这项工作得到了普渡大学化学工程学院的支持。先进光子源的使用得到了美国能源部基础能源科学办公室的支持。 DE-AC02-06CH11357。 MRCAT业务，beamline 10-BM由能源部和MRCAT成员机构支持。作者还承认使用beamline 11-ID-C。我们感谢Evan Wegener对XAS的实验帮助。

负载型2nm Pt-Cu双金属纳米粒子催化剂的合成<ol><li> 金属前体溶液的制备 <ol><li>将0.125g硝酸铜三水合物（Cu（NO 3 ） 2 ·3H 2 O）溶解在1mL水中以获得天蓝色溶液。 注意:处理化学品时请使用防护手套。 </li><li>将氨滴加到硝酸铜溶液中，形成深蓝色的氢氧化铜沉淀。 注意:使用通风橱处理碱和挥发性化学物质。 </li><li>继续加入氨，直到深蓝色沉淀物溶解形成深蓝色溶液，pH&gt; 10。 </li><li>向溶液中加入0.198g硝酸四氨基铵（（NH 3 ） 4 Pt（NO 3 ） 2 ）和另外的水，使溶液的总体积为3.5mL。如果需要添加额外的氨，以保持溶液的pH值大于10。 </li><li>将溶液加热至70℃，直到所有的四氨基十六烷基硝酸盐溶解在溶液中。让溶液冷却至室温。 </li></ol></li><li> 共浸渍金属前体溶液 <ol><li>在催化剂制备之前，确定二氧化硅载体的浸渍孔体积。小心地将约5g干二氧化硅称重到加重盘中。混合时，滴加H 2 O直到二氧化硅完全湿润，但没有过量溶液。重刷湿二氧化硅。将加入的克的克数除以样品的克数以计算孔体积。 </li><li>在陶瓷蒸发皿中一次将溶解的金属前体溶液几滴加入到5g高孔二氧化硅（SiO 2 ）中，并轻轻搅拌以分散粘附在一起的颗粒以实现溶液的均匀分布。 注意:一旦吸收了所有3.5 mL的金属前体溶液，白色二氧化硅就会变成深蓝色ñ。 <ol><li>确保二氧化硅颗粒的质地保持与干砂的质地相同。避免在浸渍过程中过量溶液的积聚。 </li></ol></li><li>将浸渍的Pt-0.7Cu / SiO 2催化剂前体放入干燥炉中，并以125°CO / N干燥。 </li></ol></li><li> 煅烧和还原 <ol><li>在250℃的炉中以5℃/ min的升温速率在空气中煅烧催化剂3小时。 注意:在较高温度下煅烧通常会导致较大的Pt纳米颗粒。 </li><li>在1"石英管反应器的中间放置2厘米的石英棉层，并通过塑料漏斗将煅烧后的Pt-0.7Cu / SiO 2催化剂装入管中，将管放置在蛤壳温度程序化的炉中。 </li><li>在室温下用N 2吹洗管5分钟后，以与N 2 （100ccm）相同的流速开始流动H 2 （室温），以将Pt-0.7Cu /SiO 2催化剂。 </li><li>以5℃/ min的升温速率将温度升至150℃并保持5分钟。 </li><li>以2.5°C / min的速度缓慢升温至250°C。每25°C保持15分钟。 注意:其他金属可能需要较低或更高的还原温度。通常可以通过检查Pt-Cu的催化剂的颜色变化（ 例如，从蓝色到黑色）确定确切的温度​​。 </li><li>以10℃/ min的速度倾斜至550℃（或反应温度，如果较高），并停留30分钟以完成还原。用N 2吹扫并冷却至室温。 </li><li>卸载Pt-0.7Cu / SiO2催化剂并储存在小瓶中以备将来使用。 