Location: Sustainable Biofuels and Co-products Research
2022 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: 1) Lab scale experiments using both pyrolysis and solvent liquefaction for conversion of biomass and waste plastics mixtures were conducted. For pyrolysis novel metal modified bio-chars from different feedstocks were synthesized and tested for the pyrolysis of biomass, plastics (polyethylene and polystyrene) and their combination. Results showed increased depolymerization of the plastic in the presence of the bio-char based catalysts compared with non-catalytic pyrolysis. 2) On the continuous scale, significant process improvements were made on the bench scale pyrolysis reactor. These process improvements will allow for longer run times to better determine catalyst lifetimes, critical data for accessing their true potential. Experiments are underway to determine long term deactivation rates for bio-char based catalysts previously reported for the production of mid-level oxygen content bio-oil. 3) For liquefaction experiments were conducted to test the co-depolymerization of polystyrene with biomass (oak and switchgrass) and isolated lignin. Analysis of the resulting bio-oil by gas chromatography-mass spectroscopy showed that compounds resulting from trapping of lignin and/or carbohydrate depolymerization intermediates were formed depending on process conditions. Efforts are currently to isolate and characterize these compounds to determine their potential utility as high value products from a combination of biomass and waste plastic feedstocks. 4) Analytical pyrolysis studies were also conducted to determine the thermochemical conversion potential of cellulosic-pulps after “lignin-first” in-situ depolymerization of biomass lignin to produced phenolic oil. Results showed that when metal catalysts (e.g. Pd/C or Ru/C) are used in the depolymerization the biomass is more delignified than when metal-free acid catalyst are used. In the former case, the cellulosic pulps are a better potential source of specialty sugar products such as levoglucosan than is raw biomass. 5) In another effort, slow pyrolysis was used to make several bio-chars (from switchgrass, oak and paper at different temperatures) for testing as antimicrobial agents in soil via an internal collaboration.
Objective 2: 1) As a continuation of bio-oil separations research, we demonstrated the isolation of bio-oil phenolics directly from bio-oil. When performed on specific pyrolysis bio-oils, the phenolic fraction is comparable in quality to that obtained from bio-oil distillates – high concentrations of phenol, cresol and their isomers, etc., We separated bio-oil phenolics into specific fractions comprising of less than 5 compounds. In particular, we isolated phenol into a fraction with > 90 wt% purity. Furthermore, o-cresol was isolated to 40 wt% purity, while efforts are ongoing to increase the purity of other fractions. 2) Borrowing from the procedure outlined in point number 1, we isolated a hydrocarbon fraction from bio-oil directly, as opposed to from bio-oil distillates. This hydrocarbon fraction consisted of 75% BTEX compounds and an oxygen content of only 3 wt%. When distilled, this hydrocarbon fraction leaves a viscous residue that can be coked into calcined coke and/or tar pitch. Previously, we found that oxygen content directly affects coke structure, but we now have found that coking kinetics and time scale improve both the crystallinity and the overall carbon yield. X-Ray Diffraction (XRD) results showed improved crystallinity with longer coking times. 3) To improve fuel compound yields, we explored the feasibility of converting bio-oil distillate residues into fuel compounds via solvent liquefaction. Using microreactors fabricated from tube joints and caps, we performed high throughput screening of solvent liquefaction conditions, by systematically varying bio-oil residue type, solvent, and catalyst/additive, while maintaining reactions at 320 degrees C for 1 hour. We found that proteinaceous residues (e.g. spirulina biomass-based) produced many aliphatic compounds when ethanol was used as the liquefaction solvent. Residues from lower oxygen content (<15 wt%) bio-oil produced phenolic compounds when sodium hydroxide was used.
Objective 3: 1) Brown grease lipids (BGL) in the form of trap grease and sewage scum grease, collected from local municipal underground grease traps and wastewater treatment plants, respectively, were obtained from Environmental Fuels LLC. Unrefined biodiesel produced from this feedstock was also obtained. Protocols to purify brown grease lipids and reduce them to free fatty acids (FFA) were developed using saponification/acidulation and distillation (wiped film evaporation, WFE) methods. The biodiesel was subjected to distillation (WFE and spinning band distillation) and the pot residue was analyzed to quantify and identify sulfur-bearing molecules using GC equipped with a sulfur chemiluminescence detector and GC-MS.
Objective 4: Based on a new setup for isolating phenols, we have significantly altered the downstream process by which pure phenol is produced. We are calculating yields and setting up process parameters as setup for TEA/LCA. It is anticipated that while the yields of phenol will significantly improve – especially at the benefit of not requiring catalytic synthesis – it’s possible coke yield may decrease. TEA will be required to ascertain this fact. We will need to evaluate scenarios of: a) spinning band distillation alone and b) spinning band distillation with pentane recrystallization. Updating of the processing and economic models for these scenarios is underway.
Accomplishments
1. High purity biophenol from biomass. Phenol is a chemical with a $19.4 billion global market that is made from petroleum and is used to make many everyday products, such as plastics, pharmaceutical drugs, and herbicides. U.S. companies produce more than 1 million tons of phenol per year (with increasing demand), and they are under pressure to make it in a way that is environmentally friendly and cost-effective. ARS scientists in Wyndmoor, Pennsylvania, successfully made phenol from non-food biomass. The scientists first took switchgrass (though other grasses, woods, and crop residues would similarly work) and used a high temperature process called catalytic pyrolysis to convert it into bio-oil that is similar to petroleum but contains relatively high levels of phenol. Then they separated out the phenol from the other components using processes similar to what are used in oil refineries but with novel hardware changes. The result is a method to make phenol without expensive additives and with less complicated processes. The remainder of the oil is used to produce biofuels, and production of phenol as a high value co-product can reduce the minimum selling price of that fuel. Advancing this technology will reduce the need for both fossil base fuels and phenol and thereby decreased fossil greenhouse gas emissions.
Review Publications
Mullen, C.A., Strahan, G.D., Elkasabi, Y.M. 2022. A comparison of the solvent liquefaction of lignin in ethanol and 1,4-butanediol. Journal of Analytical & Applied Pyrolysis. 164:105522. https://doi.org/10.1016/j.jaap.2022.105522.
Elkasabi, Y.M., Mullen, C.A., Strahan, G.D., Wyatt, V.T. 2022. Biobased tar pitch produced from biomass pyrolysis oils. Fuel. https://doi.org/10.1016/j.fuel.2022.123300.
Strahan, G.D., Mullen, C.A., Stoklosa, R.J. 2022. Application of diffusion ordered NMR spectroscopy to the characterization of sweet sorghum bagasse lignin isolated after low moisture anhydrous ammonia (LMAA) pretreatment. BioEnergy Research. https://doi.org/10.1007/s12155-021-10385-y.
