FUEL
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2020
·
IF 5.578
Hao Sun,Kang Sun,Fei Wang,Yanyan Liu,Linfei Ding,Wei Xu,Yunjuan Sun,Jianchun Jiang
This study reports a one-step facile synthesis of a novel heterogeneous granule base catalyst, dubbed CaO/AC that contains small calcium oxide (CaO) nanoparticles embedded within hierarchical activated carbon (AC). The CaO/AC hybrid exhibited a 98.59 wt% fatty acid methyl esters yield, with 89.75% less catalyst compared to pristine CaO. In addition, the CaO/AC granular catalyst, which was easily recovered without any post-treatment, presented sustainable catalytic activity after two cycles of transesterification. The calcium cations penetrated into the cell wall of coconut shell by vacuum impregnation, and the carbonization of cell wall suppressed the agglomeration of calcium compound, which was essential for the catalytic self-activation of Ca-doped coconut shell. The pyrolysis atmosphere and dwelling time were investigated to demonstrate the dual function of calcium. Owing to the catalytic effect of Ca during the self-activation process, the hierarchical activated carbon with improved mesopores was manufactured. On the other hand, CaO nanoparticles with an average size of 14.7 nm were in-situ encapsulated within the mesopores of hierarchical carbon matrices. The additional formation of mesopores and high dispersion of CaO nanoparticles were responsible for the enhanced inner mass transfer and the number of accessible alkaline sites in transesterification of triglycerides, leading to the high catalytic activity and stability of CaO/AC.
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高影响因子
CERAMICS INTERNATIONAL
·
2020
·
IF 3.83
Mithun Nath,Shengqiang Song,Ning Liao,Tengteng Xu,Hang Liu,Himansu Sekhar Tripathi,Yawei Li
Obtaining a stable Cr 3+ phase at higher temperatures in the presence of hydraulic calcium aluminates (the phases found in calcium aluminate cement, CAC) in the Al 2 O 3 –CaO–Cr 2 O 3 system remains a significant challenge in many application areas, as the formation of toxic, carcinogenic, and water-soluble Cr 6+ compounds often occur. To address the issue, recently, we synthesized a high-temperature stable Cr 3+ ternary compound (CaAl 2 Cr 2 O 7 ) with space group P3 (143). In the present work, we investigated the formation-stability of CaAl 2 Cr 2 O 7 with in-situ calcium aluminate phases at 1500 °C under the CO 2 atmosphere in the Al 2 O 3 –CaO–Cr 2 O 3 system through solid-oxide reactions route varying Cr 2 O 3 content (at constant Al 2 O 3 :CaO ratio). It co-existed with hydraulic calcium aluminates and other phases over the full investigated composition range of 2.76–68.3 mol% Cr 2 O 3 (5–80 wt%). Apart from CAC phases (CaAl 2 O 4 , CaAl 4 O 7 ), major Cr 3+ -phases are CaAl 2 Cr 2 O 7 and (Al,Cr) 2 O 3 while (α,β)-CaCr 2 O 4 and Ca(Al,Cr) 12 O 19 formed as minor phases. At a constant Al 2 O 3 :CaO ratio of 5.6:4.4 mol% (7:3 wt%), the formation of the CaAl 2 Cr 2 O 7 phase increases with Cr 2 O 3 content (up to the investigated composition of 26.43 mol%) and then decreases gradually. The solid solubility of Al and Cr in the CaAl 2 Cr 2 O 7 phase limited over a narrow range, and presumably dependent more on heat treatment condition rather than composition as reflected from the lattice parameter calculations. Though XRD revealed the presence of only Cr 3+ -phases in the partial CO 2 atmosphere, however, traces of Cr 6+ could be detected using XPS and leaching tests. However, leachable Cr 6+ content (0.095–1.252 mg/L) were much below the United States Environmental Protection Agency (US-EPA) permissible limit of 5 mg/L. The formation mechanism of the CaAl 2 Cr 2 O 7 and other phases with plausible reactions were also discussed.
