Reduction Temperature Research Articles

Machine Learning Assisted for Preparation of Graphene Supported Cu-Zn Catalyst for CO2 Hydrogenation to Methanol.

Graphene has emerged as a promising support material for Cu-Zn catalysts in CO2 hydrogenation to methanol due to its high surface area and potential for functionalization with heteroatoms like nitrogen and oxygen, with nitrogen believed to contribute to the reaction. In this study, we combined machine learning and data analysis with experimental work to investigate this effect. Machine learning (using a decision tree model) identified copper particle size, average pore diameter, reduction time, surface area, and metal loading content as the most impactful features for catalyst design, while nitrogen doping showed negligible influence on methanol space-time yield. However, experimental results indicated that nitrogen doping on graphene support improved the space-time yield by up to four times compared to pristine graphene. This improvement is attributed to nitrogen's role in lowering the catalyst's reduction temperature, enhancing its quality under identical reduction conditions, though nitrogen itself does not directly affect methanol formation. Moreover, machine learning provided insights into the critical features and optimal conditions for catalyst design, demonstrating significant resource savings in the lab. This work exemplifies the integration of machine learning and experimentation to optimize catalyst synthesis and performance evaluation, providing valuable guidance for future catalyst design.

An insight into biomass-derived low-cost biochar supported FeNi3/NiFe2O4 catalyst: effect of hydrothermal treatment and carbothermal reduction temperature

An insight into biomass-derived low-cost biochar supported FeNi3/NiFe2O4 catalyst: effect of hydrothermal treatment and carbothermal reduction temperature

Defective TiO2 for CO2 photoreduction: Influence of alkaline agent and reduction temperature modulation

Defective TiO2 for CO2 photoreduction: Influence of alkaline agent and reduction temperature modulation

High-Temperature Growth of CeO x on Au(111) and Behavior under Reducing and Oxidizing Conditions.

Inverse oxide-metal model catalysts can show superior activity and selectivity compared with the traditional supported metal-oxide architecture, commonly attributed to the synergistic overlayer-support interaction. We have investigated the growth and redox properties of ceria nanoislands grown on Au(111) between 700 and 890 °C, which yields the CeO2-Au(111) model catalyst system. We have observed a distinct correlation between deposition temperature, structural order, and oxide composition through low-energy electron microscopy, low-energy electron diffraction, intensity-voltage curves, and X-ray absorption spectroscopy. Improved structural order and thermal stability of the oxide have been achieved by increasing the oxygen chemical potential at the substrate surface using reactive oxygen (O/O2) instead of molecular O2 during growth. In situ characterization under reducing (H2) and oxidizing atmospheres (O2, CO2) indicates an irreversible loss of structural order and redox activity at high reduction temperatures, while moderate temperatures result in partial decomposition of the ceria nanoislands (Ce3+/Ce4+) to metallic cerium (Ce0). The weak interaction between Au(111) and CeO x would facilitate its reduction to the Ce0 metallic state, especially considering the comparatively strong interaction between Ce0 and Au0. Besides, the higher reactivity of atomic oxygen promotes a stronger interaction between the gold and oxide islands during the nucleation process, explaining the improved stability. Thus, we propose that by driving the nucleation and growth of the ceria/Au system in a highly oxidizing regime, novel chemical properties can be obtained.

Metallic molybdenum obtained by atomic layer deposition from Mo(CO)6

A feasibility study was conducted into the atomic layer deposition (ALD) of metallic molybdenum from the molybdenum hexacarbonyl [Mo(CO)6] precursor. Without the use of a coreactant, Mo(CO)6 decarbonylates in a nonself-limiting fashion to form molybdenum oxycarbide (MoCxOy) films in the low-temperature regime between 100 and 250 °C. Introducing (atomic) hydrogen as a coreactant, in an attempt to drive self-limiting growth and provide metallic molybdenum films, caused hardly a difference in both film composition and growth kinetics. With ozone as a coreactant, an ALD process was developed to grow molybdenum oxide (MoO3) films without carbon contamination. The MoO3 ALD cycle times were optimized and the existence of an ALD window was investigated. The MoO3 films were subsequently reduced by atomic hydrogen to form metallic molybdenum at temperatures between 150 and 450 °C. The degree of reduction was shown to increase with the reduction temperature, with the limitation that the film exhibited multiple cracks after reduction at 450 °C. Spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and scanning and transmission electron microscopy were employed for thin-film characterization.

