Deoxidation Reaction Research Articles

Electrolytic Routes to Titanium: Methodological Innovations, Key Findings, and Prospects for Sustainable Production

Titanium is an indispensable strategic metal, and the greening of titanium production processes is a key safeguard for the further development of the titanium industry. Traditional titanium extraction methods involve high-temperature molten salts and high energy consumption, accompanied by significant environmental issues. The electrolytic method for the production of titanium is a more environmentally friendly and promising production process. This review examines recent advancements in electrolytic titanium production, focusing on methods like the FFC, OS, SHS-ED, and USTB processes. These methods offer more efficient and environmentally friendly alternatives to traditional titanium extraction. Key findings include improvements in anode materials, electrolyte compositions, and process optimizations, which enhance titanium purity and production efficiency. The SHS-ED method, in particular, has shown significant advantages by shortening the deoxidation reaction path, improving process efficiency, and reducing the formation of undesirable phases. Despite these advancements, challenges remain in improving current efficiency, reducing energy consumption, and scaling up production. This article aims to provide guidance for future research directions and to discuss how to further promote the development of electrolytic titanium technology for more efficient and environmentally friendly titanium production.

In-depth analysis on the mechanism and reaction efficiency of hydrogen deoxidation in ultra-low carbon steel

The reaction mechanism and efficiency of hydrogen deoxidation used in ultra-low carbon steel are explored in this work. A combination of first-principle simulations and thermodynamic calculations were performed on the reaction mechanisms of hydrogen with dissolved oxygen. Laboratory thermal state experiments were used to analyze the effects of different initial oxygen contents of steel and different hydrogen injection flow rates on the deoxidation ability. The results show that the hydrogen deoxidation mainly happens with the gas state of H2 since there are more reactive sites of H atoms in the gas bubble compared to the dissolved H. Higher initial oxygen content and larger hydrogen blowing flow rate are beneficial to the deoxidation reaction efficiency. With hydrogen deoxidation, the inclusion number can be reduced by half compared to Al deoxidation, and the finally total oxygen content can reach 6.8 × 10–6. The actual reaction hydrogen utilization efficiency fluctuates between 0.13 %-1.17 % in this study, which can be improved by extending the resistance time of H2 bubbles in the molten steel. This paper provides in-depth theoretical support and atomic-scale insights into the reaction between hydrogen and oxygen in steel, building a foundation for the hydrogen application in the production of ultra-low-carbon steel.

Effect of alloying on the cleanliness of Ti-stabilised interstitial-free (IF) steel during Ruhrstahl–Heraeus (RH) treatment

To understand the alloying process on the cleanliness of Ti-stabilised interstitial-free (IF) steel, two different alloying operation processes were conducted during Ruhrstahl–Heraeus (RH) treatment. It was found that the Ti–Fe alloy contains extremely high oxygen and nitrogen contents. After Al addition, [Al]–[O] deoxidation reaction can quickly get close to equilibrium (within 1 min), and most inclusions are pure Al2O3. After Ti–Fe addition, the TiO x content in the inclusions increases first and then drops. Because the average content of TiO x is lower than 10 mass%, most inclusions should be solid. The addition of Ti–Fe alloy just after Al addition would not evidently weaken the yield of Ti–Fe alloy, or influence the removal efficiency of the inclusions. Due to the longer RH circulation time after Ti–Fe addition, the inclusions and impurities in the alloy can be further removed, resulting in better steel cleanliness.

Fabrication of NiZn bimetallic oxides catalysts supported on carbon black waste for catalytic pyrolysis of fatty acid

Herein, NiZn bimetallic oxides derived from calcination treatment of metal-organic frameworks (MOFs) were successfully loaded onto the carbon black waste as support obtained from the oil refinery. The resulting hybrids could serve as environmentally friendly and cost-effective catalysts for the deoxygenation of biomass-derived fatty acids under an inert atmosphere. An online pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) system was employed to evaluate their deoxygenation performance. The optimized catalysts demonstrated remarkably high stearic acid conversion of 99.6% and selectivity towards C8-C17 olefins of 57.2%. Furthermore, these catalysts with varying metal loadings also exhibited excellent efficiency in deoxygenation reactions of other types of fatty acids, such as myristic acid and palmitic acid, achieving conversion exceeding 85% and selectivities towards olefins of ca. 50%. When converting coconut oil, the supported NiZn bimetallic oxides showed excellent selectivity towards olefins (>60%). Furthermore, in-situ DRIFTS results suggest that fatty alcohols might be the key intermediates in the deoxidation reactions of fatty acid. This study not only demonstrates the great potential for obtaining valuable chemicals from biomass but also provides some insights into the fabrication of catalyst materials by using industrial solid waste.

