JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
·
2021
·Vol. 147
·期 3
·2239-2251
·
IF 4.626
Zhao Qian,Wang Bowen,Qin Chenyuan,Li Qiuxuan,Liu Chuntai,Shen Changyu,Wang Yaming
In this work, biodegradable poly(lactic acid) (PLA)/Ti 3 C 2 T x MXene nanocomposites were prepared through melt compounding. The roles of MXene in nonisothermal melt and cold crystallization of PLA were explored. The morphology, structure and crystallization behavior were studied using polarized optical microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. For nonisothermal melt crystallization, the presence of MXene increases the crystallinity and shortens the half-crystallization time but does not change the crystallization peak temperature of PLA. For nonisothermal crystallization from the glassy state, the incorporation of MXene decreases the cold crystallization peak temperature and reduces the crystallinity marginally but does not affect the half-crystallization time of PLA. The crystallization kinetics analysis based on the Avrami equation shows that, for both the melt and cold crystallization, the crystallization mechanism is unchanged irrespective of the addition of MXene. The investigation would be useful for understanding the correlation between processing and properties of PLA/MXene nanocomposites.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
THEORETICAL FOUNDATIONS OF CHEMICAL ENGINEERING
·
2023
·Vol. 57
·期 3
·391-402
·
IF 0.8
Zheng Dan
Abstract This work presents a novel approach for the growth of potassium sulfate (K 2 SO 4 ) from supersaturated solutions by reaction-extractive crystallization in a fluidized-bed crystallizer (FBC), in which K 2 SO 4 is transformed into potassium chloride and sulfuric acid based on a reactive extraction-crystallization process using triisooctylamine (TOA) in n -octanol as the extraction system. This paper uses the moment transformation method to solve the population balance equations of K 2 SO 4 in the extractive crystallization process, and the crystallization kinetic parameters are obtained by nonlinear regression. The kinetic equations of crystal nucleation, growth, and agglomeration rate in the crystallization process of potassium sulfate are determined, and experiments verify the reliability of the kinetic parameters. The results show that in a specific range, higher supersaturation and fluidization rate are conducive to the nucleation, growth, and aggregation of K 2 SO 4 . Suspension density promotes crystal nucleation and growth but has the opposite effect on accumulation. At the same time, based on the constant calculation equation of particle number and the constant calculation equation of mass, the extraction crystallization coupling mathematical model of the crystal in the fluidization state is established. The effects of suspension density, Reynolds number, extraction rate, feeding rate, and extraction concentration on potassium sulfate’s nucleation, growth, and aggregation rate were studied by combining model calculation with experimental research. A process coupling model of the potassium sulfate extraction crystallization process in a fluidized bed was proposed. The model agrees with the experimental results, which have specific guiding significance for industrial production.
研究领域:
化学工程
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材料科学
✓ 已验证
DOI
高影响因子
CHINESE JOURNAL OF CHEMICAL ENGINEERING
·
2015
·
IF 1.098
Zhijuan Sun,Xiao Wang,Fei Guo,Chunyue Jiang,Qinmin Pan
Bio-sourced nylon 69, one of promising engineering plastics, has a great potential in developing sustainable technology and various commercial applications. Isothermal and nonisothermal crystallization kinetics of nylon 69 is a base to optimize the process conditions and establish the structure–property correlations for nylon 69, and it is also highly beneficial for successful applications of nylon products in industry. Isothermal and nonisothermal crystallization kinetics has been investigated by differential scanning calorimetry for nylon 69, bio-sourced even–odd nylon. The isothermal crystallization kinetics has been analyzed by the Avrami equation, the calculated Avrami exponent at various crystallization temperatures falls into the range of 2.28 and 2.86. In addition, the Avrami equation modified by Jeziorny and the equation suggested by Mo have been adopted to study the nonisothermal crystallization. The activation energies for isothermal and nonisothermal crystallization have also been determined. The study demonstrates that the crystallization model of nylon 69 might be a two-dimensional (circular) growth at both isothermal and nonisothermal crystallization conditions. Furthermore, the value of the crystallization rate parameter ( K ) decreases significantly but the crystallization half-time ( t 1/2 ) increases with the increase of the isothermal crystallization temperature. To nonisothermal crystallization, the crystallization rate increases as the cooling rate increases according to the analysis of Jeziorny's theory. The results of Mo's theory suggest that a faster cooling rate is required to reach a higher relative degree of crystallinity in a unit of time, and crystallization rate decreases when the relative degree of crystallinity increases at nonisothermal crystallization conditions.
