水和醇类分子及其混合物在纳米孔道材料中的传输扩散

随着计算机科学技术的飞速发展,理论计算特别是分子动力学模拟技术在研究受限流体的性质时发挥着独特的作用.本文综述了近年来水和醇类分子及其混合物在纳米孔道材料中传输扩散的研究进展,包括单组分水、甲醇和乙醇等在多种纳米孔道材料中的传输扩散,以及甲醇/水和乙醇/水等混合物在碳纳米管和沸石膜中的吸附和分离,讨论了体系温度、分子浓度以及纳米孔道材料结构等因素对水和醇类分子传输扩散过程的影响.     

典型醇类物质超临界水氧化反应途径研究

采用自主设计的连续流动气封壁超临界水氧化反应装置,研究了典型醇类物质甲醇、乙醇和异丙醇在超临界水中氧化的反应途径,并归纳了醇类物质超临界水氧化反应的规律及特点。研究结果表明,甲醇超临界水氧化反应的主要中间产物为甲醛,同样条件下转化率较乙醇和异丙醇低;乙醇和异丙醇超临界水氧化反应的主要中间产物为丙酮、乙酸、乙醛和甲醇等。三种醇超临界水氧化过程中均涉及到大量活性自由基的相互作用,表现为脱氢、裂解和聚合等反应形式;产物包括碳链增长、不变、降低三种类型。总体来看,醇类物质超临界水氧化反应的趋势是向碳链降低的方向进行,即通过一系列中间产物最后生成CO₂和水。     

典型醇类物质超临界水氧化反应途径研究

采用自主设计的连续流动气封壁超临界水氧化反应装置,研究了典型醇类物质甲醇、乙醇和异丙醇在超临界水中氧化的反应途径,并归纳了醇类物质超临界水氧化反应的规律及特点。研究结果表明,甲醇超临界水氧化反应的主要中间产物为甲醛,同样条件下转化率较乙醇和异丙醇低;乙醇和异丙醇超临界水氧化反应的主要中间产物为丙酮、乙酸、乙醛和甲醇等。三种醇超临界水氧化过程中均涉及到大量活性自由基的相互作用,表现为脱氢、裂解和聚合等反应形式;产物包括碳链增长、不变、降低三种类型。总体来看,醇类物质超临界水氧化反应的趋势是向碳链降低的方向进行,即通过一系列中间产物最后生成CO2和水。     

构建Cu台阶位促进电催化CO2还原制醇类化学品的研究(英文)

电催化CO₂制备高附加值的化学品是解决当前碳排放问题的可行技术路线之一.其中,合成醇类化合物因具有广泛用途和高价值而备受关注.在电催化CO₂还原合成多碳醇反应中,关键中间体*CH₂CHO容易发生热力学有利的脱氧反应而生成C2H4,降低了醇类产物的选择性.由于电催化CO₂还原是一个表面结构敏感的反应,因此可以通过设计Cu基催化剂的特定表面结构,实现对反应路径的有效调节,从而提升醇类产物的选择性.本课题组前期通过密度泛函理论(DFT)计算和主成分分析法等对Cu基催化剂的构效关系进行解析,说明配位不饱和的台阶位点有望高效地促进醇类产物的生成.本文进一步从实验角度,证明了配位不饱和的台阶位点是生成醇类产物的活性位点.本文采用CO分子作为还原剂制备了CuO衍生的金属Cu催化剂(COD-Cu),利用CO分子对Cu表面的重构作用,获得了具有丰富台阶位点的Cu催化剂.而通过H₂还原制备的金属Cu催化剂(HOD-Cu)对照样表面则多为平面位点.X射线衍射和原位拉曼光谱结果表明, CuO前驱体经过...     

C_2H_3与C_2H_5OH和CH_3HCO间的脱氢反应对乙醇-碳氢混合燃料燃烧过程的影响

在QCISD(T)/6-311++G(d,p)//B3LYP/6-311G(d,p)的水平下计算了乙醇及乙醇燃烧裂解产物与C2H3之间的脱氢反应机理,利用正则变分过渡态理论(CVT)结合小曲率隧道效应模型(SCT)计算400~2000 K范围内的速率,对比OH,H及CH3等自由基相似脱氢反应速率,选择2条具有较快反应速率的通道(C2H3+C2H5OH→TS1→C2H4+C2H5O和C2H3+CH3HCO→TS4→C2H4+CH3CO).将这2个反应耦合到正庚烷/乙醇混合燃料及异辛烷/乙醇混合燃料的机理中,利用CHEMKIN程序中预混火焰模型模拟混合燃料的燃烧过程并进行路径分析.对比相应的实验数据发现,改进的动力学模型对燃烧过程中C2H3路径上相近组分的预测精度有较大改善,而对C2H3路径上较远的组分丙炔(C3H4)和乙烯基乙炔(C4H4)等影响不大.     