Tribological behavior of zirconia ceramic with micro-channels produced by nanosecond laser

Tribological performance of surface can be improved by laser texturing. For this purpose, this paper fabricated the grid-texture composed of micro-channels by nanosecond laser on the zirconia surface. To obtain micro-channel with high-quality, the effect of laser parameter on the morphology and geometry of micro-channels was investigated. The results showed that the laser power has lest effect on the taper angle and the height of pile up. Analysis of chemical properties indicated that a deoxidation reaction by laser irradiating can led to oxygen vacancy decreasing and color darkening, and this color variation can be diminished by the annealing treatment. Analysis of phase properties showed that internal stress resulting from oxygen vacancy decreasing can led to the tetragonal → monoclinic phase transformation. Finally, grid-textures composed by micro-channels with better quality obtained from the experimental results were fabricated to change the tribology of zirconia. Results of wear tests indicated that the coefficient of friction for the laser-treated is higher and more stable than that of untreated. The observation of worn surface indicated that adhered lamellar for laser-treated was less than that on the untreated surface, and abrasive particles can be observed in microgrooves produced by laser, which can decrease ploughing effect to improve the friction stability.

Investigation of deoxidation of high-silicon austenitic sulfuric acid-resistant stainless steel

The oxygen content in high-silicon austenitic sulfuric acid-resistant stainless steels is one of the most detrimental parameters to their corrosion resistance. Based on the ion-molecular coexistence theory (IMCT), a thermodynamic model of the slag-steel reaction of austenitic stainless steel containing 5.0 wt% Si with CaF2-CaO-Al2O3-MgO-SiO2 pentabasic slag was developed to investigate the deoxidation reaction and the oxygen control mechanism of the steel. The model was validated through experiments proposed in this study. The results of the slag-steel reaction indicated that the equilibrium oxygen content was determined by the greater of two factors: w[O]%, Si obtained from the [Si]-[O] equilibrium reaction controlled by the activity of SiO2 and w[O]%, Al obtained from the [Al]-[O] equilibrium reaction controlled by the activity of Al2O3. The system temperature and the basicity of slag are the most crucial among the multiple variables affecting the equilibrium oxygen content compared with Al2O3 and CaF2 in slag. However, achieving an ultra-low oxygen steel, both a basicity of slag greater than two and a low activity of Al2O3 in slag should be maintained. The total oxygen content in steel can reach a minimum value of 3.4 ppm when the slag composition encompasses w(CaF2)% = 29.38, w(CaO)% = 44.07, w(SiO2)% = 14.69, w(MgO)% = 9.89, w(Al2O3)% = 1.96. The high basicity of slag reduces the total oxygen content of stainless steel, whereas the influence of redox reactions between Si and Al results in a higher Al content in steel and the formation of more inclusions during solidification. Thus, the optimal Al2O3 content is less than 4% and the optimal basicity is 2.4 during the refining process.

Sawdust biomass promotes aquathermolysis of extra-heavy oil

The application of biomass to the enhanced oil recovery of extra-heavy oil is a promising technology. In this paper, the promoting effect of sawdust on the viscosity reduction of extra-heavy oil was discussed. During the experiment, sawdust and extra-heavy oil were co-aquathermolysis. The experimental results showed that the viscosity of extra-heavy oil can be reduced from 145 Pa·s to 10.42 Pa·s at 553 K for 24 h and the feedstock ratio of sawdust: extra-heavy oil: water is 1:50:50. Elemental analysis of extra-heavy oil showed that the H/C increased from 1.4347 to 1.6296, and the oxygen content increased from 2.05 wt% to 5.61 wt%. Compared with the upgrading oil without sawdust, the viscosity decreased by 11.03 Pa·s and the H/C increased by 0.0832. The GC–MS results show that the dehydrogenation and deoxidation reactions of small molecular substances generated by sawdust provide hydrogen and oxygen sources for the upgrading of extra-heavy oil.

