stoichiometric solvent molecule amount incorporated. Thus, the solvent-free BIPE reveals high thermal stability up to 315 °C, while BIPE solvates have a similar pattern behavior with low stability about 130 °C. The kinetic parameters of the thermal decomposition process were determined by three different methods Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and nonparametric kinetic. Crystallographic data revealed that the solvent plays the role of space filler without strong interactions with host molecules. Guest-free BIPE, BIPE0.5ACN and BIPE0.35DMSO crystallized in monoclinic C2/c (№15) space group, while BIPETOLUENE in a triclinic P - 1 (№2) one. Crystallographic and thermogravimetric data show a good correlation between molecular structures and activation energies.

Thermal decomposition mechanism of diisopropyl azodicarboxylate and its thermal hazard assessment

Thermal decomposition behavior and decomposition mechanism of diisopropyl azodicarboxylate (DIAD) were characterized and analyzed by C80 micro-calorimetery and STA-FTIR-MS system. And thermal hazard of DIAD was assessed by using self-accelerating decomposition temperature (SADT) as the evaluation index. The results show that only one exothermic peak appeared in decomposition process, and that the onset temperature and peak temperature increase with heating rate, whereas the released reaction heat at the heating rates remained approximately constant at 945.67±23.45 kJ/kg. Based on C80 data, the calculated activation energy of DIAD decomposition ranges from 45 kJ/mol to 77 kJ/mol by Friedman method, while the reaction progress in the range of 0.10–0.90. During thermal decomposition process of DIAD, there is only one stage of weight loss, which starts at about 80 ℃, reaches to the maximum rate of weight loss at 138 ℃, and end up at about 150 ℃. The thermal decomposition mechanism of DIAD can be mainly summarized as the route that the CO single bond breaks at first, then CC breaks, and the NN bond breaks subsequently, then the CO bond or the CN bond breaks, final products such as H2O, CO2 etc. appear from further dissociation and oxidation of molecular ionic fragments at last. According to the above-metioned results, the calculated SADT of DIAD is 89.0 ℃ based on Semenov model, when packed in 25kg standard package.

Polymerization Effects on the Decomposition of a Pyrazolo-Triazine at high Temperatures and Pressures.

4‐amino‐3‐aminopyrazole‐8‐trinitropyrazolo‐[5, 1‐c] [1, 2, 4]triazine (PTX, C5H2N8O6) has good detonation performance, thermal stability and low mechanical sensitivity, which endow it with good development prospects in insensitive ammunition applications. To study the effects of polymerization on the decomposition of PTX, the reaction processes of PTX at different conditions were simulated by quantum chemistry and molecular dynamics methods. In this paper, the effects of polymerization on the decomposition of PTX were studied in terms of species information, reaction path of PTX, bond formation and bond cleavage, evolution of small molecules and clusters, and kinetic parameters at different stages. The results show that under the high‐temperature and high‐pressure conditions, the initial reaction path of unimolecular PTX in the thermal decomposition is mainly the cleavage of C−NO2 bonds. At the same time, there are many polymerization reactions in thermal decomposition process, which may greatly affect the reaction rate and path. The higher the degree of polymerization, the larger equilibrium value of potential energy, the less energy release of thermal decomposition. Compared with the activation energy of other explosives, the activation energy of PTX is higher than that of β‐HMX and lower than that of TNT.

The Technology of Thermochemical Processing of Wastes Enterprises of the Woodworking Industry in the Regulation of Environmental Pressure

The development of industry is always accompanied by an increase in the negative impact on nature. A variety of waste generated at the production stage for a long time is stored and accumulated. This is especially true for organic waste, the amount of which is steadily increasing as the industry develops. In this regard, the issue of their processing is becoming increasingly important. Currently, one of the optimal types of organic mass processing is pyrolysis. However, in most cases, thermochemical processing technologies, used at enterprises, are not capable of meeting modern requirements for energy consumption and environmental friendliness. The article investigates the high pressure effect on the process of thermochemical treatment of wood waste. As a result of processing the obtained data, the dependences of the duration of the process of thermal decomposition of wood and the output of charcoal on the pressure in the chamber, ambient temperature, size and humidity of the pyrolized wood raw material were determined. It has been established that with an increase in the process pressure, the duration of the process of thermochemical processing of wood waste decreases, and the output of coal increases.

