CATALYSIS COMMUNICATIONS
·
2018
·
IF 3.463
Marzieh Ghadamyari,Somboon Chaemchuen,Kui Zhou,Michiel Dusselier,Bert F. Sels,Bibimaryam Mousavi,Francis Verpoort
Poly (lactic acid) (PLA) is extensively used as an eco-friendly compound for many applications. The synthesis of stereo-pure lactide, specifically l , l -lactide which is the most desired isomer for the synthesis of high-quality PLA is very important. In this work, various materials including MOFs and simple bases have been applied as catalysts for the Lactide synthesis. Herein we report the one-step synthesis of l , l -lactide with high selectivity and yield (99%) in the absence of racemization by applying a cost-effective Cs 2 CO 3 catalyst. The novel described procedure is even expected to be very efficient for industrial applications.
研究领域:
材料科学
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化学工程
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2018
·
IF 3.193
Lidong Feng,Songyang Feng,Xinchao Bian,Gao Li,Xuesi Chen
In order to obtain the mechanisms of the pyrolysis reaction that poly (lactic acid) (PLA) gives lactide in the presence of Sn, the four types of low molecular weight PLAs (L-PLA) with different end-groups were prepared, including HO-L-PLA-COOH, R-L-PLA-OH, R-L-PLA-COOH, and R-L-PLA-R, and depolymerized by thermogravimetry at different heating rates. As for the pyrolysis reactions of the L-PLAs, their activation energy ( E a ) were estimated by the several isoconversional model-free methods and their kinetic models were also explored by the Malek method. The random degradation behavior of L-PLAs was determined by the plots of ln { − ln [ 1 − ( 1 − w ) 0.5 ] } vs. 1/T for experimental data from TG for L-PLAs and model reactions. The experimental results showed that the E a values and the possible kinetic models for the pyrolysis reactions of the L-PLAs were different due to the different end-groups and thereof the mechanisms for the pyrolysis reactions of PLA that give lactide were proposed under the catalysis of Sn. The pyrolysis reactions of R-L-PLA-OH and R-L-PLA-R trend to be controlled by a single kinetic model. The pyrolysis reactions of HO-L-PLA-COOH and R-L-PLA-COOH are more complex and controlled by not less than two kinetic processes. The pyrolysis reaction of PLA selectively produces lactide through the unzipping and intramolecular transesterification reactions, including the backbiting reaction caused by the Sn-carboxylate and Sn-alkoxide chain ends, which are directly formed from the hydroxyl and carboxyl end-groups of PLA, and the lactide selective elimination at the random position of the polymeric backbone.
研究领域:
材料科学
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化学工程
✓ 已验证
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2024
·
IF 4.8
Xue-Juan Chen,Xi Hong,Bing Zhan,Xiu-Feng Hou
A series of nanosized “rice ball” like hierarchical beta zeolite aggregates (RBZ x A y , x = 6, 9, 12 or 15; y = 2, 4 or 6) with hierarchical structures are successfully synthesized via gel aging and hydrothermal method without mesoporous template. The as-prepared RBZ x A y zeolites possess two ranges of inter-crystalline mesoporous that formed by zeolite nanoparticles aggregation compared to the non-aged samples (B 12 Z 4 ). The effects of Si/Al ratio and crystallization time on the morphology, structure and surface acidic properties of RBZ x A y were systematically investigated. Meanwhile, RBZ x A y as catalysts were applied in the conversion of lactic acid (LA) to lactide (LT) to investigate their catalytic performance. Benefitting from smaller crystal size, hierarchical structures and higher acid content, the representative catalyst (RBZ 12 A 4 ) exhibited outstanding catalytic activity that the LA conversion was high to 98 % and the LT yield up to 94 %. In addition, RBZ 12 A 4 presented perfect regeneration ability after 10 times recycles. This work provides an effective and facile route to directly synthesis nanocrystals aluminosilicate zeolite with hierarchal structure, and constructs an approach for efficiently converting LA to LT, it has greatly significance for the development of polylactic acid industry.
