Location: Sustainable Biofuels and Co-products Research
2023 Annual Report
Objectives
Objective 1: Develop thermochemical and/or catalytic, carbon efficient biomass conversion processes to produce bio-oils and bio-gas containing fractions suitable for use towards advanced commercially viable bio-fuels (jet, diesel, and gasoline carbon ranges). This includes co-conversion of biomass with other carbon sources (e.g., plastics from both agricultural and environmental waste) to enhance carbon efficiency. [NP306, C3, PS3A]
Objective 2. Develop pre- and post-process thermo-catalytic depolymerization, distillation and extraction technologies to produce renewable chemicals and biocarbon materials from biomass, biochar, lignin and/or condensed phase bio-oils (furans, phenolics, chiral anhydrosugars, aromatics, biocoke fibers). [NP306, C3, PS3A]
Objective 3: Identify and develop new feedstocks and accompanying technologies to produce biodiesel, renewable hydrocarbon diesel and biojet fuels from fats and oils. [NP306, C3, PS3A]
Objective 4. Accurately estimate the economic values of thermolysis conversion processes to produce bio-based fuels and chemicals. [NP306, C3, PS3C]
Approach
Efficient processes will be developed for the thermo-catalytic conversion of lignocellulosic biomass and alternative fats and oils into advanced biofuels and renewable chemicals. For lignocellulose, advanced pyrolysis processes will be developed that balance deoxygenation and carbon efficiency for thermochemical biomass conversion in multifaceted ways. Processes that reduce the severity of deoxygenation during pyrolysis and produce stable, mid-level oxygen (~20-25 wt%) content (MLO) bio-oil will be developed. Some oxygen containing species can be valuable products in the petrochemicals space. Additionally, processes will be developed that achieve a high level of deoxygenation (
Progress Report
Objective 1: Pyrolysis of biomass (switchgrass) and waste agricultural plastic (polyethylene hay bale covers) were pyrolyzed both catalytically and non-catalytically in Eastern Regional Research Center's bench scale fluidized bed pyrolysis reactor. Plastic waste, particularly polyolefins, can act as an inexpensive source of carbon and hydrogen rich feedstocks to supplement the oxygen rich and hydrogen poor biomass. Previous small-scale studies have indicated that the presence of plastic can increase the conversion of bioderived carbon into final fuel products. Now in continuous processes, we have shown that the oxygen content of the pyrolysis oil was decreased over that made exclusively from biomass both catalytically and non-catalytically. The mixture proportions were set at 15 wt% plastic as a preliminary analysis indicates that at that level of fossil carbon included, the subsequent refining product would still qualify as sustainable aviation fuel based on greenhouse gas reduction targets. For non-catalytic processes, changes in downstream processes include addition of a “tar pot” to the condensation system which alleviated process interruptions by trapping plastic derived waxes before they were able to block cooler portions of the condensing system. Catalysts tested included zeolites (HY, Zeolite Socony Mobil–5, ZSM-5) and a titanium oxide, (TiO2 ). The use of HY in an ex-situ fashion eliminated wax formation, increasing the proportion of plastic carbon input into the liquid phase. Pyrolysis oils have been provided to collaborators at a university for studies on co-hydrodeoxygenation with vegetable oils for production of sustainable aviation fuel.
On the same pyrolysis unit atmospheric pressure hydropyrolysis pyrolysis of biomass (oak) was studied using both pallidum on carbon (Pd/C) and cerium oxide (CeO2) catalysts in an ex-situ arrangement. Conditions of pyrolysis at 500 °C, and catalysis at 400 °C over Pd/C were found as conditions that can increase the concentration of phenolic monomers in pyrolysis oil, indicating a stabilization of reactive components derived from lignin via the presence of active hydrogen species. In another effort to improve the quality of pyrolysis oils, the effect of an alkaline biomass pretreatment on pyrolysis behavior of herbaceous crop residues (corn stover and barley straw) and energy crops (switchgrass and sorghum biomass) was studied. The reaction kinetics were studied using thermal gravimetric analysis (TGA) data and pyrolysis products were quantified by micro-pyrolyzer coupled to a gas chromatography-flame ionization detector (Py-GC/FID). The results showed that the pretreated biomass produced a significantly less acidic bio-oil than the non-pretreated biomass, while the activation energy of the reaction was not affected.