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高影响因子
WASTE MANAGEMENT
·
2023
·
IF 8.1
Danni Li,Rui Shan,Jing Gu,Yuyuan Zhang,Xianhai Zeng,Lu Lin,Haoran Yuan,Yong Chen
To relieve the secondary contamination of heavy metals (HMs), the synergistic effect of co-pyrolysis of textile dyeing sludge (DS)/litchi shell (LS) and CaO on the migration of HMs was demonstrated in this study. The proportions of Cu, Zn, Cr, Mn, and Ni in the F4 fraction increased to 75%, 55%, 100%, 50%, and 62% at the suitable CaO dosages. When 10% CaO was added, the RI value of DLC-10% was reduced to 7.89, indicating low environmental risk. The characterizations of the physicochemical properties of biochar provided support for the HMs immobilization mechanism. HMs combined with inorganic minerals or functional groups to form new stable HMs crystalline minerals and complexes to achieve immobilization of HMs. The pH value and pore structure also play an important role in improving the immobilization performance of HMs. In conclusion, the results provided a new direction for the subsequent harmless treatment of HMs-enriched waste.
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DOI
PubMed
高影响因子
POWDER TECHNOLOGY
·
2023
·
IF 5.2
Yuxiang Cheng,Zhongjie Shen,Feng Lv,Dayang Wan,Yongchuan Gao,Yiru Yang,Haifeng Lu,Zhenghua Dai,Haifeng Liu
During the Ca(OH) 2 /CaO thermochemical energy storage process, the cyclability of reactions and the consolidation properties of powder storage are important issues to consider. In this study, experiments were conducted to assess the evolution of reaction conversion, particle size and penetration resistance of Ca(OH) 2 /CaO powder fixed bed. The results revealed that the final conversions of both the hydration and dehydration reactions stabilized between 70 and 80%. The particle size distributions of Ca(OH) 2 increased initially and then decreased with the increasing cycle number and degree of dehydration. The dehydration conversion was the dominant factor for changing Ca(OH) 2 bed penetration resistance force. The particle size and penetration resistance of the CaO bed remained stable during long-term storage at high temperatures. The theoretical analysis of the inter-particle forces agreed with the trend of the experimental results, with particle size and moisture content being the main factors affecting cohesion.
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Journal of Materials Chemistry A
·
2018
·Vol. 6
·期 8
·3462-3470
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IF 9.931
Rui Han,Jihui Gao,Siyu Wei,Yanlin Su,Yukun Qin
High-temperature sorption of CO2via calcium looping is a promising technology for the implementation of carbon capture and storage (CCS). However, the major drawback of this technology is the rapid deactivation of CaO sorbents due to sintering. Here, a facile and cost-effective limited-space metal organic chemical vapor deposition approach is proposed to develop CaO-based sorbents exhibiting a very high and cyclically stable CO2 uptake. The TEM results show that Al2O3 nanoparticles (4–8 nm) are uniformly coated onto CaO crystalline grains, thus effectively inhibiting the sintering of sorbents. After 20 severe cycles, the synthetic sorbent, stabilized by 10 mol% Al2O3, exceeded the CO2 uptake of the benchmark CaO by more than 300%. Furthermore, the influence of Ca-based precursors on the synthetic sorbent's cyclic CO2 uptake was established. The result shows that the sorbents synthesized from different Ca-based precursors all demonstrate high cycling stability, which means that low-cost and high-performance sorbents can be synthesized through selecting a low-cost Ca precursor, such as CaCO3.
