Spray Jet Flames for Supported Gold Catalysts: New Catalysts by Intelligent Design

摘要提案编号：0626063主要研究员：Beaucage，Gregory所属单位：辛辛那提大学主校区提案标题：支持金催化剂的喷射火焰：智能设计的新催化剂智力优点：火焰为纳米颗粒生长提供了一个独特的环境，因为它们包含高度的过饱和度，极高的温度和快速淬火条件，锁定动力学结构。喷射火焰为纳米颗粒的形成提供了最通用和可控的热解条件。一股有机金属液体喷雾可以被点燃，以产生大量的纳米材料，其形貌令人惊讶地受控。这种喷射火焰工艺（SFP）在纳米材料，特别是氧化物和负载金属的大量生产方面具有很大的潜力。由于光发射、高温（2000 ℃）、流速接近声速，这种纳米材料的生长难以观察，总生长跨越几毫秒。在这种快速生长条件下的颗粒生长的动力学的研究需要能够快速检测的原位技术，并且对极高的温度、明亮的光发射和高噪声不敏感。该提案旨在通过理解这种复杂的“共沉淀”反应中的结构成核和生长的基础来设计支撑型金纳米催化剂的SFP合成。这种设计，现在可以作出由于最近的进展，在表征纳米粒子的成核，生长和聚集在火焰中使用原位X射线散射。在拟议的工作中，反常散射（ASAXS）是用来隔离的贡献，由于金的支持，通过对比度匹配。这类似于TEM中的暗场成像，除了ASAXS具有元素分辨率而不是晶体分辨率。拟议的工作将是第一次原位使用ASAXS多相气溶胶纳米粉末。原位ASAXS可以独立地测量Au和支持（TiO 2）Sauter平均直径的演变，尺寸分布，体积分数，数浓度，和聚集体质量分形维数，每个聚集体的初级颗粒的尺寸和数量以及火焰中的分支含量，空间分辨率为50微米，曝光时间为20 ms。与ETHZ合作，将通过二维相位多普勒风速仪（PDA）测量液滴速度，并通过傅里叶变换红外（FTIR）发射/透射光谱测量气体温度。在以前的测量单组分喷雾火焰，液滴蒸发，纳米材料的成核和聚集，包括颗粒的生长速度，聚集和分支的细节已被直接观察到。更广泛的影响：该项目将支持博士候选人和2名本科生在这方面的努力。计划继续与ETHZ（苏黎世）的研究人员进行互动。该提案包括继续开发UC纳米粉末网络课程。该项目还将涉及开发一个新的纳米级催化技术共享课程，重点是支持的金属催化剂和纳米尺寸/形状效应，这将涉及瑞士合作者的贡献。本课程将在UC和ETHZ联合提供。自2000年以来，网络课程一直是向社区传播信息的有效手段，有超过130，000个独立IP点击课程套件（约60/天）。

ABSTRACTProposal Number: 0626063Principal Investigator: Beaucage, GregoryAffiliation: University of Cincinnati Main CampusProposal Title: Spray Jet Flames for Supported Gold Catalysts: New Catalysts by Intelligent DesignIntellectual Merit:Flames offer a unique environment for nano-particle growth since they contain high degrees of super-saturation, extremely high temperatures and rapid quench conditions, locking in kinetic structures. Spray jets flames offer the most versatile and controllable of pyrolytic conditions for nano-particle formation. A jet of organometallic liquid spray can be ignited to produce copious quantities of nano-materials with surprisingly controlled morphologies. This spray flame process (SFP) is of great potential for mass production of nano-materials, especially oxides and supported metals. Observation of the growth of such nano-materials is difficult due to light emission, high temperature ( 2000 C), flow rates approaching the speed of sound with the total growth spanning a few milliseconds. The study of the dynamics of particle growth under such rapid growth conditions requires in situ techniques capable of rapid detection and being insensitive to extremely high temperatures, brilliant optical emission, and high noise. This proposal seeks to design SFP synthesis of supported gold nano-catalysts by understanding the basis of structural nucleation and growth in this complex "co-precipitation"- like reaction. Such design can now be made due to recent advances in characterization of nanoparticle nucleation, growth and aggregation in flames using in situ x-ray scattering. In the proposed work, anomalous scattering (ASAXS) is used to isolate the contribution due to gold from that of the support through contrast matching. This is similar to dark field imaging in TEM except that ASAXS has elemental resolution rather than crystallographic resolution. The proposed work will be the first in situ use of ASAXS for multiphase aerosol nano-powders. In situ ASAXS can measure independently the evolution of Au and support (TiO2) Sauter mean diameters, size distribution, volume fraction, number concentration, and aggregate mass fractal dimension, size and number of primary particles per aggregate as well as branch content in the flame with 50 micron spatial resolution and 20 ms exposure time. In collaboration with ETHZ, droplet velocities will be measured by 2D-Phase Doppler Anemometry (PDA) and gas temperature by Fourier transform infrared (FTIR) emission/transmission spectroscopy. In previous measurements on single component spray flames, droplet evaporation, nano-material nucleation and aggregation including details on the rate of particle growth, aggregation and branching have been directly observed.Broader Impacts:The project will support a PhD candidate and 2 undergraduates in this effort. Continued interaction with researchers at ETHZ (Zurich) are planned. The proposal includes continued development of a web course on Nano-powders at UC. The project will also involve development of a new shared course on Nano-Scale Catalytic Technology focusing on supported metal catalysts and nano-size/shape effects that will involve contributions from the Swiss collaborators. This course will be jointly offered at UC and ETHZ. The web course has been an effective means to disseminate information to the community with over 130,000 independent IP hits to the course suite since 2000 (~60/day).