注意:使用不同量的Cu（NO 3 ） 2 ·3H 2 O和（NH 3 ） 4 Pt（NO 3 ） 2重复类似的合成程序以制备另一种Pt-X Cu / SiO 2 </s（X = 0.7,2.3和7.3，代表Cu:Pt原子比）和Pt / SiO2催化剂。 </li></ol></li></ol>丙烷脱氢性能试验<ol><li> 催化剂装载 <ol><li>取3/8"石英管反应器，将1厘米的石英棉层放在中间的凹坑处。 注意:处理石英棉时请使用防护手套，因为细针可以嵌入皮肤。 </li><li>称取40mg Pt-0.7Cu / SiO 2催化剂和960mg二氧化硅用于稀释。将颗粒（总重量为1g）混合在空的小瓶中。 </li><li>使用塑料漏斗将所有催化剂混合物装入反应管。用无毛巾擦拭两个管端的外壁，以清除任何污垢，以便与O型圈保持良好的密封。 </li><li>将管接头插入石英反应管的两端，并将其连接到装有蛤壳式炉的反应器系统中。 </li></ol></li> &lt;泄漏试验和催化剂预处理 <ol><li>打开通过管式反应器的50 cm 3 / min N 2流量。 1分钟后，关闭反应器出口上的球阀。等待系统压力增加到5 psig。关闭入口N 2线上的球阀，以停止N 2流动并密封反应堆系统。 </li><li>等待1分钟，记录从量规读取的压力。如果压力下降，打开反应器出口上的球阀以释放压力并重新连接配件。如果没有，首先打开反应器出口上的球阀，以通过打开入口N 2管线上的球阀来重新启动N 2流，释放压力，以清洗系统1分钟。 </li><li>在运行反应之前开始流动50cm 3 / min的5％H 2 / N 2用于催化剂还原并停止N 2流。开始将管加热至550℃的反应温度食用10°C / min。炉子达到设定点30分钟后，使系统温度稳定在目标温度。 </li></ol></li><li> 丙烷脱氢反应试验 <ol><li>启动反应器系统中的气相色谱仪（GC），并选择适当的气体成分分析方法。 <ol><li>将反应堆气流切换到旁路管路。流量为100cm 3 / min的5％丙烷/ N 2和100cm 3 / min的5％H 2 / N 2 。等待1分钟，使丙烷流量稳定并将旁路流注入GC作为参考样品。 </li></ol></li><li>将气流切换回反应管管线，开始反应并记录时间。 </li><li>反应进行4分钟后，将反应器出口气体流（GC样品）注入GC以获得出口气体成分信息。每4分钟注入样品，运行测试直到转换达到稳定状态<html> te或转换非常低。 </li><li>使用相应的峰分析软件分析每个峰。 <ol><li>单击以选择峰的起点和终点。使用积分功能获得峰值区域。记下丙烷（C 3 H 8 ）反应物的峰面积;丙烯（C 3 H 6 ）产物;和副产物甲烷（CH 4 ），乙烷（C 2 H 4 ）和乙烯（C 2 H 6 ）。 注意:对于每次注射，获得具有多个峰的GC模式，其面积与不同气体种类的摩尔数相关。 </li></ol></li><li>使用响应因子将峰面积转换为每个物种的摩尔数。