烯丙醇在亲核取代反应中的研究进展

烯丙醇的亲核取代反应在有机合成化学中具有十分重要的地位,该反应可被广泛应用于具有生物活性的药物以及天然产物的合成.烯丙基化反应也是一类十分重要的引入C-3结构单元的合成方法学.这种合成方法的优点在于双键的保留,使得分子的官能团可以进行进一步转化.传统的Tsuji-Trost烯丙基化方法会产生大量的废弃物,相比之下直接以烯丙醇烯丙基化方法是一种绿色的合成方法.综述了烯丙醇在路易斯酸或者布朗斯特酸催化下与不同的亲核试剂发生分子内和分子间亲核取代反应,构筑C—X(X=C,N,O,S)键的最新研究进展,涉及到芳基化合物、羰基化合物、氨基或者磺胺类化合物以及醇类等不同种类亲核试剂.最后就烯丙醇烯丙基化研究及应用中存在的问题和难点对其前景进行了展望.     

FeCl_3催化合成新型烯丙基醚类化合物

以烯丙基醇类化合物(1a~1i)和乙醇为起始原料,FeCl_3为催化剂,经分子间亲核取代反应合成了9个烯丙基醚类化合物(2a~2i,其中2c,2e~2i为新化合物),收率80%~95%,其结构经1H NMR,13C NMR和HRESI-MS表征。研究了催化剂,溶剂,反应温度和反应时间对2a产率的影响。结果表明:在最优反应条件[1a 0.5mmol,Fe Cl34 mg,Et OH 2.5 mmol,CH2Cl2为溶剂,于室温反应0.8 h]下,2a收率95%。     

若干羰基化反应研究新进展

 直接在化合物分子内引入羰基的羰基化反应是当前绿色化学化工研究的前沿领域之一, 也是实现 C1 资源高值化利用的重要途径. 综述了胺/氨基醇类化合物氧化羰化、环氧化合物氢酯基化、碘代芳烃的羰化 Suzuki 偶联、羰化 Sonogashira 以及双羰基化等重要羰基化反应的研究状况, 特别是结合本课题组近年来在该领域中的工作, 并对羰基化反应的发展及应用前景进行了展望.     

SAPO-34分子筛的合成及用于乙醇脱水的研究

磷酸铝系列分子筛是八十年代开发的新一代分子筛.SAPO-34分子筛是其中的一个成员.SAPO-34属于小孔,大分子不能进入孔道,孔道为三维结构,又无大笼,因此容易结碳的稠环化合物不会形成.由于孔道较小,在C_1分子的催化反应、甲醇脱水制乙酸及甲醇转化成低碳烯烃等方面的应用研究已有较多的报道,但乙醇分子能否顺利进行反应则尚未见报导.考虑到石油资源不丰富的地区以乙醇为化工原料的开发工作有着重要意义,我们研究了乙醇在SAPO-34分子筛上的脱水反应.     

MnO2纳米溶胶-甲醛化学发光体系及其分析应用研究

Na2S2O3在中性水溶液中还原KMnO4可制备得到暗棕色的可溶性MnO2溶胶.所制备的MnO2溶胶透明、稳定,最大吸收波长位于357 nm处,平均粒径约40 nm.研究发现,所制备的MnO2纳米溶胶在酸性介质中与甲醛反应可产生弱的化学发光.考察了近30种药物分子在MnO2纳米溶胶-甲醛体系中的化学发光行为.结果表明,吩噻嗪类药物、氨基硫醇类药物等对该体系的化学发光信号具有显著的增强作用.据此,建立了利用这一化学发光体系测定五种吩噻嗪类药物和四种氨基硫醇类药物新的流动注射化学发光分析方法.所建立的方法被成功地用于片剂中奋乃静含量和猪饲料中盐酸氯丙嗪含量的测定.通过对化学发光光谱、荧光光谱、紫外可见吸收光谱等实验的研究,提出了可能的化学发光反应机理.所有反应的化学发光光谱的最大发射波长均位于630～640 nm间,与分析物的种类无关.当向反应体系中加入单线态氧清除剂叠氮化钠和三亚乙基二胺时,反应的化学发光强度被不同程度的抑制,这表明单线态氧可能是该化学发光反应的发光体.     

