Magnetic Resonance Signal Amplification by Reversible Exchange of Selective PyFALGEA Oligopeptide Ligands Towards Epidermal Growth Factor Receptors

The biorelevant PyFALGEA oligopeptide ligand, which is selective towards the epidermal growth factor receptor (EGFR), has been successfully employed as a substrate in magnetic resonance signal amplification by reversible exchange (SABRE) experiments. It is demonstrated that PyFALGEA and the iridium catalyst IMes form a PyFALGEA:IMes molecular complex. The interaction between PyFALGEA:IMes and H₂ results in a ternary SABRE complex. Selective 1D EXSY experiments reveal that this complex is labile, which is an essential condition for successful hyperpolarization by SABRE. Polarization transfer from parahydrogen to PyFALGEA is observed leading to significant enhancement of the ¹H NMR signals of PyFALGEA. Different iridium catalysts and peptides are inspected to discuss the influence of their molecular structures on the efficiency of hyperpolarization. It is observed that PyFALGEA oligopeptide hyperpolarization is more efficient when an iridium catalyst with a sterically less demanding NHC ligand system such as IMesBn is employed. Experiments with shorter analogues of PyFALGEA, that is, PyLGEA and PyEA, show that the bulky phenylalanine from the PyFALGEA oligopeptide causes steric hindrance in the SABRE complex, which hampers hyperpolarization with IMes. Finally, a single-scan ¹H NMR SABRE experiment of PyFALGEA with IMesBn revealed a unique pattern of NMR lines in the hydride region, which can be treated as a fingerprint of this important oligopeptide.     

Reprocessing polyurethane foam using dynamic covalent chemistry in extrusion

Thermoset polyurethanes (PUs) pose recycling challenges due to their crosslinked structure. This study investigates the possibility to directly reprocess PU foams through (dynamic) carbamate exchange using reactive extrusion. By varying compounding temperature and catalyst (dibutyltin dilaurate, DBTDL) concentration, the extrusion process is examined using torque measurements. We clearly show that it is possible to reprocess the PU foam at temperatures well below 200°C and that DBTDL catalyst greatly enhances bond exchange rates during compounding. Reproducible extrusions at 160°C with 0.3 wt% DBTDL result in a material with a gel fraction of 0.90 displaying typical dynamic covalent network behavior, as confirmed by stress relaxation measurements. The measured characteristic relaxation times display an Arrhenius-type temperature dependence with an activation energy of 41 kJ/mol. Successful extrusion of fully crosslinked PU foam at milder temperatures with DBTDL catalyst demonstrates potential for PU foam recycling using reactive extrusion, and generally highlights the feasibility of dynamic crosslink reconfiguration for waste reduction and improved sustainability.     

TiCl4改性离子交换树脂催化合成甲缩醛

大孔阳离子交换树脂的磺酸基团与TiCl4络合,形成新的不会被阳离子交换而失活的Lewis酸中心。本文采用液固溶剂法制备金属改性离子交换树脂催化剂,应用于合成甲缩醛反应体系。实验考察了TiCl4负载量、负载温度和负载时间等工艺条件对催化活性的影响,通过正交实验获得了催化剂的较佳制备条件。研究结果显示,经TiCl4负载改性后的阳离子交换树脂的ggwis酸中心大幅度降低,催化活性显著提高。在相同实验条件下,合成甲缩醛的反应收率比改性前最大提高了13．5％,催化剂重复使用6次,催化活性无明显降低。     

强酸性阳离子交换树脂催化合成丁二酸二丁酯

以强酸性阳离子交换树脂为催化剂催化正丁醇和丁二酸反应，合成了丁二酸二丁酯，在0.025 mol丁二酸、0.2 mol正丁醇、1.5 g强酸性阳离子交换树脂和回流分水120 min的条件下，丁二酸二丁酯收率为95.7%，树脂重复使用4次，其活性变化不大。     

Preparation of cost-effective Pt–Co electrodes by pulse electrodeposition for PEMFC electrocatalysts

Low loading platinum–cobalt (Pt–Co) cathode catalyst on a Nafion(Na⁺)-bonded carbon layer is fabricated by using galvanostatic pulse technique to show the advantage of electrodeposition for high utilization of catalyst in proton exchange membrane fuel cell (PEMFC). We observed that Pt–Co catalysts evenly exist on the surface of carbon electrode and its thickness is about 5.8 μm, which is four times thinner than conventional Pt/C. Improved single cell power performance of Pt–Co cathode catalysts with a ratio of 3.2:1 compared with Pt/C is clearly presented.     