研究领域:
化学
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材料科学
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催化
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高分子科学
✓ 已验证
DOI
高影响因子
JOURNAL OF POLYMER RESEARCH
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2015
·Vol. 22
·期 5
·1-7
·
IF 1.92
Teng Lijing,Xu Xiaohong,Nie Wangyan,Zhou Yifeng,Song Linyong,Chen Pengpeng
Star-shaped polylactide (PLLA) is a potential candidate in many biomedical applications owing to its short degradation time; however, non-bioresorbable polyols have been used in most syntheses of star-shaped polylactide and these are a potential hazard. In this work, reaction of natural xylitol with l -lactide (LLA) was used to synthesize a star-shaped polyester via ring-opening polymerization. The chemical structures of the prepared star-shaped PLLA were characterized by means of 1 H NMR and gel permeation chromatography (GPC). The crystallization behaviors of the polymers were examined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD curves of all the star-shaped PLLA based on various xylitol molar fractions were similar, but the crystallinity decreased with the increase of the xylitol molar fraction. These polymers were amorphous when the molar fraction of xylitol was higher than 6 %, whereas they were semicrystalline when the molar ratio of xylitol fell below 6 %. Finally, the degradation of the star-shaped PLLA was studied in phosphate buffer solution (pH 7.4) at 37 °C, which indicated that the degradation rate of polymers increased with the increase of xylitol molar fraction.
研究领域:
材料科学
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生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
APPLIED ORGANOMETALLIC CHEMISTRY
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2016
·Vol. 31
·期 9
·e3688
·
IF 2.452
Baolong Wang,Jianing Zhang,Huanqin Zhao,He Huang,Junpei Zheng,Liying Wang,Junmin Sun,Yongfeng Zhang,Zhenzhu Cao
Monomeric bis(isopropoxy) titanium complexes LTi(O i Pr) 2 (L = ─ OC 6 H 2 –4-R 1 –6-R 2 –2-CH 2 N[(CH 2 ) 2 N(R 3 ) 2 ]CH 2 –4-R 4 –6-R 5 -C 6 H 2 O ─ , R 1 = R 2 = t Bu, R 3 = Et, R 4 = R 5 = Cl, (L 1 )Ti(O i Pr) 2 ; R 1 = R 2 = Me, R 3 = Et, R 4 = R 5 = Me, (L 2 )Ti(O i Pr) 2 ; R 1 = R 2 = t Bu, R 3 = Et, R 4 = OMe, R 5 = t Bu, (L 3 )Ti(O i Pr) 2 ; R 1 = R 4 = OMe, R 3 = Et, R 2 = R 5 = t Bu, (L 4 )Ti(O i Pr) 2 ; R 1 = R 2 = t Bu, R 3 = Me, R 4 = OMe, R 5 = t Bu, (L 5 )Ti(O i Pr) 2 ) supported by amine bis(phenolate) ligands were synthesized and characterized using NMR spectroscopy and elemental analysis. The solid-state structure of (L 3 )Ti(O i Pr) 2 was determined using single-crystal X-ray diffraction. (L 1 –5 )Ti(O i Pr) 2 were all found to initiate the ring-opening polymerization of l -lactide and rac -lactide in a controlled manner at 110–160°C. As shown by kinetic studies, (L 1 )Ti(O i Pr) 2 polymerized l -lactide faster than did (L 2 –5 )Ti(O i Pr) 2 . In addition, good number-average molecular weight and narrow polydispersity index (1.00–1.71) of polymers were also obtained. The microstructure of the polymers and a possible mechanism of coordination–insertion of polymerization were evidenced by MALDI-TOF and 1 H NMR spectra of the polylactides.
研究领域:
有机化学
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高分子化学
✓ 已验证
DOI
高影响因子
Asia-Pacific Journal of Chemical Engineering
·
2025
·
IF 1.6
Xiaoxia Ma,Huijian Guo,Yujia Sui,Yun Li,Jilin Cao
Lactide, a key raw material for polylactic acid, is prone to hydrolysis during synthesis from lactic acid using zeolite beta, reducing yield. To address this issue, zeolite beta with hydrophobic pores was synthesized by template-free method with in situ silicon source modification by tetraethoxyfluorosilane (TEFS). The effect of TEFS addition on the morphology, acidity, and wettability of the synthesized zeolite beta was investigated. The modification with F groups increases the total acid amount and the strength of strong acid sites, especially the Brønsted acid sites; simultaneously, the hydrophobicity of pores was also improved. F group–modified zeolite beta achieved a lactide yield of 84%, significantly higher than the 70% yield of unmodified zeolite beta. This enhancement could be attributed to the increase in Brønsted acid sites and the improvement of the hydrophobic pore microenvironment. This could improve the catalytic reaction activity; additionally, the rapid removal of water from near acid sites could promote the forward movement of the reaction equilibrium and inhibit the hydrolysis of lactide. This work provides a new approach to improve the hydrophobicity of the pores of zeolites as solid acid catalysts, which is beneficial to the efficient production of lactide.
