Derek R. Vardon

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.

This CRADA advanced the use of atomic layer deposition (ALD) catalyst coatings to improve sulfur tolerance and demonstrate improved catalyst durability for biomass conversion chemistries. This project leveraged National Laboratory and industry expertise for ALD catalyst coating development between NREL, ALD NanoSolutions, Inc. ("ALD NanoSolutions"), and Johnson Matthey PLC ("Johnson Matthey"). To better understand the role of ALD coatings on catalyst activity and durability, a joint experimental and computational effort combined bench-scale ALD catalyst synthesis, material characterization, catalyst testing, and modeling of catalyst surface energetics. In addition, to demonstrate the commercial relevance of this technology, scaled ALD coated catalysts were subjected to continuous testing and accelerated aging to validate performance gains. Results were used to inform ALD catalyst coating manufacturing cost models, as well as biobased chemical process cost models.

Hybrid processes, featuring biological conversion of lignocellulose to small molecules followed by chemo-catalytic conversion to larger molecules suitable for difficult-to-electrify transport modes, are a promising route to biomass-derived fuels in demand for climate stabilization.

Supercritical methanol (SCM) solvolysis and catalysis has recently emerged as a promising pathway to produce gasoline‐range light alcohols from woody biomass through staged depolymerization and hydro‐deoxygenation (DHDO). Here, structure–property relationships of Cu“M”AlO_x catalysts (M = Mg, Zr, and Ce) are examined for upgrading delignified hybrid poplar via SCM‐DHDO. CuCeAlO_x displays the highest activity, increasing the C₂C₇ alcohol production rate and selectivity by twofold in batch reactions, and >50% in semicontinuous reactions relative to the current state‐of‐the‐art CuMgAlO_x. The performance of CuCeAlO_x is correlated with its high reducibility and acidity. Cu sintering and biogenic impurity poisoning are identified as possible deactivation mechanisms over 60 h of continuous testing. The gasoline‐range SCM‐DHDO products are comprised of primarily aliphatic alcohols that result in improved energy density and favorably reduced vapor pressure, relative to ethanol, with the tradeoff of nonsynergistic octane blending with conventional gasoline and lower oxidation stability. Overall, this work highlights the potential to produce suitable light oxygenates by SCM‐DHDO processing for gasoline bioblendstock applications.

Correction for ‘Thermochemical wastewater valorization via enhanced microbial toxicity tolerance’ by Lahiru N. Jayakody et al. , Energy Environ. Sci. , 2018, 11 , 1625–1638, DOI: 10.1039/C8EE00460A.