Location: Sustainable Biofuels and Co-products Research
2017 Annual Report
Objectives
1: Develop pyrolysis processes that enable the commercial production of marketable, partially-deoxygenated pyrolysis oil intermediates.
2: Develop post-pyrolysis technologies that enable the commercial upgrading of pyrolysis oils into marketable fuels and/or chemicals.
3: Develop scalable technologies that enable commercially-viable pyrolysis oil-based products and co-products.
Approach
A three-tier developmental approach at the analytical, pilot and field scales will be followed to overcome the scientific, engineering and economic barriers that have challenged production and blending of biomass pyrolysis oils (bio-oil) into hydrocarbon fuels. In doing so three specific thrust areas including catalytic pyrolysis, reactive/co-reactant assisted pyrolysis, and upgrading of pyrolysis oils produced from these processes, already advanced at ARS, will be strengthened. The step-wise approach includes (i) the quest for novel processing strategies that address bio-oil stability issues directly at the farm site; (ii) enabling robust catalytic deoxygenation processes that will allow for effective separation of critical (valuable or detrimental) chemical species present within bio-oils; (iii) production of an intermediate bio-oil product that can support interim markets (e.g. home heating oil) and; (iv) production of hydrocarbons suitable for refining into fuels and for manufacture of specialty chemicals. Additionally, extensive physical and chemical property data will be collected to enable operations from the farm to the refinery. Data will be used to demonstrate compatibility of the liquid hydrocarbon product with petroleum refining unit operations and for economic and environmental assessment of the process life cycle.
Progress Report
Progress was made on all objectives, all of which fall under National Program
213 – Biorefining, Problem Statement 3.1 – “Pyrolysis processes to produce marketable bio-oils” and 3.2 – “Accurately estimate the economic value of pyrolysis-based conversion technologies” of Component 3 of the ARS Biorefining Action Plan, Pyrolysis.
Under Objective 1, progress was made in several areas: (1) Through the interagency project, FarmBio3, and following up our own in-house work from the previous year’s progress using microscale experiments in elucidating the beneficial effects of gallium incorporation into HZSM-5 catalysts for production of partially deoxygenated bio-oil, we tested these on the process development unit/small pilot scale. An experimental campaign revealed that gallium modified catalysts resisted coke formation and had longer active lifetimes than HZSM-5 without Ga modification. These results build on the work previously done on the role of silicon/aluminum ratio that was reported in the previous year’s report, towards development of a suite of catalysts for producing deoxygenated bio-oil containing higher concentrations of target renewable petrochemical replacements. (2) On reactive atmosphere pyrolysis named tail gas reactive pyrolysis (TGRP), an alternative process to catalytic fast pyrolysis invented in-house, we have continued to study the role of process parameters including gas flow rates, residence times and reaction atmosphere for producing stable, deoxygenated bio-oils. A smaller scale fluidized bed reactor was designed, fabricated and assembled so these systematic tests of these variables can be done more rapidly than possible at the pilot scale. (3) We have continued to engage in a specific cooperative agreement (SCA) with the University of Delaware to develop chemical-mathematical models of the chemical mechanisms underlying tail gas reactive pyrolysis. These have yielded identification of potential key intermediates that have then been detected by experiments; we are beginning to experimentally validate the model. (4) In collaboration with Drexel University via FarmBio, an ASPEN-plus model for the conversion of biomass (specifically horse litter but broadly applicable) to fuels and chemicals via TGRP using our lab’s pilot scale data was developed and a technoeconomic analysis on the process was completed. (5) We completed a study testing the long term effects on catalyst activity during the co-catalytic pyrolysis of agricultural plastics with switchgrass, indicating that the addition of plastic can decrease coke formation and increase catalyst lifetimes. (6) Our final task on NIFA funded coordinated agricultural projects (CAP) program led by Penn State University called Northeast Woody/Warm-season Biomass Consortium (NewBio) was completed by testing the effects of hot water extraction pretreatment on willow biomass for pyrolysis, concluding that hot water extraction pretreatment can result in bio-oil with lesser acidity.