根据下列公式确定每个样品的丙烷转化率和丙烯选择性: <img alt="方程" src="/files/ftp_upload/56040/56040eq1.jpg" /> ad / 56040 / 56040eq2.jpg"/&gt; 哪里<img alt="方程" src="/files/ftp_upload/56040/56040eq3.jpg" />是丙烷的转化， <img alt="方程" src="/files/ftp_upload/56040/56040eq4.jpg" />是丙烯选择性， <img alt="方程" src="/files/ftp_upload/56040/56040eq5.jpg" />是丙烷的摩尔数， <img alt="方程" src="/files/ftp_upload/56040/56040eq6.jpg" />是丙烯的摩尔数。 </li><li>通过使用指数拟合外推推测测量的转化率和选择性对时间上的时间，获得t = 0时的初始转化率和选择性值。 </li></ol></li><li> 后反应 <ol><li>关闭温度程序停止加热反应堆。将气体流量切换到10厘米3 /分钟N 2 。 </li><li>将气相色谱仪切换回待机方式，以降低载气的流量。 </li><li>冷却后从石英固定床反应器中取出所用的催化剂室内温度。在指定的废物处理区域收集催化剂重量。 </li></ol></li></ol> 3.催化剂样品的表征<ol><li> 扫描透射电子显微镜 4，20 <ol><li>将催化剂装入研钵中，并用研杵将其研磨成小于100目的粉末。 </li><li>将约30mg催化剂粉末分散在小瓶中的约5mL异丙醇中。摇动小瓶完全混合，然后让小瓶放置5分钟以使沉积较大的颗粒。 注意:所得悬浮液应包含非常小的负载催化剂颗粒。 </li><li>将Au TEM准备好的栅格放置在蒸发皿上。将盘子加热至80°C。将三滴催化剂悬浮液加入电网。 注意:异丙醇会迅速蒸发，并将催化剂颗粒留在其上电网。 </li><li>将网格加载到样品架上进行电子显微镜样品成像。 </li></ol></li><li> 原位 X射线吸收光谱 3,4，19，20 <ol><li>将催化剂装入砂浆中，并用研杵将其研磨成小于100目的粉末。将细粉末装入模具组并用手指按压以形成自支撑晶片。 </li><li>将〜100毫克样品装入样品架。 </li><li>将样品架置于石英管反应器中，并以50 cm 3 / min 3％H 2 / He进行减压，对样品进行预处理。 </li><li>冷却至室温后，密封管并将其转移到同步加速器束线以收集XAS数据。 </li></ol></li><li> 原位 X射线衍射 19,20 <ol><li>罗将催化剂加入砂浆中，并用研杵将其研磨成小于100目的粉末。 </li><li>使用标准7 mm直径的模具压制薄片。 注意:模具包含一个女性件和顶部和底部男性件。 <ol><li>将底部阳件连接到女性部件。将样品装载到底部的抛光表面上。将顶部的阳件连接并将模具转移到压机的样品台上。按适当的力量按压。 </li></ol></li><li>卸载晶片并将其转移到专用样品台的陶瓷杯中（参见材料表 ）。密封舞台，并将其固定在束线上的样品台上。 </li><li>通过流动并将温度升高到550℃来减少样品。在550℃下冷却至RT 20后，在3％H 2 / He气流下收集原位 X射线衍射数据。 </li></ol></li></ol>

