Electrochemical reduction of biomass-derived platform molecules is an emerging route for the sustainable production of fuels and chemicals. However, understanding gaps between reaction conditions, underlying mechanisms, and product selectivity have limited the rational design of active, stable, and selective catalyst systems. In this work, the mechanisms of electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction, are explored through a combination of voltammetry, preparative electrolysis, thiol-electrode modifications, and kinetic isotope studies. It is demonstrated that two distinct mechanisms are operable on metallic Cu electrodes in acidic electrolytes: (i) electrocatalytic hydrogenation (ECH) and (ii) direct electroreduction. The contributions of each mechanism to the observed product distribution are clarified by evaluating the requirement for direct chemical interactions with the electrode surface and the role of adsorbed hydrogen. Further analysis reveals that hydrogenation and hydrogenolysis products are generated by parallel ECH pathways. Understanding the underlying mechanisms enables the manipulation of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels.

Biorefineries aim to convert biomass into a spectrum of products ranging from biofuels to specialty chemicals. To achieve economically sustainable conversion, it is crucial to streamline the catalytic and downstream processing steps. In this work, a route that combines bio- and electrocatalysis to convert glucose into bio-based unsaturated nylon-6,6 is reported. An engineered strain of Saccharomyces cerevisiae was used as the initial biocatalyst for the conversion of glucose into muconic acid, with the highest reported muconic acid titer of 559.5 mg L(-1) in yeast. Without any separation, muconic acid was further electrocatalytically hydrogenated to 3-hexenedioic acid in 94 % yield despite the presence of biogenic impurities. Bio-based unsaturated nylon-6,6 (unsaturated polyamide-6,6) was finally obtained by polymerization of 3-hexenedioic acid with hexamethylenediamine.

Electrocatalysis is evolving as a competitive alternative to conventional heterogeneous catalysis for the conversion of platform chemicals from biomass. Here, we demonstrate the electrocatalytic conversion of cis,cis-muconic acid, a fermentation product, to trans,trans-muconic acid, trans-3-hexenedioic acid, and adipic acid used for the production of biobased polyamides and polyesters such as nylon, nylon derivatives, and polyethylene terephthalate (PET). The electrocatalytic hydrogenation in this work considers a wide range of early, late, and post-transition metals (Cu, Fe, Ni, Mo, Pb, Pd, Sn, and Zn) with low and high hydrogen overpotentials, and varying degrees of metal hydrogen binding strengths. The binding strength was determined to be an important factor for the conversion rate, faradaic efficiency, and product distribution. Selectivities are also discussed in relation to thermodynamic data, which suggests the possibility to tune the kinetics of the reaction to allow for the variable production of multiple biobased monomers.

Ligand-capped metal entities come in two sizes, (1) molecular clusters of 10–200 metal atoms and (2) nanoparticles of 2000–10000 metal atoms. In numerous cases, certain “magic sizes” have been found to be most accessible and stable, clusters of 25, 38, 55, and 102 atoms and nanoparticles of 3500–5000 atoms or 4–5 nm. The most familiar and studied system is that of gold (metal) and thiol (ligand). Herein, the methods of synthesis of these gold clusters versus gold nanoparticles are carefully compared. In the cluster case, an important intermediate is the (Au+SR–) n polymer, which is not the case in the synthesis of nanoparticles either from metal (vapor) atoms or metal ions. Also, it is shown that thiol can act as both a reductant (Au3+ → Au+) and as an oxidant (Au0 → Au+). The thermodynamic forces responsible for the favored formation of certain size clusters and nanoparticles are discussed.

