Toward a comprehensive understanding of textiles functionalized with silver nanoparticles

This article provides a comprehensive understanding of development of textiles functionalized with silver nanoparticles (AgNPs). There are three established methods to fabricate textiles functionalized with AgNPs, namely, solution‐immersion, layer‐by‐layer deposition, and sonochemical. In addition, several textile types such as cotton, wool, polyester, silk, cotton/polyester blend, polyamide, and regenerated cellulose have been used for the fabrication. The AgNP deposition mechanism on textiles is mainly due to electrostatic interaction between AgNPs and textile constituents. It was exhibited that the deposition of AgNPs on textiles can transform their textiles colors. In addition, it was demonstrated that the deposition of AgNPs on textiles is not permanent, particularly against washing treatment. Textiles modified with AgNPs have several promising applications such as antibacterial, antifungal, catalyst, electronic devices, water treatment, sun protection, air treatment, and surface‐enhanced Raman scattering, which are comprehensively discussed in this article. Future challenges in fabricating textiles functionalized with AgNPs remain on how this can be carried out to improve long‐term stabilization of AgNPs on textiles to achieve their permanent deposition by employing greener approaches.     

Stabilization of Copper Catalysts for Liquid‐Phase Reactions by Atomic Layer Deposition

Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid‐phase catalytic reactions (e.g., hydrogenation of biomass‐derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid‐phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X‐ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of γ‐Al₂O₃. Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under‐coordinated copper atoms on the nanoparticle surface.     

Engineering Catalyst Microenvironments for Metal‐Catalyzed Hydrogenation of Biologically Derived Platform Chemicals

It is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur‐containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA‐overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA‐overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine.     

MOFs在不饱和醛选择加氢中的应用研究进展

不饱和醛多相催化选择加氢制备不饱和醇常常被选作C=O键选择性加氢的代表性反应,长期以来一直备受关注,然而获得兼具高活性及高选择性的催化剂依然具有很大的挑战。近年来,由于金属有机骨架（Metal-organic frameworks MOFs）材料具有的独特性能,应用在加氢领域的研究越来越多,常用做催化剂载体或直接作为催化剂,以提高不饱和醇的收率。因此,本文综述了不同MOFs及其衍生物在不饱和醛选择性加氢应用中的最新进展和技术挑战,并对这些材料的性能进行了讨论,试图通过催化剂结构、催化剂性能、反应机理等分析,为进一步合理设计有效的催化剂,实现更高的不饱和醇收率提供研究思路。     

Ziegler-type hydrogenation catalysts made from group 8–10 transition metal precatalysts and AlR3 cocatalysts: A critical review of the literature

Ziegler-type hydrogenation catalysts (group 8–10 transition metal precatalysts plus AlR₃ cocatalysts) are one of the most important families of industrial hydrogenation catalysts, especially for polymer hydrogenation. Despite their ～40 year history of industrial use, there is a need for improved fundamental understanding in order to make further, rationally directed improvements in these catalysts. This review examines the existing literature on Ziegler-type hydrogenation catalysts, specifically: (i) the variables important to catalyst synthesis, (ii) the catalyst formation reaction mechanism, (iii) the compositional and structural nature of the active catalyst species, and (iv) the mechanism of catalytic hydrogenation. This review also (v) discusses the current approaches to the homogeneous versus heterogeneous catalysis question, with the goal of identifying if Ziegler-type hydrogenation catalysts are homogeneous (e.g., monometallic) versus heterogeneous (e.g., nanoclusters) as the true catalyst(s). A summary of the main insights from each section of the review is also given.     

Omniphobic membranes for distillation: Opportunities and challenges

As an emerging thermal-driven membrane technology, membrane distillation (MD) has attracted immense attention for desalination and water purification. The membranes for MD generally have hydrophobic or superhydrophobic properties to enable vapor permeation without liquid passage (e.g., wetting). However, conventional MD membranes cannot undergo long term stable operations due to gradual wetting in practical applications where the feed solution often contains multiple low-surface tension contaminants (e.g., oil). Recently, omniphobic membranes repelling all sorts of liquids and typically having ultralow surface energy and re-entrant structures have been developed for robust MD to mitigate wetting and fouling. In this paper, we aim to provide a comprehensive review of recent progress on omniphobic membranes. Fundamentals, desirable properties, advantages and applications of omniphobic membranes are discussed. We also summarize the research efforts and methods to engineer omniphobic membranes. Finally, the challenges and future research directions on omniphobic membranes are discussed.     