离子交换树脂催化合成L-（＋）-酒石酸二乙酯的研究

以L-（＋）-酒石酸和乙醇为原料,直接合成了L-（＋）-酒石酸二乙酯,其结构经过IR确证,比旋光度经旋光仪测定。通过正交实验得优化反应条件为：L-（＋）-酒石酸0.6mol,n（酒石酸）∶n（乙醇）为1：5,带水剂CCl4用量70mL,催化剂用量为20g,酯化反应温度69℃,回流反应约5h,酯收率93%。催化剂使用寿命较长,再生能力较强。     

Oxygen pathways in methane selective oxidation over silica-supported molybdena

Oxygen pathways for CH₄ partial oxidation over a silica-supported molybdena catalyst were investigated using a series of oxygen isotopic exchange experiments and steady state oxygen isotope transients. The initial source of oxygen in the products is masked by rapid and extensive oxygen exchange between the catalyst and the products CO₂ and HCHO. This exchange process occurs at the surface molybdena site and is accompanied by rapid O interchange between the surface and support phases which allows access to the bulk of the support. Laser desorption Fourier transform mass spectra, LDFTMS, indicate equal enrichment of¹⁸O in both the silica and molybdena fragments.     

阳离子交换树脂催化水解多元酸酯的研究

以阳离子交换树脂作为水解催化剂,对2-膦酸丁烷-1,2,4-三羧酸五甲酯水解制备α-膦酸丁烷-1,2,4-二三羧酸（PBTCA）的反应进行了研究,确定了适宜的工艺条件：水酯质量比为（1．1～1．2）：1,催化剂质量分数（占酯总质量）3．5％～4％,反应温度115～120℃,反应时间16h。以阳离子交换树脂代替液体酸作催化剂催化水解2-膦酸丁烷-1,2,4-三羧酸五甲酯,具有不腐蚀设备,反应后易于分离,催化剂用量少且可以再生重复利用,反应时间短,产品质量较高等优点;经^31P NMR谱测定,确认产品为PBTCA,并测得产品中PBTCA的物质的量分数为90．5％。     

固定床固体酸催化乙酸/丙烯酯化合成乙酸异丙酯

在固定床反应系统中,考察了几种固体酸催化剂对于乙酸／丙烯酯化反应的催化作用,研究了温度、压力、进料空速以及原料中水的含量对催化剂活性的影响。实验发现：对于ＨＤ－１催化剂,在１３０℃、１１ＭＰａ、乙酸进料空速（ＬＨＳＶ）为２５２ｈ－１的条件下,乙酸单程转化率可达８８６％,生成乙酸异丙酯的选择性可达９９％,催化剂连续运转１００ｈ,活性无明显的变化。     

High utilization platinum deposition on single-walled carbon nanotubes as catalysts for direct methanol fuel cell

This research aims to enhance the activity of Pt catalysts, thus to lower the loading of Pt metal in fuel cell. Highly dispersed platinum supported on single-walled carbon nanotubes (SWNTs) as catalyst was prepared by ion exchange method. The homemade Pt/SWNTs underwent a repetition of ion exchange and reduction process in order to achieve an increase of the metal loading. For comparison, the similar loading of Pt catalyst supported on carbon nanotubes was prepared by borohydride reduction method. The catalysts were characterized by using energy dispersive analysis of X-ray (EDAX), transmission electron micrograph (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrum (XPS). Compared with the Pt/SWNTs catalyst prepared by borohydride method, higher Pt utilization was achieved on the SWNTs by ion exchange method. Furthermore, in comparison to the E-TEK 20 wt.% Pt/C catalyst with the support of carbon black, the results from electrochemical measurement indicated that the Pt/SWNTs prepared by ion exchange method displayed a higher catalytic activity for methanol oxidation and higher Pt utilization, while no significant increasing in the catalytic activity of the Pt/SWNTs catalyst obtained by borohydride method.     

