手性修饰的介孔树脂材料负载铂催化剂上丙酮酸乙酯的不对称氢化反应

采用氯铂酸和二氯四氨合铂为前体通过浸渍法分别制备了介孔树脂材料FDU-14负载的质量分数为5%的铂催化剂Pt/FDU-14, 并利用XRD, TEM, N₂气吸附和CO化学吸附等手段对催化剂进行了表征. 考察了经过手性分子辛可尼定修饰后的Pt/FDU-14催化剂在丙酮酸乙酯不对称氢化反应中的催化性能. 以氯铂酸为前体制备的Pt/FDU-14催化剂因其具有较小的铂粒子和较高的分散度而表现出较高的活性, 乙酸溶剂中的初始活性(TOF)可以达到21902 mol/(mol?h); 而以二氯四氨合铂为前体制备的Pt/FDU-14催化剂则具有较强的手性诱导能力, 乙酸溶剂中(R)-(+)-乳酸乙酯的光学选择性可以达到81.4% e.e.. 更重要的是, 由于FDU-14具有较强的疏水性, Pt/FDU-14催化剂在水溶剂中也表现出较高的催化性能, 并且还可以重复使用10次以上.     

手性修饰的介孔碳材料MPC-61负载铂催化剂上α-酮酸酯的不对称氢化反应

采用氯铂酸乙醇溶液和氯铂酸水溶液为前体,通过浸渍法制备了介孔碳材料MPC-61负载Pt质量分数分别为4%和10%的Pt/MPC-61催化剂,并利用XRD,TEM,N2吸附-脱附和CO化学吸附等手段对催化剂进行了表征.考察了经过手性分子辛可尼定修饰后的Pt/MPC-61催化剂在丙酮酸乙酯不对称氢化反应中的催化性能.以氯铂...     

金属前躯体溶剂对Pt/ZSM-22催化剂临氢异构性能的影响

将Pt前驱体分别溶解于水、乙醇、丙酮、乙酸中,采用浸渍法制备了一系列成型Pt/ZSM-22催化剂。通过XRD、BET、TEM、CO-chemisorption、CO-FTIR和Py-FTIR等表征手段对催化剂的物相结构、织构性质、金属性质和酸性进行了系统地考察并以正十二烷为模型化合物,研究了前躯体溶剂对临氢异构反应性能的影响。结果表明,溶剂极性是造成Pt分散差异的主要原因;以乙醇、丙酮和乙酸为浸渍溶剂制备的催化剂,Pt多分布于ZSM-22分子筛上,并与酸性位相互作用造成Pt缺电子;而以水为溶剂则造成Pt多分布于氧化铝黏结剂上,对Pt的电子性质影响较小。在临氢异构反应中,与Pt落位于氧化铝相比,Pt分布于ZSM-22分子筛上表现出更高的活性和异构选择性,表明缩短酸性位与金属位间距可使反应物和异构中间体迅速扩散至金属位上发生脱氢和加氢反应。     

制备方法对Pt-Sn-K-Mg/γ-Al2O3催化剂正十二烷脱氢性能的影响

以正十二烷脱氢反应为探针反应,采用顺序浸渍、乙醇共浸渍、盐酸共浸渍的方法制备了Pt-Sn-K-Mg/γ-Al2O3催化剂,并采用NH3-TPD、CO脉冲吸附、H2-TPR、准原位XPS等表征手段探究浸渍顺序和溶剂对催化剂构效关系的影响。结果表明,盐酸水溶液共浸渍的方法制备的催化剂表现出了最佳的初始活性和较好的稳定性。催化剂的弱酸性位点的增加有利于Pt的分散,从而提高催化性能。采用乙醇为溶剂的共浸渍方法更有利于PtSn间形成更强的相互作用生成更多的PtSn合金,这对初始活性不利,但对选择性影响较小。     