Роль декоративно-отделочных, облицовочных материалов стен и потолков, покрытий полов в развитии пожара и формировании его опасных факторов

Проанализирована роль декоративно-отделочных, облицовочных материалов и покрытий полов в формировании опасных факторов пожара (ОФП). Проведены расчеты распространения ОФП в модельном помещении с учетом вклада облицовочного материала стен и потолка. Показана возможность применения рассмотренного подхода для моделирования условий (стандартных и нестандартных) испытаний строительных материалов и конструкций на пожарную опасность (например, фасадных систем) и гибкого нормирования при использовании декоративно-отделочных, облицовочных материалов и покрытий полов в зданиях и сооружениях.Article presents the study of the possibility to describe thermal decomposition and thermal oxidation processes of fire load finishing materials by means of the kinetic parameters. These parameters are defined by results of termogravimetric analysis for modeling the dynamics of fire development. Nowadays the problem of modeling the distribution of hazardous fire factors (HFF) in buildings and constructions has wide practical application, however techniques of HFF modeling do not take into account as fire load finishing and facing materials of building and construction premises in development of a fire, so they are not considered at an estimation of safe evacuation of people from buildings and constructions as well as at calculation of fire risk, too. When describing a seat of fire there are used fire hazard indicators having essential uncertainty according to the technical literature sources and experimental data while formation should be based on the possibility of their thermodestruction and thermooxidation under the influence of heat loads of various intensity. At the same time, the speed of the specified processes should be interconnected with values of heat loads. The presented work is of current importance because it is necessary to describe thermodestruction and thermooxidation processes of fire load material at modeling the dynamics of HFF distribution in buildings and constructions by means of kinetic parameters received as the results of thermogravimetric analysis. On the example of calcium silicate and wood composition there are carried out calculations of HFF distribution in a test premise taking into account the contribution of wall and ceiling facing material. There is shown the prevailing, in comparison with a seat of fire, contribution of wall and ceiling facing material to HFF formation at its initial stage which is especially important from the point of view of ensuring safe evacuation of people at fire in buildings and constructions. On the basis of the conducted analysis of research results there are developed proposals for applying the considered approach to model conditions for (standard and non-standard) tests of building materials and structures for fire hazard (for example, front systems) and flexible rationing of use of decorative - finishing and facing materials as well as floor coverings in buildings and structures.

Master-eğriler kinetik yönteminin izotermal olmayan selüloz pirolizine uygulanması ve piroliz işleminin termodinamik analizi

Kinetic modeling of thermochemical conversion methods such as pyrolysis is one of the most challenging issues for bio-refineries. It is known that cellulose together with hemicellulose and lignin mainly affect the characteristics of biomass pyrolysis. However, there is still limited knowledge about the thermal behaviors of biopolymers that go into complex multi-phase pyrolysis reactions in the literature. Therefore, cellulose pyrolysis kinetics and thermodynamics were investigated in this study. Kinetic parameters of the pyrolysis process were calculated by a combined method of master-plots and Friedman method. Active pyrolysis of cellulose is found to occur between 263 and 455 °C. Applied Friedman method was perfectly fitted with the experimental data and activation energy of the thermochemical conversion process was found between 150.8 and 190.2 kJ/mol while the mean activation energy was calculated as 164.3 kJ/mol. The comparison of kinetic models used of solid-state thermal decomposition processes indicated that the cellulose pyrolysis mechanism is a diffusion-controlled (D3) degradation process at lower conversions (0<α<0.5) and the process can be explained by reaction-based mechanisms at higher conversion degrees.

Ab-initio molecular dynamics study on chemical decomposition reaction of α-HMX

In this work, the ab-initio molecular dynamics simulations were performed to investigate thermal decomposition reaction of α-HMX. It is found that the initiation of reactions main involves unlooping of C-N rings and NO2 groups detachment from C-N rings for α-HMX molecules at 1800 K. More than 20 species were observed with the main products H2O, CO2, NO, C-H, N-H, C-N groups. Using the atomic tracking method, we discussed the main reaction path of thermal decomposition process for α-HMX. This work has an important significant for revealing the reaction mechanism of α-HMX.