Surface reaction and deoxidation mechanism of titanium powder deoxidized by calcium in atmospheric pressure argon

A new deoxidation in solid-state (DOSS) process was carried out in atmospheric-pressure argon to solve various difficulties associated with high-vacuum conditions, and the surface reaction and contact deoxidation mechanism were examined. The oxygen concentration of the Ti powder was decreased to 750 ppm at 800 °C by DOSS in atmospheric-pressure argon. Craters were formed on the surface of the deoxidized Ti powder, and the surface roughness increased. The craters were formed of Ca-Ti-O intermediate compounds during the reduction process and deoxidation. As the surface oxides of the Ti powder were reduced by deoxidation, the oxidation state decreased. When the deoxidation reaction reached equilibrium, the surface oxide was completely deoxidized, and the surface oxides were minimized upon re-passivation after pickling. As a result, the surface deoxidation reaction of the Ti powder was caused by the formation and decomposition of the Ca-Ti-O ternary compound on the surface.

Direct oxygen removal from titanium aluminide scraps by yttrium reduction

Titanium aluminum (TiAl) scraps with a high oxygen content were treated with yttrium (Y) in a liquid chemical deoxidization process for recycling. The Gibbs free energy and the equilibrium constant of the deoxidization reaction were calculated, and the effects of the yttrium content and the system pressure on the oxygen content in the product were determined. The results showed that the oxygen in TiAl scraps could be removed by yttrium, and the oxygen content of the deoxidized TiAl scraps had only 10% of the original content after deoxidization. Furthermore, the oxygen content of the deoxidized TiAl scraps was decreased with the increase of yttrium addition. The higher the chamber pressure, the greater the oxygen content in the final TiAl alloys. These results were consistent with calculated values. The microstructure of the deoxidized alloys was akin to that of the original material; however, Y2O3 particles were observed in the deoxidized alloys.

A quantum chemistry study of the deoxidation of lignite during hydrothermal dewatering treatment

ABSTRACT To investigate the deoxidation mechanism of lignite under hydrothermal dewatering (HTD) condition, the removal mechanism of carboxyl and methoxy groups was calculated at the B3LYP-D3/6-311 G(d,p) level by using density functional theory. The feasibility of deoxidation was analyzed from the perspective of thermodynamics and kinetics, and the influences of hydrogen bond on the deoxidation process were analyzed. The results showed that the activation energy of decarboxylation was lower than that of demethoxide, indicating that the carboxyl group had high reactivity. Through the hydrogen bonding between the carboxyl group and water, the activation energy of indirect decarboxylation (lignite-C6H5-COOH→lignite-C6H6-COO→lignite-C6H6+ CO2) decreased by 10 kJ/mol, whereas the activation energy of direct decarboxylation increased by 8 kJ/mol. The activation energy of demethylation was reduced by 25 kJ/mol, and the change in activation energy of subsequent decarbonylation was similar to that of decarboxylation. The two-step elementary reaction benefitted the deoxidation reaction.

Composition and Morphological Analysis of MnO–SiO 2 –Al 2 O 3 Inclusions during Solidification of Steel

To understand the extent of the temperature dependence on the deoxidation reactions during cooling of molten steel and the influence of solute microsegregation during solidification on the formation of oxide inclusions, changes in the morphology and composition of Mn–Si–Al deoxidation products of two actual steel samples are experimentally investigated herein. It is found that from 1823 K to just above the liquidus temperature of steel, oxide inclusion composition does not change significantly, suggesting that the temperature dependence of the deoxidation reactions on oxide inclusion formation can be ignored. Meanwhile, during solidification from the liquidus to the solidus temperature of steel, it is found that positive segregation of Mn and Si in the residual molten steel phase largely influences oxide inclusion composition such that the equilibrium oxide phase shifts from high- to low-Al2O3 region. It is confirmed that the higher Al2O3 oxide inclusions are present in the solid, while the lower Al2O3 oxide inclusions are present in the liquid steel phase. These results suggest that the microsegregation behavior of solute elements in molten steel plays an important role in the formation of inclusions, which is of great importance in the production of high-quality steels.