助剂Sn对丙烷脱氢制丙烯Pt氧化铝催化剂性能的影响

采用高压浸渍法制备了Pt-Sn/Al2O3催化剂,Pt含量为0.25%,以丙烷脱氢制丙烯的反应评价了催化剂的性能,考察了氧化铝晶型、制备方法、Sn添加量和空速对催化剂性能的影响。结果表明θ型的氧化铝载体比?型氧化铝活性高,?型氧化铝制备的样品活性较低,与常规浸渍法相比,高压浸渍法制备的催化剂活性较高,助剂Sn的添加量对催化剂上丙烷的转化率、丙烯选择性和稳定性具有较大的影响,催化剂的分散度与活性是正相关的,当Pt与Sn的摩尔比为1∶2.5时催化剂活性和分散度最高,转化率为35.6%,选择性大于95%,反应72 h内催化剂性能稳定,较优的丙烷反应空速为1 500/h。     

2,3,6-三氯吡啶选择性脱氯制2,3-二氯吡啶的研究

采用过量浸渍法制备了Pd/C催化剂,用2,3,6-三氯吡啶选择性脱氯制备2,3-二氯吡啶的反应,评价了催化剂的性能,考察了钯负载量、反应温度和缚酸剂对催化剂活性的影响。结果表明,在钯负载量为0.5%(wt)、反应温度为140℃的条件下,催化剂上2,3,6-三氯吡啶的转化率达100%,产物2,3-二氯吡啶的选择性大于71%,在溶剂甲醇中添加三乙胺后能够有效的提高目标产物的选择性,较优条件下2,3-二氯吡啶的选择性可以达到80%。     

Pt/WO3/ZrO2 催化甘油选择性脱羟基制 1,3-丙二醇反应的溶剂效应

 考察了不同溶剂中 Pt/WO3/ZrO2 催化剂催化甘油加氢制 1,3-丙二醇的反应性能. 结果表明, 质子溶剂乙醇和水有利于甘油转化为 1,3-丙二醇. 含有乙醇或水的二元混合溶剂表现出明显的溶剂组分协同效应, 使用混合溶剂时 1,3-丙二醇选择性超过使用单一溶剂, 而且混合溶剂的组成对反应性能影响很大.     

凹凸棒土负载铂催化剂上对氯硝基苯的高活性高选择性液相加氢反应

分别采用乙醇-异丙醇、H2和NaBH4还原方法制备了凹凸棒土负载铂催化剂(分别标记为Pt/PAL(I)、Pt/PAL(II)和Pt/PAL(III)), 其在对氯硝基苯(p-CNB)的催化选择加氢反应中表现出不同的催化性能. 在Pt/PAL(II)催化剂上, 对氯苯胺(p-CAN)的选择性达到了100%, 并且在p-CNB 完全转化的情况下, 脱氯反应得到了完全的抑制. 在Pt/PAL(I)和Pt/PAL(III)催化剂上, 尽管脱氯反应没有得到完全的抑制, 但也分别得到99.7%和99.9%的p-CAN选择性. Pt/PAL(I)催化剂表现出最高的催化活性,转化频率(TOF)值高达27010 h-1. Pt/PAL(II)和Pt/PAL(III)催化剂表现出稍微低的催化活性, TOF值分别为17193 和24871 h-1. 利用透射电镜(TEM)、X射线衍射(XRD)和傅里叶变换红外光谱(FTIR)对催化剂样品进行了表征, 结果表明优异的催化性能主要归因于铂粒子尺寸和凹凸棒土载体的影响.     

