Jochen Lauterbach

The Materials Super Highway: Integrating High-Throughput Experimentation into Mapping the Catalysis Materials Genome

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.Graphical Abstract

Metal oxide arrays from block copolymer thin film templates

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.

High-Throughput Investigation of Catalysts for JP-8 Fuel Cracking to Liquefied Petroleum Gas

Portable power technologies for military applications necessitate the production of fuels similar to LPG from existing feedstocks. Catalytic cracking of military jet fuel to form a mixture of C₂-C₄ hydrocarbons was investigated using high-throughput experimentation. Cracking experiments were performed in a gas-phase, 16-sample high-throughput reactor. Zeolite ZSM-5 catalysts with low Si/Al ratios (≤25) demonstrated the highest production of C₂-C₄ hydrocarbons at moderate reaction temperatures (623-823 K). ZSM-5 catalysts were optimized for JP-8 cracking activity to LPG through varying reaction temperature and framework Si/Al ratio. The reducing atmosphere required during catalytic cracking resulted in coking of the catalyst and a commensurate decrease in conversion rate. Rare earth metal promoters for ZSM-5 catalysts were screened to reduce coking deactivation rates, while noble metal promoters reduced onset temperatures for coke burnoff regeneration.

In situ spectroscopic investigation of a Pd local structure over Pd/CeO2 and Pd/MnOx–CeO2 during CO oxidation

The high activity observed on Pd impregnated MnOx–CeO2 solid solution catalysts for low temperature CO oxidation is investigated through in situ extended X-ray absorption fine structure (EXAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments. The change in the Pd local structure on CeO2 and MnOx–CeO2 is studied to identify the role of oxidized Pd nanoparticles during CO oxidation. EXAFS analysis of the calcined samples confirms the formation of PdO structures on CeO2 and MnOx–CeO2 supports. The structural model applied to the Ce1−xPdxO2−δ interaction phase could not predict the second and third near-neighbor coordination shells of Pd. Sintering and re-dispersion of Pd is observed on CeO2 during H2 reduction and subsequent oxidation with air. During CO oxidation, PdO species are reduced by CO on CeO2, forming a mixture of Pdn+/Pd0 species. These reduced Pd particles can be re-oxidized and re-dispersed on the CeO2 surface forming larger PdO crystallites. In the case of Pd/MnOx–CeO2, Pdn+ species can be stabilized during the reaction and no obvious Pd0 formation could be detected. Due to the formation of similar PdO species after CO oxidation on both CeO2 and MnOx–CeO2 supports, the different low temperature CO oxidation activities can be associated with the oxygen storage properties and oxygen mobility of the support.

Ethylene Epoxidation Catalyzed by Ag Nanoparticles on Ag-LSX Zeolites formed by Pressure- and Temperature-Induced Auto-Reduction

Ag+ -Exchanged LSX (Ag-LSX: Ag96 Al96 Si96 O384 ⋅nu2009H2 O), a large pore low silica analogue (Si/Al=1.0) of faujasite, was prepared and post-synthetically modified using pressure and temperature in the presence of various pore-penetrating fluids. Using high-resolution synchrotron X-ray powder and single crystal diffraction we derive structural models of the as-prepared and post-synthetically modified Ag-LSX materials. In the as-prepared Ag-LSX model, we located 96 silver cations and 245 H2 O molecules distributed over seven and five distinctive sites, respectively. At 1.4(1)u2005GPa pressure and 150u2009°C in ethanol the number of silver cations within the pores of Ag-LSX is reduced by ca. 47.4u2009%, whereas the number of H2 O molecules is increased by ca. 40.8u2009%. The formation of zero-valent silver nanoparticles deposited on Ag-LSX crystallites depends on the fluid present during pressurization. Ag-nanoparticle-Ag-zeolite hybrid materials are recovered after pressure release and shown to have different chemical reactivity when used as catalysts for ethylene epoxidation.

Evaluation of Mn and Sn-Modified Pd-Ce-Based Catalysts for Low-Temperature Diesel Exhaust Oxidation

Pd-impregnated Ce-based catalysts were tested for carbon monoxide (CO) and hydrocarbon (HC) oxidation under challenging low-temperature diesel combustion conditions. The results indicate that the light-off temperatures for CO over Pd/CeO2, Pd/MnOx-CeO2 (Pd/MC), and Pd/SnO2-MnOx-CeO2 (Pd/SMC) catalysts shift to higher temperatures in the presence of simulated diesel exhaust gas. The lowest T50 for CO is observed over Pd/MC at 173xa0°C, whereas Pd/CeO2 is shown to oxidize most of the HCs at temperatures below 400xa0°C. In all catalysts, the oxidation of HCs starts right after the onset of CO oxidation, revealing that the competitive adsorption of CO, NO, and alkenes controls the catalytic activity. Further evaluation of the catalytic activity in the presence of only CO and C3H6 reveals the immediate inhibiting effect of C3H6 at catalyst temperatures below 150xa0°C. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments performed over Pd/CeO2, Pd/MC, and Pd/SMC show that C3H6 inhibits the formation of carbonyl species on Pdn+ sites, which limits the catalytic activity for CO. Such inhibition is observed on all supports, implying that the activity is independent of oxygen storage capacity (OSC) or lattice oxygen reducibility of the supports in the presence of C3H6.

High-Throughput Screening Using Fourier-Transform Infrared Imaging

ABSTRACT Efficient parallel screening of combinatorial libraries is one of the most challenging aspects of the high-throughput (HT) heterogeneous catalysis workflow. Today, a number of methods have been used in HT catalyst studies, including various optical, mass-spectrometry, and gas-chromatography techniques. Of these, rapid-scanning Fourier-transform infrared (FTIR) imaging is one of the fastest and most versatile screening techniques. Here, the new design of the 16-channel HT reactor is presented and test results for its accuracy and reproducibility are shown. The performance of the system was evaluated through the oxidation of CO over commercial Pd/Al 2 O 3 and cobalt oxide nanoparticles synthesized with different reducer-reductant molar ratios, surfactant types, metal and surfactant concentrations, synthesis temperatures, and ramp rates.

Synthesis-Structure-Activity Relationships in Co3O4 Catalyzed CO Oxidation

In this work, a statistical design and analysis platform was used to develop cobalt oxide based oxidation catalysts prepared via one pot metal salt reduction. An emphasis was placed upon understanding the effects of synthesis conditions, such as heating regimen and Co2+ concentration on the metal salt reduction mechanism, the resultant nanomaterial properties (i.e., size, crystal structure, and crystal faceting), and the catalytic activity in CO oxidation. This was accomplished by carrying out XRD, TEM, and FTIR studies on synthesis intermediates and products. Additionally, high-throughput experimentation was employed to study the performance of Co3O4 oxidation catalysts over a wide range of reaction conditions using a 16-channel fixed bed reactor equipped with a parallel infrared imaging system. Specifically, Co3O4 nanomaterials of varying properties were evaluated for their performance as CO oxidation catalysts. Figure-of-merits including light-off temperatures and activation energies were measured and mapped back to the catalyst properties and synthesis conditions. Statistical analysis methods were used to elucidate significant property-activity relationships as well as the design rules relevant in the synthesis of active catalysts. It was found that the degree of grain boundary consolidation and anisotropic growth in fcc and hcp CoO intermediates significantly influenced the catalytic activity. By utilizing the discovered synthesis-structure-activity relationships, CO oxidation light off temperatures were decreased to <90°C.