Publications

The low temperature CO oxidation activity of Pd doped MnOx-CeO2 (MC) solid solution catalyst is evaluated to determine the role of Pd speciation and oxygen transfer. Dynamic reduction behavior of Pd2+ species in the presence of CO at low temperatures is characterized by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) and X-ray absorption spectroscopy (XAS). H2 temperature-programmed reduction (TPR) and CO/O2 transient pulse experiments are conducted to evaluate the lattice oxygen reducibility of Pd/CeO2 and Pd/MC. Our results show that highly dispersed PdO species form on the freshly calcined CeO2 and MC supports. Despite the fact that similar Pd species form on the CeO2 and MC supports, PdO can be reduced immediately on CeO2 in the presence of CO, while the MC support can preserve the oxidized Pd species during CO reduction. In the case of CO oxidation, Pd2+ species are maintained through lattice oxygen transfer facilitated by the MC support. CO/O2 transient pulse experiments confirm the higher reducibility of the MC support, which can favor CO oxidation at 50°C.

We present a simple, though uncommonly used, method to produce versatile, well-ordered, nanoscale arrays of metal oxides such as MgO, Al2O3, TiO2, MnO2, Fe2O3, Co3O4, NiO, CuO, ZnO, ZrO2, RuO2, SnO2, or Ce2O3 by decoupling metal oxide precursor incorporation from block copolymer (BCP) template formation. In this work, neat BCP thin films were cast and annealed, using standard techniques, to generate templates. The templates were immersed in a precursor solution and formed metal-polymer complexes in one polymer domain. Finally, the organics were removed in an oxidative environment to leave the templated metal oxides. As a concrete example of the methods applicability, we show that the templating method produced ordered TiO2 arrays that exhibited a 13% increase in photocatalytic activity over TiO2 produced by EISA. Furthermore, the addition of gold nanoparticles further improved photocatalytic activity by 43% on our templated TiO2, whereas gold nanoparticles on EISA TiO2 exhibited no improvement. The simplicity and modularity of the templating method makes it amenable to additional applications in catalysis, optics, and sensors.

Pt and Gd loaded ZSM-5 catalysts were synthesized by ion exchange method to investigate the effect of metal promoters on catalyst activity, coking and regeneration during military aviation fuel (JP-8) cracking into petroleum gas (PG) at 723K. Multiple cracking and regeneration cycles were performed over the ZSM-5 based catalysts and their crystalline structure, oxidation profile, coke band and acidity were characterized. It was revealed that addition of Gd metal to the ZSM-5 catalyst prevented formation of complex aromatic coke and increased the number of Lewis acid sites, while Pt promoted ZSM-5 catalyst showed a decrease in the coke oxidation temperature. The effect of Pt and Gd promoters enhanced the coke burn-off ability, formed hydrogen rich carbon species and reduced oxidation temperature of coke substantially. Furthermore, agglomeration of Pt particles was partially impeded by coexisting Gd metal on the regenerated ZSM-5 catalyst. Synergetic effects of Pt and Gd promoters stabilized the PG yield and product distribution over the Pt–Gd/ZSM-5 catalyst during the cracking and regeneration cycles.

Pd deposited on CeO2, MnOx–CeO2 and SnO2–MnOx–CeO2 solid solution were tested for low temperature CO oxidation activity. Among them, Pd–MnOx–CeO2 (Pd–MC) and Pd–SnO2–MnOx–CeO2 (Pd–SMC) showed excellent low temperature activity and over 90% of CO conversion was obtained at room temperature. SO2 poisoning tests with 200ppm at room temperature showed that Pd–SMC could keep high CO conversion as compared to Pd–MC. The high CO oxidation activity of Pd–SMC at low temperatures could be attributed to strong oxidation ability of highly oxidized Pd species and interactions between Pd and solid solution support.

In this study, we demonstrate the production of long-chain hydrocarbons (C8+) from 2-methylfuran (2MF) and butanal in a single step reactive process by utilizing a bi-functional catalyst with both acid and metallic sites. Our approach utilizes a solid acid for the hydroalkylation function and as a support as well as a transition metal as hydrodeoxygenation catalyst. A series of solid acids was screened, among which MCM-41 demonstrated the best combination of activity and stability. Platinum nanoparticles were then incorporated into the MCM-41. The Pt/MCM-41 catalyst showed 96% yield for C 8+ hydrocarbons and the catalytic performance was stable over four reaction cycles of 20 hour each. The reaction pathways for the production of long-chain hydrocarbons is probed with a combination of infrared spectroscopy and steady-state reaction experiments. It is proposed that 2MF and butanal go through hydroalkylation first on the acid site followed by hydrodeoxygenation to produce the hydrocarbon fuels. This journal is © the Owner Societies 2014.

The materials genome initiative (MGI) aims to accelerate the process of materials discovery and reduce the time to commercialization of advanced materials. Thus far, the MGI has resulted in significant progress in computational simulation, modeling, and predictions of catalytic materials. However, prodigious amounts of experimental data are necessary to inform and validate these computational models. High-throughput (HT) methodologies, in which hundreds of materials are rapidly synthesized, processed, and characterized for their figure of merit, represent the key experimental enabler of the theoretical aspects of the MGI. HT methodologies have been used since the early 1980s for identifying novel catalyst formulations and optimizing existing catalysts. Many sophisticated screening and data mining techniques have been developed and since the mid-1990s, this approach has become a widely accepted industrial practice. This article will provide a short history of major developments in HT and will discuss screening approaches combining rapid, qualitative primary screens via thin-film techniques with a series of quantitative screens using plug flow reactors. An illustrative example will be provided of one such study in which novel fuel-flexible sulfur tolerant cracking catalysts were developed. We will then illustrate a path forward that leverages existing HT expertise to validate, provide empirical data to and help guide future theoretical studies.

Traditionally, the synthesis of CoFe nanoparticles with tunable particle sizes and narrow particle size-distributions is accomplished via the use of expensive and air sensitive precursors and strong non-polar capping agents. Such strong capping agents can be difficult to remove from the nanoparticles and thus render them catalytically inactive. We report a novel solution-based methodology to synthesize CoFe alloy nanoparticles with narrow size-distributions using a combination of robust and inexpensive metal precursors and an easily removable polar capping agent. High resolution transmission electron microscope images show that the CoFe alloy nanoparticles are well crystallized, and the particle size is tunable from 9 to 24 nm while keeping a particle size standard deviation of 10%. The CoFe alloy nanoparticles show superior activity for NaBH4 hydrolysis compared with the best-known CoFe catalysts. This work represents a substantial improvement in the synthesis of transition metal nanoparticles, opening the pathway for their application to a number of technologically important catalytic applications.