Evaluation of Reduction Behavior of the Acid Pellets Prepared with Sinter-Grade Iron Ore Fines by 55% H2–35% CO–10% N2 and 100% H2

Hydrogen is receiving much attention as a reducing agent in iron and steel production processes. Hydrogen-based DRI (Direct-Reduced Iron) production in a shaft furnace is currently under development in many countries. However, due to the limited resources for DR-grade pellets, the hydrogen reduction technology of the pellets produced with sinter-grade iron ore fines is highly anticipated. In this study, the reduction characteristics of the acid pellets produced with sinter-grade iron ore fines were investigated by a typical reformed natural gas (55% H2–35% CO–10% N2), and 100% H2 at temperatures ranging from 973 to 1173 K. The lab-made acid pellet exhibited an average cold crushing strength of 335 kg. When the pellets were reduced by 55% H2–35% CO–10% N2, the degree of metallization was satisfied only at 1173 K. On the other hand, when the pellets were reduced by 100% H2, the degree of metallization was acceptable: 93.04 and 95.54% at 1073 and 1173 K, respectively. The reduction time by 100% H2 at 1073 K was 29 min, whereas that by 55% H2–35% CO–10% N2 at 1173 K was 57 min. Accordingly, the hydrogen reduction process can reduce the reduction time by 51%, although the reduction temperature by 100% H2 is 100 K lower than that by 55% H2–35% CO–10% N2.Graphical

Sticking and Swelling of Iron Ore Pellets: Mechanisms and Controlling Factors

The sticking and breakage of iron ore pellets during high-temperature reduction pose significant challenges in shaft furnace ironmaking. As the steel industry transitions towards decarbonization, hydrogen-based shaft furnace processes are expected to play an increasingly important role in achieving low-emission steel production. One of the critical challenges in this transition is the global decline in iron ore quality. This review critically examines how degrading ore quality and changes in reduction mechanisms affect adverse pellet behaviors, such as sticking and swelling. The mechanisms of pellet sticking and swelling are discussed. Key contributors include the formation of iron whiskers, dense metallic iron, and low-melting eutectic phases. The impact of impurity oxides, such as SiO₂, Al₂O₃, MgO, CaO, TiO₂, and alkali oxides, on sticking and swelling indices is assessed, along with the mineralogy of iron ores. Lower-grade iron ores are tend to exhibit lower sticking and swelling. SiO₂ and MgO effectively mitigate these issues; SiO₂ forms a glassy silicate layer that inhibits iron whisker growth, while MgO enhances magnetite stability through the formation of high-melting spinel phases, promoting uniform distribution in the wüstite lattice. While the role of CaO is quite complex, a basicity (CaO/SiO₂) range of below 0.2 or above 0.8 is recommended to prevent adverse sticking and swelling behaviors. In contrast, alkali oxides have a detrimental effect on pellet performance. Furthermore, induration and reduction conditions including pellet size, induration temperature, reduction temperature, and reducing gas composition significantly affect these pellet behaviors. Higher reduction temperatures are correlated with increased sticking and swelling due to enhanced diffusion and crystallization of iron whiskers. Temperatures below 900 °C are recommended to prevent sticking in uncoated pellets. Importantly, the presence of hydrogen in the reducing atmosphere transitions the reduction mechanism from chemical-reaction control to diffusion control, thereby reducing iron whisker formation.Graphical

Unveiling the Role of Rhenium Precursors in Supercritical CO₂ Hydrogenation: A Comparative Study of ReOx/TiO₂ Catalysts