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高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Mithun Nath,Shengqiang Song,Hang Liu,Yawei Li
Despite huge potential, Al 2 O 3 –CaO–Cr 2 O 3 system has been one of the least investigated one due to the generation of carcinogenic and toxic Cr(VI) compounds. Herein, we investigated the system under air atmosphere varying Cr 2 O 3 while keeping Al 2 O 3 :CaO ratio constant in order to identify the Cr(VI) dominant region, eventually to avoid it. The Ca 4 Al 6 Cr VI O 16 phase predominantly formed in the air atmosphere with Cr 2 O 3 content up to ∼12 mol%. However, an unprecedented Cr(III) phase appeared under air at higher Cr 2 O 3 content (26.43 mol%). We then synthesized the new polycrystalline ternary Cr(III) compound (CaAl 2 Cr 2 O 7 ) at 1500 °C under air atmosphere for the first time. A trigonal symmetry of hexagonal crystal family with space group P3 (143), lattice parameters a = b = 7.7909 Å and c = 7.6506 Å were determined from the X-ray powder diffraction pattern study. Electron microscope studies revealed uniform hexagonal microcrystals with similar lattice parameters. Most significantly, the binding energies of 586.1 and 576.2 eV for Cr2p 1/2 and Cr2p 3/2 respectively implied the +3 oxidation state of Cr in this compound.
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高影响因子
Journal of Cleaner Production
·
2024
·
IF 9.7
Zhihui Shen,Tiantian Wu,Jianlong Wang,Song Mao,Xianchen Wang
Efficient pretreatment of fine-disseminated gold ore is a challenge in effective gold extraction due to the invisible occurrence of the most encapsulated gold. In this study, we investigated the mechanism of co-pretreatment with eco-friendly CaO and Na 2 CO 3 to improve gold extraction from fine-disseminated gold ore using element content and valence measurement, phase composition analysis, micromorphology and structure characterization, and thermodynamic calculation . The results indicated that more than 75% of gold was encapsulated in pyrite, quartz and calcite . The gold leaching rate evidently increased with the reagent content and slurry temperature of the pretreatment , reaching a maximum of 86.55% at 60 °C and CaO and Na 2 CO 3 concentrations of 16 and 32 g/L, respectively. At lower concentrations of OH − or CO 3 2− , pyrite oxidation and quartz corrosion were both limited. Interestingly, at higher concentrations of OH − and CO 3 2− , pyrite was ultimately converted to Fe 2 O 3 and SO 4 2− under aerobic conditions ; meanwhile, partial dissolution products of quartz reacted with the intermediates of pyrite oxidation, generating a new phase of Fe 2 SiO 4 . In addition, the soluble intermediate ferric carbonate complexes, formed by the induction of sufficient CO 3 2− , inhibited the accumulation of the passivation layer on the pyrite surface, resulting in constant oxidation of pyrite. Furthermore, the oxidation of pyrite was the maximum at 60 °C, but limited at 90 °C due to the hindrance of oxidation product coating. As a result, the phase transition of gold-bearing pyrite and quartz could be enhanced by the synergistic pretreatment of CaO and Na 2 CO 3 , resulting in an approximately 30% increase in both exposed gold content and gold leaching rate. This research proposes a promising green pretreatment with cost benefits for fine-disseminated gold ore and provides significant insights into phase transition regulation to improve gold leaching.
