Progress 09/01/23 to 08/31/24
Outputs
Target Audience:We received sample almond shells and hulls from the Central CaliforniaAlmond Growers Association. CCAGA is kept updated on our activities. Changes/Problems:1. A substantial part of the first year was spent establishing a second, northern Californialaboratory where the PI leads Distributed Extraction and Efficient Conversion. The co-PI leads Green Polymerization in the first, southern California lab. A one year No Cost Extension was obtained to accomodate this delay. 2. The value of solvent extracted polymeric xylan over hydrothermally produced xylose was recognized, and initial demonstration of deep eutectic solvent (DES) extraction are promising. The advantages of xylan include value as an intermediate product, transportability, and opportunity to increase the efficiency of conversion to THF. DES extraction experiments were added in parallel with planned hydrothermal extraction experiments. What opportunities for training and professional development has the project provided?This project has provided professional development for scientists and engineers working on polymerization and biomass distributed extraction. This development includes new experience with polymer catalysis, biomass structure, deep eutectic solvents, and hydrothermal extraction. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, we will continue our lab scale progress with Distributed Extraction and Green Polymerization and we will begin Efficient Conversion. Distributed Extraction will further optimize hydrothermal and DES fractionation with the goal of high yield of high polymers of xylan. We will select an optimized process. Currently Professor Deepak Kumar at SUNY ESF is evaluating our almond shells for hydrothermal extraction of xylan. If his evaluation is promising for either xylan or xylose extraction, we will proceed with a subcontract.Ifhigh polymers at high yield cannot be acheived, we will use hydrolysis to produce xylose. Secondary goals of distributed extraction include recovery of high polymers of lignin and cellulose pulp. Both these materials have markets. In particular, pulp produced at the huller can be sold to existing cusotmers that purchasealmond hulls as dietary supplement for ruminants. Efficient Conversion depends on catalysis. In the next reporting period, we will first try to leverageextraction of xylanto avoid hydration to xylose and subequent dehydration to furfural. If these opportunities are not realized then we will dehydrate xylose to furfural. Green Polymerization will build on our demonstration of PTMEG. The primary hydroxyl content will be measured by 13C NMR. Hydroxyl number andmolecular weight will be controlled. The process willtransition from batch to continuous polymerization. Hydroxyl number depends oninitiator and promoter molecules. These additives can also control molecular weight. Development will target both product specifications and process economics. Continuous polymerization calls for development of a hetergenous catalyst.
Impacts
What was accomplished under these goals?
No Cost Extension This project received a NCE extending the end date to 8/31/2026 to accomodate first year administrative delays in funding, and establishment of a second lab in N. California. Distributed Extraction 1. Hydrothermal extraction at 10g/hr bench scale has shown poor hemicellulose yield. Much of the hemicellulose is hydrolyzed at 180C/10 minutes. We recovered 10-12% of the initial xylan and the balance was hydrolyzedto xylose. Our strategy is to recover the xylan as a high polymer, not xylose. The xylan polymer can have immediate value as a product, it is easier to separate than xylose, and therefore cost effective to transport from the huller to the chemical processing plant (objective #3), and it promises a more direct chemical path to THF. Thehydrolysate liquid additionally contains hot water extractables and 4-25% of the initial lignin. Further hydrothermal extraction experiments are planned to reduce hydrolysis byminimizingthe extractiontemperature, and chemically limiting hydrolysis. Hydrothermal extraction operates at temperatures above the lignin glass transition (100-180C) or even above the melting temperature (180C) in order to softenthe lignin matrix and free the entangled hemicellulose. These high temperatures promotexylan hydrolysis. Hydrolysis cuts up xylan, which has a degree of polymerization of about 150, to xylose monosaccharide. Thissmall moleculequicklyexits the lignin matrix, but subsequent capture and utilization of xylosecan be expensive. The lignin that largely remains with the cellulose after hydrothermal extraction is both a lost asset and a detriment to further use of the cellulose. Fractionation with green, deep eutectic solvents (DES) is also being investigated to producehigh polymers of both xylanand lignin at lower temperature, 70C. The low temperature is possible because the solvent plasticizes (rather than heats) the lignin to soften it. Native lignin has a very high molecular weight so some cleavage of aryl alkyl internal bonds is required. Lignin iscovalently bonded to hemicellulose via ferulic esters, which must also be cleaved.The DES, two step strategy uses a first solvent plus cleavage additives to extract high molecular weight lignin and a second solvent to extract high molecular weight xylan. Our best DES extraction so far yielded88% of the initial lignin and 88% of the initial xylan. 2. Both hydrothermal and DES extraction recover cellulose, but it is not pure. The hydrothermal process leaves lignin in the cellulose and the DES process leaves solvent remaining solids. The remaining solids porosity is increased substantially by processing, but the cellulose is not highly pulped. Contaminants and crystallinity are obstacles to use as feed. Use of the glucan will be further investigated after the xylan yield target is acheived. 3. DES extractionfollowed by NaOH extraction of the remaining lignin xylan yields a solid, high MW xylan polymer. It can be transported easily as sheets, powder, or slurry. It may have commercial value as a nutraceutical and as a packaging material. If xylan yieldsof ~90% can be acheived, then objective 3 appears well within reach. Nothing to report on subsequent Distributed Extraction objectives Efficient Conversion Nothing to report on Efficient Conversion objectives Green Polymerization 1. A batch, bench scale polymerization (1 g/hr) with a green catalyst has been demonstrated for PTMEG from THF. The catalyst and THF can both be recycled. CapX and OpX inputs are low compared to the incubment Dupont process. Our PTMEG is a diol, while phase I only demonstrated a single hydroxyl functionality. The primary hydroxyl content, molecular weight and polydispersity of the diol is being optimized. Nothing to report on subsequent Green Polymerization objectives
Publications
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