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In response to the needs of land backflow drainage reuse, a polymer with high saline water resistance and moderate temperature resistance was synthesized through optimization of synthesis processes such as monomer ratio and functional monomer content. A set of high saline variable-viscosity fracturing fluid was developed using the target product. The polymer that constitutes the fracturing fluid system is obtained by copolymerizing of acrylamide, acrylic acid, salt-resistant monomer 2-acrylamido-2-methylpropanesulfonic acid, temperature-resistant monomer N-vinylpyrrolidone, and hydrophobic monomer N-(4-ethylphenyl) acrylamide. The optimal synthesis conditions are: a ratio of acrylamide to acrylic acid of40 ∶12, a content of salt-resistant monomer at 30%, a content of temperature-resistant monomer at 15%,and a content of hydrophobic monomer at 0.5%. The variable-viscosity fracturing fluid composed of this polymer is suitable for backflow drainage. It has excellent viscosity enhancement performance in water with mineralization degree greater than 70 000 mg·L-1and calcium and magnesium ion concentrations greater than 5 000 mg·L-1, meeting the on-site adjustment of low, medium, and high viscosity systems.Experimental tests have shown that the fracturing fluid system has a drag reduction rate of over 70% and exhibits excellent performance in gel breaking and proppant carrying. The fracturing fluid was applied in more than 50 layers on site, and the construction effect was good.
Electrolysis of water for hydrogen production is a vital technology for the storage and conversion of renewable energy, where the high overpotential of the oxygen evolution reaction(OER) severely limits the overall efficiency. Covalent organic frameworks(COFs) have shown great potential in the field of electrocatalysis due to their excellent structural characteristics. However, their inherent poor electrical conductivity and limited active sites restrict their catalytic performance. In this work, a highly efficient non-pyrolyzed COF-based oxygen evolution catalyst was constructed by incorporating redox-active diarylamino units and metal active sites coordinated by bipyridine ligands into the COF. Experimental results/indicate that the Fe/Co-COF catalyst exhibits an overpotential of only 303 mV at a current density of10 mA·cm-2, which is superior to most non-pyrolyzed COF catalysts. It also maintains good stability after 2 000 cyclic voltammetry scans and 20 h of chronoamperometric testing. Further mechanistic studies indicate that the diarylamino unit can generate stable radical cations during the oxygen evolution reaction,which interact with the metal active sites coordinated by bipyridine ligands to participate in the OER process. This research offers new insights into the construction of COF-based catalysts that do not require thermal pyrolysis.
The rotary energy recovery device is the key energy-saving equipment of the reverse osmosis desalination system, and the friction pairs in the device are vulnerable parts, which need to be regularly maintained or replaced. To improve the maintenance-free period of the device, it is crucial to select the friction pair materials. Based on MVF-2ASW multi-functional vertical reciprocating friction and wear testing machine, the friction and wear characteristics of materials with different friction pairs were studied in the form of ring-ring sliding contact under water lubrication environment. Meanwhile, the worn surface morphologies of friction pairs were characterized to analyze their worn mechanisms. The results show that the friction and wear performance of LFPEEK-316L pair is the best under the rated working conditions of 200 N and 140 r·min-1, the friction coefficient is 0. 088 3, the specific wear rate is 5. 451 4× 10-7mm3·N-1·m-1, and the lining thickness of 2 mm can meet the requirements of 13 000 h maintenance-free cycle. The LFPEEK-316L pair can maintain its good friction and wear performance below 350 N. However, when the load increases to 400 N, its friction coefficient and specific wear rate rise sharply, and the worn mechanism changes from abrasive wear to adhesive wear. In the rotational speed range of 140 r·min-1to 280 r·min-1, the friction coefficient and specific wear rate of LFPEEK are always at the lowest level, and the surface wear condition does not deteriorate significantly with the increase of rotational speed.
The use of biomass-based platform molecules oxidation reaction(BOR) to replace oxygen evolution reaction can achieve both economic and safety improvement of green power for hydrogen production, which is important for China to achieve the goals of “carbon peaking” and “carbon neutrality” as soon as possible. Cobalt-based catalysts have received widespread attention not only for their excellent catalytic performance in BOR, but also for their advantages in terms of reserves and cost compared to noble metal-based catalysts. In this paper, the surface reaction mechanisms of cobalt-based catalysts and the oxidation reaction pathways of common biomass-based platform molecules such as glucose, glycerol,and 5-hydroxymethylfurfural are summarized. In addition, the synthesis methods and modification strategies of cobalt-based catalysts suitable for BOR have been systematically reviewed. Notably, the structurefunction relationship exhibited by cobalt-based catalysts in BOR is highlighted. Finally, the current status and future development of cobalt-based catalysts in BOR are prospected.
Although dual-terminal hydroxyl low-molecular-weight poly(2,6-dimethyl-1,4-phenylene ox-/ide)(LMW-PPO-2OH) is recognized as an ideal material for high-frequencyhigh-speed copper-clad laminates, complex synthesis processes, prolonged reaction durations and poor polymer dispersity significantly limit its practical application. In this work, LMW-PPO-2OH is synthesized using Cu(Ⅱ)-ionic liquid(IL) as catalyst via redistribution andin situcopolymerization strategies, effectively addressing the dispersity limitations inherent in conventional methods, which has good performance in terms of low molecular weight(Mn≤4. 1×103) and narrow polydispersity index(PDI≤1. 47). Spectroscopic analyses including FTIR,~1H NMR, and GPC confirm the successful incorporation of 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane(TMBPA) into the polymer chains, endowing LMW-PPO-2OH with dual terminal hydroxyl groups and low polydispersity. Meanwhile, the obtained LMW-PPO-2OH possesses good thermal stability(Td5%= 429. 55—439. 46 ℃), low dielectric constant(2. 55—2. 56, 1 MHz) and dielectric loss(2. 01×10-3—2. 77×10-3, 1 MHz), indicating that LMW-PPO-2OH has exceptional thermostability and dielectric performance for advanced thermosetting composites in high-frequency ~/high-speed copperclad laminates. This study provides new insight for preparing high-performance LMW-PPO-2OH applicable to high-frequency ~/high-speed copper-clad laminate substrates.
