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Porous ultrathin-shell microcapsules designed by microfluidics for selective permeation and stimuli-triggered

《化学科学与工程前沿(英文)》   页码 1643-1650 doi: 10.1007/s11705-022-2201-z

摘要: Microcapsules are versatile delivery vehicles and widely used in various areas. Generally, microcapsules with solid shells lack selective permeation and only exhibit a simple release mode. Here, we use ultrathin-shell water-in-oil-in-water double emulsions as templates and design porous ultrathin-shell microcapsules for selective permeation and multiple stimuli-triggered release. After preparation of double emulsions by microfluidic devices, negatively charged shellac nanoparticles dispersed in the inner water core electrostatically complex with positively charged telechelic α,ω-diamino functionalized polydimethylsiloxane polymers dissolved in the middle oil shell at the water/oil interface, thus forming a porous shell of shellac nanoparticles cross-linked by telechelic polymers. Subsequently, the double emulsions become porous microcapsules upon evaporation of the middle oil phase. The porous ultrathin-shell microcapsules exhibit excellent properties, including tunable size, selective permeation and stimuli-triggered release. Small molecules or particles can diffuse across the shell, while large molecules or particles are encapsulated in the core, and release of the encapsulated cargos can be triggered by osmotic shock or a pH change. Due to their unique performance, porous ultrathin-shell microcapsules present promising platforms for various applications, such as drug delivery.

关键词: microcapsule     emulsion     microfluidics     selective permeation     stimuli-triggered release    

ethylene-co-vinyl alcohol) molecular weight and vinyl alcohol content on morphology, antifouling, and permeation

《化学科学与工程前沿(英文)》 2023年 第17卷 第10期   页码 1484-1502 doi: 10.1007/s11705-023-2331-y

摘要: Various hydrophilic poly(ethylene-co-vinyl alcohol) (EVOH) were used herein to precisely control the structure and hydrodynamic properties of polysulfone (PSF) membranes. Particularly, to prepare pristine PSF and PSF/EVOH blends with increasing vinyl alcohol (VOH: 73%, 68%, 56%), the non-solvent-induced phase separation (NIPS) technique was used. Polyethylene glycol was used as a compatibilizer and as a porogen in N,N-dimethylacetamide. Rheological and ultrasonic separation kinetic measurements were also carried out to develop an ultrafiltration membrane mechanism. The extracted membrane properties and filtration capabilities were systematically compared to the proposed mechanism. Accordingly, the addition of EVOH led to an increase in the rheology of the dopes. The resulting membranes exhibited a microporous structure, while the finger-like structures became more evident with increasing VOH content. The PSF/EVOH behavior was changed from immediate to delayed segregation due to a change in the hydrodynamic kinetics. Interestingly, the PSF/EVOH32 membranes showed high hydrophilicity and achieved a pure water permeability of 264 L·m–2·h–1·bar–1, which was higher than that of pure PSF membranes (171 L·m–2·h–1·bar–1). In addition, PSF/EVOH32 rejected bovine serum albumin at a high rate (> 90%) and achieved a significant restoration of permeability. Finally, from the thermodynamic and hydrodynamic results, valuable insights into the selection of hydrophilic copolymers were provided to tailor the membrane structure while improving both the permeability and antifouling performance.

关键词: polysulfone     blend modification     ultrafiltration membrane     formation hydrodynamics     poly(ethylene-co-vinyl alcohol) copolymer    

用于灵敏快速测量超阻隔渗透的预测仪器 Article

完颜剑峰, 曹坤, 陈志平, 李云, 刘晨曦, 吴润卿, 张晓东, 陈蓉

《工程(英文)》 2021年 第7卷 第10期   页码 1461-1470 doi: 10.1016/j.eng.2021.02.017

摘要:

测量柔性有机显示器件对水蒸气的高阻隔性,是确保其可靠性所面临的重大工程挑战。一方面,目前缺少10-6 g·m-2·d-1量级的水渗透率测试手段;另一方面,目前也没有标准的超阻隔样品用于渗透率测量的校准。为了对渗透过超阻隔材料的痕量水蒸气流量进行高灵敏、短周期测量,本文将渗透模型集成至基于渗透分子动态积累、检测和抽空的高灵敏质谱测量中,从而开发出了一种具有预测功能的测量仪器。通过使用标准聚合物样品进行校准,确保了测量结果的可靠性。校准后的水蒸气渗透检测下限在10-7g·m-2·d-1量级,满足超阻隔渗透的测量灵敏度要求。本文利用渗透实验数据对所开发的预测渗透模型进行了测试评估,使得利用非稳态数据预测稳态渗透率成为可能,实现在更短的时间内有效开展超阻隔测量。