ВИЗНАЧЕННЯ КРИТИЧНИХ РЕЖИМІВ РОЗВИТКУ ПРОЦЕСІВ ГОРІННЯ ПІРОТЕХНІЧНИХ НІТРАТНО-МЕТАЛЕВИХ СУМІШЕЙ В УМОВАХ ЗОВНІШНІХ ТЕРМІЧНИХ ДІЙ

Currently, models of combustion of mixtures based on Mg + NaNO3 have been developed and investigated in detail to calculate the combustion rates of pyrotechnic mixtures. As for other pyrotechnic mixtures, the results of theoretical studies on the modeling of their combustion processes under different external conditions are very limited, and in most cases absent. The purpose of this work is to develop a model of combustion of compacted mixtures of Ti powders and nitrate-containing oxidizing agent (NaNO3, Ba(NO3)2, Sr(NO3)2) to determine the critical modes of their persecution by calculating the dependence of the propagation of the combustion front on charges and technological factors conditions. Developed mathematical model of combustion of pyrotechnic nitrate-metal mixtures allows to determine with accuracy of 8… 10 % the influence of high heating temperatures and external pressures (for a wide range of change of component ratios and dispersion) on the stage of design and subsequent bench testing of pyrotechnic articles with precision and dispersion, sustainable propagation of combustion in conditions of thermal impact. This makes it possible to predict different fire situations that occur in the external thermodynamic conditions to which the products are exposed during their operation. The mechanism is established and mathematical models of the pyrotechnic nitratemetal combustion process are used, which use kinetic characteristics of the processes of thermal decomposition of oxidizer, high-temperature oxidation, ignition and combustion of metal fuel particles on the combustion surface of the mixtures. The example of nitrate-titanium mixtures shows that models with a relative error of 8…10 % allow to determine the dependence of the rate of development of the combustion process of the mixture on the parameters of external thermal actions (increased heating temperatures and external pressures) for different values of their technological parameters (the ratio of components and dispersion), which makes it possible to find critical modes of combustion, the excess of which leads to the explosive destruction of pyrotechnic articles.

Environmentally sustainable facile synthesis of nanocrystalline holmium hafnate (Ho2Hf2O7): Promising new oxide-ion conducting solid electrolyte

A2B2O7 oxides with defect-fluorite structure are one of the potential candidates for solid oxide fuel cell electrolyte material due to their excessive thermodynamic stability in oxygen potential gradient at elevated temperature between 500 and 900 °C. Holmium hafnate nanoparticles have been synthesised through the Leeds Alginate Process (LAP) using inorganic salts of holmium and hafnium as starting materials immobilized in alginate beads. Ion exchange with sodium alginate and its subsequent thermal treatment have been used to prepare the nanopowder of Ho2Hf2O7. Thermal decomposition of dried beads is carried out at 700 °C for 2 h and 6 h to obtain the nanoparticles of Ho2Hf2O7. This calcination temperature was determined after carrying out simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). High Temperature X-ray Diffraction (HT-XRD) was carried out to gain further insight into the thermal decomposition process in static ambient environment. HT-XRD analysis corroborated with the results obtained from TGA/DSC. Nano-crystalline powder of single phase Ho2Hf2O7 has been obtained by calcination of oven dried ion-exchanged alginate beads in relatively low temperature range of 500–700 °C. Rietveld refinement of X-ray diffraction (XRD) data confirmed the formation of single phase defect fluorite structure of Ho2Hf2O7. The crystallographic parameters calculated from TEM and XRD analysis are in excellent agreement with each other. Furthermore, TEM–EDX analysis confirms that the Ho2Hf2O7 synthesised by the facile alginate process is nearly stoichiometric. Raman spectroscopy gives evidence of the presence of oxide-ion vacancy in holmium hafnate which is supported with ac-impedance spectroscopy measurement at selected three temperatures. The present study suggests that the LAP has the capability of yielding on a large scale single phase defect-fluorite nanoparticles of electrolyte materials for solid oxide fuel cells in environmentally sustainable, economical and energy efficiently manner.

Studying the Process of (NH4)2[IrCl6] Thermal Decomposition by X-Ray Photoelectron Spectroscopy and Electron Microscopy

Thermal decomposition of ammonium hexachloroiridate(IV) in inert and reducing atmospheres are studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Particular attention is paid to the formation of metallic iridium particles. The processes of thermal decomposition proceed similarly in an inert atmosphere and in a vacuum as is evidenced by equal charge states of Ir, Cl, and N at different decomposition stages in these two cases. According to XPS data, the decomposition process can be described as consisting of three main stages. At the first stage, an intermediate product with atomic charge states corresponding to {Ir(NH3)xCl6−x}(x−3) (1 ≤ x ≤ 3) and metallic iridium are formed. At the second stage, atomic charge states indicate formation of {IrClx}3−x, NH4Cl. The metal nanoparticles appearing at these stages have different shapes: spherical, “flakes”, dendritic networks. The final decomposition product (metallic iridium) is agglomerates of regularly shaped spherical nanoparticles of uniform sizes. The process of thermal decomposition in a reducing atmosphere leads to the formation of nanoporous metal crystallites with a shape similar to that of the initial complex salt. Such crystallites are formed as a result of complicated channels that are developed due to the release of gaseous products (N2 and HCl) and are directed from the bulk of the crystallite to its surface. The atomic charge states of the intermediate decomposition product correspond to {IrClx}3−x.

