SAPO-34提升铁钒基催化剂抗碱性能研究

采用浸渍法制备Fe-VO_x/SAPO-34和Fe-VO_x/TiO₂脱硝催化剂,探究SAPO-34分子筛与TiO₂两种载体负载铁钒基氧化物催化活性及抗碱性能的差异。借助X射线衍射(XRD)、X射线光电子能谱(XPS)、氨气程序升温脱附(NH₃-TPD)、氢气程序升温还原(H₂-TPR)、原位红外漫反射(in-situ DRIFTs)等表征手段对催化剂的骨架结构、表面物化性质、氧化还原能力以及对反应气体的吸脱附情况进行分析。结果表明:SAPO-34分子筛内部特定的孔道结构和稳定的骨架,有利于活性组分在载体上均匀分散,降低碱金属对表面活性中心的物理覆盖作用;同时其表面丰富的酸位点能够作为碱金属捕获位,保护催化剂表面的活性中心,保证催化剂的吸附-反应过程能够正常进行,从而使Fe-VO_x/SAPO-34表现出良好的抗碱金属能力。     

Proton exchange membrane prepared by blending polybenzimidazole with poly (aminophosphonate ester)

In this article, we report a new amorphous-crystalline polymer blend system consisting of poly (4, 4′-diphenylether-5, 5′-bibenzimidazole) (OPBI) and poly (aminophosphonate ester) (PAPE) polymers, the membranes of which were fabricated using the solution blending route. A series of blend membranes at different ratios were prepared and systematically analysed for chemical interactions, morphological changes and their physico-chemical properties studied for use as proton exchange membrane. While FT-IR spectroscopy established the hydrogen bonding interactions between N–H of OPBI and phosphonate ester group of PAPE, X-ray diffraction studies revealed the development of crystallinity in the membrane matrix. Interestingly, the gradual induction of crystallinity in an amorphous OPBI matrix was found to influence the properties of the blend membranes favourably. For instance, the blend membrane containing 25 wt% PAPE in OPBI matrix displayed the maximum property enhancement in terms of storage modulus, glass transition temperature (T_g), phosphoric acid (PA) doping level (37 mol/OPBI repeat unit) and most importantly proton conductivity (0.135 S/cm at 180 °C) which is almost twice the value for pristine OPBI (0.05 S/cm at 180 °C) under identical conditions. Although improved properties were observed at other blend ratios as well, the studies ascertain that the membrane with 25 wt% PAPE was found to be the threshold ratio up to which properties increase and beyond which i.e. at >25 wt% PAPE, there is a decrement in properties like mechanical stability and proton conductivity. An important reason for this was attributed to the creation of a right balance of amorphous and crystalline domains and appropriate intra and inter-polymer hydrogen bonding interactions in the matrix of 75/25 (OPBI/PAPE) blend membrane.     

三种分子筛催化苯胺缩合制二苯胺性能研究

分别以HY,Hβ,HMOR为母体,与拟薄水铝石、铝溶胶混合,采用机械挤出法制备催化剂,采用XRD、N₂等温吸附-脱附（N₂-sorption）、NH₃-TPD、吡啶吸附红外光谱（Py-IR）等分析手段进行表征,探讨了其物化性能的差异,并采用固定床反应器考察了上述催化剂对苯胺缩合制二苯胺反应的催化性能.结果表明,分子筛中强酸对催化剂活性有决定性作用,酸类型对催化性能影响不大;分子筛孔径对二苯胺选择性有显著影响,较小的孔径不利于二苯胺的生成和扩散,降低了目标产物的选择性.因此,在设计和选择苯胺缩合制二苯胺催化剂时应考虑酸性质和孔道尺寸对苯胺转化率和二苯胺选择性的影响来优化催化剂.     

改性纳米ZSM-11分子筛及其催化苯与甲醇烷基化反应的性能

采用先NaOH溶液碱处理后用柠檬酸溶液酸处理的方法对纳米ZSM-11分子筛进行改性.采用X射线衍射(XRD)、N_2吸附-脱附、扫描电镜(FE-SEM)、NH_3-TPD和热重(TG)等技术对改性前后的样品进行表征,将得到的催化剂应用于苯与甲醇烷基化制甲苯反应,结果表明:采用经改性处理的纳米ZSM-11分子筛催化剂,在反应温度为350℃,压力为0.2 MPa,质量空速(WHSV)为6 h~(-1),苯与甲醇进料摩尔比为1∶1的条件下,苯与甲醇烷基化反应产物中甲苯选择性明显提高,苯转化率达到44.7%,甲苯和二甲苯总选择性达到97.4%,其中甲苯选择性为86.5%,甲苯收率为37.8%.     

HZSM-5分子筛催化合成乙酰水杨酸——推荐一个半微量有机化学实验

设计了一个以水杨酸和乙酸酐为原料,以HZSM-5分子筛为催化剂,在室温或加热条件下高效合成乙酰水杨酸的半微量有机化学实验。与经典实验方法相比,新实验具有反应易于操作、产率高、污染小等优点,更符合绿色化学教学理念。     

二次生长法NaA沸石分子筛膜的合成与表征——推荐一个研究型综合实验

介绍一个研究型综合实验——二次生长法NaA沸石分子筛膜的合成与表征。实验预先利用热浸渍法在α-Al_2O_3多孔载体管外表面引入NaA沸石分子筛晶种,再通过二次生长法合成NaA沸石分子筛膜。用扫描电子显微镜和X射线衍射仪表征载体管和NaA沸石分子筛及膜的形貌和结构,并利用渗透蒸发乙醇脱水膜分离装置测试膜的分离性能。通过本实验使学生了解膜分离技术这一科学前沿领域,激发学生对科学研究的兴趣,培养学生的科研探究能力。本实验涵盖合成、表征及性能测试,知识要点多、学科覆盖面广,有利于提升学生的实践操作能力、创新意识和综合运用知识的能力。     