<ol>
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作者没有什么可以披露的。

本工作中制备的Pt-Cu催化剂包含大小为2nm的均匀纳米颗粒，类似于符合工业应用的非均相催化剂。与分离的单金属颗粒相反，所有Pt和Cu前体形成双金属结构。这种双金属相互作用和小粒径通过对合成方法的仔细控制来实现。浸渍过程利用金属离子与某些氧化物载体21的表面之间的强静电吸附（SEA）。氧化物材料如二氧化硅在表面具有羟基，其可以根据pH在溶液中被质子化或去质子化。二氧化硅在pH = 4 22附近具有特征的零电荷点（PZC），这意味着该表面在该pH下是电子中性的。如果溶液的pH高于其PZC，则氧化物表面将被去质子化并吸附阳离子，而在P时h值低于PZC，它会质子化并吸附阴离子。通过添加氨将前体溶液的pH调节到大于10，如步骤1.1.3所示，溶液处于碱性条件下，因此二氧化硅羟基被充分去质子化，能够强烈吸附阳离子如铂四胺[（NH 3 ） 4 Pt] 2+和四氨合铜[（NH 3 ） 4 Cu] 2+ 。阳离子和脱质子化羟基之间的电子吸引力将前体锚定在催化剂上，并且阳离子之间的排斥有助于它们的分散，这两者有助于防止在煅烧和还原时金属物质的附聚。两种不同金属前体的浸渍过程是并行进行的。与顺序浸渍相比，共浸渍法确保两种金属前体在溶液中的均匀分布，使其最大化混合。所得到的负载型Pt-Cu催化剂显示出强的双金属相互作用，并且不形成单金属颗粒。浸渍也在初始湿度下进行，其通过毛细管效应优化前体溶液在载体氧化物的孔中的分散。浸渍的Pt-Cu催化剂在250℃下煅烧以除去附着于金属的配体，同时使氧化物簇的生长最小化。浸渍过的金属前体的煅烧温度已被证明影响尺寸的减小的金属纳米粒子23，24。 对于二氧化硅上的Pt，颗粒尺寸随着温度的升高而增加，并且250℃附近的温度是必需的，以得到小的纳米颗粒。其他金属和支撑体的最佳煅烧温度不同。当还原Pt-Cu催化剂时，高H 2流速和较慢的r在Pt的还原温度附近使用停止速率以快速除去还原期间形成的水，从而抑制金属核的生长。目的是将温度升高到刚刚低于发生快速还原的程度，以缓慢降低金属氧化物，同时快速除去还原过程中形成的水​​。因此，重要的是缓慢地进行还原并在该温度下保持足够的时间，同时在高流量下除去水。一旦降低，温度可以快速升高到反应温度。重要的是将催化剂的总量减少到在反应条件下将暴露于其最高温度，使得当反应运行时它们不经过额外的烧结。一旦减少，在室温下暴露于空气将氧化颗粒表面而不是整个颗粒。进一步的再还原将产生几乎相同的粒度。因此，如果整个粒子i减少，每个分析的尺寸将被固定（ 即 ，动力学，红外（IR）光谱，XAS，XRD等的粒径将是相同的）。整个催化剂合成方案也可应用于在各种应用25用来获得强的双金属相互作用其它金属催化剂的制备方法，和更小的或较大的颗粒尺寸可通过协议的小的修改而获得。 进行原位同步加速器XRD研究2-nm Pt-Cu纳米粒子的晶体结构。对于尺寸小于3nm的载体纳米粒子，使用实验室仪器19测量衍射是非常困难的。由于单元电池的重复有限，衍射峰强度变宽，强度非常低。此外，负载金属催化剂的金属负载通常低（≤5％），这进一步降低了衍射信号。此外，大部分原子在颗粒表面（对于2nm纳米颗粒接近50％），并且在空气中测量时被氧化。因此，为了获得有意义的结构信息，必须使用高通量X射线原位收集衍射，通常只能与同步加速器一起使用。在这种情况下，首先在还原后的550℃下在3％H 2 / He下测定X射线衍射图，然后在冷却后在相同气氛下在室温下测定。通过使用在相同条件下拍摄的图案减去SiO 2载体和样品池衍射，从原始数据中分离出催化剂中的金属的衍射信号。两个图案显示相同的相，表明在两个不同温度下催化剂的晶体结构不变。 原位 XRD和XAS表明，对于具有增加的Cu:Pt原子比的Pt-Cu催化剂，一系列替代物形成具有增加的Cu含量百分比的固体固溶体结构。在固溶体结构中，Pt和Cu原子随机分布;因此，Pt原子不一定彼此结合。然而，通过Cu的Pt原子的分离实现在高Cu:Pt比，并且Pt位置分离的程度随着Cu的原子百分比的增加而改善。活性位点结构的这种变化意味着Pt-Cu催化剂的PDH选择性的改善（ 图1C ），证实了位点分离与高脱氢选择性之间的关系。对于具有最高Cu含量的Pt-7.3Cu催化剂，几乎所有的Pt原子都被分离，如EXAFS所示。结果，在不同的初始转化下，该催化剂的选择性保持很高（接近100％）。除了选择性的变化之外，改进的位置隔离还引入了增加量的与Pt原子键合的Cu邻位并以电子方式修改Pt活性位点。结果，PDH催化剂的周转率也随着Cu:Pt原子比的增加而延续（ 图1D ）。的0.98秒的TOR -1的Pt-7.3Cu大于0.06秒-1对单金属铂的TOR高16倍，并且还比典型的TOR值高（0.1-0.5秒-1）的铂-锡催化剂下类似的反应条件1 。 在手稿中，我们已经展示了合成双金属Pt-Cu催化剂的方便方法，以及丙烷脱氢和表征的性能测试。该催化剂形成了一个取代的固溶体结构，其粒径约为2nm左右，粒径小，均匀，这是通过对催化剂制备过程中浸渍，煅烧和还原步骤的仔细控制而实现的，并通过先进的原位同步加速技术进行鉴定。催化剂性能连续y随着Cu:Pt原子比的增加而提高。