Role of hydrogen in catalytic dehydrogenation: Film diffusion controlled deactivation

The function of hydrogen used as carrier gas in catalytic dehydrogenation is to increase the selectivity and stability of catalysts. It slows down catalyst deactivation by either inhibiting deposition of potential coke precursors or facilitating their desorption by rehydrogenation. This function, in gas-solid catalytic dehydrogenation appears to be interphase mass transfer controlled by increased hydrogen linear flow velocities decreasing the extent of deactivation. Besides, deactivation appears to progress through two regimes, an initial short term followed by a long term deactivation.     

Conversion of Polysaccharides to Sugar Alcohols: A Modeling Approach Based on Oligosaccharides

We extend our former kinetic and experimental study of hydrogenolysis of di‐ and trisaccharides using Ru/C in combination with a molecular acid as a catalyst system, to longer oligosaccharides up to heptasaccharide. The extended kinetics, despite the considerably more complex reaction network, reconfirms our previous hypothesis that reactions of oligosaccharides proceed through two competing reaction pathways, namely hydrolysis of oligosaccharides and their hydrogenation to a reduced form. This challenges the widely accepted supposition that conversion of polysaccharides to sorbitol passes consecutively through hydrolysis to monosaccharides followed by hydrogenation to sorbitol. This works also sets forth the hypothesis that hydrogenation of long‐chain oligosaccharides increases the rate of hydrolysis to a considerable extent and presents a significant alternative pathway in sorbitol formation.     

Direct Non‐Oxidative Methane Conversion in a Millisecond Catalytic Wall Reactor

Direct non‐oxidative methane conversion (DNMC) has been recognized as a single‐step technology that directly converts methane into olefins and higher hydrocarbons. High reaction temperature and low catalyst durability, resulting from the endothermic reaction and coke deposition, are two main challenges. We show that a millisecond catalytic wall reactor enables stable methane conversion, C₂₊ selectivity, coke yield, and long‐term durability. These effects originate from initiation of the DNMC on a reactor wall and maintenance of the reaction by gas‐phase chemistry within the reactor compartment. The results obtained under various temperatures and gas flow rates form a basis for optimizing the process towards lighter C₂ or heavier aromatic products. A process simulation was done by Aspen Plus to understand the practical implications of this reactor in DNMC. High carbon and thermal efficiencies and low cost of the reactor materials are realized, indicating the technoeconomic viability of this DNMC technology.     

Kinetic Modeling of Secondary Methane Formation and 1‐Olefin Hydrogenation in Fischer–Tropsch Synthesis over a Cobalt Catalyst

A detailed kinetic model of Fischer–Tropsch synthesis (FTS) product formation, including secondary methane formation and 1‐olefin hydrogenation, has been developed. Methane formation in FTS over the cobalt‐based catalyst is well known to be higher‐than‐expected compared to other n‐paraffin products under typical reaction conditions. A novel model proposes secondary methane formation on a different type of active site, which is not active in forming C₂₊ products, to explain this anomalous methane behavior. In addition, a model of secondary 1‐olefin hydrogenation has also been developed. Secondary 1‐olefin hydrogenation is related to secondary methane formation with both reactions happening on the same type of active sites. The model parameters were estimated from experimental data obtained with Co/Re/γ‐Al₂O₃ catalyst in a slurry‐phase stirred tank reactor over a range of conditions (T = 478, 493, and 503 K, P = 1.5 and 2.5 MPa, H₂/CO feed ratio = 1.4 and 2.1, and X _CO = 16–62%). The proposed model including secondary methane formation and 1‐olefin hydrogenation is shown to provide an improved quantitative and qualitative prediction of experimentally observed behavior compared to the detailed model with only primary reactions.     

Pd/ZnO在乙炔选择加氢反应中的不同催化机制研究(英文)

