JOURNAL OF SUPERCRITICAL FLUIDS
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2025
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IF 4.4
Wei Yang,Cong Cong Wang,Lingjun Wang,Li Bao,Fan Yang,Shengji Wu,Lei Che
The hydrolysis mechanism of ball milled bamboo impregnated with deionized water (B-ball), H 2 SO 4 (B-H 2 SO 4 ), HCl (B-HCl) and CH 3 COOH (B-CH 3 COOH) in subcritical water was investigated in the present study. Various mechanochemical reactions were induced during acid-associated mechanical milling and bamboo with improved solubility, reduced thermal stability and solubility was obtained. Acid-associated mechanical treatment also significantly affected the hydrolysis behavior of bamboo in subcritical water. The hydrolysis kinetics of pretreated bamboo could be well expressed by the Coats-Redfern method. The acid strength dominated the hydrolysis of bamboo during ball milling and subcritical water treatment. H 2 SO 4 and HCl possessed the highest ability to dissociate the glycosidic bond and holocellulose-lignin chemical linkages. The above ability, together with their catalytic effects resulted in the lower activation energies required to initiate the hydrolysis of B-H 2 SO 4 (38.87 kJ mol −1 ) and B-HCl (38.23 kJ mol −1 ) compared with those of raw bamboo (74.34 kJ mol −1 ), B-ball (104.42 kJ mol −1 ) and B-CH 3 COOH (90.65 kJ mol −1 ) in subcritical water. The cleavage of holocellulose-lignin chemical linkages liberated the polycondensation of monomer and hydrolysable oligomers from holocellulose for glucose char and aromatic-linked polymer char production, leading to the increase of solid residue yield at elevated reaction temperature. It also promoted the glycosidic bond cleavage and ring scission reactions during hydrolysis in subcritical water, resulting in the improved yields of carbohydrate, 5-hydroxymethylfurfural and furfural.
研究领域:
林业科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2023
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IF 4.2
Yanni Guo,Jiayao Qi,Fei Wang,Binbin Fan,Wenming Hao,Ruifeng Li
Two industrial Y zeolites were treated sequentially by steaming and citric acid to investigate the Al migration and acidity of the modified Y zeolites. Even though the two parent Y zeolites displayed similar properties including crystallinity, Si/Al ratio, and textural structure, they showed different acidic and textural properties upon identical post-treatments by steaming and citric acid due to the different Al migration rules, resulting in their different activity and cracking ability in the methylcyclohexane transformation. Steaming treatment performed the prominent dealumination, leading to the increase of the framework Si/Al ratio from ca. 2.5 to ca. 5.0 and the formation of extra-framework Al species. During steaming treatment, the dealumination is related with the transformation from Al(IVb) to Al(V). The following citric acid leaching hardly removed the framework Al but removed the extra-framework Al species that existed in the form of Al(V) readily and some residual Na+ ions. The remaining framework-associated Al species are related to the generation of Lewis acid sites.
研究领域:
材料科学
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催化化学
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Communications
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2024
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IF 3.7
He Lian,Yuqiong Zhao,Liping Wang,Ying Wang,Guojie Zhang,Yongfa Zhang
This study developed a low-corrosive method for preparing porous carbons with a concentrated pore distribution for CH 4 /N 2 separation. Pine chips were impregnated with H 3 PO 4 and activated with CO 2 or C 6 H 5 K 3 O 7 to obtain microporous carbon. The differences in physical structure and surface chemistry of the porous carbons were analyzed to explore their impact on the CH 4 adsorption properties. The carbonization mechanism of pine chips was preliminarily explored. The results showed that H 3 PO 4 impregnation caused the pine chips to swell and form low molecular compounds, which promoted deeper penetration of C 6 H 5 K 3 O 7 into the carbon matrix. Further etching of K + promoted the formation of narrow microporous structures and introduced extra oxygen groups on the material surface. The CH 4 adsorption performance of porous carbon is closely related to the volume of ultramicropores between 0.45 and 0.7 nm, specific oxygen groups and specific surface area. Correspondingly, owing to its narrow pore size distribution , higher specific surface area (1341 m 2 /g) and greater microporous volume (0.57 cm 3 /g), HCK5.5 (C 6 H 5 K 3 O 7 addition ratio of 5.5) exhibited an impressive adsorption capacity of 1.77 mol/g for CH 4 at 298 K, surpassing that of most MOF and carbon materials. Moreover, the prepared adsorbents exhibited reasonable heat of adsorption and excellent regenerability. This study provides new insights into the development of narrow microporous carbon materials for CH 4 /N 2 separation.
研究领域:
材料科学
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
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2024
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IF 13.3
Zhu-yu Li,Le-ran Li,Sheng Li,Ding-can Wang,Qi Niu,Kai Li,Ji Liu,Qiang Lu
Calcium-based thermochemical heat storage (TCHS) is an economical and environmentally friendly technology for efficient heat storage. It can strengthen the flexibility in power systems of renewable energy and promote the recovery and storage of waste heat in energy-intensive industries. However, CaO/CaCO 3 is extremely prone to sintering at operational temperatures. Consequently, a cost-effective approach was proposed to synthesize calcium-based TCHS materials modified by pyroligneous acid (PA) impregnation and co-doping with dual transition metals. The heat storage performance, physicochemical property, and anti-sintering mechanism of synthesized CaO were comparatively examined. The sample prepared with a molar ratio of Ca: Co: Mn = 100:3:7 (PACa-Co3Mn7) exhibited an initial energy storage density of 1.76 MJ/kg, which gradually rose to 1.88 MJ/kg. After 20 cycles, the value decreased by only 4.39 % from its peak, indicating outstanding TCHS performance. Characterization results indicated that the specific surface area and pore volume of PACa-Co3Mn7 were 10.48 m 2 /g and 0.035 cm 3 /g, which were 2.34 and 2.69 times those of CaO stemmed from the calcination of limestone, respectively. The fruitful pores provided pathways for CO 2 diffusion within the CaO particles or CaCO 3 product layer. The uniformly distributed Co and Mn elements combined to form Ca 3 CoMnO 6 . Ca 3 CoMnO 6 could serve as the inert carrier that mitigated the grain-growth of CaO, thereby stabilizing the pore structure and resisting the sintering of PACa-Co3Mn7. Furthermore, density functional theory (DFT) calculations demonstrated that the free Mn and Co elements efficiently promoted the electrons transfer between CaO and CO 2 , which improved the reactivity of PACa-Co3Mn7. Therefore, CaO modified by PA impregnation and co-doping with dual transition metal is a promising candidate for the TCHS system.
研究领域:
材料科学
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能源工程
✓ 已验证
产品关联
DOI
高影响因子
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