丙烷脱氢（PDH）是生产丙烯的关键加工步骤，利用页岩气，国内增长最快的天然气来源1 。该反应在丙烷分子中断裂两个CH键以形成一个丙烯和分子氢。贵金属催化剂，包括Pd纳米颗粒，对PDH的选择性差，破坏CC键以产生高产率的甲烷，随之产生焦炭，导致​​催化剂失活。最近的报告表明，选择性PDH催化剂可以通过加入像Zn或在与Pd 2，3，4的启动子来获得。促进的催化剂对PDH的选择性接近100％，而相同尺寸的单金属Pd纳米颗粒的催化剂相对于小于50％。选择性的巨大改善归因于PdZn或PdIn金属间化合物的形成（IMC）结构。 IMC中两种不同类型的原子的有序阵列用非催化的Zn或In原子几何地分离Pd活性位点，这导致由相邻Pd活性位点的整体（组）催化的副反应。 铂在丙烷脱氢贵金属中的固有选择性最高，但商业用途仍然不令人满意1 。典型地，锡，锌，在，或Ga被添加作为启动子的Pt 5，6，7，8，9，10，11，12，13。基于几何活性位置隔离有助于高选择性的想法，任何形成合金的非催化元素与Pt结合，如Cu，也应潜在地促进催化剂性能14 。一些以前的研究表明，添加铜的确实提高了Pt的PDH选择性催化剂15，16，17，18。然而，没有报道直接证据来确定Pt和Cu是否形成双金属纳米颗粒或有序结构，这对于理解Cu的促进作用至关重要。在Pt的Cu的二元相图，两个不同的结构类型是可能在很宽的组成范围内16，18:金属间化合物，其中Pt和铜各自占据特定的结晶位点，和固溶体，其中铜在随机代铂格。 IMCs在低温下形成，并在大约600-800℃下转变成固溶体，用于散装材料即 550℃）附近，纳米颗粒的转变温度可能较低。因此，必须在反应条件下研究Pt-Cu的原子顺序。对于具有小的颗粒尺寸的纳米颗粒的支持，这是非常具有挑战性的，以获得使用实验室仪器19有意义的结构信息。单元电池的有限重复导致非常宽的衍射峰，具有非常低的强度。由于在空气中被氧化的纳米粒子1-3nm的表面原子的高分数，必须使用通常用同步加速技术的高通量X射线原位收集衍射。 先前报道的Pt-Cu系催化剂PDH均大于5nm的尺寸15，16，17，18。然而，对于贵金属纳米颗粒催化剂，总是有强烈的愿望，通过合成催化剂具有高分散体（通常大约或尺寸小于2nm）19以最大化每单位成本的催化活性。尽管通过标准浸渍方法可以制备这种尺寸的双金属纳米颗粒，但是合理控制方法是必要的。需要控制金属前体，浸渍溶液的pH和支持体，以优化金属物质在高表面积载体上的锚定。还应仔细控制随后的煅烧和还原热处理以抑制金属纳米颗粒的生长。 本文介绍了合成支持的2 nm Pt-Cu双金属纳米粒子催化剂和丙烷脱氢性能测试的方案。通过扫描T研究催化剂的结构传输电子显微镜（STEM）， 原位同步加速器X射线吸收光谱（XAS）和原位同步加速器X射线衍射（XRD），有助于阐明引入Cu时催化剂性能的改善。

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synthesis and testing of supported pt-cu solid solution nanoparticle catalysts for propane dehydrogenation

这里证明了合成双金属Pt-Cu催化剂的方便方法和丙烷脱氢和表征的性能测试。该催化剂形成一个取代的固溶体结构，其粒径约为2nm左右。这通过仔细控制催化剂制备过程中的浸渍，煅烧和还原步骤而实现，并通过先进的原位同步加速技术进行鉴定。催化剂丙烷脱氢性能随着Cu:Pt原子比的增加而不断提高。