研究领域:
催化化学
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材料科学
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绿色化学
✓ 已验证
产品关联
DOI
高影响因子
ACS Sustainable Chemistry & Engineering
·
2023
·
IF 8.4
Zhihao Zhang,Jiayu Xue,Zewen Sun,Jiale Wang,Guochao Xu,Ye Ni
Hydrogen-borrowing redox-neutral cascade reactions are promising for the synthesis of lactones from the perspective of sustainable chemistry. In this study, a novel NADPH-dependent Baeyer–Villiger monooxygenase AjBVMO was identified from Acinetobacter johnsonii with a specific activity of 0.96 U·mg–1 in the oxidation of cyclohexanone into ε-caprolactone. To achieve cofactor matching, NADP+-dependent KpADHT215V and CgKR1 with high oxidative activities toward cyclohexanol and 1,6-hexanediol were constructed for developing “substrate-supplied” and “product-convergent” hydrogen-borrowing redox-neutral cascade reactions. The effects of buffer systems on the activities and spontaneous hydrolysis of ε-caprolactone and the ratios of ADHs and BVMO on the conversion rates were explored. In the “substrate-supplied” system employing KpADHT215V and AjBVMO, as high as 68.6 mM ε-caprolactone could be obtained from 100 mM cyclohexanol, with a maximum TOF of 7.2 min–1 and a TTN of 337. In the “product-convergent” system employing CgKR1 and AjBVMO, 115.1 mM ε-caprolactone was produced from 100 mM cyclohexanone, with a maximum TOF of 5.7 min–1 and a TTN of 757. The product-convergent system is more efficient than the substrate-supplied system. Moreover, these two redox-neutral cascade systems could also be applied in the synthesis of lactones with different chain lengths such as γ-butyrolactone and δ-valerolactone. This study established efficient redox-neutral cascade systems for the synthesis of lactones featuring a high atomic economy with only H2O as a byproduct.
研究领域:
生物化学
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可持续化学
·
酶工程
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产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2018
·
IF 3.141
Guocai Wang,Shigui Tang,Fei Cao,Hongli Wu,Honghua Jia,Ping Wei,Pingkai Ouyang
During the lactide producing process, volatile impurities, such as lactic acid and its dimer, are simultaneously distilled out with lactide. To remove these impurities, many post-treatments were needed. Herein, we present a novel approach to obtain high purity lactide by adding high-boiling-point alcohols to immobilize these volatile impurities. A series of high-boiling-point alcohols were screened and pentaerythritol was found to be the best immobilization reagent. When the molar ratio of lactic acid’s carboxylic group and pentaerythritol’s hydroxyl group was 15:1, lactide with 99% GC purity was directly distilled out and no traces of lactic acid and its dimer were detected. The results of HPLC-MS revealed that the distillation residues were esters of pentaerythritol with lactic acid or its oligomer. This indicated that volatile impurities were immobilized in distillation residues. The distillation residues were reused for 4 runs, and the purities of lactide were all over 98%.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2019
·
IF 3.621
Rui Feng,Suyun Jie,Pierre Braunstein,Bo-Geng Li
The ring-opening polymerization (ROP) of lactones is an effective method for the preparation of biocompatible and biodegradable aliphatic polyesters, for which the development of efficient organocatalysts with high activity and good controllability is highly desirable. A series of novel pyridyl-urea catalysts has been synthesized and applied in the solvent-free ROP of lactones and trimethylene carbonate. Combined with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), the pyridyl-urea/MTBD systems showed a fast and living/controlled behavior in the ROP, generating polymers with narrow molecular weight distributions. The influences of catalyst structure, type of base, pyridyl-urea/base ratio, feed ratio of monomer/initiator and reaction temperature on the catalytic properties were investigated. A possible mechanism was proposed on the basis of NMR titration and dilution experiments.