Progress was also made in several areas under Objective 2: (1) In collaboration with University of South Carolina and as part of the Biomass Resource and Development Initiative (BRDI) FarmBio3 grant, we developed stable oxygen-reducing (termed, hydrodeoxygenation) catalysts by strong electrostatic adsorption (SEA) and compared with more traditional hydrodeoxygenation catalysts. It was determined that cheaper base metals like nickel and copper can perform hydrodeoxygenation reactions similar to that accomplished by the more expensive catalysts (Ru, Pt), but their stabilities need improvement for long-term use. The combination of nickel-copper on carbon support gave the best results for deoxygenating and producing higher-value aromatic compounds. Compared with carbon-supported catalysts mesoporous alumina-supported catalysts generally produced more aromatics. While there existed little difference in hydrodeoxygenation between catalysts prepared using strong electrostatic adsorption (ruthenium, platinum) and traditionally prepared catalysts, the stabilities of strong electrostatic adsorption based Ru-Pt catalysts are superior to those of traditional catalysts. The aforementioned results complete the condensed-phase upgrading project for FarmBio3. (2) Further upgrading of bio-oil distillate residues was investigated for potential coprocessing with vacuum gas oil, a heavy fraction of petroleum. When these two materials are blended together and undergo high-temperature cracking (fragmentation) reactions in the presence of a catalyst, a synergistic production of higher-value compounds was observed. These include aromatic compounds and olefins. The effect was greatest for switchgrass-based oil residues. (3) A technoeconomic assessment on both the pyrolysis and catalytic refining of guayule biomass was carried out. We successfully used Pro-II simulation software to model experimental data from tail gas reactive pyrolysis of guayule and catalytic upgrading of guayule bio-oil. It was found that, under economically favorable conditions, the guayule-based biorefinery could potentially lower the minimum fuel selling price to $3.63/gal for gasoline, with an average of $7.12/gal for typical economic constraints. (4) In collaboration with industry, improvements to the quality of biorenewable calcined coke were accomplished. By modifying the heat treatment methods applied to bio-oil distillate residues, increased crystallinity of the coke product was observed. (5) Construction of a continuous distillation process was completed. The process consists of a two-stage flash distillation, and preliminary tests on the first stage have been completed using model bio-oil mixtures, which so far validate the tests done on batch scale. Tests using real bio-oil are currently underway.
Under Objective 3, modifications and design improvements to our mobile pyrolysis demonstration scale unit the Combustion Reduction Integrated Pyrolysis System (CRIPS) are underway. These improvements include (1) injecting recycled condensate to mitigate fouling of the hot ductwork; (2) constructing a heat exchanger to utilize the combustion bed exhaust to preheat the recycled tail gas to the pyrolysis bed; and (3) design and construction of an improved combustion and pyrolysis bed assembly based on “lessons learned” while operating the CRIPS. In order to ensure rapid turnaround in our studies towards the understanding of tail gas reactive pyrolysis mechanisms for producing deoxygenated bio-oils we designed and fabricated a bench-scale (38 mm ID) pyrolysis reactor for producing deoxygenated bio-oils. We have also embarked on the design and fabrication of an intermediate-scale (100 mm ID) pyrolysis reactor system with assembly and commissioning underway. This system is designed for longer on-stream operating times and generating larger quantities of bio-oil than the smaller pyrolysis reactor systems. This system is also designed to easily accommodate the addition or removal of unit operations. Combined with the aforementioned 38 mm ID and mobile (1 ton per day) reactors we will soon have 4 different reactor scales (ranging from 0.6 to 60 kg/h) for performing continuous pyrolysis operations. With regard to combustion of pyrolysis oil for home and industrial furnace heating, previously we successfully combusted bio-oil with no dilution (100% bio-oil) using our modified burner design. Now, modifications are underway to test the previously installed industrial-scale horizontal furnace (nominal 350,000Btu/h capacity) to fire under load conditions using 100% bio-oil.