关键词: 水蒸气渗透     超阻隔     预测模型     四极杆质谱仪    

Recent advances in selective acetylene hydrogenation using palladium containing catalysts

Alan J. McCue, James A. Anderson

《化学科学与工程前沿(英文)》 2015年 第9卷 第2期   页码 142-153 doi: 10.1007/s11705-015-1516-4

摘要: Recent advances with Pd containing catalysts for the selective hydrogenation of acetylene are described. The overview classifies enhancement of catalytic properties for monometallic and bimetallic Pd catalysts. Activity/selectivity of Pd catalysts can be modified by controlling particle shape/morphology or immobilisation on a support which interacts strongly with Pd particles. In both cases enhanced ethylene selectivity is generally associated with modifying ethylene adsorption strength and/or changes to hydride formation. Inorganic and organic selectivity modifiers (i.e., species adsorbed onto Pd particle surface) have also been shown to enhance ethylene selectivity. Inorganic modifiers such as TiO change Pd ensemble size and modify ethylene adsorption strength whereas organic modifiers such as diphenylsulfide are thought to create a surface template effect which favours acetylene adsorption with respect to ethylene. A number of metals and synthetic approaches have been explored to prepare Pd bimetallic catalysts. Examples where enhanced selectivity is observed are generally associated with decreased Pd ensemble size and/or hindering of the ease with which an unselective hydride phase is formed for Pd. A final class of bimetallic catalysts are discussed where Pd is not thought to be the primary reaction site but merely acts as a site where hydrogen dissociation and spillover occurs onto a second metal (Cu or Au) where the reaction takes place more selectively.

关键词: acetylene     ethylene     selective hydrogenation     palladium     bimetallic    

Preparation of polysulfone-based block copolymer ultrafiltration membranes by selective swelling and

《化学科学与工程前沿(英文)》 2022年 第16卷 第5期   页码 745-754 doi: 10.1007/s11705-021-2038-x

摘要: Selective swelling of block copolymers of polysulfone-b-poly(ethylene glycol) is an emerging strategy to prepare new types of polysulfone ultrafiltration membranes. Herein, we prepared nanoporous polysulfone-b-poly(ethylene glycol) ultrafiltration membranes by selective swelling and further promoted their porosity and ultrafiltration performances by using CaCO3 nanoparticles as the sacrificial nanofillers. Different contents of CaCO3 nanoparticles were doped into the solution of polysulfone-b-poly(ethylene glycol), and thus obtained suspensions were used to prepare both self-supported and bi-layered composite structures. Selective swelling was performed on the obtained block copolymer structures in the solvent pair of ethanol/acetone, producing nanoporous membranes with poly(ethylene glycol) lined along pore walls. The CaCO3 nanoparticles dispersed in polysulfone-b-poly(ethylene glycol) were subsequently etched away by hydrochloric acid and the spaces initially occupied by CaCO3 provided extra pores to the block copolymer layers. The porosity of the membranes was increased with increasing CaCO3 content up to 41%, but further increase in the CaCO3 content led to partial collapse of the membrane. The sacrificial CaCO3 particles provided extra pores and enhanced the connectivity between adjacent pores. Consequently, the membranes prepared under optimized conditions exhibited up to 80% increase in water permeance with slight decrease in rejection compared to neat membranes without the use of sacrificial CaCO3 particles.

关键词: block copolymers     selective swelling     ultrafiltration     CaCO3 nanoparticles     sacrificial nanofillers    

Mechanistic insights into the selective photocatalytic degradation of dyes over TiO/ZSM-11

《环境科学与工程前沿(英文)》 2023年 第17卷 第8期 doi: 10.1007/s11783-023-1701-5

摘要:

● TiO2/ZSM-11 was prepared by a facile solid state dispersion method.

关键词: Selective dye degradation     Photocatalysis     TiO2     ZSM-11     Chemisorption    

Highly efficient and selective removal of vanadium from tungstate solutions by microbubble floating-extraction