化学选择性是评价催化剂性能最重要的参数之一,它直接决定了产物的经济价值及后续的分离成本.传统的负载型金属催化剂由于其金属粒径分布不均,且不同原子数组成的粒子通常具有特征产物选择性,从而限制化学选择性的提高;另一方面,对于金属多原子活性中心,反应物在催化剂表面可以存在多种吸附构型进而衍化为不同产物,产物可控性差.因此,获得金属尺寸均一,且具有原子分散的活性中心,即单原子催化剂,成为官能团多相催化转化高选择性的迫切需求.本课题组通过400 oC还原1%-Pd/ZnO得到PdZn金属间化合物,依据其规律排布的Pd-Zn-Pd单元获得Pd基单原子催化剂.该催化剂在乙烯化工中少量乙炔的加氢转化反应中获得令人欣喜的催化性能——兼具有乙炔的高转化率和乙烯的高选择性.结合微量吸附量热、理论计算等表征,Pd活性中心在PdZn金属间化合物中的特殊空间排布是其优异催化性能的根源,即乙炔以较强的σ键吸附在两个相邻的单Pd金属中心,易吸附活化加氢生成乙烯,而乙烯则吸附于单Pd金属中心,较弱的π键形式吸附有利于其脱附避免过渡加氢.基于前期研究,构筑具有均一单金属中心的负载型单原子催化剂是获得高选择性的另一有效方法,且较之于PdZn金属间化合物催化剂,该类单原子催化剂兼具有原子利用率最大化的优点.本文采用等体积浸渍法制备Pd/ZnO催化剂,通过降低Pd金属含量(1 wt%→0.1 wt%→0.01 wt%)并在较低的温度下(100 oC)还原(H2-TPR表明高温还原形成PdZn金属间化合物型合金)得到负载型单原子催化剂(Pd1/ZnO SAC).高分辨电镜结果表明,当Pd负载量由1%降至0.1%,金属纳米颗粒的粒径尺寸显著降低,而在0.01%-Pd/ZnO催化剂表面,Pd活性中心则以单原子状态分散于载体ZnO表面.X-射线吸收光谱及电子能谱表明,随着负载量的降低,Pd活性物种具有更高的正电性.该催化剂在乙炔选择性加氢反应中表现出更加优越的催化性能,具有与PdZn催化剂相当的高选择性,而更优的比活性.这归结于Pd1/ZnO单原子催化剂的Pdδ+单原子活性中心有助于其与乙炔的静电相互作用并吸附活化加氢生成乙烯,并促使乙烯以较弱的π键吸附,从而易于从催化剂表面脱附获得高选择性.     

Multiply Confined Nickel Nanocatalysts Produced by Atomic Layer Deposition for Hydrogenation Reactions

To design highly efficient catalysts, new concepts for optimizing the metal–support interactions are desirable. Here we introduce a facile and general template approach assisted by atomic layer deposition (ALD), to fabricate a multiply confined Ni‐based nanocatalyst. The Ni nanoparticles are not only confined in Al₂O₃ nanotubes, but also embedded in the cavities of Al₂O₃ interior wall. The cavities create more Ni–Al₂O₃ interfacial sites, which facilitate hydrogenation reactions. The nanotubes inhibit the leaching and detachment of Ni nanoparticles. Compared with the Ni‐based catalyst supported on the outer surface of Al₂O₃ nanotubes, the multiply confined catalyst shows a striking improvement of catalytic activity and stability in hydrogenation reactions. Our ALD‐assisted template method is general and can be extended for other multiply confined nanoreactors, which may have potential applications in many heterogeneous reactions.     

HZSM-5催化乙醇脱水停料效应的研究

在HZSM-5分子筛催化乙醇脱水反应中观察到了停料效应：即当停止乙醇-水进料一定时间,恢复进料后乙烯选择性明显提高。通过考察不同反应条件下的停料效应,发现乙醇质量分数控制在55%附近、延长停料时间、升高反应温度和降低乙醇进料空速会提高停料效应强度,并较长时间维持高乙烯选择性。500 h的催化剂稳定性测试表明,停料效应可有效延长催化剂的使用寿命。结合含水乙醇脱水反应机理和实验结果,推测HZSM-5催化乙醇脱水停料效应产生的原因是停料时乙氧基中间体的积累和催化活性空位的再生。     

Naphthalene and perylene diimides for organic transistors

The development of ambient stable organic n-channel semiconductor molecules for thin-film transistors has experienced a tremendous impetus in the last decade to close the gap in performance in comparison to that of their p-channel counterparts. Especially naphthalene and perylene tetracarboxylic diimides (NDI and PDI) have shown to be the most valuable building blocks to achieve this challenging goal and to gain insight into the molecular structure-transistor performance relationship. Remaining challenges and new emerging research fields for these n-type semiconductors are the optimization of their deposition on flexible substrates, the control of their long term ambient stability and their implementation in complementary transistor circuits, display and sensor devices.     