研究领域:
材料科学
·
聚合物科学
✓ 已验证
产品关联
DOI
高影响因子
MOLECULES
·
2025
·Vol. 30
·期 4
·897
·
IF 4.6
Yu Jing,Jinxu Zhang,Shengping You,Mengfan Wang,Rongxin Su,Wei Qi
γ-aminobutyric acid, a critical neurotransmitter, is experiencing an increasing demand in the medical and health fields. Conventional processes for γ-aminobutyric acid purification from fermentation broth encounter significant challenges, such as high ethanol usage, low yield, complex process flow, and environmental pollution. Therefore, a purification process based on crystallization techniques was developed to address the above issues. The process was implemented in two stages: desalination and γ-aminobutyric acid treatment. Na 2 SO 4 was effectively removed through a cooling crystallization technique. γ-aminobutyric acid with a purity of 98.66% and a yield of 67.32% was further obtained through a designed “antisolvent-cooling” crystallization process in a 3.2 L system. Moreover, the new process reduced ethanol usage compared to conventional processes, streamlined the purification process flow, and was more environmentally sustainable. Furthermore, we established an industrial-scale model for γ-aminobutyric acid production. Techno-economic analysis indicates that an investment in a plant with an annual capacity of 74.16 tons of γ-aminobutyric acid is projected to achieve payback in 1.98 years. In conclusion, the crystallization-based purification process is poised for industrial-scale γ-aminobutyric acid production due to its high efficiency, economic viability, energy conservation, and environmental compatibility.
研究领域:
生物工程
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化学工程
·
制药工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Chemical Engineering and Processing-Process Intensification
·
2024
·
IF 3.8
Dishika Gupta,Andrew T.C. Mak,Richard Lakerveld
Pharmaceutical cocrystals consist of an active pharmaceutical ingredient and a coformer in a fixed stoichiometric ratio. They can improve the manufacturability and properties of a drug powder. However, the manufacture of cocrystals is often more complicated compared to crystals of an active ingredient due to the possible formation of different solid-state forms. Cocrystallization through anti-solvent addition is a commonly used technique. However, the risk of nucleation of multiple solid-state forms is often high due to the high supersaturation levels achieved during anti-solvent crystallization. Therefore, intensifying a solution-mediated phase transformation is important. In this work, the ability of tubular flow crystallizers to intensify the phase transformation process in the carbamazepine-saccharin cocrystal system is characterized and compared to a conventional stirred tank crystallizer. The influence of the flow rate, tubular crystallizer type, and ratio of residence time in the tube to that in the tank are documented. The phase transformation process is substantially faster with the tubular crystallizers compared to that in a stirred tank crystallizer, which we explain through increased nucleation rates. We show that such intensification can be achieved either by recirculating the slurry through a static mixer or by installing a tubular crystallizer upstream of a stirred tank crystallizer.
研究领域:
制药工程
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化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2013
·Vol. 130
·期 2
·1328-1336
·
IF 1.395
Ting Wang,Yong Yang,Chuanzhi Zhang,Zhaobin Tang,Haining Na,Jin Zhu
A series of 1,3,5-trialkyl-benzenetricarboxylamides (BTA-Rs) with different side-chain lengths of n -alkyl are synthesized to use as nucleating agents of poly (lactic acid) (PLA). Crystallization rate of PLA is detailed discussed in nonisothermal melt-crystallization with addition of the synthesized nucleating agents. Among these BTA-Rs, BTA-n-butyl (BTA-nBu) shows the most excellent nucleation ability for PLA. The influences of BTA-nBu on the nonisothermal melt-crystallization and cold-crystallization from the glassy state, isothermal crystallization, crystalline structure, and spherulite morphology of PLA are investigated. It is found that 0.8 wt % is the optimal weight fraction of BTA-nBu to improve the crystallization of PLA. In the case of isothermal melt-crystallization from melt, the addition of BTA-nBu shortens the crystallization half-time and speeds up the crystallization rate of PLA with no discernible effect on the crystalline structure. Besides, BTA-nBu nucleated PLA exhibits smaller spherulites size and larger nucleation density than that of pure PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1328-1336, 2013
研究领域:
高分子科学
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材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
ChemistrySelect
·
2024
·Vol. 9
·期 2
·e202304152
·
IF 1.9
Xiaojun Dai,Yan Cheng,Tingting Liu,Lingjuan Mao
Graphical The effects of synthesis medium and synthesis conditions on the physicochemical properties of SAPO-11 molecular sieve were explored by combining the hydrothermal crystallization method with the fractional crystallization method. SAPO-11 molecular sieve has been widely used as the support of bifunctional catalyst for hydroisomerization of n-alkanes because of its mild acidity and unique one-dimensional pore structure, and has been widely used in industry. However, how to further improve and improve the physicochemical properties of SAPO-11 molecular sieve is still worth studying. In this work, fractional crystallization method was used to synthesize graded SAPO-11 molecular sieve. The effects of medium system, feed SiO 2 /Al 2 O 3 , crystallization time and crystallization temperature of the second crystallization process on the physicochemical properties of SAPO-11 molecular sieve were investigated from the perspectives of crystallinity, textural properties and acidity. The suitable synthesis medium and the best synthesis conditions were determined. It is expected to provide reference for the fractional crystallization synthesis of high performance SAPO-11 molecular sieve.