《化学科学与工程前沿(英文)》 2023年 第17卷 第5期   页码 581-593 doi: 10.1007/s11705-022-2235-2

摘要: Selective separation of dissolved tungsten and vanadium is of great significance for the utilization of the secondary resources of these elements. In this work, selective removal of vanadium from tungstate solutions via microbubble floating-extraction was systematically investigated. The results indicated that vanadium can be more easily mineralized over tungsten from tungstate solutions using methyl trioctyl ammonium chloride as mineralization reagent under weak alkaline conditions. Owing to the higher bubble and interface mass transfer rates, high-efficiency enrichment and deep separation of vanadium could be achieved easily. Additionally, the deep recovery of tungsten and vanadium from the floated organic phase could be easily realized using a mixed solution of sodium hydroxide and sodium chloride as stripping agents. The separation mechanism mainly included the formation of hydrophobic complexes, their attachment on the surface of rising bubbles, and their mass transfer at the oil–water interface. Under the optimal conditions, the removal efficiency of vanadium reached 98.5% with tungsten loss below 8% after two-stage microbubble floating-extraction. Therefore, the microbubble floating-extraction could be an efficient approach for separating selectively vanadium from tungstate solutions, exhibiting outstanding advantages of high separation efficiency and low consumption of organic solvents.

关键词: tungsten     vanadium     selective separation     reagent mineralization     microbubble floating-extraction    

Highly selective and green recovery of lithium ions from lithium iron phosphate powders with ozone

《化学科学与工程前沿(英文)》 2023年 第17卷 第6期   页码 749-758 doi: 10.1007/s11705-022-2261-0

摘要: Since lithium iron phosphate cathode material does not contain high-value metals other than lithium, it is therefore necessary to strike a balance between recovery efficiency and economic benefits in the recycling of waste lithium iron phosphate cathode materials. Here, we describe a selective recovery process that can achieve economically efficient recovery and an acceptable lithium leaching yield. Adjusting the acid concentration and amount of oxidant enables selective recovery of lithium ions. Iron is retained in the leaching residue as iron phosphate, which is easy to recycle. The effects of factors such as acid concentration, acid dosage, amount of oxidant, and reaction temperature on the leaching of lithium and iron are comprehensively explored, and the mechanism of selective leaching is clarified. This process greatly reduces the cost of processing equipment and chemicals. This increases the potential industrial use of this process and enables the green and efficient recycling of waste lithium iron phosphate cathode materials in the future.

关键词: lithium iron phosphate powder     stoichiometric number     selective leaching     lithium recovery    

Effect of PEG additives on properties and morphologies of polyetherimide membranes prepared by phase inversion

Jian CHEN, Jiding LI, Xia ZHAN, Xiaolong HAN, Cuixian CHEN,

《化学科学与工程前沿(英文)》 2010年 第4卷 第3期   页码 300-306 doi: 10.1007/s11705-009-0280-8

摘要: This study investigated the effect of poly(ethylene glycol) (PEG) additive as a pore-former on the structure formation of membranes and their permeation properties connected with the changes in thermodynamic and kinetic properties in the phase inversion process. The membranes were prepared by using polyetherimide/-methyl-2-pyrrolidone/PEG (PEI/NMP/PEG) casting solution and water coagulant. The resulting membranes, prepared by changing the ratio of PEG to PEI, were characterized by scanning electron microscope (SEM) observations, measurements of water flux and -globin rejection. The thermodynamic and kinetic properties of the membrane-forming system were studied through viscosity. The pore radius distribution curves were especially obtained by differential scanning calorimetry (DSC). Furthermore, the membranes were characterized for pure water flux and rejection of solute and by SEM observation. The filtration results agreed well with the SEM observations. As expected, PEG with a fixed molecular weight (PEG 600) acted as a pore forming agent, and membrane porosity increased as the PEG content of the casting solution increased.

关键词: permeation     ethylene     filtration     PEI/NMP/PEG     membrane    

Shape selective catalysis in methylation of toluene: Development, challenges and perspectives

Jian Zhou, Zhicheng Liu, Yangdong Wang, Dejin Kong, Zaiku Xie

《化学科学与工程前沿(英文)》 2018年 第12卷 第1期   页码 103-112 doi: 10.1007/s11705-017-1671-x

摘要: Toluene methylation with methanol offers an alternative method to produce -xylene by gathering methyl group directly from C1 chemical sources. It supplies a “molecular engineering” process to realize directional conversion of toluene/methanol molecules by selective catalysis in complicated methylation system. In this review, we introduce the synthesis method of -xylene, the development history of methylation catalysts and reaction mechanism, and the effect of reaction condition in -selective technical process. If constructing -xylene as the single target product, the major challenge to develop -selective toluene methylation is to improve the -xylene selectivity without, or as little as possible, losing the fraction of methanol for methylation. To reach higher yield of -xylene and more methanol usage in methylation, zeolite catalyst design should consider improving mass transfer and afterwards covering external acid sites by surface modification to get short “micro-tunnels” with shape selectivity. A solid understanding of mass transfer will benefit realizing the aim of converting more methanol feedstock into -methyl group.