在初始丙烷转化率下测量的Pt和Pt-Cu催化剂的丙烯选择性对时间约为20％， 如图1A所示 。 Pt催化剂具有61％的初始选择性，随着催化剂失活1小时，随着时间的推移，其增加到约82％。 Pt-0.7Cu催化剂显示72％的较好的初始丙烯选择性。对于Pt-2.3Cu和Pt-7.3Cu催化剂，其初始选择性分别达到90％和96％，并保持反应时间。 图1B显示Pt和Pt-7.3Cu催化剂的初始丙烯选择性与初始丙烷转化率的变化。虽然Pt催化剂的选择性在较高的转化率下降低，但Pt-7.3Cu催化剂在不同的丙烷转化率下保持高丙烯选择性，超过95％。当比较不同的催化剂时，似乎催化剂选择性增加在Pt-Cu催化剂中Cu的含量几乎线性变化，以原子百分比表示， 如图1C所示。铜含量的增加也提高了丙烷脱氢的周转率（TOR）。 图1D替代了TOR与Cu与Pt的催化剂原子比之间的接近线性关系。在所有反应试验中，碳平衡接近100％，尽管在整个反应过程中发生轻微的焦炭形成。 收集了具有不同金属负载量和Cu:Pt比率的单金属Pt和三种Pt-Cu催化剂的STEM图像，如原子吸收光谱所证实的。通过STEM成像测定的所有催化剂的粒度在2和3nm之间。 图2A示出了Pt-2.3Cu催化剂的STEM图像，其是其它样品的典型图像。确定样品的平均粒径d为2.2nm，标准偏差为0.4nm。对于Pt-0.7Cu和Pt-7.3Cu，所获得的STEM粒径为2.5±0.4nm和2.1±0.4nm。 在 Pt和Cu边缘处的近边界光谱的原位 X射线吸收已经进行，以在类似于反应环境的条件下确定Pt和Cu的价态。发现Pt和Cu都完全还原成金属状态。 图2B中显示Pt和III -Pt催化剂在Pt L III边缘的扩展X射线吸收精细结构（EXAFS）光谱的k 2加权傅立叶变换的幅度。在Pt L III边缘，Pt催化剂显示Pt-Pt散射典型的三峰图案。对于Pt-0.7Cu，三峰图案的峰位置转移到较低的R值，这表明Pt-Pt散射通过具有较短键距离的第二Pt-Cu散射的干扰。 Pt-2.3Cu和Pt-7.3Cu的EXAFS光谱，其c存在相对较高量的Cu，仅显示一个峰，典型的Pt-Cu金属散射。随着Cu:Pt原子比的增加，散射图的变化表明，随着Cu含量的增加，双金属纳米颗粒的形成。 图2C显示Pt和Pt-Cu催化剂的背景扣除原位同步加速器X射线衍射（XRD）图案和所鉴定的Pt-Cu相的相应的模拟XRD图案。没有发现超晶格衍射，Pt-Cu催化剂的组成与有序合金的理想组成不同，表明Pt和Cu在Pt-Cu催化剂中形成固溶体结构。随着Cu:Pt原子比的增加，催化剂的衍射峰偏移到较高的角度，归一化强度降低，这都证实了固溶体在Cu中变得更加富集。固体溶液的组成由使用的衍射图计算<html>布拉格法和维加法。 <img alt="图1" class="xfigimg" src="/files/ftp_upload/56040/56040fig1.jpg" /> 图1:Pt和Pt-Cu催化剂的丙烷脱氢性能。 （ A ）丙烯选择性对于Pt（黑色正方形），Pt-0.7Cu（红色圆圈），Pt-2.3Cu（蓝色三角形）和Pt-7.3Cu（品红色三角形）催化剂在550℃测量的时间。 （ B ）对于Pt（黑色正方形）和Pt-7.3Cu（品红色三角形）催化剂，在550℃测量的丙烯选择性对丙烷转化率。 （ C ）脱氢选择性与原子百分比中的Cu含量。 （ D ）周转率相对于每个催化剂的Cu:Pt原子比<a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56040/56040fig1large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> 内容"fo:keep-together.within-page ="1"&gt; <img alt="图2" class="xfigimg" src="/files/ftp_upload/56040/56040fig2.jpg" /> 图2:Pt和Pt-Cu催化剂的结构。 （ A ）Pt-2.3Cu催化剂的STEM高角度环形暗场（HAADF）图像。 （ B ）Pt（ II ），Pt-0.7Cu（红色），Pt-2.3Cu（蓝色）和Pt-7.3Cu（品红色）的EXAFS的傅立叶变换的Pt L III边缘幅度。 在原位 X射线衍射图案（C）背景减除:铂（黑色，固体）和Pt-0.7Cu钎（红，固体）和Pt-2.3Cu（蓝色，固体），和Pt-7.3Cu（品红色，固体）进行比较模拟的XRD图案分别为:主体FCC Pt（黑色，虚线），Pt 0.70 Cu 0.30 （红色，虚线），Pt 0.32 Cu 0.68 （蓝色，虚线）和Pt 0.13 Cu 0.87 （品红色，虚线）。 <a href="//ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56040/56040fig2large.jpg" target="_blank">请点击这里查看更大的ve</a>这个数字的rsion。