We present muconic acid, an unsaturated diacid that can be produced from cellulosic sugars and lignin monomers by fermentation, emerges as a promising intermediate for the sustainable manufacture of commodity polyamides and polyesters including Nylon-6,6 and polyethylene terephthalate (PET). Current conversion schemes consist in the biological production of cis,cis-muconic acid using metabolically engineered yeasts and bacteria, and the subsequent diversification to adipic acid, terephthalic acid, and their derivatives using chemical catalysts. In some instances, conventional precious metal catalysts can be advantageously replaced by base metal electrocatalysts. Here, we show the economic relevance of utilizing a hybrid biological-electrochemical conversion scheme to convert glucose to trans-3-hexenedioic acid (t3HDA), a monomer used for the synthesis of bioadvantaged 6. Potential roadblocks to biological and electrochemical integration in a single reactor, including electrocatalyst deactivation due to biogenic impurities and low faradaic efficiency inherent to side reactions in complex media, have been studied and addressed. In this study, t3HDA was produced with 94% yield and 100% faradaic efficiency. With consideration of the high t3HDA yield and faradaic efficiency, a technoeconomic analysis was developed on the basis of the current yield and titer achieved for muconic acid, the figures of merit defined for industrial electrochemical processes, and the separation of the desired product from the medium. On the basis of this analysis, t3HDA could be produced for approximately $2.00 kg -1. The low cost for t3HDA is a primary factor of the electrochemical route being able to cascade biological catalysis and electrocatalysis in one pot without separation of the muconic acid intermediate from the fermentation broth. AbstractMuconic acid, an unsaturated diacid that can be produced from cellulosic sugars and lignin monomers by fermentation, emerges as a promising intermediate for the sustainable manufacture of commodity polyamides and polyesters including Nylon-6,6 and polyethylene terephthalate (PET). Current conversion schemes consist in the biological production of cis,cis-muconic acid using metabolically engineered yeasts and bacteria, and the subsequent diversification to adipic acid, terephthalic acid, and their derivatives using chemical catalysts.In some instances, conventional precious metal catalysts can be advantageously replaced by base metal electrocatalysts. Here, we show the economic relevance of utilizing a hybrid biological-electrochemical conversion scheme to convert glucose to trans-3-hexenedioic acid (t3HDA), a monomer used for the synthesis of bioadvantaged Nylon-6,6. Potential roadblocks to biological and electrochemical integration in a single reactor, including electrocatalyst deactivation due to biogenic impurities and low faradaic efficiency inherent to side reactions in complex media, have been studied and addressed. In this study, t3HDA was produced with 94% yield and 100% farad...

Biorefineries aim to convert biomass into aspectrum of products ranging from biofuels to specialty chemicals.T o achieve economically sustainable conversion, it is crucial to streamline the catalytic and downstream processing steps.I n this work, ar oute that combines bio-and electrocatalysis to convert glucose into bio-based unsaturated nylon-6,6 is reported. An engineered strain of Saccharomyces cerevisiae was used as the initial biocatalyst for the conversion of glucose into muconic acid, with the highest reported muconic acid titer of 559.5 mg L À1 in yeast. Without any separation, muconic acid was further electrocatalytically hydrogenated to 3-hexenedioic acid in 94 %y ield despite the presence of biogenic impurities. Bio-based unsaturated nylon-6,6 (unsaturated polyamide-6,6) was finally obtained by polymerization of 3-hexenedioic acid with hexamethylenediamine.

Gold-acetone-dodecanethiol and gold-acetone-phenylethanethiol colloids were prepared by the solvated metal atom dispersion method. Hydrogen evolution occurred at fairly low temperature, when the melting acetone-gold solvate encountered the thiol molecules, due to S-H bond scission. The gas inside the reactor was analyzed by gas chromatography, and the moles of H(2) was determined by calibration curves obtained from a series of known concentration samples. The gold-to-thiolate ratio was calculated using thermal gravimetric analysis. The average particle diameter was also calculated using the gold-to-thiolate ratio.

The integration of microbial and electrochemical conversions in hybrid processes broadens the portfolio of products accessible from biomass. For instance, sugars and lignin monomers can be biologically converted to cis,cis-muconic...