Surface characterization of Ti and Ti–6Al–4V alloy by Ca vapor deoxidation: Relation between surface morphology and deoxidation reaction

Ca vapor deoxidation—which involves controlling oxygen through deoxidation on the surface of Ti—is important to ensure the quality of Ti and its alloys. We systematically investigated various surface properties before and after Ca vapor deoxidation of bulk Ti and Ti–6Al–4V alloy with small specific surface areas. The relationship between surface characteristics and deoxidation is discussed. The oxygen concentrations of Ti and Ti–6Al–4V decreased to 555 and 565 ppm, respectively, upon Ca vapor deoxidation. Moreover, the surface roughness increased, the surface oxide layer was slightly thinned, and the oxygen content of the matrix decreased. The surface chemical states of Ti before and after the deoxidation were mainly the tetravalent oxidation state (TiO2) and metallic state toward the inside. The deoxidation produced a Ca oxide layer on the surfaces of Ti and Ti–6Al–4V and increased the surface roughness by creating craters on the surface. The deoxidation reactions included heterogeneous Ca/CaO nucleation and growth on the Ti surface, resulting in localized oxygen diffusion. Craters were formed on the surfaces of Ti and Ti–6Al–4V owing to the Ca oxide layer. Local oxygen diffusion and reactions with Ti and Al components enlarged the craters.

CO2-enriched CBM accumulation mechanism for low-rank coal in the southern Junggar Basin, China

This paper mainly focused on the genesis of coalbed methane (CBM), CO2 origin and the CBM accumulation mechanism in the southern Junggar Basin using a combination of geochemical and geological analysis methods. From this work, it is found that the degree of early coalification and the current structural and hydrogeological conditions jointly determine the regional differences in CBM genesis, accumulation and gas-bearing capacity. Microbial (biogenic) gases are widely developed in the whole study area, while their generation types and contributions vary greatly in different areas and structural belts. The CBM in the eastern Urumqi (ER) and Jimusaer (JMSE) areas is primary microbial (biogenic gas) that have been generated through CO2 reduction pathway and mixed with a small amount of early mature thermogenic gas. The Baiyang River (BYR) area has a mixed gas source of early mature thermogenic gas, primary microbial gas and secondary microbial gas. The CBM in other areas is mixed gas of thermogenic and secondary microbial origins. Abnormally high CO2 concentration and extremely positive δ13C-CO2 are all related to microbial methanogenesis. The CO2 in the ER and JMSE areas and partial CO2 in the BYR area are produced by the microorganism-mediated degradation of sedimentary organic matter. The selective consumption by microbial reduction and differential dissolution of groundwater result in an increase in CO2 concentration with increasing burial depth in the ER and BYR areas. The CO2 in other areas is originally derived from the deoxidation reaction of early coalification which then undergoes secondary biotransformation. The CO2 intervention commonly runs through the whole process of CBM accumulation in low-rank coal in the study area. Due to isotope fractionation caused by groundwater flow and differential modification of microorganisms, the vertical variations of δ13C-CH4 and δ13C-CO2 are positively correlated with burial depth, and the genetic types and gas-bearing characteristics of CBM have obvious vertical zoning under the condition of high-dip structures.

Effect of Fe2O3 on Electro-Deoxidation in Fe2O3-Al2O3-NaCl-KCl System

The reduction of Fe2O3-Al2O3 is one of the important reactions in the resource utilization of iron-containing oxide waste. Fe2O3-Al2O3 was electro-deoxidized in the NaCl-KCl system by molten salt electrolysis to prepare FeO/Al2O3. The effect of the Fe2O3 content on the electro-deoxidation reaction process was studied. The results show that under the conditions of 850 °C, 2.3 V, and electro-deoxidation for 4 h, FeO/Al2O3 could be obtained by controlling the content of Fe2O3. The deoxidation process was divided into three stages: electric double layer charging, Fe2O3 electro-deoxidation to Fe3O4, and Fe3O4 electro-deoxidation to FeO. With the increase in the Fe2O3 content, the deoxidation reaction rate increased, and the low-valence iron oxide particles obtained by electro-deoxidation became larger. The mechanism of the influence of Fe2O3 on the electro-deoxygenation process was determined by analyzing the experimental results. The increase in the Fe2O3 content increased the concentration of activated molecules in the system, while it reduced the resistance of electro-deoxidation. The migration of active particles in the cathode was smoother, which increased the percentage of deoxygenation of activated molecules, thereby shortening the process of the deoxidation reaction.