Watch this Scientific Journal Video about Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation at JoVE.com

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

这里报道了合成2nm负载的双金属纳米颗粒Pt-Cu催化剂用于丙烷脱氢的方便方法。 原位同步加速器X射线技术允许确定催化剂结构，这通常使用实验室仪器无法获得。

用于丙烷脱氢的负载型Pt-Cu固溶体纳米粒子催化剂的合成与测试

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are ...

synthesis-testing-supported-pt-cu-solid-solution-nanoparticle

Nanyang Technological University

Research

JoVE Journal

Chemistry

11.8K 次观看.  Purdue University. 这里报道了合成2nm负载的双金属纳米颗粒Pt-Cu催化剂用于丙烷脱氢的方便方法。 原位同步加速器X射线技术允许确定催化剂结构，这通常使用实验室仪器无法获得。 

视频: Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3]2- or [Pb2Ch3]2- anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a &#181;-PbSe ligand (i.e., the heaviest-known CO homolog).
In contrast, the solid-state synthesis of a phase of the nominal composition &#34;K2PbSe2&#34; by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]4-. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2]2- or [BiSe3]3- anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route.
All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by 205Pb and 77Se or 127Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the &#181;-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4]4- anion is mainly due to a suitable stabilization within the crystal lattice.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV

The synthesis of chalcogenidoplumbates(II,IV) via the in situ reduction of nominal "PbCh2" (Ch = Chalcogen) and via a solid-state reaction and subsequent solvothermal reactions is presented. Additionally, reactivities of plumbate(II) solutions are portrayed, which yield the heaviest-known CO homolog known to date: the &#181;-PbSe ligand.

结合固态和基于解决方案的技术合成及Chalcogenidoplumbates的反应（II或IV）

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica ...

科研

化学

Measurement of Particle Size Distribution in Turbid Solutions by Dynamic Light Scattering Microscopy

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a technique used to measure the size distribution of polymer solutions or colloidal particles. Although this technique is widely used for the assessment of polymer solutions, it is difficult to measure the particle size in concentrated solutions due to the multiple scattering effect or strong light absorption. Therefore, the concentrated solutions should be diluted before measurement. Implementation of the confocal optical component in a dynamic light scattering microscope1 helps to overcome this barrier. Using such a microscopic system, both transparent and turbid systems can be analyzed under the same experimental setup without a dilution. As a representative example, a size distribution measurement of a temperature-responsive polymer solution was performed. The sizes of the polymer chains in an aqueous solution were several tens of nanometers at a temperature below the lower critical solution temperature (LCST). In contrast, the sizes increased to more than 1.0 &#181;m when above the LCST. This result is consistent with the observation that the solution turned turbid above the LCST.

A protocol for the direct measurement of particle size distribution in concentrated solutions using dynamic light scattering microscopy is presented.

通过动态光散射显微镜混浊解决方案粒度分布的测定

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a ...

Protocol for the Solid-phase Synthesis of Oligomers of RNA Containing a 2'-O-thiophenylmethyl Modification and Characterization via Circular Dichroism

Solid-phase synthesis has been used to obtain canonical and modified polymers of nucleic acids, specifically of DNA or RNA, which has made it a popular methodology for applications in various fields and for different research purposes. The procedure described herein focuses on the synthesis, purification, and characterization of dodecamers of RNA 5&#39;-[CUA CGG AAU CAU]-3&#39; containing zero, one, or two modifications located at the C2&#39;-O-position. The probes are based on 2-thiophenylmethyl groups, incorporated into RNA nucleotides via standard organic synthesis and introduced into the corresponding oligonucleotides via their respective phosphoramidites. This report makes use of phosphoramidite chemistry via the four canonical nucleobases (Uridine (U), Cytosine (C), Guanosine (G), Adenosine (A)), as well as 2-thiophenylmethyl functionalized nucleotides modified at the 2&#39;-O-position; however, the methodology is amenable for a large variety of modifications that have been developed over the years. The oligonucleotides were synthesized on a controlled-pore glass (CPG) support followed by cleavage from the resin and deprotection under standard conditions, i.e., a mixture of ammonia and methylamine (AMA) followed by hydrogen fluoride/triethylamine/N-methylpyrrolidinone. The corresponding oligonucleotides were purified via polyacrylamide electrophoresis (20% denaturing) followed by elution, desalting, and isolation via reversed-phase chromatography (Sep-pak, C18-column). Quantification and structural parameters were assessed via ultraviolet-visible (UV-vis) and circular dichroism (CD) photometric analysis, respectively. This report aims to serve as a resource and guide for beginner and expert researchers interested in embarking in this field. It is expected to serve as a work-in-progress as new technologies and methodologies are developed. The description of the methodologies and techniques within this document correspond to a DNA/RNA synthesizer (refurbished and purchased in 2013) that uses phosphoramidite chemistry.