关键词: shape selective catalysis     methylation of toluene    

Insight into the promotion mechanism of activated carbon on the monolithic honeycomb red mud catalyst for selective

《环境科学与工程前沿(英文)》 2021年 第15卷 第5期 doi: 10.1007/s11783-020-1337-7

摘要:

• Activated carbon was proposed to be an efficient accelerant for molded red mud catalyst.

关键词: NOx     Selective catalytic reduction     Iron-based catalyst     Red mud     Monolithic catalyst     Activated carbon    

Selective pseudosolubilization capability of

Fei HUA, Hongqi WANG

《环境科学与工程前沿(英文)》 2013年 第7卷 第4期   页码 539-551 doi: 10.1007/s11783-013-0498-z

摘要: Pseudosolubilized ability of sp. DG17 on -alkanes, role of biosurfactants in -octadecane uptake and trans-membrane transport mechanism of -octadecane were studied by analyzing amount of pseudosolubilized oil components in water phase, and the fraction of radiolabeled C -octadecane in the broth and cell pellet. GC-MS results showed that pseudosolubilized oil components were mainly C to C of -alkanes. In -octadecane broth, pseudosolubilized -octadecane could be accumulated as long as pseudosolubilized rate was faster than mineralization rate of substrate, and the maximum concentration of pseudosolubilized -octadecane achieved to 45.37 mg·L . All of these results showed that sp. DG17 mainly utilized alkanes by directly contacting with pseudosolubilized small oil droplets in the water phase. Analysis of C amount in cell pellet revealed that an energy-dependent system mainly controlled the trans-membrane transport of -octadecane.

关键词: Pseudomonas     alkane     uptake     pseudosolubilization     trans-membrane transport    

Transition metal-doped heteropoly catalysts for the selective oxidation of methacrolein to methacrylic

Yanxia Zheng,Heng Zhang,Lei Wang,Suojiang Zhang,Shaojun Wang

《化学科学与工程前沿(英文)》 2016年 第10卷 第1期   页码 139-146 doi: 10.1007/s11705-015-1548-9

摘要: Heteropoly compounds with the general formula Cs M H P Mo VO (M= Fe, Co, Ni, Cu or Zn) and Cs Cu H P Mo VO ( = 0.1, 0.3 or 0.7) were synthesized and then used as catalysts for the selective oxidation of methacrolein to methacrylic acid. The effects of the transition metals on the structure and activity of the catalysts were investigated. FTIR spectra showed that the transition metal-doped catalysts maintained the Keggin structure of the undoped catalysts. X-ray diffraction results indicated that before calcination, the catalysts doped with Fe and Cu had cubic secondary structures, while the catalysts doped with Co, Ni or Zn had both triclinic and cubic phases and the Co-doped catalyst had the highest content of the triclinic form. Thermal treatment can decrease the content of the triclinic phase. NH temperature-programmed desorption and H temperature-programmed reduction results showed that the transition metals changed the acid and redox properties of the catalysts. The addition of Fe or Cu had positive effects on the activities of the catalyst which is due to the improvement of the electron transfer between the Fe or Cu and the Mo. The effects of the copper content on structure and catalytic activity were also investigated. The Cs Cu H P Mo VO catalyst had the best performance for the selective oxidation of methacrolein to methacrylic acid.

关键词: heteropoly compounds     transition metals     selective oxidation     methacrolein    

Design and operational considerations for selective catalytic reduction technologies at coal-fired boilers

Jeremy J. SCHREIFELS, Shuxiao WANG, Jiming HAO

《能源前沿(英文)》 2012年 第6卷 第1期   页码 98-105 doi: 10.1007/s11708-012-0171-4

摘要: By the end of 2010, China had approximately 650 GW of coal-fired electric generating capacity producing almost 75% of the country’s total electricity generation. As a result of the heavy reliance on coal for electricity generation, emissions of air pollutants, such as nitrogen oxides (NO ), are increasing. To address these growing emissions, the Ministry of Environmental Protection (MEP) has introduced new NO emission control policies to encourage the installation of selective catalytic reduction (SCR) technologies on a large number of coal-fired electric power plants. There is, however, limited experience with SCR in China. It is therefore useful to explore the lessons from the use of SCR technologies in other countries. This paper provides an overview of SCR technology performance at coal-fired electric power plants demonstrating emission removal rates between 65% and 92%. It also reviews the design and operational challenges that, if not addressed, can reduce the reliability, performance, and cost-effectiveness of SCR technologies. These challenges include heterogeneous flue gas conditions, catalyst degradation, ammonia slip, sulfur trioxide (SO ) formation, and fouling and corrosion of plant equipment. As China and the rest of the world work to reduce greenhouse gas emissions, carbon dioxide (CO ) emissions from parasitic load and urea-to-ammonia conversion may also become more important. If these challenges are properly addressed, SCR can reliably and effectively remove up to 90% of NO emissions at coal-fired power plants.

