7 Search Results

Reactive carbon capture (RCC), whereby a dual function material (DFM) captures dilute CO₂ and subsequently converts it within the same reactor, can address persistent cost concerns in carbon capture and utilization technology advancement. Many DFMs utilize costly precious metals (e.g., Pt or Ru) or oxidation-sensitive transition metals (e.g., Ni and Cu), the latter of which can hinder utilization of CO₂ sources containing O₂ and/or increase the H₂ demand for oxide-metal reduction cycles. We report a precious metal-free, K-modified Zn-Al mixed oxide (ZnAlO_x) DFM that exhibited 99% selectivity to CO at temperatures more than 250 °C lower than conventional RCC-to-CO routes.more » While unmodified ZnAlO_x catalysts were effective for RCC, K-modification was found to significantly increase CO₂ adsorption capacity, improve retention of adsorbed CO₂ through the reactive desorption step, and suppress the formation of unreactive spectator species during reactive desorption. These effects combined to improve CO yield (53%) far beyond equilibrium-limited predictions for CO₂-to-CO under conventional steady state reaction conditions (<1%). The DFM also exhibited remarkable oxidative stability, with negligible performance loss over 25 RCC cycles using simulated flue gas with 5% O₂, demonstrating its promise as a robust, low-cost material to enable highly selective conversion of CO₂ to CO in a single unit operation.« less

Abstract An extensive dataset consisting of adsorption energies of pernicious impurities present in biomass upgrading processes on common catalysts and support materials has been generated. This work aims to inform catalyst and process development for the conversion of biomass-derived feedstocks to fuels and chemicals. A high-throughput workflow was developed to execute density functional theory calculations for a diverse set of atomic (Al, B, Ca, Cl, Fe, K, Mg, Mn, N, Na, P, S, Si, Zn) and molecular (COS, H ₂ S, HCl, HCN, K ₂ O, KCl, NH ₃ ) species on 35 unique surfaces for transition-metal (Ag, Au, Co,more » Cu, Fe, Ir, Ni, Pd, Pt, Re, Rh, Ru) and metal-oxide (Al ₂ O ₃ , MgO, anatase-TiO ₂ , rutile-TiO ₂ , ZnO, ZrO ₂ ) catalysts and supports. Approximately 3,000 unique adsorption geometries and corresponding adsorption energies were obtained.« less

A novel RCC process using modified CZA DFMs to produce renewable MeOH is presented. K/CZA provides exceptionally high productivity of MeOH compared to previously reported attempts of RCC to MeOH.

Polyoxymethylene ethers (POMEs) are a class of low-soot and high-cetane oxygenate oligomers of structure RO-(CH₂O-)_$$n$$-R, with different chain lengths ($$n$$) and end-groups (R) that determine their diesel-like fuel properties. Commercial POMEs with methyl end-groups (MM-POME_3-6) exhibit undesirably low energy density and high-water solubility. A previous computational assessment indicated that the lower heating value (LHV) and water solubility for MM-POME_3-6 both improve upon end-group exchange with larger butyl, $iso$-butyl and $iso$-pentyl end-groups. Here, we expanded upon our initial trans-acetalization reaction that employed 1-butanol to install butyl end-groups to also include branched, higher carbon-number end-groups using $iso$-butanol and fusel oil as reagents.more » Additionally, these new products are termed $$i$$B*POME_1-6, and FOil*POME_1-5, respectively, and collectively referred to as R*POMEs. They possess the advantaged properties of the parent MM-POME_3-6 while exhibiting higher LHV (31 MJ kg^-1 and 28 MJ kg^-1 for $$i$$B*POME_1-6, and FOil*POME_1-5, respectively) and much reduced water solubility (2.7 g L^-1 and 1 g L^-1 for $$i$$B*POME_1-6, and FOil*POME_1-5, respectively). Additional fuel property analyses were performed using 20 vol% blends of the R*POMEs with a base diesel fuel. Overall, the greater energy density and decreased water solubility of the R*POMEs, as well as their synergistic blending with diesel at moderate blend levels, provide the greatest benefits to consumers and position this group of products as an environmentally friendlier blendstock alternative to the commercially available MM-POME_3-6.« less

The thermocatalytic hydrogenation of CO₂ to hydrocarbons using a composite catalyst system in a single reactor under mild reaction conditions was investigated, by combining methanol synthesis, methanol dehydration and dimethyl ether homologation catalysts. High selectivity to isoparaffins, which are versatile precursors to sustainable aviation fuels, was achieved. The use of Cu/BEA significantly improved both the conversion of oxygenates and the hydrocarbon yield compared to HBEA by facilitating H-incorporation in the C-chain growth during the homologation reaction. A study of catalyst composition and reaction conditions revealed that nearly complete conversion of oxygenates was achieved using a stacked-bed configuration, providing high C-selectivitymore » to C₄₊ hydrocarbons (34.1% among all products and 95.5% in products excluding CO). The ability to completely convert oxygenates to hydrocarbons and achieve high CO-free selectivity to desired hydrocarbon products is unprecedented in CO₂-to-hydrocarbon reports, and advantageous for downstream separation, as CO can be easily separated and recycled to improve overall hydrocarbon production in an integrated process.« less