Protocol for the Solid-phase Synthesis of Oligomers of RNA Containing a 2'-O-thiophenylmethyl Modification and Characterization via Circular Dichroism

This article provides a detailed procedure on the solid-phase synthesis, purification, and characterization of dodecamers of RNA modified at the C2&#39;-O-position. UV-vis and circular dichroism photometric analyses are used to quantify and characterize structural aspects, i.e., single-strands or double-strands.

用于固相合成含有2&#39;-<em&gt; 0</em通过圆二色性修饰和表征

Solid-phase synthesis has been used to obtain canonical and modified polymers of nucleic acids, specifically of DNA or RNA, which has made it a popular ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

用于跟踪纳米粒子自组装的液体细胞透射电子显微镜

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

化学沉淀法合成铌2O5改性高比表面积镍催化剂

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

原位金纳米粒子合成快速 Nanoprobe 信号增强

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

直接溶液还原法快速合成金、钯、铂气凝胶的研究

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of solid-phase synthesis, regenerating Michael (REM) linker strategies, and 1,3-dipolar cycloaddition, a library of structurally similar heterocycles, both with and without a spirocyclic center, can be constructed. The main advantages of the solid-support synthesis are as follows: first, each reaction step can be driven to completion using a large excess of reagents resulting in high yields; next, the use of commercially available starting materials and reagents keep the costs low; finally, the reaction steps are easy to purify via simple filtration. The REM linker strategy is attractive because of its recyclability and traceless nature. Once a reaction scheme is completed, the linker can be reused multiple times. In a typical solid-phase synthesis, the product contains either a part of or the whole linker, which can prove undesirable. The REM linker is &#34;traceless&#34; and the point of attachment between the product and the polymer is indistinguishable. The high diastereoselectivity of the intramolecular 1,3-dipolar cycloaddition is well documented. Limited by the insolubility of the solid support, the reaction progression can only be monitored by a change in the functional groups (if any) via infrared (IR) spectroscopy. Thus, the structural identification of intermediates cannot be characterized by conventional nuclear magnetic resonance (NMR) spectroscopy. Other limitations to this method stem from the compatibilities of the polymer/linker to the desired chemical reaction scheme. Herein we report a protocol that allows for the convenient production of spirocyclic heterocycles that, with simple modifications, can be automated with high-throughput techniques.

Here we present a protocol to demonstrate an efficient method for the synthesis of spirocyclic heterocycles. The five-step process utilizes solid-phase synthesis and regenerating Michael linker strategies. Generally difficult to synthesize, we present a customizable method for the synthesis of spirocyclic molecules otherwise inaccessible to other modern approaches.

[4.4] 刺环氧基的固相合成

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of ...

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, &#60;10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 &#176;C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol&#183;g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(&#8801;Si-O-)Hf(&#951;2&#960;-MeNCH2)(&#951;1-NMe2)(&#951;1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)]. [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is correlated to the catalytic performance.

A new group IV metal catalyst for imine metathesis is prepared by grafting amine metal complex onto dehydroxylated silica. Surface metal fragments are characterized using FT-IR, elemental microanalysis, and solid-state NMR spectroscopy. Further dynamic nuclear polarization surface enhanced NMR spectroscopy experiments complement the determination of the coordination sphere.

利用表面有机金属化学方法，利用硅支持的催化剂进行Imine金属分析

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

调整二苯醚氢氧化的Pt/CNT催化剂的酸度

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...