研究领域:
材料科学
·
化学工程
·
催化
✓ 已验证
DOI
高影响因子
MACROMOLECULES
·
2017
·
IF 5.835
Dongdong Zhou,Shaoyong Huang,Jingru Sun,Xinchao Bian,Gao Li,Xuesi Chen
The crystallization behaviors and microstructures of poly(l-2-hydroxyl-3-methylbutanoic acid)/poly(l-lactide) blends [P(L-2H3MB)/PLLA] were investigated by OM, DSC, SAXS, in situ temperature-dependent WAXD, and in situ synchrotron WAXS. The blends exhibited a homogeneous state at 250 °C. In the cooling process, P(L-2H3MB), with higher melting temperature, crystallized first at 166.7 °C and drove the formation of the phase separation and microstructure. And the amorphous P(L-2H3MB) and PLLA were excluded into the interlamellar and interfibrillar regions of the former P(L-2H3MB) crystallites. For P(L-2H3MB)/PLLA (5/5), the amorphous P(L-2H3MB) in the interfibrillar regions continued to form crystallites sequentially at 134.6 °C, which clearly confirmed the fractional crystallization of P(L-2H3MB). In our knowledge, this unique fractional crystallization has not been reported yet, of the component in miscible blend, which crystallized first under little confinement. This work provided a new viewpoint and understanding of the relationship between fractional crystallization and microstructures in crystalline/crystalline blends.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF POLYMER SCIENCE
·
2021
·Vol. 39
·期 9
·1211-1216
·
IF 3.603
Xiang Ming-Yue,Lyu Dong,Liu Ling-Zhi,Men Yong-Feng
Crystallinity of bottlebrush polymers due to side chain crystallization has been considered to be related to the length of the side chains only under the assumption of complete participation of crystallization by all side chains. Recent experimental results revealed that in poly( n -alkyl methacrylate)s a fraction of side chains could not crystallize due to constraints imposed by the trapped main chain entanglements and required expansion of main chain-main chain distance. This result renders the original simplified consideration of the origin of crystallinity in bottlebrush polymers questionable. In this work, we introduce a new parameter f c , the fraction of crystallizable side chains, to better describe the crystallinity of bottlebrush polymers. A linear relationship between the melting enthalpy and the number of alkyl groups in side chains for bottlebrush polymers reported repeatedly indicates that f c remains essentially unchanged when bottlebrush polymers had the same main chain structure and grafting degree but different side chain lengths. The slope of the above-mentioned linear relationship is thus \(\Delta H_{\text{CH}_2}\times f_{c}\) , where \(\Delta H_{\text{CH}_2}\) stands for the melting enthalpy of one mole alkyl group packed into the crystal. With a known value of f c , it is possible to estimate the value of \(\Delta H_{\text{CH}_2}\) . In case of poly( n -alkyl methacrylate)s, we estimated \(\Delta H_{\text{CH}_2}\) of hexagonal crystal being at most 5.74 kJ/mol with the knowledge of possibly smallest f c of 0.67 obtained from small angle X-ray scattering data. Therefore, the crystallinity of bottlebrush polymer would be calculated based on the equation \(X_{\rm{c}}=f_{\rm{c}}\times\frac{N_{\rm{c}}}{N}\) with N and N c being the number of alkyl groups in a side chain and those packed in the crystalline structure, respectively. Both chemical structure and grafting degree of bottlebrush polymers affect f c .
