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When fractionating corn cobs using the acetosolv process, the type of acid catalyst and their concentrations significantly affect the structure of the resulting lignin fraction as well as its catalytic deconstruction to aromatic monomers. Gel permeation chromatography (GPC) results show that the average molecular weight (~55,750 g/mol) of the sulfuric acid-pretreated corn cob lignin (H2SO4-CCL) is much greater than that (~39,400 g/mol) of hydrochloric acid-pretreated corn cob lignin (HCl-CCL) at similar acid concentrations, suggesting increased condensation reactions when using sulfuric acid. Further, a significant amount of bound sulfur content (~2900 ppm) was measured in H2SO4-CCL. This sulfur presence poisons the Pd/C catalyst used in the downstream catalytic conversion of the lignin in methanol to form monolignols and derivatives thereof. X-ray photoelectron spectroscopy (XPS) results reveal that both sulfide and sulfate groups are formed with the surface Pd sites, rendering them inactive and amenable to possible leaching. Elemental mapping of spent catalysts using scanning transmission electron microscopy-high angle annular dark field (STEM-HAADF)/energy dispersive x-ray (EDX) technique corroborate overlapping presence of Pd, S and O in the micrographs. 2D 1H/13C HSQC nuclear magnetic resonance (NMR) spectroscopy reveals that the use of H2SO4 preserves aryl ether linkages only at low concentrations. In contrast, the use of HCl in the acetosolv process preserves such linkages even at high concentrations while also mitigating sulfur poisoning of the Pd/C catalyst. Consequently, the yield of aromatic monomers during catalytic fractionation of HCl-CCL was doubled compared to H2SO4-CCL at identical operating conditions. 

Non-toxic resins formulated with renewable components have been receiving increased attention as sustainable alternatives to petroleum-based resins. In this work, we demonstrate a new class of lignin-amino acid (LA) resins, formulated with non-toxic components that are abundant and can be renewably sourced from field leftovers (corn cobs) and lysine (from bio-based sugars). NMR (1H, 31P, 13C-1H HSQC, 15N-1H HSQC, and 15N-1H HMBC), FTIR, thermogravimetric, gel permeation chromatography and elemental analyses provide insights into the physicochemical properties of the resins, including the presence of LA linkages such as C-N cross linking. The LA resin creates strong bonds between pieces of wood, metals (aluminum and stainless steel) and plastics. Internal bond strengths (IBS) of balsa wood and medium density fiberboard specimens glued with LA resins, measured using an Instron instrument, were comparable to those bonded with commercial polyurethane (PU) and polyvinyl acetate (PVAc) resins. Resins prepared with ozone-pretreated lignin have significantly larger molar masses and display increased bond strengths with glued substates as inferred from IBS measurements. This is attributed to the creation of reactive oxygen-based functionalities in the lignin upon ozone pretreatment. Lignin-amino acid resins thus show promise as a feasible and sustainable alternative to petroleum-based resins. 

We shed light on the mechanism and rate-determining steps of the electrochemical carboxylation of acetophenone as a function of CO 2 concentration by using a robust finite element analysis model that incorporates each reaction step. Specifically, we show that the first electrochemical reduction of acetophenone is followed by the homogeneous chemical addition of CO 2 . The electrochemical reduction of the acetophenone-CO 2 adduct is more facile than that of acetophenone, resulting in an Electrochemical–Chemical–Electrochemical (ECE) reaction pathway that appears as a single voltammetric wave. These modeling results provide new fundamental insights into the complex microenvironment in CO 2 -rich media that produces an optimum electrochemical carboxylation rate as a function of CO 2 pressure.