Electrooxidation of Several Organic Compounds on Simply Prepared Metallic Nanoparticles: A Comparative Study

The electrooxidation of several fuel compounds was studied using metallic nanoparticles of Au, Pd, Pt, AuPd and AuPt synthesized by direct electrodeposition by applying a constant potential of ‐200 mV (vs. Ag/AgCl) to pencil graphite in an acidic medium. Scanning electron microscope (SEM) images and X‐ray diffraction (XRD) data show that monometallic (Au, Pd and Pt) and alloys of bimetallic nanoparticles of AuPd and AuPt have been formed. The catalytic performance of the prepared electrodes was investigated in a neutral medium (100 mM phosphate buffer, pH 7) by cyclic voltammetry. Amongst all fuels, the highest current densities were obtained by the electrooxidation of formic acid (ca. 9.8 mA cm^?2) and formaldehyde (ca. 9.7 mA cm^?2) on the AuPt catalyst.     

Ternary CoPtAu Nanoparticles as a General Catalyst for Highly Efficient Electro‐oxidation of Liquid Fuels

Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO₂. Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1₀‐structure and Au segregates on the surface to alloy with Pt. The L1₀‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg_Pt, 1.49 A/mg_Pt, and 11.97 A/mg_Pt, respectively in 0.1 m HClO₄. The L1₀‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C?C bond more efficiently for ethanol oxidation.     

Advanced Catalytic Performance of Au–Pt Double‐Walled Nanotubes and Their Fabrication through Galvanic Replacement Reaction

Bimetallic tubular nanostructures have been the focus of intensive research as they have very interesting potential applications in various fields including catalysis and electronics. In this paper, we demonstrate a facile method for the fabrication of Au–Pt double‐walled nanotubes (Au–Pt DWNTs). The DWNTs are fabricated through the galvanic displacement reaction between Ag nanowires and various metal ions, and the Au–Pt DWNT catalysts exhibit high active catalytic performances toward both methanol electro‐oxidation and 4‐nitrophenol (4‐NP) reduction. First, they have a high electrochemically active surface area of 61.66 m² g^?1, which is close to the value of commercial Pt/C catalysts (64.76 m² g^?1), and the peak current density of Au–Pt DWNTs in methanol oxidation is recorded as 138.25 mA mg^?1, whereas those of Pt nanotubes, Au/Pt nanotubes (simple mixture), and commercial Pt/C are 24.12, 40.95, and120.65 mA mg^?1, respectively. The Au–Pt DWNTs show a markedly enhanced electrocatalytic activity for methanol oxidation compared with the other three catalysts. They also show an excellent catalytic performance in comparison with common Au nanotubes for 4‐nitrophenol (4‐NP) reduction. The attractive performance exhibited by these prepared Au–Pt DWNTs can be attributed to their unique structures, which make them promising candidates as high‐performance catalysts.     

Au Nanoparticles Modified with Pt,Ru and SnO2 as Electrocatalysts for Ethanol Oxidation Reaction in Acids

The anodic reaction in direct ethanol fuel cells (DEFCs), ethanol oxidation reaction (EOR) faces challenges, such as incomplete electrooxidation of ethanol and high cost of the most efficient electrocatalyst, Pt in acidic media at low temperature. In this study, core‐shell electrocatalysts with an Au core and Pt‐based shell (Au@Pt) are developed. The Au core size and Pt shell thickness play an important role in the EOR activity. The Au size of 2.8 nm and one layer of Pt provide the most optimized performance, having 6 times higher peak current density in contrast to commercial Pt/C. SnO₂ as a support also enhances the EOR activity of Au@Pt by 1.73 times. Further modifying the Pt shell with Ru atoms achieve the highest EOR current density that is 15 and 2.5 times of Pt/C and Au@Pt. Our results suggest the importance of surface modification in rational design of advanced electrocatalysts.     