研究领域:
材料科学
·
有机化学
·
生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2017
·Vol. 41
·期 13
·5669-5677
·
IF 3.269
Baolong Wang,Huanqin Zhao,Liying Wang,Junmin Sun,Yongfeng Zhang,Zhenzhu Cao
Zirconium complexes (L2Zr, L = –OC6H2-4-R1-6-R2-2-CH2-N[(CH2)3-N(CH2CH2)2O]-CH2-4-R1-6-R2-C6H2O–, R1 = Me, R2 = tBu, complex 1; R1 = R2 = tBu, complex 2) containing two symmetrical amino-bis(phenolate) ligands were prepared. Moreover, titanium complexes (LTi(OiPr)2, L = –OC6H2-4-R1-6-R2-2-CH2-N[(CH2)3-N(CH2CH2)2O]-CH2-4-R1-6-R2-C6H2O–, R1 = Me, R2 = tBu, complex 3; R1 = R2 = tBu, complex 4) based on symmetrical amino-bis(phenolate) ligands were synthesized. These complexes were characterized by 1H and 13C NMR spectroscopy and elemental analyses. The solid-state structures of complexes 2 and 3 were determined by X-ray diffraction. Complexes 1, 2, 3, and 4 were highly active initiators for the ring-opening polymerization of L-lactide (L-LA) and rac-lactide (rac-LA). The experimental results show that complexes 1 and 2 are highly active and excellent catalysts for the immortal ring-opening polymerization (iROP) of L-lactide and rac-lactide in the melt state. The monomer-to-complex ratio reached 200 000/1, which is the highest feeding molar ratio of lactide so far, to the best of our knowledge. Meanwhile, a narrow polydispersity index (1.11–1.58) of polymers was obtained, and the number-average molecular weight approached 8.64 × 104 g mol−1. The turnover frequency (TOF) reached 6593 h−1, and the polymerization proceeded smoothly even in an air environment.
研究领域:
材料化学
·
有机化学
✓ 已验证
产品关联
DOI
高影响因子
BIORESOURCE TECHNOLOGY
·
2023
·
IF 11.4
Chunying Si,Sheng Wang,Zhen Chen,Guoming Hu,Xuanying Zhao,Ping Sun,Quanxing Zhang,Wei Jiang
The utilization of wasted Poly(lactic acid) (PLA) as low-cost carbon sources in solid-phase denitrification is hindered by its low biodegradability, which can be attributed to its high molecular weight . This study presents a new approach by blending high-molecular-weight PLA with a small amount of ʟ-lactide (PLA/LA x ) to treat nitrate-contaminated wastewater. The addition of ʟ-lactide enhanced the release of carbon from high-molecular-weight PLA. An impressive denitrification efficiency of 96.7% was achieved, accompanied by extremely low levels of accumulated NO 2 - - N (0.1 mg/L) and NH 4 + - N (0.4 mg/L). The quantity of ʟ-lactide used significantly impacted the bacterial community structure. A high abundance of the phyla Bacteroidota and Chloroflexi associated with polymer degradation was observed. The most dominant denitrifier was the genus unclassified_f__Rhodocyclaceae belonged to the phylum Proteobacteria . This study demonstrates that blending PLA with just 5 wt% lactide can transform it into a highly effective solid-phase carbon source to eliminate nitrates.
研究领域:
环境工程
·
微生物学
·
污水处理
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHINESE JOURNAL OF POLYMER SCIENCE
·
2021
·Vol. 39
·期 6
·709-715
·
IF 3.603
Wang Zhen-Yu,Xu Guang-Qiang,Zhou Li,Lv Cheng-Dong,Yang Ru-Lin,Dong Bing-Zhe,Wang Qing-Gang
The isoselective ring-opening polymerization of racemic lactide was achieved by combining N -heterocyclic olefin (NHO) with mono(thio)ureas or bis(thio)ureas as catalytic systems. The polymerization process shows high stereoselectivity, controllability and reactivity, delivering multi-block isotactic polylactides with high chain-end fidelity and narrow molecular weight distributions. The enhancement of catalytic performance was observed in the following order: bisthiourea (DTU) < monothiourea (TU) < bisurea (DU) < urea (U). The highest P m (probability of forming a meso dyad) = 0.91 was observed at −70 °C when using NHO/U1 catalytic system and the high stereoselectivity was attributed to chain-end control mechanism.
研究领域:
高分子化学
·
有机催化
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）