Heterogeneous rhenium catalysts supported on various oxides, particularly TiO2, have demonstrated effectiveness in converting carbon dioxide (CO2) to methanol via hydrogenation, showing high selectivity under diverse reaction conditions. However, the impact of different rhenium precursors on the catalytic performance and physicochemical properties of ReOx/TiO2 has not yet been elucidated. Herein, we compared catalysts prepared from NH4ReO4 and Re2O7 precursors with varying rhenium content (4 to 14 wt% Re) synthesized using a wet impregnation approach. These catalysts were evaluated under different reaction temperatures (200‐250 ºC), pressures (100‐200 bar), and H2/CO2 ratios (1‐4). This study revealed that both catalytic performance and physicochemical properties varied not only with the type of precursor but also with the rhenium content. Variation in reduction temperature, particle size, oxidation states of Re and surface Re=O terminals were observed. In batch system, catalysts derived from NH4ReO4 demonstrated a higher selectivity for methanol production under high pressure and stoichiometric conditions, regardless of temperature. In contrast, Re2O7‐based catalysts demonstrated higher methanol selectivity at 200°C, with H2/CO2 ratios between 1 and 3, regardless of the total pressure. These findings provide a deeper and valuable insight on the choice of precursors for the preparation of ReOx/TiO2 catalysts for CO2 hydrogenation.

Evaluation of anion exchange membrane water electrolysis performance using synthesised NiMoO4/Ni cathode via solution combustion synthesis in applied thermal reduction approach

Evaluation of anion exchange membrane water electrolysis performance using synthesised NiMoO4/Ni cathode via solution combustion synthesis in applied thermal reduction approach

Synthesis of silica and silicon from rice husk feedstock: A review.

Synthesis of silica and silicon from rice husk feedstock: A review.

Layered perovskite-derived Ni/La2-2xPr2xO3 catalysts for hydrogen production via auto-thermal reforming of acetic acid

Layered perovskite-derived Ni/La2-2xPr2xO3 catalysts for hydrogen production via auto-thermal reforming of acetic acid

Synergistic dielectric regulation strategy of one-dimensional MoO2/Mo2C/C heterogeneous nanowires for electromagnetic wave absorption

Synergistic dielectric regulation strategy of one-dimensional MoO2/Mo2C/C heterogeneous nanowires for electromagnetic wave absorption

Two-step electro-thermochemical cycle for CO2 splitting in a solid oxide electrochemical cell

Two-step electro-thermochemical cycle for CO2 splitting in a solid oxide electrochemical cell

Catalytic Combustion of Biodiesel Wastewater on Red Mud Catalyst.

The resource utilization of red mud (RM) has attracted widespread attention for achieving the waste-to-waste treatment goal. In this work, the RM catalysts were synthesized at different calcination temperatures by a simple method. The calcination temperature had a great effect on catalyst activity in the catalytic combustion of biodiesel wastewater. The RM catalyst calcined at 350 °C (RM350) exhibited the best catalytic activity. The chemical oxygen demand (COD) and COD removal rate of the treated wastewater reached almost 0 mg/L and 100%, respectively. The COD removal rate was significantly higher than 90.703% of the catalyst prepared by α-Fe2O3 at the same calcination temperature. Characterization results showed that the RM catalyst exhibited a high specific surface area of 60.03-64.15 m2/g and a well-developed mesoporous structure, as the calcination temperature did not exceed 400 °C, which was beneficial for adsorption and diffusion. Meanwhile, most of the Fe2O3 in the catalyst existed in an amorphous form and was abundantly presented on the catalyst surface, significantly lowering the reduction temperature of the catalyst and enhancing its reducibility. Furthermore, the α-Fe2O3 in the catalyst had higher dispersion, leading to an increase in utilization efficiency.

Manipulating the interfacial integration mode of a bio-templated porous ZSM-5 platform with an Au/CuZnOx catalyst for enhanced efficiency and recycling stability in glycerol conversion to 1,3-dihydroxyacetone.

Despite the potential to significantly enhance the economic viability of biomass-based platforms through the selective conversion of glycerol to 1,3-dihydroxyacetone (DHA), a formidable challenge persists in simultaneously achieving high catalytic activity and stability along this reaction pathway. Herein, we have devised a strategic approach to manipulate the interfacial integration within composite catalysts to address the performance trade-off. Through the modulation of the composite process involving a bio-templated porous ZSM-5 zeolite platform (bZ) and an Au/CuZnOx catalyst, three distinct interfacial bonding modes were achieved: physical milling, encapsulation by zeolite, and in situ growth on zeolite. The catalyst prepared via the physical milling mode (denoted as Au/CuZnOx@bZ) demonstrated remarkable catalytic efficiency with a glycerol conversion rate of 93% and a DHA selectivity of 86%. In particular, Au/CuZnOx@bZ maintained over 72% of glycerol conversion and DHA selectivity even after five cycles, exhibiting superior stability that surpasses the majority of current catalysts. The differences in interfacial integration modes play a crucial role in regulating the surface Au+ content and the reduction temperatures of the catalysts and minimizing Au nanoparticle agglomeration during cycling, as confirmed by comprehensive characterization and experimental analyses.