Cresol refining is an effective way to increase the added value of coal-based crude phenol and realize the efficient utilization of coal resources. However, the composition of coal-based cresol is complex, and a complete separation system has not been established. Therefore, understanding and mastering the development of cresol refining field is helpful to the development of efficient separation methods.Firstly, the challenges of cresol refining were introduced, and then the research progress of special distillation, adsorption, crystallization, alkylation and complexation methods on cresol refining was systematically introduced. Finally, the advantages and disadvantages of various separation methods were summarized, and the future research focus and development direction were summarized and prospected, so as to provide new methods and new ideas for the technical transformation and industrial upgrading of cresol refining.
To address the problem of low fluorine recovery during the dihydrate wet-process phosphoric acid production, this study systematically investigated the use of potassium sulfate(K_2SO4) as a precipitant for fluorine recovery. Based on single-factor experiments(reaction temperature 50 ℃, K_2SO4 dosage 1.5 times the theoretical amount and reaction time 60 min), response surface methodology was employed to optimize the process conditions and establish a mathematical model. The optimal parameters were determined to be a reaction temperature of 48 ℃, K_2SO4 dosage at 1.5 times the theoretical amount and a reaction time of 86 min, under which the fluorine recovery rate reached 85.5%. Characterization by XRD, SEM, and chemical analysis confirmed that the solid product was high-purity K_2SiF6( purity>98%), demonstrating the successful transformation of fluorine in wet-process phosphoric acid into a high-value-added chemical product, while the defluorinated phosphoric acid could be further utilized for the production of downstream products such as industrial-grade monoammonium phosphate. Kinetic studies indicated that the fluoride recovery reaction followed a second-order reaction kinetic model. This work provides both theoretical basis and process reference for the efficient recovery and resource utilization of fluorine from wet-process phosphoric acid.
Gas leaks on offshore platforms are highly dynamic,and conventional static assessments cannot capture the attendant time-dependent risks.To enhance real-time predictive accuracy,an accident pathway was first developed using fault-tree/event-tree logic;representative leak scenarios were identified accordingly,and 4 320 cases were simulated in FLACS to obtain the equivalent flammable gas volume Q9.A convolutional neural network(CNN) was then trained to predict the Q9 time series,achieving a validation MSE of 0.003 and R2=0.9968,with all prediction errors confined to(±30) %,thereby replacing time-consuming CFD calculations.The CNN-predicted Q9 values were fed as external evidence into a dynamic Bayesian network(DBN) to update,in real time,gas concentration,ignition probability and explosion probability;side-on overpressure was evaluated with the TNO multi-energy method to classify explosion severity.A normalised index RNORM(t) was finally introduced to produce continuous risk curves under various wind speeds.The proposed framework delivers second-orders computational speed while maintaining high predictive accuracy,providing effective support for dynamic leak-risk warning and response on offshore platforms.
The crystallization behavior of polyethylene glycol(PEG) has a significant impact on its mechanical, thermal, and solubable properties. This study prepared melt blended materials by adding three types of chlorides(sodium, potassium, calcium) to the molten state of PEG, and investigated the effects of the three chlorides on the crystallization properties of PEG. Differential scanning calorimetry(DSC)and polarizing optical microscope(POM) equipped with a hot stage were used to study the non-isothermal crystallization behavior, crystallization kinetics, crystal morphology, and growth rate of different samples. Then the effects of three chlorides on the molecular structure of PEG were studied using X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FT-IR). The research results indicate that all three types of chlorides can destruct the crystallization of PEG, among which KCl and NaCl only hinder PEG crystallization by impeding molecular chain segment movement. CaCl2 forms a coordination polymer with PEG, which affects the crystallization process. After adding 3% CaCl2 to PEG, the crystallization peak temperature decreased by 7 ℃ and the half crystallization time increased by 21. 8 s, with a significant increase in viscosity. Conductivity meter and FT-IR confirmed the complexation between PEG and CaCl2. As the mass fraction of CaCl2 increases, the crystallization temperature and crystallinity of the mixed system gradually decrease, and the complexation effect increases.
Using methyl acrylate(MAC), maleic anhydride(MA), and sodium allylsulfonate(SAS) as monomers, the reaction was conducted at 80℃ for 4 h with a monomer molar ratio ofn(MA) ∶n(SAS) ∶n(MAC)= 2. 0 ∶1. 0 ∶1. 0. The ternary copolymer scale inhibitor MAC-MA-SAS synthesized under these conditions exhibits excellent scale inhibition performance in aqueous systems. According to the national standard method GB/T 16632—2019, the average scale inhibition rate measured at an inhibitor concentration of 200 mg·L-1was 93. 56%. Its structure was analyzed via Fourier Transform Infrared Spectroscopy(FTIR), and its scale inhibition performance was evaluated using the static scale inhibition method.Calcium carbonate scale was characterized using X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM) to investigate changes in crystal structure and morphology before and after adding the MAC-MA-SAS polymeric scale inhibitor. Results indicate significant influence on calcium carbonate crystal growth: characteristic calcite peaks markedly decrease while vaterite and aragonite peaks emerge. Carboxyl groups in the copolymer effectively induce lattice distortion and chelation, while sulfonate and ester groups further enhance calcium carbonate scale inhibition.