Microwave-assisted pyrolysis of biomass and plastic mixtures was carried out with preliminary work focused on determining the discrepancy between measured and actual pyrolysis temperature during microwave heating. By comparing microwave pyrolysis oil composition with the pyrolysis vapor composition determined analytically via pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS), it was shown that the product composition from microwave pyrolysis is representative of higher temperature pyrolysis products. The actual temperature during microwave pyrolysis is estimated to be 140 °C greater than the measured temperature, which may be attributed to a few factors: (1) selective heating by microwaves leading to large temperature gradients in the material, (2) hotspot formation due to standing waves, and (3) the location of temperature measurement. A new microwave reactor system is being procured, which will produce a more predictable field distribution that will eliminate most of these factors and the temperature determination will be estimated with greater confidence.
Objective 2: 1) Substantial progress was made in bio-oil separations methods via solvent-mediated extraction. Previously, bio-oils needed to undergo distillation in order to extract phenolics and hydrocarbons from the distillates. Now, we have refined a method for extraction of phenolics without the need to distill. Dissolving bio-oil in toluene precipitates a toluene insoluble (TI) fraction, and the extraction from the soluble portion proceeds while dissolved. Then the TI fraction dissolves in isopropyl alcohol (IPA), and this precipitates an IPA-insoluble fraction. IPA insolubles can undergo further cracking to recover more phenolics and aromatics. Cost savings are expected due to bypassing distillation units. 2) In collaboration with the Dairy and Functional Foods research unit, ice cream waste underwent hydrothermal liquefaction (HTL) experiments for the purpose of producing fuels and chemical coproducts of value. Specifically, oils largely containing paraffinic carboxylic acids were produced at 16% dry yield, alongside solid hydrochar product, without any catalyst or additives. Preliminary results show that when methanol is added, fatty acid methyl esters are also produced. Project scientists plan to optimize further with the plan to process biomass and ice cream waste together. 3) In collaboration with a university, bio-oil distillation residues were dissolved and processed into films that underwent a laser writing process for direct carbonization into graphene films which are approximately 100 microns in thickness. Preliminary results show the films to have Raman spectra and electrical properties similar to other graphene films.
Objective 3: 1) Unrefined biodiesel produced from brown grease lipids (BGL) in the form of trap grease and sewage scum grease were obtained from Environmental Fuels LLC. It was subjected to distillation (wiped-film and spinning band distillation) and the pot residue was analyzed to quantify sulfur-bearing molecules using a total sulfur analyzer. Quantification and identification of the sulfur-bearing molecules were performed using a gas chromatograph (GC) equipped with a sulfur chemiluminescence detector and GC-MS. Protocols to synthesize hard-to-remove sulfur compounds suggested by GC-MS are being developed to assist with confirmation experiments. 2.) Studies to convert purified free fatty acids FFA to renewable hydrocarbon diesel (RHD) and sustainable aviation fuel have been initiated by establishing protocols to select hydro-isomerization and hydro-cracking catalysts. Studies designed to identify and remove potential catalyst-poisoning metals from the FFA have also been initiated.
Accomplishments
Review Publications
Mullen, C.A., Ellison, C.R., Elkasabi, Y.M. 2023. Pyrolytic conversion of cellulosic pulps from “lignin-first” biomass fractionation. Energies. https://doi.org/10.3390/en16073236.
Elkasabi, Y.M., Jones, K.C., Mullen, C.A., Strahan, G.D., Wyatt, V.T. 2023. Spinning band distillation of biomass pyrolysis-oil phenolics to produce pure phenol. Separation and Purification Technology. https://doi.org/10.1016/j.seppur.2023.123603.
Mullen, C.A. 2022. Thermochemical and catalytic conversion of lignin. In: Nghiem, N.P., Kim, T.H., Yoo, C.G., editors. Biomass Utilization: Conversion Strategies. New York, NY: Springer. p. 133-200. https://doi.org/10.1007/978-3-031-05835-6_7.
Raymundo, L.D., Mullen, C.A., Elkasabi, Y.M., Strahan, G.D., Boateng, A.A., Trierweiler, L.F., Trierweiler, J.O. 2022. Online separation of biomass fast pyrolysis liquids via fractional condensation. Energy and Fuels. https://doi.org/10.1021/acs.energyfuels.2c02624.
Wyatt, V.T., Arrey, I.T., Nguyen, A., Asare-Okai, P.N., Besong, S., Aryee, A.N., Jones, K.C. 2022. Quality characteristics and volatile compounds of oil extracted from njangsa seed. Journal of the American Oil Chemists' Society. https://doi.org/10.1002/aocs.12639.