Encapsulation of Crabtree's Catalyst in Sulfonated MIL‐101(Cr): Enhancement of Stability and Selectivity between Competing Reaction Pathways by the MOF Chemical Microenvironment

Crabtree's catalyst was encapsulated inside the pores of the sulfonated MIL‐101(Cr) metal–organic framework (MOF) by cation exchange. This hybrid catalyst is active for the heterogeneous hydrogenation of non‐functionalized alkenes either in solution or in the gas phase. Moreover, encapsulation inside a well‐defined hydrophilic microenvironment enhances catalyst stability and selectivity to hydrogenation over isomerization for substrates bearing ligating functionalities. Accordingly, the encapsulated catalyst significantly outperforms its homogeneous counterpart in the hydrogenation of olefinic alcohols in terms of overall conversion and selectivity, with the chemical microenvironment of the MOF host favouring one out of two competing reaction pathways.     

ZnZrOx-HZSM-5双功能催化剂催化甲苯与合成气烷基化制对二甲苯

作为重要的有机化工原料,近些年来随着聚酯行业的高速发展,对二甲苯(PX)需求量逐年增高.目前,PX主要通过传统的石油路线生产,例如石脑油催化重整、甲苯歧化和C₈芳烃异构化,这些路线的后续精馏能耗较高.甲醇作为碳源与甲苯烷基化制备PX有效提高了目标产物的选择性,且已实现工业化.然而,由于甲醇生成甲氧基烷基化物种的能垒较高,使反应温度较高,促进了甲醇制烯烃(MTO)副反应的进行,降低了甲醇利用率;且由于积炭的形成,催化剂容易失活.合成气是非石油基资源如煤炭、天然气和生物质等利用的重要平台,在转化为醇类、烯烃以及芳烃路径中将经过甲氧基中间体,因此,本文研发以合成气代替甲醇与甲苯烷基化制备PX的催化剂和催化过程.基于本课题组关于CO₂加氢耦合甲苯烷基化制PX的研究基础,本文将ZnZrO_x(ZZO)与ZSM-5(Z5)混合制得双功能催化剂,用于合成气转化耦合甲苯烷基化制PX.研究结果表明,通过优化催化剂的组成和烷基化反应条件,调控CO加氢反应和甲苯烷基化反应的匹配性,在甲苯转化率为10.3%时,可获得64.8%的二甲苯选择性(不计水煤气变换反应),其中PX占81.8%,气态烃副产物的选择性为10.9%;在相同条件下采用甲醇为烷基化试剂时,二甲苯选择性仅38.5%,其中PX占38.8%,此时气态烃副产物的选择性达26.2%.同位素效应实验结果表明,二甲苯中新增甲基来自于合成气,而非甲苯的歧化反应.催化剂构效研究结果表明,PX的选择性与分子筛孔径、酸性强度以及Br?nsted酸性位点有关;原位红外结果也证实了该反应呈现逆同位素效应(k_H2/k_D2=0.92),表明反应中甲酸盐物种(HCOO*)加氢可能是反应的决速步骤.与传统的甲醇甲苯烷基化路径相比,采用来源广泛和成本较低的合成气与甲苯进行烷基化反应的温度(340℃)更低,有效避免了MTO副反应的发生,同时,该催化剂可在100 h内保持良好稳定性.综上,本工作结果为高效制备高值芳烃PX提供了新思路.     

