Kinga A. Unocic

To be used as transportation fuels, CO₂ can be converted into long-chain hydrocarbons via the CO₂ hydrogenation pathway [ 1]. Co catalysts modified with Mn oxides are catalyst candidates of interest since they exhibit high C-C coupling activity in similar CO hydrogenation reactions [ 2]. In general, CoO reduction under H₂ occurs at ∼400°C. However, the addition of Mn can shift the CoO reduction to higher temperatures allowing for controlled Co speciation with Mn concentration and reduction temperature. Therefore, an investigation of the Co species in Co-Mn oxide system is appealing.

Additive manufacturing is becoming a decisive technology for structural materials in a wide range of applications including nuclear, naval, aerospace, electronic devices, land transportation, and even in jewelry and art decorations [ 1-5]. The prospect of on-the-fly fabrication of materials, tailored to meet specific component requirements, holds considerable allure. Nevertheless, there is currently insufficient in situ experimental data to capture material interaction at nano- and atomic-scale levels, hindering the enhancement of exciting models and simulations for seamless direct fabrication of the components. This gap obstructs detailed investigations into solidification and solid-state phase transformations occurring during and after laser beam interactions. In our research, we employed in situ laser system integrated into both a secondary electron microscope (SEM) and scanning transmission electron microscope (STEM) to explore the formation of non-equilibrium phase transformations and their evolution during in situ laser beam interaction with Fe-Cr-Ni structural material at multiscale level (µm-nm-Å).

The production of advanced biofuels represents a near-term opportunity to decarbonize the heavy vehicle transportation sector. However, important barriers must be overcome and successful deployment of these technologies will require (i) catalyst and process development to reduce cost and improve carbon utilization and (ii) industry-relevant validation of operability to de-risk scale-up. Herein, we seek to address these challenges for an integrated two-step process involving catalytic fast pyrolysis (CFP) followed by co-hydrotreating of bio-oil with refinery streams. Technoeconomic and lifecycle analysis based on the data presented herein reveal the potential to generate low-carbon transportation fuels and chemical co-products with a modelled selling price of $2.83 gasoline gallon equivalent (2016$) and a 78% reduction in greenhouse gas emissions compared to fossil-based pathways. The feedstock for this research was a blend of 50 wt% loblolly pine and 50 wt% waste forest residues, and the CFP step was performed using an ex situ fixed bed of Pt/TiO₂ with co-fed H₂ at atmospheric pressure. Compared to previous state-of-technology benchmarks, advancements in catalyst design and synthesis methodology enabled a four-fold reduction in Pt loading and a 400% increase in time on stream without negatively impacting upgrading performance. Additionally, a first-of-its-kind integrated assessment of waste gas adsorption showed near quantitative recovery of acetone and 2-butanone, which collectively represent approximately 5% of the biomass carbon. The valorization of these co-products opens opportunities to support decarbonization of the chemical sector while simultaneously improving the overall process carbon efficiency to >40%. After condensation, the CFP-oil was co-hydrotreated with straight run diesel (10 : 90 vol%) to achieve 95% biogenic carbon incorporation. The oxygen content of the hydrotreated oil was below detection limits, and the diesel fraction exhibited a cetane number and cloud point suitable for a finished fuel. This manuscript concludes by highlighting remaining research needs associated with improving thermal management during catalyst regeneration, mitigating catalyst deactivation due to inorganic deposition, and demonstrating the durability of biomass feeding systems when operated in hydrogen-rich environments.

Controlled synthesis of Ni_2−xRh_xP nanoparticle catalysts enables an understanding of composition-dependent selectivity for the hydrodeoxygenation reaction of phenolic molecules.

Direct conversion of ethanol to C₃₊ olefins is an attractive pathway to produce sustainable aviation fuels [ 1]. We recently reported a copper-containing catalyst supported on dealuminated (DeAl) beta zeolite that is capable of catalyzing cascade ethanol to olefins reactions with high olefins selectivity (88% C₃₊ olefin selectivity at 100% ethanol conversion). However, one of the deactivation mechanisms of the catalyst is copper sintering [ 2]. It was found that copper agglomerates can be redispersed through a simple oxidative treatment. To better understand the kinetics and process conditions conducive to redispersion, we studied the atmosphere and temperature dependent Cu species in Cu/DeAl-Beta catalyst under conditions matching those of the working catalyst.

Reaction-bonded SiC-B₄C-Si ceramic composites were binder jet 3D-printed and subsequently pressureless-melt-infiltrated with molten Si. The addition of B₄C aided the Si infiltration to produce a highly dense composite. The microstructures and phases of these composites were examined. The measured hardness values of each constituent with Vickers and nanoindentation matched the bulk values, and the macro-hardness values with Knoop and spherical indentation represented the bulk, composite hardness values of all three phases together, which was close to a rule of mixtures value. For particulate-based composites, this is a significant finding. The interfacial bonds of SiC and Si were imaged using scanning transmission electron microscopy to view intimacy, whereas the crack propagation was examined with carefully placed indents. This work demonstrated that pressureless melt infiltration with a reactive particle provides a method to shape non-wetting reaction-bonded ceramic composites with limited shrinkage and high density and provides insights into the mechanical behavior with numerous indentation techniques.

Silica-supported phosphoric acid and metal phosphate catalyzed 1,3-butadiene (BDE) production from 2,3-butanediol (2,3-BDO) was studied using experimental and computational techniques. The catalyst was initially tested in a continuous flow reactor using commercially available 2,3-BDO, leading to maximum BDE yields of 63 C%. Quantum chemical mechanistic studies revealed 1,2-epoxybutane is a kinetically viable and thermodynamically stable intermediate, supported by experimental demonstration that this epoxide can be converted to BDE under standard reaction conditions. Newly proposed E2 and SN2’ elementary steps were studied to rationalize the formation of BDE and all detected side-products. Additionally, using QM/MM (ONIOM) calculations, we modeled silica-supported phosphate catalysts to study the effect of the alkali metal center. Natural population analysis showed that phosphate oxygen atoms are more negatively charged in CsH2PO4/SiO2 than in H3PO4/SiO2. In combination with temperature-programmed desorption experiments using CO2, the results of this study suggest that the improved selectivity achieved when adding the metal center is related to an increase in the basicity of the catalyst.