包围型催化剂：理念、设计及催化性能研究

负载型催化剂广泛应用于多相催化过程,其中活性相和载体之间的界面相互作用及界面密度对催化反应机制及性能的影响一直以来备受关注。利用反向设计思路构造包围型催化剂,并开发一种简易普适的制备方法,即离子交换逆负载法,使载体前体的金属离子通过离子交换反应取代活性金属氢氧化物前体的金属离子,经焙烧、还原形成活性核被载体包围的催化剂。调控离子交换程度及金属、载体前体种类,得到不同结构及种类丰富的包围型催化剂。相比传统负载型催化剂,包围型结构具有更高的界面密度和相互改变的界面性质,且因活性相被载体物理隔离具有高稳定性,在催化反应中表现出更优越的催化性能,有望成为负载型催化剂的升级版进而推动工业催化技术进步。     

Surrounded catalysts: concept,design and catalytic performance

Supported catalysts are widely used in heterogeneous catalysis processes, in which the interfacial interaction between the active phase and the support and the influence of the interfacial density on the catalytic reaction mechanism and performance have always attracted attention. The main preparation method for traditional supported catalysts is impregnation method, in which a metal precursor is deposited onto the outer surface of support, normally rendering limited contact area and relatively weak interface interaction between the active species and the support. We use the reverse design idea to construct the surrounding catalyst, and develop a simple and universal preparation method, namely the ion exchange reverse loading method, so that the metal ions of the carrier precursor can replace the metal ions of the active metal hydroxide precursor through the ion exchange reaction. After calcination and reduction, a catalyst with an active core surrounded by a carrier is formed. The unique surrounded structure presents not only high interface density and mutually changed interface, but also high stability due to the physical isolation of active phase, revealing superior catalytic performance to the traditional supported catalyst, suggesting the great potential of this new surrounded catalyst as the upgrade of supported catalyst.     

Molecular‐Level Investigation of Critical Gap Size between Catalyst Particles and Electrolyte in Hydrogen Proton Exchange Membrane Fuel Cells

Molecular dynamics simulations have been performed to study the structure and transport at the electrode/electrolyte interface in hydrogen‐based proton exchange membrane fuel cells. We examine the wetting of catalyst surfaces that are not immediately adjacent to a Nafion membrane, but rather are separated from the membrane by a hydrophobic gap of carbon support surface (graphite). A mixture of Nafion, water and hydronium ions is able to wet small gaps (7.4 Å) of graphite and reach the catalyst surface, providing a path for proton transport from the catalyst to the membrane. However, for gaps of 14.8 Å, we observe no wetting of the graphite or the catalyst surface. Using a coarse‐grained model, we found that the presence of a graphite gap of 7.4 Å width slowed down the transport of water by at least an order of magnitude relative to a system with no gap. The implication is that catalyst particles that are not within nominally 1 nm of either the proton exchange membrane or recast ionomer in the electrode leading to the membrane do not possess a path for efficient proton transport to the membrane and consequently do not contribute significantly to power production in the fuel cell.     