Pt/MO2/CNTs催化剂上乙醇电氧化研究

应用循环伏安法研究了几种催化剂Pt/MO2/CNTs（M = Sn, Ti, Ce）和Pt/CNTs对乙醇在H2SO4溶液中的电催化氧化过程。结果表明,金属氧化物的加入有利于乙醇的电氧化,其中,Pt/CeO2/CNTs对乙醇电氧化中间态产物具有显著的氧化性能。综合初始氧化电位、峰电流、总氧化峰面积等参数可以得出Pt/SnO2/CNTs催化剂性能最佳。     

Pt/MO2/CNTs（M=Sn,Ti,Ce）催化剂上乙醇电氧化研究

应用循环伏安法研究了几种催化剂Pt/MO2/CNTs(M=Sn,Ti,Ce)和Pt/CNTs对乙醇在H2SO4溶液中的电催化氧化过程.结果表明,金属氧化物的加入有利于乙醇的电氧化.其中,Pt/CeO2/CNTs对乙醇电氧化中间态产物具有显著的氧化性能.综合初始氧化电位、峰电流和总氧化峰面积等参数,可以得出Pt/SnO2/CNTs催化剂性能最佳.     

High loading Pt nanoparticles on ordered mesoporous carbon sphere arrays for highly active methanol electro-oxidation

Three-dimensionally (3D) ordered mesoporous carbon sphere arrays (OMCS) are explored to support high loading (60 wt%) Pt nanoparticles as electrocatalysts for the methanol oxidation reaction (MOR). The OMCS has a unique hierarchical nanostructure with ordered large mesopores and macropores that can facilitate high dispersion of the Pt nanoparticles and fast mass transport during the reactions. The prepared Pt/OMCS exhibits uniformly dispersed Pt nanoparticles with an average size of 2.0 nm on the mesoporous walls of the carbon spheres. The Pt/OMCS catalyst shows significantly enhanced specific electrochemically active surface area (ECSA) (73.5 m² g^-1) and electrocatalytic activity (0.69 mA cm^-2) for the MOR compared with the commercial 60 wt% Pt/C catalyst.     

One step NaBH4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis and characterization

The ternary catalyst Pt₇₅Ru₅Ni₂₀ was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt₇₅Ru₅Ni₂₀/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.     

石墨烯的制备及石墨烯载Pd催化剂对甲酸的电催化氧化

以纳米石墨为原料,用两种方法分别制得石墨烯GN-1和GN-2。结果表明,用两种方法制备的石墨烯比表面积比纳米石墨都有显著增加。两种方法制备的石墨烯GN-1和GN-2形貌不同,孔径分布也有很大的差异。分别以两种方法制备的石墨烯为载体制备了Pd催化剂Pd/GN-1和Pd/GN-2。Pd/GN-1和Pd/GN-2催化剂的电化学比表面积分别为34.66和71.25 m2/g。这两种催化剂对甲酸的电催化氧化活性都较纳米石墨作载体制备的催化剂Pd/G有显著的提高,甲酸在Pd/GN-1和Pd/GN-2催化剂上的氧化峰电流密度分别为66.0和95.8 mA/cm2。两种催化剂对甲酸的氧化都有很好的稳定性。     

Influence of Substrate Steps on the Catalytic Properties of Pt Layers: The Ethanol Electrooxidation Reaction

The ethanol oxidation reaction (EOR) is investigated on Pt/Au(hkl) electrodes. The Au(hkl) single crystals used belong to the [n(111)x(110)] family of planes. Pt is deposited following the galvanic exchange of a previously deposited Cu monolayer using a Pt²⁺ solution. Deposition is not epitaxial and the defects on the underlying Au(hkl) substrates are partially transferred to the Pt films. Moreover, an additional (100)‐step‐like defect is formed, probably as a result of the strain resulting from the Pt and Au lattice mismatch. Regarding the EOR, both vicinal Pt/Au(hkl) surfaces exhibit a behavior that differs from that expected for stepped Pt; for instance, the smaller the step density on the underlying Au substrate, the greater the ability to break the C?C bond in the ethanol molecule, as determined by in situ Fourier transform infrared spectroscopy measurements. Also, we found that the acetic acid production is favored as the terrace width decreases, thus reflecting the inefficiency of the surface array to cleave the ethanol molecule.