Effect of Pre-existing Inclusions on the Size and Morphology of Al2O3: Single Stage Deoxidation with Varying Levels of Supersaturation

The effects of supersaturation and steel composition on the morphology of Al2O3 inclusions were investigated. Thermodynamic calculations with Factsage 7.0® were used to predict the degree of supersaturation and select the starting aluminum and oxygen amounts for the experiment. Deoxidation experiments were performed by melting the charge material and using specially designed samplers to study the local deoxidation reactions. The inclusions in the collected steel samples were analyzed on filter paper in 3D after extraction from the steel. The observed Al2O3 morphologies consisted of dendrites and clusters and results showed that increasing supersaturation had the strongest influence on the length of the dendrite. The observed clusters resulted from collision, heterogeneous nucleation and growth on existing Al2O3 inclusions, and possibly oxygen gradients and liquid steel convection during nucleation and growth of Al2O3.

Oxygen Solubility in the Hafnium-Containing Fe–Co Melts

A thermodynamic analysis of the oxygen solutions in the hafnium-containing Fe–Co melts is performed. The equilibrium constants of the deoxidation reaction of iron-cobalt melts with hafnium, the activity coefficients at infinite dilution, and the interaction parameters for melts differing in composition are determined. The dependences of the oxygen solubility in the melts under study on the cobalt and hafnium contents are calculated.

Development of a New Titanium Powder Sintering Process with Deoxidation Reaction Using Yttrium Metal

Oxygen (O) contamination in titanium (Ti) is difficult to control using conventional Ti powder-metallurgy technologies, owing to the strong affinity between Ti and O. In this study, we developed a new sintering process that can remove O from Ti by placing Ti green and yttrium (Y) in molten salt. This study demonstrates that the O concentration in Ti can be reliably controlled in the range of 200–2000 ppm O by varying aY in the Y/Y2O3 equilibrium at 1300 K in NaCl–KCl (l), such that the sintering reaction of Ti powder simultaneously proceeds. Furthermore, it is also shown that the O concentration in Ti can be reduced to 30–60 ppm O in YCl3 (l) in the sintering process, when the Y/YOCl/YCl3 equilibrium is employed. This study demonstrates the feasibility of a new sintering process that can control the O concentration in Ti to approximately 30–2000 ppm O. The process ensures economical rationality because the cost of Y metal is negligibly small in recent years. By developing this process, inexpensive high-O-concentration Ti powder can be applied for fabricating the desired low-O-concentration Ti products.

Comparison of deoxidation capability of solid solution and intermetallic titanium alloy powders deoxidized by calcium vapor

A comparison of the deoxidation capability of solid solution and intermetallic titanium alloy powders deoxidized by calcium vapor was investigated. The oxygen concentration of Ti–6Al–4V, Ti–27Nb, Ti–42Nb, Ti–35V–15Cr, Ti–25Fe–5Al, and Ti65Fe35 alloy powders before deoxidation were 2,610 ppm, 3,300 ppm, 3,780 ppm, 5,880 ppm, 1,725 ppm, and 4,635 ppm, respectively. After deoxidation, the oxygen concentration of the Ti–6Al–4V, Ti–27Nb, Ti–42Nb, and Ti–35V–15Cr solid-solution alloy powders were 355 ppm, 210 ppm, 330 ppm, 95 ppm, respectively, while the Ti–25Fe–5Al and Ti65Fe35 intermetallic alloy powders were 385 ppm and 1250 ppm, respectively. Compared with the oxygen concentration before deoxidation, the solid-solution Ti alloy powders showed a high oxygen reduction rate of approximately 80% or more, while the intermetallic Ti alloy powders showed a lower oxygen reduction rate of approximately 70%. Based on the theoretical deoxidation limit of pure Ti and the actual deoxidation result of pure Ti powder, solid-solution Ti alloy powders have reduced oxygen solubility due to the addition of alloying elements, resulting in reduced oxygen concentration after deoxidation. However, the intermetallic Ti alloy powders showed a difference in oxygen concentration among them due to the effect of TiFe intermetallic phase with high equilibrium oxygen concentration in the deoxidation reaction.