W掺杂多级孔SiO2纳米球负载Pt用于催化甘油氢解制1,3-丙二醇

合成了原位W掺杂的多级孔SiO₂纳米球材料(W-HPSN), 系统考察了W-HPSN合成过程中短链醇类共溶剂(甲醇、乙醇、正丙醇)的加入对Pt/W-HPSN催化剂甘油氢解制1,3-丙二醇(1,3-PDO)性能的影响. 与仅以水为溶剂合成的材料制备的Pt/W-HPSN-H₂O催化剂相比, 加入醇类共溶剂后, 催化剂的比表面积均有不同程度的增大, 并在除1.4 nm的微孔和>2 nm的介孔以外, 在1.7 nm处出现了新的微孔结构. 在甘油氢解反应中, 加入醇类共溶剂合成的材料制备的催化剂的催化性能也更高. 在最佳的以甲醇作为共溶剂合成的Pt/W-HPSN-Me催化剂上, 甘油转化率和1,3-PDO选择性分别为88.8%和56.3%, 而Pt/W-HPSN-H₂O催化剂上二者分别为64.1%和40.7%. 根据表征结果, 推测更小的Pt粒径、更多原位产生的Brønsted酸位, 有利于提高Pt/W-HPSN催化剂的催化性能. 通过对W-HPSN-Me的组成进行优化, 发现当W/Si物质的量比为1/320时, Pt/W-HPSN-Me催化剂在423 K、氢气压力4 MPa、反应时间仅为12 h的反应条件下, 甘油转化率和1,3-PDO选择性进一步提高至98.7%和58.8%, 1,3-PDO得率可达58.0%, 展示了HPSN材料作为甘油选择氢解制1,3-PDO催化剂载体的良好应用前景.     

基于Cu-Fc配位聚合物衍生的Pt-Cu/CuxFeyO@C催化1,4-丁炔二醇加氢性能研究

1,4-丁烯二醇是精细化工领域的重要中间体,有着广泛的应用.采用异丙醇还原氯铂酸制备Pt纳米颗粒,并通过浸渍法将其负载于1,1’-二茂铁二羧酸(Fc)与CuCl_2·2H_2O水热法合成的Cu-Fc配位聚合物,干燥焙烧后制备得到Pt-Cu/Cu_xFe_yO@C催化剂,利用XRD、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、热重分析仪(TG)、N_2吸附脱附仪等表征手段对所制备的催化剂进行表征,对比了催化剂焙烧前后加氢效果,并考察了催化剂与底物的物质的量之比对1,4-丁炔二醇加氢制备1,4-丁烯二醇的影响.结果表明,以焙烧后制备的5%Pt-Cu/Cu_xFe_yO@C催化剂,在n催化剂∶n原料=1∶2 000,温度为120℃,H_2压力为4 MPa,反应时间为30 min的条件下,加氢反应的转化率为100%,生成1,4-丁烯二醇选择性为96.1%.     

微乳液法制备Pt/ZrO2催化剂及其催化加氢活性研究

采用十六烷基三甲基溴化铵（CTAB）/正丁醇/环己烷/H2PtCl6微乳液体系,以N2H4.H2O为还原剂,ZrO2为载体,制备Pt/ZrO2催化剂。以对氯硝基苯（p-CNB）选择加氢反应为探针,考察微乳液组成及载体焙烧温度对Pt/ZrO2催化剂催化活性的影响。由TEM、XRD对载体和催化剂进行表征。结果表明,采用微乳...     

Carbon-supported Pt^Ag nanostructures as cathode catalysts for oxygen reduction reaction

Pt(m)^Ag nanostructures (m being the atomic Pt/Ag ratio, m = 0.1-0.6) were prepared by reflux citrate reduction of PtCl(6)(2-) ions in aqueous solution containing colloidal Ag (6.3 ± 3.9 nm). A distinct alloying of Pt with Ag was detected due to an involvement of the galvanic replacement reaction between PtCl(6)(2-) and metallic Ag colloids. The nanostructure transformed from a structure with an Ag-core and an alloyed PtAg-shell to a hollow PtAg alloy structure with the increase in m. Compared to a commercial E-TEK Pt/C catalyst, the catalytic performance of Pt in the Pt(m)^Ag/C samples for the cathode oxygen reduction reaction (ORR) strongly correlated with the electronic structure of Pt, as a consequence of varied Pt dispersion and Pt-Ag interaction. With either H(2)SO(4) or KOH as an electrolyte, Pt in the Pt(m)^Ag nanostructures with a relatively high m (≥0.4) showed significantly enhanced intrinsic activity whereas Pt in those catalysts with low m (≤0.2) appeared less active than the Pt/C catalyst. These data are used to discuss the role of electronic structure and geometric effects of Pt toward ORR.     