A long-term decline in downward surface solar radiation.

Downward surface solar radiation (DSSR) is critical for the Earth system. It is well-known that DSSR over land has fluctuated on decadal timescales in the past. By utilizing a combination of station observations and the latest CMIP6 simulations, here we show that DSSR had a global consistent decline during 1959-2014, with comparable contributions from greenhouse gases (GHGs) and anthropogenic aerosols. The role of GHGs is even more important in the satellite period. The contribution from GHGs comes through rising temperature, which reduces the DSSR by increasing water vapor but is partly offset by reduced cloud. Future changes of DSSR are heavily dependent on climate change scenarios, which can be predicted well by global mean surface temperature (GMST) and aerosol concentrations. The sharp aerosol reduction and weak temperature rise in the SSP245/SSP126 scenarios will limit or stop the long-term decline of DSSR thus leading to a brighter future.

Highly loaded copper on mesoporous silica as catalysts for acetaldehyde production from ethanol: their synthesis, characteristics, and catalytic properties

AbstractBACKGROUNDThe present study investigates copper (Cu)/mesoporous catalysts supported on mesocellular foam silica (MCF‐Si) and Santa Barbara Amorphous‐15 (SBA‐15) for ethanol dehydrogenation, focusing on catalyst synthesis, performance, and stability. Cu catalysts were impregnated on the MCF‐Si and SBA‐15 supports with different pore morphologies – spherical and hexagonal structure, respectively – using the wetness impregnation method and incipient wetness impregnation (IW), with a Cu loading of 60 wt%. The synthesized catalysts underwent physical and chemical characterization via scanning electron microscopy combined with energy‐dispersive X‐ray spectroscopy, X‐ray fluorescence, X‐ray diffraction (XRD), transmission electron microscopy, N2 physisorption, X‐ray photoelectron spectroscopy, thermogravimetric analysis (TGA), carbon monoxide chemisorption, hydrogen temperature‐programmed reduction (H2 TPR), ammonia temperature‐programmed desorption, and carbon dioxide temperature‐programmed desorption.RESULTSIt was observed that copper impregnation of the support in either method did not alter the structural characteristics. Incipient wetness resulted in superior catalytic activity, particularly with Cu/MCF‐Si (IW), having pure ethanol conversion of 99.4% and acetaldehyde yield of 95.7%, attributed to effective Cu dispersion and a lower reduction temperature. Further investigation of time‐on‐stream (TOS) behavior revealed sustained ethanol conversion rates exceeding 95% with a 10% ethanol feed. However, catalyst deactivation due to coke formation occurred with 100% ethanol, highlighting the importance of understanding catalyst stability and deactivation mechanisms.CONCLUSIONIncipient wetness resulted in superior performance compared to wetness impregnation, with Cu/MCF‐Si (IW) achieving exceptional ethanol conversion rates due to effective Cu dispersion and a lower reduction temperature. TOS testing revealed sustained ethanol conversion; however, catalyst deactivation was observed with pure ethanol feed due to carbon deposition (coke formation). Characterization techniques, including XRD, TGA, and H2 TPR analyses, provided valuable insights into the deactivation processes, highlighting the need for strategies to mitigate oxidation‐induced deactivation. © 2025 Society of Chemical Industry (SCI).

