In this paper, the oxygen supplied properties of NiO/NiAl2O4 synthesized via different methods were investigated Imp OCs showed the highest effective oxygen amounts of 1408% (932%(NiO) and 476% (NiAl2O4)) and medium oxygen releasing rate via CO-TGA The O transfer rate of OCs synthesized with the precipitation method is slow due to the big particle size The supplied oxygen content is much less at the first stage for OCs, because NiO is inside the NiAl2O4, and the strong interaction is between NiO and NiAl2O4 The supplied O rate of Imp OCs is proper (not too fast or too slow) due to the uniform distribution and moderate particle size of NiO, and there is a proper interaction between NiO and NiAl2O4 The CH4 chemical looping re-forming varied from the full oxidation (CH4 → CO2) to partial oxidation (CH4 → CO) followed by cleavage reaction (CH4 → H2 + C), depending on the content of effective supplied oxygen amount in OCs Moreover, it also proved that CO-TGA and CH4 chemical looping re-forming in the 

Supplied Oxygen Properties of NiO/NiAl2O4 in Chemical Looping Re-Forming of Biomass Pyrolysis Gas: The Influence of Synthesis Method

Enrichment of Hydrogen Production from Biomass‐Gasification‐Derived Syngas over Spinel‐Type Aluminate‐Supported Nickel Catalysts

In 2021, global alumina production reached over 135 million tons and discharged approximately 200 million tons of red mud, leading to severe environmental safety hazards. More than 70% of raw materials originated from gibbsitic bauxite. This work reviews existing and potential process from open literature to treat gibbsitic bauxite and reduce red mud discharge from the alumina production process, which are divided into two categories. The first strategy involves non-Bayer methods such as smelting reduction, reduction roasting, sub-molten salt, ammonium sulfate roasting, acid leaching, and calcification–carbonation. The current obstacle to implementing these methods is the lack of economics, making industrial application challenging. The second potential industrial application strategy is to modify the current Bayer process, with critical measures involving the enhancement digestion of inert aluminum-bearing minerals, dissociation and recovery of iron minerals, and separation of desilication products. Analyzing the reaction mechanism and process flow clarify that the modified Bayer method is more favorable to the cost-effectively and synergistic extraction of aluminum, iron, and other elements. The red mud obtained by the modified Bayer process can be efficiently utilized. Therefore, a mini-summary of the areas where red mud is expected to be substantially dissipated (e.g., the steel industry, cement building materials, and ecological restoration of red mud stockpiles) is provided. The review can advance the current technology on the comprehensive utilization of gibbsitic bauxite, especially process discharge reduction approaches and large-scale abatement ways for red mud. Our results can contribute to the future development of sustainable green alumina production. 

Toward sustainable green alumina production: a critical review on process discharge reduction from gibbsitic bauxite and large-scale applications of red mud

Preparation of Macro-Porous NiAl2O4 as Catalytic Support for Synthetic Natural Gas Synthesis in Fluidized-Bed Process

In this study, aluminum hydroxide (Al(OH)3) was synthesized by Bayer process and sodium contained in Al(OH)3 was removed with the acid solution such as HCl and acetic acid for the synthesis of high purity alumina. The bauxite produced in Queensland of Australia was used for the production of alumina by Bayer, and was crushed to a particle size of below 10 um by attrition mill. The crushed bauxite was treated in sodium hydroxide solution of 5 N for the elution of aluminum component. The elution of aluminum from bauxite was carried out at 140 ℃ and 3.4 atm in autoclave. The sample solution was separated to the red mud and liquid solution by filter paper. The elution of aluminum from bauxite was confirmed with changing a structure and alu- minum content in both bauxite and red mud analyzed by XRD and EDX. Aluminum contained in the separated solution was crys- tallized to Al(OH)3 with the addition of aluminum hydroxide used as the seed material. Al(OH)3 powder obtained during the crys- tallization process was purified by several times washing with distillated water. It was also confirmed that the sodium remained in Al(OH)3 powder is removed with acid solution. The purity of Al(OH)3 powder produced in this study was 99.3% and the content of sodium was reduced to approximately 0.009% after the acid treatment.

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Park No-Kuk

Papers

Preparation of Macro-Porous NiAl2O4 as Catalytic Support for Synthetic Natural Gas Synthesis in Fluidized-Bed Process

Removal of Sodium Contained in Al(OH) 3 Synthesized by Bayer Process