ВИКОРИСТАННЯ ПРИРОДНИХ СОРБЕНТІВ В ПРОЦЕСАХ ОЧИЩЕННЯ ПОГЛИНАЛЬНИХ РОЗЧИНІВ ПОТАШУ ВИРОБНИЦТВ АМІАКУ

Today, the problem of purification of monoethanolamine (MEA) solutions and potassium-based, deethanolamine (DEA) activated solutions to purify gases from carbon dioxide is very acute at the enterprises of chemical industry for the production of ammonia in the synthesis scheme, at the stage of carbon monoxide conversion. Long-term use of such solutions (Carsol solution (25-28 % of КНСО3 and 1,.8 % of diethanolamine) and Benfield solution (29-30 % of КНСО3 and 2,9 % of diethanolamine)) leads to a decrease in their absorption capacity. At the stage of high-temperature regeneration, indirect processes of thermal diethanolamine decomposition occur in the volume of solutions, resulting in the formation of resinous substances and corrosion-active compounds, for removal of which additional stage for filtration of solutions on carbon filters is introduced into the flow chart. Experimental studies have been conducted at the Department of Chemical Technology and Water Purification to determine the adsorption capacity of activated bentonite clays for absorption of solutions of resinous substances and corrosion-active compounds. During the work, it has been established that bentonite clays activated by acid and alkaline activation have sufficient absorption capacity for resinous substances and corrosion-active compounds to replace the activated carbon used for these production purposes. It is revealed that the clay of acid activation is characterized by the lowest degree of absorption of the target components of the potassium solution. The clay of alkaline activation also absorbs K2CO3, KHCO3, diethanolamine and V2O5 in the process of adsorption but to a greater extent than the clay of acid activation. Activated carbon has the highest degree of absorption. Activated carbon has the highest degree of absorption. This disadvantage of activated carbon necessitates the constant replenishment of the absorbent solution with new portions of K2CO3, KHCO3, diethanolamine, which increases the production costs for purification of synthesis gas from carbon monoxide (IV).

Imparting superhydrophobicity and flame retardancy simultaneously on cotton fabrics

An eco-friendly hydrophobic flame retardant, ammonium salt of octadecyl phosphate (AMOP) was synthesized and its structure was verified by 1HNMR, 13CNMR and 31PNMR. AMOP imparted flame retardancy and superhydrophobicity to cotton fabrics simultaneously. The water contact angles and limiting oxygen index values of treated cotton reached 161.8° and 27%, respectively. After 30 laundering cycles, the hydrophobicity sustained very well. Thermogravimetric analysis and thermogravimetric-infrared spectroscopy suggested AMOP changed the thermal decomposition path of cotton fibers and the treated sample released less flammable gas during the thermal decomposition process. Cone calorimetry results showed the total heat release and the heat release rate of treated cottons were much lower than those of control cottons. Fourier-transform infrared spectroscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy suggested the AMOP successfully grafted on cotton fabrics through P-O-C groups. Scanning electron micrography showed AMOP caused a rough surface.

Nanoscale Co3O4 powders prepared by an enhanced solid-state reaction method

This work is focused on the mechanism study of nanoscale Co3O4 powders prepared by an enhanced solid-state reaction method. The as-prepared powders are characterized by thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with the powders ball milled for different times as the control. The results show that ball milling can accelerate the thermal decomposition process by approximately 18.2%. Moreover, the apparent thermal decomposition activation energy of CoCO3 powders pretreated by the enhanced solid-state method declined by 33.2%. To elucidate this,the thermal decomposition kinetic equations of CoCO3 powders, with and without ball milling, are calculated. And the thermal decomposition kinetic equation of the ball-milled powders is dα/dt = (2.42E6~2.19E7) exp [(8.74E3~9.96E3)/T] 4/3(1-α) [-ln(1-α)]1/4; while that of the powders lack of ball milling is dα/dt = (1.08E10–1.07E11) exp [(1.43E4~1.51E4)/T] 2/3α−1/2, respectively. The reaction process at different time points can be forecasted by the obtained equations.