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2017
·
IF 3.671
Yongqi Feng,Piming Ma,Pengwu Xu,Ruyin Wang,Weifu Dong,Mingqing Chen,Cornelis Joziasse
The effects of six nucleating agents (NAs), i.e., orotic acid (OA), potassium salt of 3,5-bis(methoxycarbonyl)benzenesulfonate (LAK-301), substituted-aryl phosphate salts (TMP-5), talc (TALC), N' 1 , N' 6 -dibenzoyladipohydrazide (TMC-306) and N 1 , N 1′ -(ethane-1,2-diyl)bis( N 2 -phenyloxalamide) (OXA), on the crystallization behavior of poly(lactic acid) (PLA) were compared by DSC . Under the same dosing of 0.5 wt%, the nucleation effect of the NAs for PLA declines in the order of TMC-306 ≈ OXA > TALC ≫ TMP-5 ≈ LAK-301 ≈ OA. The nucleation efficiency (NE) of TMC-306 and OXA is around 50%, which is almost 2 times of the NE of TALC. In the best case of the PLA/TMC-0.5% sample, the half-time of crystallization decreases from 30 s to 9 s with decreasing the crystallization temperature from 120 °C to 100 °C, which is of great significance to the fast production of highly crystallized PLA materials. As high-efficient NAs, TMC-306 and OXA are able to accelerate the crystallization rate of PLA even upon fast cooling at 50 °C/min, while make no difference on PLA crystal form, as identified by WAXD . DMA analysis shows that the storage modulus of PLA is significantly improved by TMC-306 and OXA.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2018
·
IF 6.735
Shifeng Jiang,Yuande Zhang,Zhibao Li
Sodium bicarbonate (NaHCO 3 ) has been conventionally manufactured by a carbonation synthesis from the reaction of sodium carbonate (Na 2 CO 3 ) and CO 2 in a carbonation column. To enhance the quality and the production yield of NaHCO 3 , it is imperative to carefully control supersaturation in the carbonation crystallization process and make NaHCO 3 concentration of filtrate obtained from column bottom possibly least. A new method of NaHCO 3 production was proposed with help of common ion effect by adding Na 2 CO 3 as feed in filtering liquor. A cooling crystallizer was incorporated in the system after the carbonation tower to generate more NaHCO 3 . The crystallization kinetics of NaHCO 3 including nucleation and crystal growth was experimentally and theoretically investigated in a continuous mixed-suspension-mixed-product removal (MSMPR) crystallizer cooled from 353 to 308 K. The effect of Na 2 CO 3 concentration and additives on the crystallization of NaHCO 3 was studied. The growth and nucleation rate G V = 6.618 × 10 - 15 σ 0.290 , B 0 = 2.560 × 10 - 32 G V - 3.82 M T 1.11 were determined by moments analysis based on the experimental crystal size distribution (CSD) data. The kinetic parameters in two empirical equations were estimated by linear regression with the 0.290 of the relative supersaturation rate order, indicating that the meant surface integration and diffusion play an equally importance to the growth of NaHCO 3 crystal. The growth rate order of −3.82 suggested that nucleation of NaHCO 3 from the Na 2 CO 3 -rich solution in the MSMPR crystallizer was particle size-limiting.
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 JOURNAL OF INORGANIC CHEMISTRY
·
2019
·Vol. 2020
·期 3
·318-326
·
IF 2.578
Mingjian Luo,Mingxu Liu,Yadong Fu,Wenxin Chen,Baohui Wang,Guoliang Mao
Graphical Three-stage SAPO-34s have higher purity, smaller crystal size, more acidic sites, longer catalytic lifetime and better olefin selectivity. The crystallization mechanism and the relationship between properties and performance are discussed. Acidity and 2–4 nm mesopores have little effect on MTO performance, which mainly depends on the size and dispersity of the crystallites and the purity of SAPO-34. SAPO-34 zeolites were synthesized by one-, two-, and three-stage crystallization processes with fumed silica (FS), acidic silica sol (AS), basic silica sol (BS) and tetraethoxysilane (TEOS) as silicon sources. Properties of samples were characterized by XRD, SEM, EDX, N 2 -adsorption/desorption, NH 3 -TPD and 29 Si NMR. In contrast with one- and two-stage processes, the three-stage one favors the formation of SAPO-34s with higher purity, higher Si/Al ratio, smaller crystallite/crystal size, better dispersion and more acidic sites. Crystallization mechanism was proposed. It is supposed that three-stage process favors the formation of high supersaturated SBUs (secondary building units) and CBUs (composite building units) before nucleation. Thus massive nuclei are formed during nucleation and well-dispersed small size SAPO-34 crystals are formed in three-stage process. Three-stage SAPO-34s are longer catalytic lifetime and better olefin selectivity in MTO process. TEOS-3 has the best MTO performance. It was found that acidity of sample and mesopores in 2–4 nm range have little effect on the MTO performance of SAPO-34. Catalytic lifetime and olefin selectivity are mainly depending on the size of crystallites, the dispersity of crystallites, and the purity of SAPO-34.
研究领域:
材料科学
·
催化化学
✓ 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）