Nonthermal Plasma‐Catalytic Dry Reforming of Methane in Parallel‐Plate Dielectric Barrier Discharge Reactor Using Mg‐Modified Ni Catalysts

The conversion of greenhouse gases, particularly CO2 and CH4, into syngas via dry reforming of methane (DRM) has effectively mitigated global warming and climate change issues. The research objectives are to enhance the DRM efficiency and reduce coke formation using Ni catalysts supported on Mg‐modified Al2O3 in parallel plate dielectric barrier discharge. Raising the Ni calcination temperature from (Ni/Mg–Al2O3‐500) to 700 °C (Ni/Mg–Al2O3‐700) enhances NiO reduction temperatures, thus diminishing their reducibility. This indicates that Ni/Mg–Al2O3‐700 exhibits stronger NiO–Al2O3 interaction, resulting in increased metal dispersion and decreased crystallite and particle sizes. As the Ni calcination temperature increases from 700 to 800 °C (Ni/Mg–Al2O3‐800) the intensity of the Ni0.8Mg0.11Al2O4 spinel structure is enhanced. The increased Ni calcination temperature enhances the metal‐support sintering processes and promotes the metal nanoparticle cluster formation, leading to increased particle and crystallite sizes, alongside decreased dispersion of Ni and Mg particles on the catalyst surface. The Ni/Mg–Al2O3‐700 exhibits lowest NiO reducibility, strongest NiO–Al2O3 interaction, highest metal dispersion, highest specific surface area, smallest particle, and crystallite sizes. Consequently, it attains the highest CH4 and CO2 conversions, H2 and CO selectivities, and energy efficiency, as well as the lowest coking rate, carbon deposition, carbon loss, and specific energy consumption.

Refining Surface Copper Species on Cu/SiO2 Catalysts to Boost Furfural Hydrogenation to Furfuryl Alcohol.

Controllable hydrogenation of carbonyl groups (C=O) is crucial for converting furfural into high-value furfuryl alcohol. Instead of traditional impregnation method, a novel Cu-based catalyst (Cu/SiO2) is prepared using the ammonia evaporation method (AE) for the efficient hydrogenation of furfural to furfuryl alcohol under mild conditions. At the reaction conditions of 90 °C and 1 MPa H2, the 5Cu/SiO2-AE sample showed optimal performance with higher turnover frequency (36.0 h-1) and furfuryl alcohol selectivity (>99.9%). After five cycles, the catalyst recycled still showed a high reaction activity and selectivity for furfuryl alcohol. Characterization results such as XRD, H2-TPR, FT-IR, and XPS showed that the excellent catalytic performance of 5Cu/SiO2-AE catalyst was attributed to the formation of layered copper silicate and the high dispersion of Cu species. Furthermore, the formation of layered copper silicate resulted in a higher ratio of Cu+/(Cu0+Cu+) at a reduction temperature of 250 °C, which was also responsible for the optimum activity. This work showed the importance of controllable synthesis of layered copper silicate in improving the catalytic performance of copper-containing catalyst.

THE ROLE OF MIXTURE ADDITIVES ON THE SELECTIVE REDUCTION OF SAPROLITIC NICKEL LATERITE: SODIUM SULFATE - CALCIUM SULFATE

High energy consumption and production costs during the metal-slag smelting in the pyrometallurgical process caused many alternative methods to be developed. Selective reduction technology emerges as a potential solution, enabling the processing of nickel laterite into ferronickel concentrate at lower operational temperatures ranging from 1000°C to 1250°C with the presence of some additives. This work investigated the effect of a combination of two additives, i.e. sodium sulfate and calcium sulfate, on the reduction process of saprolitic nickel laterite on nickel and iron grade and recovery in ferronickel concentrate, phase transformation, and the morphology of the resulting ferronickel particles. The saprolitic nickel laterite, coal as a reductant, sodium sulfate and calcium sulfate as additives were mixed and then pelletized into a 10 - 15 mm diameter. The reduction process of pellets was carried out in a muffle furnace from 1050°C to 1250°C for 60 min, and a magnetic separation process was continued to segregate the ferronickel and impurities. Techniques such as XRF, XRD, and SEM-EDS are employed to ascertain the content of nickel and iron, phase changes, and the microstructure of the ferronickel. The study found that the addition of 10 wt. % of the mixture additives, with the composition ratio of 75 : 25 for sodium sulfate and calcium sulfate, at a reduction temperature of 1250°C, generated the optimum of the nickel content and recovery of 17.06 % and 57.01 %, respectively. It also enlarges the particle size of ferronickel up to 26.94 μm. The combination of sodium sulfate and calcium sulfate as additives could enhance the nickel content and recovery in ferronickel by the mechanism of segregating the nickel and iron from the magnesium silicates phase in saprolite and providing the formation of low-melting point phase of troilite promotes the aggregation of ferronickel particle, respectively.