Engineering topics
Publications and source records attributed to Dreiling, Reagan J..
When excess base is required to drive desired reactions, such as in lignin alkaline oxidation, Sr(OH) 2 can offer a reversibly-soluble alternative to NaOH that allows simple recycle of the excess base with concomitant cost and environmental benefits.
Production of oxidized aromatic monomers from lignin has been an intriguing process for decades, but widespread implementation has been inhibited by the high hydroxide:lignin ratios required for significant aldehyde yields. The high hydroxide loading in most scenarios renders the process uneconomical even for high-value products such as vanillin. In this work, we explore alkaline oxidation of a lignin-rich enzymatic hydrolysis residue isolated from corn stover, using alkaline earth metal hydroxides, such as Sr(OH)2 and Ba(OH)2 as base promoters. These materials are soluble at reaction temperature, but mostly insoluble at room temperature, allowing recovery and reuse by simple filtration. We show that monomer yields and profiles using these bases is similar to that obtained using NaOH as base, and that Sr(OH)2 can be recovered in yields above 90%. Preliminary TEA and LCA suggest that replacing NaOH with Sr(OH)2 can decrease monomer production costs by 40% and decrease global warming potential in lignin depolymerization by 30%, enabling a more economical and sustainable process.
Production of oxidized aromatic monomers from lignin has been an intriguing process for decades, but widespread implementation has been inhibited by the high hydroxide:lignin ratios required for significant aldehyde yields. The high hydroxide loading in most scenarios renders the process uneconomical even for high-value products such as vanillin. In this work, we explore alkaline oxidation of a lignin-rich enzymatic hydrolysis residue isolated from corn stover, using alkaline earth metal hydroxides, such as Sr(OH)2 and Ba(OH)2 as base promoters. These materials are soluble at reaction temperature, but mostly insoluble at room temperature, allowing recovery and reuse by simple filtration. We show that monomer yields and profiles using these bases is similar to that obtained using NaOH as base, and that Sr(OH)2 can be recovered in yields above 90%. Preliminary TEA and LCA suggest that replacing NaOH with Sr(OH)2 can decrease monomer production costs by 40% and decrease global warming potential in lignin depolymerization by 30%, enabling a more economical and sustainable process.
Reductive catalytic fractionation (RCF) is a promising lignin-first biorefining strategy that selectively extracts and depolymerizes lignin from whole biomass. Flow-through (FT)-RCF enables physical separation of the biomass and catalyst, but this process configuration typically operates at high solvent-to-biomass ratios. Here, we demonstrate multi-pass FT-RCF, wherein the lignin-enriched solvent obtained after an initial FT-RCF step is recycled and used in subsequent FT-RCF without intermediate lignin recovery. Multi-pass FT-RCF reduces the solvent-to-biomass ratio from 48 to 1.9 L/kg, which is a lower solvent loading than is accessible in batch reactors, without negative impacts on delignification and monomer yield with up to 12 wt % lignin in the solvent. Overall, this work demonstrates that solvent demand in RCF processes, which is a key cost and energy driver to enable this process at scale, can be reduced by recycling lignin oil between RCF reactions.
The movement to transfer from petroleum-based products and materials to renewables does not necessarily have to bypass the use of oil. A new type of "black-gold" is readily abundant from the earth's most abundant source of aromatic carbon: lignin. While fractionation of petroleum yields fuels and chemicals for a diverse set of industries, lignin fractionation using targeted catalysts has demonstrated the ability to generate monomers and oligomers rich in functional groups for polymer synthesis. This study explores the use of lignin-oil, generated from reductive catalytic fractionation of popular wood, to a hydroxyl-rich mixture of aromatics that is used to synthesize a thermoplastic non-isocyanate polyurethane. The lignin-oil is first converted to a cyclocarbonated derivative using a benign synthetic sequence and further polymerized with a diamine to yield the non-isocyanate TPU. While more work is underway to optimize the reaction conditions and meet typical mechanical properties of commercial materials, initial analysis shows thermoplastic behavior and flexible properties consistent with traditional thermoplastic polyurethanes.