A Review of Proton Exchange Membrane Fuel Cell Catalyst Layer by Electrospinning北大核心CSCD

The limitation of catalyst layer for proton exchange membrane fuel cell (PEMFC) in cost, durability and performance constitutes the bottleneck for the commercialization of fuel cell vehicles.Electrospun catalyst layer, with high catalyst utilization, increased triple phase boundary (TPB) and triple phase channel (TPC), has been developed by many researchers.This paper reviews the research progress in the electrospun catalyst layer for PEMFC, combined with the author's work.Firstly, the development progress of catalyst layer is summarized, and the catalyst layer is classified and analyzed based on its fabrication method and struc¬ture character.Next, the fabrication process, physical property characterization, electrochemical performance analysis and durability characterization of the electrospun nanofiber catalyst layer are described.Finally, further develoment tendency in catalyst layer for PEMFC is viewed by comparion of three kinds of catalyst layers from the viewpoints of TPB, TPC and mass production.Future re¬search topics are discussed. © 2018 Chinese Chemical Society. All rights reserved.     

Acid Treated Carbon as Anodic Electrocatalysts toward Direct Ascorbic Acid Alkaline Membrane Fuel Cells; [酸处理的碳作为阳极电催化剂用于直接抗坏血酸碱性膜燃料电池]北大核心CSCD

In order to improve the hydrophilicity and electrocatalytic activity, commercial carbon black (BP 2000) was subjected to acid treatment to obtain acid-treated carbon (ATC).The generation of rich oxygen-containing groups on the surface of the ATC was proved by X-ray photoelectron spectra (XPS), Fourier transform-infra red spectra (FTIR), thermogravimetric analysis (TG) and contact angle measurement.UV-vis spectra were firstly recorded to calculate activation energy (Ea) of ascorbic acid (AA) chemical oxidation in alkaline conditions by oxygen in air and the Ea value was determined to be 37.1 kJ·mol-1.Additionally, electrochemical impedance spectra (EIS) were used to evaluate unprecedented Eaelectrochem of ATC as electrocatalysts toward ascorbic acid (AA) oxidation in alkaline media.The Eaelectrochem values of electrochemical oxidation in alkaline membrane electrode assembly (MEA) setup of a single cell without and with ATC as the anodic electrocatalysts were calculated to be 34.5 and 26.5 kJ·mol-1, respectively.The diminished Eaelectrochem suggests that ATC does function as an effective anodic electrocatalyst.Furthermore, the ATC was applied in direct ascorbic acid alkaline membrane fuel cell (DAAFC) for the first time.We optimized a series of parameters for the fabrication of MEAs including catalyst coated membrane (CCM) or catalyst coated gas diffusion layer membrane (CDM), loading of anodic electrocatalyst, and ionomer content in the electrocatalyst slurry.It turned out that the CCM with the ATC loading of 0.5 mg·cm-2 and 25wt% ionomer reached a high power density of 18.5 mW·cm-2, which is higher than that of using PtRu/C as anodic electrocatalyst (less than 5.0 mW·cm-2).In addition, the DAAFC fed with 15 mL·min-1 of the fuel containing 0.5 mol·L-1 AA and 1 mol·L-1 NaOH aq.could stably hold a power density at 4 mW·cm-2 for 25 min. © 2018 Journal of Electrochemistry. All rights reserved.     

Stabilization Strategies of Pt Catalysts for Proton Exchange Membrane Fuel Cells北大核心CSCD

The low service lifetime of proton exchange membrane fuel cells (PEMFCs) is the main bottleneck for their commercial applications.One of the main factors is that the expensive metal Pt catalyst is easy to degradation under the harsh working environment of PEMFC (such as variable voltage, strong acidity, gas-liquid two-phase flow), which leads to the inevitable decay of the catalytic performance, thus, seriously restricting the lifetime of PEMFC.Therefore, the electrochemical stability of Pt-based electrocatalysts has become an important and hot topic to improve the PEMFC lifetime.In this paper, we review the recent development in enhancing the stability of Pt electrocatalysts for PEMFC, mainly focusing on the achievements obtained by our group, especially, the polymer stabilization strategy, carbon encapsulation/confinement stabilization strategy, and support stabilization strategy.In addition, the challenges in these Pt catalyst stabilization strategies are summarized, and the corresponding measures and future research trends in facing these challenges are suggested.,,,,. © 2018 Chinese Chemical Society. All rights reserved.     

高性能T型沸石膜的合成及水热/耐酸性能

考察了晶种尺寸形貌及晶化温度对T型沸石膜的形成演化过程以及分离性能的影响,调查表明采用小尺寸的晶种可制备出致密的沸石膜,且膜的生长速率受晶化温度影响,低温下合成同性能的膜需更长的晶化时间。当晶种尺寸分别为0.4和0.6μm时,423 K晶化4 h可制得高性能的T型沸石膜,348 K分离90%(w/w)异丙醇/水混合物体系,其通量分别高达6.21和5.98 kg·m~(-2)·h~(-1),分离因子均10 000。实验发现,膜的形成过程受外延生长机理控制,与晶种形貌尺寸和晶化温度无关,且所制得的高性能T型沸石膜具有很好的水热稳定性及耐酸性。