Accomplishments
1. Production of renewable crystalline biocoke as a coproduct from bio-oil. Previously, ARS researchers at Wyndmoor, Pennsylvania produced a biomass-sourced (biorenewable) calcined coke (termed ‘biocoke’), using residues from the distillation of biomass-derived pyrolysis oil. This biocoke has properties that are similar to or better than analogous materials made from petroleum and therefore are highly desirable to producers of aluminum metal who use them and want to reduce their environmental footprint. However, the crystalline structure of the biocoke (crystallinity) was deficient and needed to be optimized for it to compete in the aluminum production anode market. We have devised a modified process for producing biocoke that has improved biocoke crystallinity, marking the first known time this has been accomplished using simple process steps. This led to the filing of a new patent application (DN: 0009.17), allowing for the initiation of a new MTRA with a major international research organization.
2. Production of phenols and furans as chemical coproducts to biofuels from biomass catalytic pyrolysis. Because of the small profit margins associated with fuel production, petroleum refiners make almost half of their profits from non-fuel chemical products (petrochemicals), and for biorefiners to be successful, they will need to make similarly high valued products. For fuel production, the focus of biomass conversion processes has been to remove oxygen from biomass; however, oxygenated products are often more valuable than their hydrocarbon analogs. ARS researchers at Wyndmoor, Pennsylvania have modified a zeolite catalyst traditionally used in biomass pyrolysis to increase the production of the valuable oxygenated chemicals (phenols and furans), and optimized conditions for their production. First reported in a 2017 journal article, this work also substantiated that phenols can be produced not only from the lignin portion of the biomass polymer, as traditionally thought, but also from cellulose thanks to such catalyst modifications. The impact of this work, because it expands on the potential to produce valuable coproducts from biomass, is potential improvement in the profitability of fast pyrolysis biorefineries.
Review Publications
Schultz, E.L., Mullen, C.A., Boateng, A.A. 2017. Aromatic hydrocarbon production via eucalyptus urophylla pyrolysis over several metal modified ZSM-5 catalysts – an analysis by py-GC/MS. Energy Technology. 5:196-204.
Carrasco, J.L., Gunukula, S., Boateng, A.A., Mullen, C.A., Desisto, W.J., Wheeler, C.M. 2017. Pyrolysis of forest residues: an approach to techno-economics for bio-fuel production. Fuel. 193:477-484.
Mullen, C.A., Tarves, P.C., Boateng, A.A. 2017. Role of potassium exchange in catalytic pyrolysis of biomass over ZSM-5: Formation of alkyl phenols and furans. ACS Sustainable Chemistry & Engineering. 5:2154-2162.
Choi, Y., Elkasabi, Y.M., Tarves, P.C., Mullen, C.A., Boateng, A.A. 2017. Catalytic cracking of fast and tail gas reactive pyrolysis bio-oils over HZSM-5. Fuel Processing Technology. 161:132-138.
Serapiglia, M., Dien, B.S., Boateng, A.A., Casler, M.D. 2017. Impact of harvest time and switchgrass cultivar on sugar release through enzymatic hydrolysis. BioEnergy Research. 10:377-387.
Serapiglia, M., Mullen, C.A., Boateng, A.A., Dien, B.S., Casler, M.D. 2017. Impact of harvest time and cultivar on conversion of switchgrass to bio-oils via fast pyrolysis. BioEnergy Research. 10:388-399.
Chung, S., Liu, Q., Joshi, U.A., Regalbuto, J.R., Boateng, A.A., Smith, M.A., Coe, C.G. 2017. Using polyfurfuryl alcohol to improve the hydrothermal stability of mesoporous oxides for reactions in the aqueous phase. Journal of Porous Materials Select Science. doi: 10.1007/s10934-017-0451-9.