关键词: nitrogen oxides (NOx)     coal     selective catalytic reduction (SCR)     air pollution control    

parametric contact analysis of planetary roller screw mechanism and its application in grouping for selective

《机械工程前沿(英文)》 2024年 第19卷 第1期 doi: 10.1007/s11465-023-0775-x

摘要: The planetary roller screw mechanism (PRSM) is a novel precision transmission mechanism that realizes the conversion between linear and rotary motions. The contact characteristics of helical surfaces directly determine PRSM’s performance in load-carrying capacity and transmission accuracy. Therefore, studying the contact characteristics of PRSM forms the fundamental basis for enhancing its transmission performance. In this study, a three-dimensional parametric analysis method of contact characteristics is proposed based on the PRSM meshing principle and PyVista (a high-level API to the Visualization Toolkit). The proposed method considers the influence of machining errors among various thread teeth. The effects of key machining errors on contact positions and axial clearance, as well as their sensitivities, are analyzed. With excellent solution accuracy, this method exhibits higher calculation efficiency and stronger robustness than the analytical and numerical meshing models. The influence of nominal diameter and pitch errors of the screw, roller, and nut on the axial clearance follows a linear relationship, whereas flank angle errors have negligible effects on the axial clearance. The corresponding influence coefficients for these three machining errors on the axial clearance are 0.623, 0.341, and 0.036. The variations in contact positions caused by individual errors are axisymmetric. Flank angle errors and roller diameter errors result in linear displacements of the contact points, whereas pitch errors cause the contact points to move along the arc of the roller diameter. Based on the proposed three-dimensional parametric contact characteristics analysis method, the Fuzzy C-Means clustering algorithm considering error sensitivity is utilized to establish a component grouping technique in the selective assembly of critical PRSM components, ensuring the rational and consistent clearances based on the given component’s machining errors. This study provides effective guidance for analyzing contact characteristics and grouping in selective assembly for PRSM components. It also presents the proposed method’s potential applicability to similar calculation problems for contact positions and clearances in other transmission systems.

关键词: planetary roller screw mechanism (PRSM)     contact position     axial clearance     machining error     grouping for selective assembly    

标题 作者 时间 类型 操作

Porous ultrathin-shell microcapsules designed by microfluidics for selective permeation and stimuli-triggered

期刊论文

ethylene-co-vinyl alcohol) molecular weight and vinyl alcohol content on morphology, antifouling, and permeation

期刊论文

用于灵敏快速测量超阻隔渗透的预测仪器

完颜剑峰, 曹坤, 陈志平, 李云, 刘晨曦, 吴润卿, 张晓东, 陈蓉

期刊论文

Recent advances in selective acetylene hydrogenation using palladium containing catalysts

Alan J. McCue, James A. Anderson

期刊论文

Preparation of polysulfone-based block copolymer ultrafiltration membranes by selective swelling and

期刊论文

Mechanistic insights into the selective photocatalytic degradation of dyes over TiO/ZSM-11

期刊论文

Highly efficient and selective removal of vanadium from tungstate solutions by microbubble floating-extraction

期刊论文

Highly selective and green recovery of lithium ions from lithium iron phosphate powders with ozone

期刊论文

Effect of PEG additives on properties and morphologies of polyetherimide membranes prepared by phase inversion

Jian CHEN, Jiding LI, Xia ZHAN, Xiaolong HAN, Cuixian CHEN,

期刊论文

Shape selective catalysis in methylation of toluene: Development, challenges and perspectives

Jian Zhou, Zhicheng Liu, Yangdong Wang, Dejin Kong, Zaiku Xie

期刊论文

Insight into the promotion mechanism of activated carbon on the monolithic honeycomb red mud catalyst for selective

期刊论文

Selective pseudosolubilization capability of

Fei HUA, Hongqi WANG

期刊论文

Transition metal-doped heteropoly catalysts for the selective oxidation of methacrolein to methacrylic

Yanxia Zheng,Heng Zhang,Lei Wang,Suojiang Zhang,Shaojun Wang

期刊论文

Design and operational considerations for selective catalytic reduction technologies at coal-fired boilers

Jeremy J. SCHREIFELS, Shuxiao WANG, Jiming HAO

期刊论文

parametric contact analysis of planetary roller screw mechanism and its application in grouping for selective

期刊论文