氢钼青铜对铂催化氧还原反应的促进作用

采用循环伏安法在玻碳电极上和硫酸溶液中电沉积制备出铂催化剂(Pt)及铂-氢钼青铜复合催化剂(Pt-HxMoO3), 用旋转圆盘电极研究并比较了它们对硫酸溶液中氧还原反应的催化活性. 研究结果表明, HxMoO3能明显地提高Pt对氧还原反应的电催化活性. 通过对静态电极上氧还原的峰电流与扫描速度的关系以及旋转圆盘电极上氧还原电流与旋转速度的关系的分析发现, HxMoO3提高了铂电极氧还原反应电荷传递步骤的传递系数, 因此加快了氧还原的动力学过程.     

电化学石英晶体微天平研究碱性介质中单层级铂原子修饰的金电极上甲醇的电催化氧化

通过在Au电极表面欠电位沉积(UPD)Cu、再与Pt源(H2PtCl6或K2PtCl4)进行置换反应,制得单层级Pt原子修饰的金电极(对H2PtCl6或K2PtCl4,所制电极分别记为Pt(CuUPD-Pt4+)n/Au或Pt(CuUPD-Pt2+)n/Au,n表示欠电位沉积-置换过程的重复次数).用电化学石英晶体微天平(EQCM)技术定量研究了所制电极,评估了其在碱性环境中催化甲醇氧化的质量比活性(SECA).结果表明,以H2PtCl6为Pt源所制电极(Pt(CuUPD-Pt4+)3/Au)的活性更高,最大SECA高达35.7mAμg-1.根据EQCM结果计算了置换效率,籍此讨论了Pt原子在Au电极表面的层层组装结构,发现所制电极表面的裸Au位点分布百分数与实验结果(由AuOx还原峰电量测算)吻合.我们认为,EQCM技术是一种定量研究电极支撑的超薄催化剂的有效手段,这种高效的单层级贵金属催化剂有望在生物、能源、环境相关的电催化研究中进一步应用.     

Efficiency enhancement of methanol/ethanol oxidation reactions on Pt nanoparticles prepared using a new surfactant, 1,1-dimethyl heptanethiol

In this study, carbon-supported platinum nanoparticle catalysts were prepared using PtCl(4) and H(2)PtCl(6) as starting materials and 1-heptanethiol, 1,1-dimethyl heptanethiol, 1-hexadecanethiol and 1-octadecanethiol as surfactants. These nanoparticles can be used as catalysts for methanol and ethanol oxidation reactions in methanol and ethanol fuel cells. 1,1-Dimethyl heptanethiol was used for the first time in this type of synthesis; other surfactants were used to synthesize nanoparticles for comparison of the catalyst's performance. Cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to characterize the catalysts. It should also be stressed that AFM was employed for the first time in determining the surface topography of these catalysts. XRD, TEM and AFM height results indicate that the platinum crystallizes into a face-centered cubic structure and the surfactant plays an important role in determining the size of the platinum nanoparticles. XPS data revealed that the platinum was found in two different oxidation states, Pt(0) and Pt(IV) with a ratio of about 7.5:2.5, respectively. Electrochemical studies showed catalyst IIa to be the most active sample towards methanol/ethanol oxidation reactions (～342 A g(-1) Pt at 0.612 V for methanol (4.6 times more active than the commercial catalyst), ～309 A g(-1) Pt at 0.66 V for ethanol, (15.4 times more active than the commercial catalyst)).     