酯化法合成丙酮酸乙酯的研究

论述了以丙酮酸、乙醇为原料,离子交换树脂作催化剂,催化合成丙酮酸乙酯的新工艺。考察了催化剂种类、用量、原料配比、反应时间以及催化剂使用次数等因素对酯化率的影响,确定了催化剂种类和最佳工艺条件。结果表明,732强酸性离子交换树脂具有良好的催化活性和选择性,可多次重复使用,酯化率可达85.7%,产品质量符合国家标准。     

常温下以甲烷为燃料的质子交换膜燃料电池发电可行性研究

尝试了常温下以甲烷为燃料的质子交换膜燃料电池发电的可能性，研究了温度和阳极催化剂对其燃料电池开路电压和放电性能的影响。结果表明，甲烷在常温下能够进行电化学氧化，随着电池工作温度的升高，燃料电池的开路电压和功率密度逐渐增加。阳极催化剂的铂含量和催化剂的组成对甲烷的电化学氧化具有非常大的影响。90℃下使用Pt（40wt．％）-Ru（20wt．％）／C为阳极催化剂（催化剂担载量：（2mg Pt＋1 mg Ru）·cm^-2），在以甲烷为燃料时，质子交换膜燃料电池功率密度达到了5．4mW·cm^-2。     

A thin-film/agglomerate model of a proton-exchange-membrane fuel cell cathode catalyst layer with consideration of solid-polymer-electrolyte distribution

A thin-film/agglomerate model for the cathode part of a proton-exchange-membrane fuel cell is developed. Parameter estimation is employed to determine the exchange current density in the catalyst layer, proton conductivity of the recast ionomer, and oxygen diffusivity in the solid polymer electrolyte. The effects of catalyst and polymer electrolyte loadings in the catalyst layer on the cell performance are demonstrated using this model. The influence of polymer electrolyte distribution in the catalyst layer is correlated with the oxygen diffusion and proton migration rates within the electrolyte. It is found that proton migration in the polymer electrolyte is the dominant factor for cell current density under normal operating conditions. A better cell performance is achieved by a concentrated polymer electrolyte near the catalyst layer/membrane interface.     

阳离子交换树脂催化合成乳酸异戊酯的研究

以阳离子交换树脂为催化剂，研究了乳酸与异戊醇合成乳酸异戊酯的反应条件，结果表明：用1.0g阳离子交换树脂作催化剂、0.1mol（9g）乳酸，当乳酸与异戊醇的摩尔比为1:2，在回流条件下反应3h后，酯产率可达87.5%，本方法具有催化活性较高，对设备无腐蚀、三废排放少，催化剂可重复使用多次等特点。     

离子交换树脂催化合成丁二酸二乙酯

论述了以丁二酸,无水乙醇为原料,离子交换树脂,催化合成丁二酸二乙酯的新工艺。考察了催化剂种类,用量,原料配比,反应时间以及催化剂使用次数等因素对酯化率的影响,确定了催化剂种类和最佳工艺条件,结果表明HD－8强酸性离子交换树脂具有良好的催化活性和选择性,可多次重复使用,酯化率可达76．4％,产品质量符合国家标准。     

阳离子交换树脂作催化剂合成乙酸乙酯的研究

以DOWEX MARATHONC型强酸性阳离子树脂为催化剂,在常压液相下用乙酸和乙醇合成乙酸乙酯。考察了反应温度、反应时间、催化剂用量和反应物初始摩尔比等参数对反应体系的乙酸乙酯收率影响。通过正交实验得到优化反应条件:反应时间为55 min,反应温度为70℃,催化剂用量为110 g/L,醇与酸摩尔比为1.5∶1,乙酸乙酯收率可达62%。     

Phenol based resin as alkylation catalyst

Conventional cation exchange resin catalysts, used in the phenyl xylyl ethane (PXE) synthesis was found to deactivate after a few cycles. In the present study efforts were made to determine the concentration of residual double bonds of styrene-divinylbenzene based ion exchange resin catalyst. Bromine value of 6–7 was obtained for Indion-130 and Amberlyst-15. An alternate catalyst based on styrenated phenol and formaldehyde which does not use conventional vinylic chemistry for polymer formation was developed. PXE synthesis was explored using these new catalysts. An improvement in the catalyst performance in PXE synthesis was observed, compared to conventional catalysts. Reusability and temperature stability of the new catalysts have been verified by carrying out esterification of phthalic anhydride with 2-ethyl hexanol.