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高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2025
·
IF 9
Xuehua Shen,Ruirui Zhang,Ruiheng Zhang,Feng Xie,Han Hua,Pengju Wang,Feng Yan,Zewei Quan,Zuotai Zhang
CaO-based sorbents represent a highly viable solution for post-combustion CO 2 capture, with granulation commonly employed to mitigate elutriation in fluidized-bed reactors. Nonetheless, granulation markedly increases the density of these sorbents, thereby impairing their CO 2 uptakes and cyclic stability. In this study, a cost-effective strategy was developed by incorporating various pore-forming agents (agar, urea, straw, and biochar) into CaO-based particles (denoted as CaO+C+A, CaO+C+U, CaO+C+S, and CaO+C+B) to enhance their adsorption performance and durability. The findings revealed that the mechanical strength of uncalcined CaO-based particles remained unaltered by the incorporation of additives, whereas only the CaO+C+S particle maintained acceptable compressive strength (17.1 N) and a low attrition rate (6.6 %) after calcination. Compared with the CaO+C+A particle, the compressive strength of CaO+C+S particle was increased by 87.5 % and the attrition rate was decreased by 22.8 %. Meanwhile, the CaO+C+S particle exhibited the highest CO 2 adsorption performance, achieving 541 mg/g within 10 min, alongside outstanding cyclic stability, maintaining 217 mg/g after 20 cycles. This represents a 17.4 % increase in initial adsorption and a 25.3 % improvement in long-term stability compared to the control particle. These advancements are attributed to straw’s role in facilitating pore formation, refining CaO crystal size, and increasing the proportion of high-melting-phase (CaAl 4 Si 2 O 11 ). The first two factors markedly enhance the diffusion kinetics conditions and thus improving the CO 2 adsorption performance of CaO-based particles. Combined, these three factors enhance resistance to sintering by creating spatial physical barriers and increasing the melting point. This study offers a straightforward and cost-efficient modification approach to improve the CO 2 adsorption performance and durability of CaO-based particles.
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高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2020
·
IF 4.419
Woo Sung Yum,Jung-Il Suh,Do Hoon Kim,Jae Eun Oh
Recently, the combined use of calcium oxide (CaO) and calcium formate (Ca(HCOO) 2 ) has been proposed as an alternative activator for ground granulated blast furnace slag (GGBFS) (referred to as CaO-Ca(HCOO) 2 -activated GGBFS system). However, this clinker-free binder system produces calcium aluminate hydrate (C 2 AH 8 ), generally leading to the degradation of cementitious binder systems by its conversion to other phases. Thus, in this study, attempts to remove C 2 AH 8 from this system without losing the strength are suggested by the use of two additives (i.e., calcium sulfate (CaSO 4 ) and calcium nitrate (Ca(NO 3 ) 2 ), respectively). Results revealed that the above-mentioned additives completely remove C 2 AH 8 in the initial curing stage via its conversion to ettringite or NO 3 - and NO 2 -AFm, respectively. In addition, the additives reduced the extent of the total shrinkage and the standard deviation of strength results of triplicate samples. However, CaSO 4 exerted a beneficial effect on the strength, while Ca(NO 3 ) 2 exerted a marginal or detrimental effect on the strength. Therefore, this study suggested a new mixture form of an activator, comprising CaO , Ca(HCOO) 2 , and CaSO 4 , to activate GGBFS for maintaining strength without the conversion issue of C 2 AH 8 .
研究领域:
建筑材料学
·
材料科学
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高影响因子
Catalysts
·
2026
·Vol. 16
·期 8
·728
·
IF 4.5
Yao He,Ziming Mo,Jingyong Liu,Zhuowen Xie
Steam gasification of woody waste represents a sustainable pathway for addressing environmental issues with energy recovery. However, challenges such as low hydrogen content and high tar yield severely limit the gasification efficiency and hinder its large-scale application. In this study, a composite Ni/CaO catalyst was developed to enhance the yield of H2-rich syngas in woody waste gasification, with Ni loading serving as the active site for catalytic cracking and CaO support as the CO2sorbent for sorption-enhancement. Ni nanoparticles ranging from 18 to 28 nm in diameter are uniformly distributed on the CaO support. At 700 °C, Ni/CaO with 10 wt.% Ni loading enables the 455.4 mL/g H2yield with an H2/CO ratio of 1.93, representing increases of 137% and 230%, respectively, compared to non-catalytic conditions. Meanwhile, the tar yield was 12.1 wt.% with an aromatics selectivity of 37%, corresponding to reductions of 50.2% and 54%, respectively. Characterizations confirmed that Ni particles were uniformly distributed on the support in the form of metallic Ni. The Ni active sites promote syngas production by facilitating the cleavage of C-C and C-H bonds in volatiles, while the CaO support enhances H2generation by shifting the water–gas shift reaction equilibrium forward. This study provides a promising strategy for enhancing hydrogen-rich syngas production from woody waste gasification.