Оxygen solubility in melts of Ni – Co system at complex deoxidation by aluminium and silicon

Alloys of Ni – Co system are widely used in industry. Oxygen is one of the harmful impurities in these alloys; in metal it is present in dissolved form or in the form of nonmetallic inclusions. Getting the finished metal with a minimum oxygen concentration is one of the main tasks of production process of these alloys. With the complex deoxidation of the metal melt, the activity of oxides resulting from the deoxidation process is less than one, due to this, with the same content of deoxidizing elements, it is possible to obtain a metal with a lower oxygen concentration, therefore, more deeply deoxidized. At joint deoxidation with two deoxidizers, a stronger deoxidizer takes a predominant part in the reaction, however, if oxides of the deoxidizing elements form chemical compounds, it contributes to participation of a weaker deoxidizer in deoxidation process. A thermodynamic analysis of the joint influence of aluminum and silicon on the solubility of oxygen in the melts of Ni – Co system has been performed. Deoxidation reaction products may be formed as mullite (3Al2O3·2SiO2 ), and kyanite (Al2O3·SiO2 ). Presence of silicon in the melt enhances the deoxidizing ability of aluminum: insignificantly in the case of formation of compound 3Al2O3·2SiO2 and significantly in the case of formation of compound Al2O3·SiO2 . Oxygen solubility curves in the case of formation of compound Al2O3·SiO2 pass through a minimum, the position of which depends on the content of aluminum in the melt and doesn’t dependent on silicon content. Aluminum content in the minimum points is insignificantly reduced from nickel to cobalt as in the case of melts of Ni – Co–Al. Further additives of aluminum lead to an increase in oxygen concentration. Areas of compounds Al2O3 , 3Al2O3·2SiO2 , Al2O3·SiO2 and SiO2 depending on aluminum and silicon contents in the melt are determined. In melts of the Ni – Co system, the deoxidizing ability of aluminum and silicon increases with an increase in cobalt content in the melt. However, silicon enhances the deoxidizing ability of aluminum the weaker the higher cobalt content.

7-keto-DHEAmetabolism in humans. Pitfalls in interpreting the analytical results in the antidoping field.

7-keto-DHEA (3β-hydroxy-androst-5-ene-7,17-dione) is included in section S1 of the World Antidoping Agency (WADA) List of Prohibited Substances. The detection of its misuse in sports needs special attention, since it is naturally present in urine samples. The main goal of this study is to investigate the in vivo metabolism of 7-keto-DHEA after a single administration to healthy volunteers and to better describe the relationship between arimistane (androst-5-ene-7,17-dione) and 7-keto-DHEA after the application of the common routine procedures to detect anabolic steroids in WADA accredited antidoping laboratories. Free, glucuro-, and sulpho-conjugated steroids extracted from urine samples obtained before and after the administration of 7-keto-DHEA were analyzed by different gas chromatographic (GC)-mass spectrometric (MS) techniques. Gas chromatography coupled to tandem MS to study the effect on the endogenous steroid profile, coupled to isotope ratio mass spectrometry (IRMS) to investigate the potential formation of androgens derived from DHEA and coupled to high resolution accurate mass spectrometry (HRMS) to investigate new diagnostic metabolites. The analysis by IRMS confirmed that there is no formation of DHEA from 7-keto-DHEA. Ten proposed metabolites, not previously reported, were described. These include reduced and hydroxylated structures that are not considered part of the steroid profile in antidoping analyses. They showed considerable responses in all fractions analyzed. Some deoxidation reactions (including arimistane formation) were found and most probably can be linked to the sample preparation or instrumental analysis. This is important when interpreting the results after the application of procedures to detect steroids in urine currently used in antidoping laboratories. 7-keto-DHEA metabolism in humans for antidoping purposes was studied and unexpected results were found. This could lead to a misinterpretation of the data, depending on the procedure applied and the analytical instrumentation used.