Morphology of nanostructured platinum in mesoporous materials-effect of solvent and intrachannel surface

An intrachannel surface of host silica was functionalized through the reaction of surface silanol groups with silanes to generate a monolayer of positively charged groups, and together with the strongly adsorbed and negatively charged PtCl6(2-), resulting in nanostructured platinum-mesoporous silica composites. The highly dispersed Pt nanoparticles and nanonetworks are fabricated from (CH3O)3Si(CH2)3N(CH3)3+Cl- functionalized mesoporous silica MCM-48 with H2PtCl6 in ethanol and water solvent, and characterized by PXRD, XAS, TEM, and N2 adsorption. The solvent of H2PtCl6 solution is found to affect the mobility of Pt precursors and the resulting morphology of nanostructured metallic Pt. The effect of the intrachannel surface properties on the incorporation and the morphology of nanostructured Pt on the deposition of Pt(NH3)4Cl2 and H2PtCl6 on Al-doped or C-coated mesoporous silica MCM-41 is also studied relative to that on pure silica MCM-41.     

In situ synthesis of Pt/carbon nanofiber nanocomposites with enhanced electrocatalytic activity toward methanol oxidation

Pt/carbon nanofiber (Pt/CNF) nanocomposites were facilely synthesized by the reduction of hexachloroplatinic acid (H(2)PtCl(6)) using formic acid (HCOOH) in aqueous solution containing electrospun carbon nanofibers at room temperature. The obtained Pt/CNF nanocomposites were characterized by TEM and EDX. The Pt nanoparticles could in situ grow on the surface of CNFs with small particle size, high loading density, and uniform dispersion by adjusting the concentration of H(2)PtCl(6) precursor. The electrocatalytic activities of the Pt/CNF nanocomposites were also studied. These Pt/CNF nanocomposites exhibited higher electrocatalytic activity toward methanol oxidation reaction compared with commercial E-TEK Pt/C catalyst. The results presented may offer a new approach to facilely synthesize direct methanol fuel cells (DMFCs) catalyst with enhanced electrocatalytic activity and low cost.     

水溶性双金属催化剂在硝基化合物加氢反应中的协同效应

采用水溶性催化剂在两相体系下进行的催化反应既保持了均相催化剂的优点，又可通过简单的相分离达到使产物与催化剂分离的目的［’1．对于水溶性催化剂在两相体系中催化加氢反应，文献中大多采用水溶性铐一瞬、铱一脚和钉一碟络合物为催化剂对a、“不饱和醛、酮、酸等化合物的选择加氢进行考察［’‘．然而对水溶性把一脚络合物催化加氢反应性能研究的报道甚少［‘j．在多相催化中，双（或多）金属的协同效应是常见的现象，但在均相及高分子负载的催化体系中双（或多）金属的协同效应的报道较少［‘］．我们曾报道了高分子负载的Pd／RU双…     

电化学方法制备高分散Pt/CMK-3及其对甲醇电化学催化性能

采用直接电化学还原法在介孔碳(CMK-3)载体上直接电沉积高分散的铂纳米颗粒,制备CMK-3复合铂纳米颗粒电极(Pt/CMK-3)。 通过透射电子显微镜分析发现,铂纳米颗粒非常均匀的分布在CMK-3上,平均粒径约5 nm。 通过循环伏安测试,分析了催化剂不同负载铂含量时氯铂酸的利用率,在理论铂质量分数为20%时,这种方法制备的Pt/CMK-3所使用的氯铂酸的利用率最高,在1 mol/L CH3OH+0.5 mol/L H2SO4溶液中循环伏安测试电流密度达到382 A/g。 在相同实验条件下,Pt/CMK-3电极对甲醇电催化活性远高于Pt/XC-72(炭黑)电极和用常规电沉积方法制备的Pt/CMK-3电极。