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高影响因子
JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
·
2026
·
IF 7.1
Yong-hong Niu,Yuan Tian,Lifei Yang
Hydrogen-rich syngas was produced from co-gasification of CS and CG. • 4Ce-8Ni/C-CaO markedly enhanced H 2 formation and syngas quality. • The maximum H 2 content reached 59.71 mol%. • Ce promoted Ni dispersion, oxygen vacancy formation, and coke resistance. The catalytic co-gasification of agricultural residues and coal-derived solid wastes offers an industrially promising route for converting low-value carbon resources into hydrogen-rich syngas. In this study, a Ce-Ni/C-CaO composite catalyst was prepared by impregnation and applied to the steam-assisted co-gasification of corn stover (CS) and coal gangue (CG) in a two-stage fixed-bed system. The effects of metal loading, feedstock ratio, temperature, and steam flow rate were investigated, the structure-performance relationship of the catalyst was further examined using XRD, SEM/BET, TEM/STEM-EDS, XPS, H 2 -TPR and O 2 -TG analyses. Under the optimal conditions of CS:CG = 5:5, pyrolysis at 850 ℃, reforming at 900 ℃, and a steam flow rate of 1 mL/min, the 4Ce/8Ni-C/CaO catalyst achieved an H 2 content of 59.71 mol% and a total gas yield of 19.13 mmol/g and an H 2 /CO ratio of 5.22. Characterization results indicated that the Ce species regulated the distribution of surface oxygen species, enhanced oxygen mobility, promoted the Ce 4+ /Ce 3+ redox cycle, and influenced the evolution of catalyst pore structure during the reaction. Download: Download high-res image (221KB) Download: Download full-size image
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高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2025
·
IF 13.2
Tong Luo,Mingyang Houding,Cong Luo,Yi Zhang,Xiaoshan Li,Fan Wu,Liqi Zhang
This study presents a dual-fluid atomization spray pyrolysis (SP) synthesis to fabricate porous hollow spherical CaO heat carriers for thermochemical energy storage. Key preparation conditions, including solution concentration, molar ratio of citric acid to Ca 2+ (CA/Ca 2+ ratio), and pyrolysis temperature were systematically analyzed for their effects on cyclic energy storage/release performance, particle size, micromorphology, crystallite size and pore structure via simultaneous thermal analyzer (STA), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and N 2 isothermal adsorption-desorption methods. Results indicate that higher solution concentrations and CA/Ca 2+ ratios increased particle size and promoted surface grains coalescence. Concentration ≥2 mol∙L −1 or CA/Ca 2+ ratio ≤0.5:1 degraded cyclic performance, and the optimal values are 1 mol∙L −1 and 1:1. Pyrolysis temperature significantly influenced the microstructure by influencing the pyrolysis mechanism: At 400 °C, spray drying dominated, forming hollow spheres with uncoalesced surface grains. At 500–600 °C, mesoporous structure formed with enhanced grain coalescence. At 700–800 °C, violent pyrolysis produced irregular, macroporous particles with high initial but rapidly declining performance. The optimal temperature at 600 °C yielded CaO heat carriers with a high specific surface area of 33.24 m 2 ∙g −1 , achieving 92.8 % initial carbonation conversion and a 30-cycle accumulative energy storage density of 46.13 kJ∙g −1 , which is 2.33 times higher than commercial CaO. Correlation analysis identified the specific surface area, total pore volume, and mesoporous volume fraction as key factors influencing post-cycling carbonation conversion and accumulated energy storage density. This work demonstrates SP synthesis as a scalable approach to tailor CaO microsphere for enhanced thermochemical energy storage.
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