ZnZrOx-HZSM-5双功能催化剂催化甲苯与合成气烷基化制对二甲苯

作为重要的有机化工原料,近些年来随着聚酯行业的高速发展,对二甲苯(PX)需求量逐年增高.目前,PX主要通过传统的石油路线生产,例如石脑油催化重整、甲苯歧化和C₈芳烃异构化,这些路线的后续精馏能耗较高.甲醇作为碳源与甲苯烷基化制备PX有效提高了目标产物的选择性,且已实现工业化.然而,由于甲醇生成甲氧基烷基化物种的能垒较高,使反应温度较高,促进了甲醇制烯烃(MTO)副反应的进行,降低了甲醇利用率;且由于积炭的形成,催化剂容易失活.合成气是非石油基资源如煤炭、天然气和生物质等利用的重要平台,在转化为醇类、烯烃以及芳烃路径中将经过甲氧基中间体,因此,本文研发以合成气代替甲醇与甲苯烷基化制备PX的催化剂和催化过程.基于本课题组关于CO₂加氢耦合甲苯烷基化制PX的研究基础,本文将ZnZrO_x(ZZO)与ZSM-5(Z5)混合制得双功能催化剂,用于合成气转化耦合甲苯烷基化制PX.研究结果表明,通过优化催化剂的组成和烷基化反应条件,调控CO加氢反应和甲苯烷基化反应的匹配性,在甲苯转化率为10.3%时,可获得64.8%的二甲苯选择性(不计水煤气变换反应),其中PX占81.8%,气态烃副产物的选择性为10.9%;在相同条件下采用甲醇为烷基化试剂时,二甲苯选择性仅38.5%,其中PX占38.8%,此时气态烃副产物的选择性达26.2%.同位素效应实验结果表明,二甲苯中新增甲基来自于合成气,而非甲苯的歧化反应.催化剂构效研究结果表明,PX的选择性与分子筛孔径、酸性强度以及Br?nsted酸性位点有关;原位红外结果也证实了该反应呈现逆同位素效应(k_H2/k_D2=0.92),表明反应中甲酸盐物种(HCOO*)加氢可能是反应的决速步骤.与传统的甲醇甲苯烷基化路径相比,采用来源广泛和成本较低的合成气与甲苯进行烷基化反应的温度(340℃)更低,有效避免了MTO副反应的发生,同时,该催化剂可在100 h内保持良好稳定性.综上,本工作结果为高效制备高值芳烃PX提供了新思路.     

Improved Performance of W／HZSM-5 Catalysts for Dehydroaromatization of Methane

The dehydroaramatization of methane over W-supported ZSM-5 with varying degrees of Li^ ion-exchanged catalysts was studied with and without oxygen at 1073 K and atmospheric pressure.Catalyst activity and stability were found to be influenced by the catalyst acidity related to BrSnsted acid sites and by the presence of oxygen in the feed. The NH3-TPD and FTIR-pyridine results demonstrated that partially exchanged of H^ ions by Li^ into the W/HZSM-5 catalysts could be used to control the amount of strong acid sites on the catalyst surface. Without oxygen, the 3WHLi-Z (5:1) catalyst that has strong acid sites equal to nearly 74% of the original strong acid sites in the parent HZSM-5 exhibited the highest methane conversion and selectivity towards aromatics. However, the catalyst deactivated in a five hour period. In the presence of oxygen, the catalyst activity and stability could be improved further.The results of this study revealed that a suitable amount of strong Bronsted acid sites as well as oxygen addition in the feed increased the catalyst activity and stability. The 3WHLi-Z(5:1) catalyst exhibited improved performance in the dehydroaromatization of methane.     

High‐Performance Electrolytic Oxygen Evolution in Neutral Media Catalyzed by a Cobalt Phosphate Nanoarray

The topotactic conversion of cobalt phosphide nanoarray on Ti mesh into a cobalt phosphate nanoarray (Co‐Pi NA) via oxidative polarization in phosphate‐buffered water is presented. As a 3D oxygen evolution reaction (OER) catalyst electrode at neutral pH, the resulting Co‐Pi NA/Ti shows exceptionally high catalytic activity and demands an overpotential of only 450 mV to drive a geometrical catalytic current density of 10 mA cm⁻². Notably, this catalyst also shows superior long‐term electrochemical stability. The excellent catalytic activity can be attributed to that such 3D nanoarray configuration allows for the exposure of more active sites and the easier diffusion of electrolytes and oxygen.     

Tungsten Nitride‐Cobalt Anchored in N‐Doped Ordered Porous Carbon as an Efficient Oxygen Reduction Reaction Electrocatalyst

We prepared a non‐precious‐metal tungsten nitride‐cobalt (WN‐Co) electrocatalyst anchored in nitrogen‐doped ordered porous carbon (NOPC) through an in situ method. The WN‐Co/NOPC electrocatalyst possesses good oxygen reduction reaction (ORR) capability in alkaline media, including a high onset potential of −132 mV, a dominant four‐electron process, and a superior stability (onset potential and limiting current density were almost unchanged after 5000 cycles in 0.1 m KOH). The improved ORR performance was comparable to that of WN/NOPC and Co/NOPC with regard to three aspects: the even dispersion and uniform size of electrocatalyst particles provide more reactive sites; the nitrogen doping, high specific surface area and highly ordered mesoporous channel of catalyst support (NOPC) are conducive to the infiltration of the electrolyte; the existence of WN reinvests the catalyst with good stability, and the anchored configuration of WN and Co in the NOPC will prevent the particles from agglomerating after a long‐term cycle, thereby improving the stability of the catalyst particles.