ENERGY
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2024
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IF 9
Wei Yu,Chao Liu,Xijie Ban,Liyong Xin,Shukun Wang
When siloxanes are used as the working fluids of organic Rankine cycle systems, there is a possibility of air infiltration due to the large vacuum present in the condenser. To address this issue, experimental and simulation studies were conducted on the thermal stability and pyrolysis product characteristics of octamethyltrisiloxane (MDM) in the presence of air. The results indicated that air significantly promotes the decomposition of MDM at the temperatures above 250 °C. Air was helpful in increasing the formation of CH 2 O, CO, and CO 2 , and also enhanced polymerization of decomposition product of siloxane, leading to higher yields of MD 2 M, MD 3 M, MD 4 M, D 3 , D 4 , and D 5 . By combining reactive force field molecular dynamics (ReaxFF-MD) simulations with density functional theory (DFT) calculations, the microscopic mechanisms of MDM's oxidative decomposition by O 2 in air and H 2 O under humid conditions were elucidated. O 2 can easily combine with unsaturated Si atoms to form Si-O bonds, combine with CH 3 radicals to form C-O bonds, and undergoes hydrogen extraction reactions to initiate decomposition. H 2 O mainly undergoes initial decomposition through CH 3 radical hydrogenation and binding with unsaturated Si atoms. The generated O 2 H, O, and OH radicals tend to bind with Si atoms in molecules and radicals, facilitating polymerization reactions.
研究领域:
化学工程
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材料科学
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计算化学
✓ 已验证
产品关联
DOI
高影响因子
ENERGY
·
2023
·
IF 9
Wei Yu,Chao Liu,Luxi Tan,Qibin Li,Liyong Xin,Shukun Wang
The thermal stability and decomposition mechanism of octamethyltrisiloxane (MDM) were studied using a combination of experimental, ReaxFF simulation, and DFT calculation techniques. After heating MDM for 24 h at 250 °C and 1 MPa, the signature product CH 4 was detected, along with liquid products such as hexamethyldisiloxane (MM) and decamethyltetrasiloxane (MD 2 M). The decomposition rate of MDM remained relatively constant in the temperature range of 250 °C–320 °C but exhibited a sharp increase at 350 °C. Higher pressure was found to promote MDM polymerization. The oxygen (O) atoms displayed a large negative electrostatic potential , while the hydrogen (H) and silicon (Si) atoms exhibited a large positive potential. The electrostatic interaction facilitated the rearrangement reactions, with O and carbon (C) atoms being the most reactive for electrophilic and free radical reactions. The thermal decomposition of MDM initiated with the cleavage of Si–C bonds. Hydrogen extraction reactions between methyl radicals and MDM, as well as Si–O bond rearrangement reactions of demethylated radicals with MDM, further promoted MDM decomposition and the formation of CH 4 and siloxane oligomers . These findings are significant for the safe application of MDM as a working fluid in ORC system.
研究领域:
化学工程
·
材料科学
·
计算化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
·
2024
·
IF 5.8
Wei Yu,Xijie Ban,Chao Liu,Qibin Li,Liyong Xin,Zhengyong Huang,Shukun Wang
In actual organic Rankine cycle systems (ORCs), the inclusion of lubricating oil in the working fluid is nearly unavoidable. Under the condition of high-temperature operation, the presence of lubricating oil can potentially exacerbate the thermal stability of the working fluid. The impact of polyol ester (POE) and mineral lubricant on the thermal stability of octadethyltrisiloxane (MDM) is studied. Results indicate that both POE and mineral lubricant contribute to the decomposition of MDM to a certain extent. Specifically, at a 5.0% mass fraction of POE and mineral lubricant, MDM remains its stable at 230 °C and 210 ℃, respectively. However, as the mass fraction of lubricant increases, the decomposition of MDM intensifies, with mineral lubricant exhibiting a more pronounced effect compared to POE lubricant. Regarding pyrolysis products, the presence of lubricants leads to an increase in CH 4 , C 2 H 6 and C 2 H 4 gases. Furthermore, the addition of lubricant promotes the formation of siloxane oligomers , particularly MD 5 M to MD 9 M, and enhances the production of unidentified products. Compared to MDM, both POE and mineral lubricant molecules exhibit lower bond dissociation Gibbs free energies . The free radicals generated from lubricant decomposition are prone to hydrogen abstraction reactions with MDM to promote MDM decomposition. Moreover, ReaxFF simulation results demonstrate that lubricant molecules also enhanced the activation of MDM and increased its susceptibility to Si-C bond cleavage . Following the removal of the methyl group , the Si-O bonds in the radicals are more likely to break, leading to the formation of additional siloxane oligomers through Si-O bond recombination. Kinetic analysis reveals that the apparent activation energy of MDM decomposition drops from 134.4 kJ∙mol −1 to 110.8 kJ∙mol −1 as the mass fraction of n-hexadecane (model compounds for mineral lubricant) rises from 0% to 10.30%.
研究领域:
化学工程
·
能源科学
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材料科学
✓ 已验证
DOI
高影响因子
EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY
·
2024
·
IF 6
Yuxin Feng,Xuan Xuan,Yuemiao Hu,Jiaguo Lu,Zhiwen Dong,Ziqiang Sun,Hongying Yao,Lei Hu,Qikun Yin,Yi Liu,Hongbo Wang
Murine double minute 2 (MDM2) and homologous protein murine double minute X (MDMX) are p53 negative regulators that perform significant driving effects in tumorigenesis, and targeting these oncoproteins has became an efficient strategy in treating cancers. However, the definite antitumor activity and significance ordering of each protein in MDM family is still unclear due to the similar structure and complicated regulation. Herein, we identified two G-rich sequences ( G 1 and G 5 ) located in the promoter that could assemble the G-quadruplex to respectively inhibit and promote the transcription of the MDM2 and MDMX. Based on this target, we designed and synthesized a novel G-quadruplex ligand A3f and achieved the differentiated regulation of MDM protein. In triple-negative breast cancer (TNBC) cells, A3f could induce MDM2-dependent proliferation arrest and exhibit additive therapeutic effect with MDMX inhibitors. Overall, this study provided a novel strategy to regulate the transcription of MDM genes by targeting certain G-rich sequences, and discovered an active antitumor molecule for use in TNBC treatment.
研究领域:
肿瘤学
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分子生物学
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癌症治疗
✓ 已验证
DOI
PubMed
高影响因子
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