Project : USDA ARS

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Research Project: Farm-Scale Pyrolysis Biorefining

Location: Sustainable Biofuels and Co-products Research

2016 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
Objective 1: (1) Based on the previous year’s progress on the use of microscale experiments in elucidating the role of Si/Al ratio on HZSM-5 catalyzed pyrolysis (via the NIFA funded Biomass Research & Development Initiative project, FarmBio3, for which we are the principal investigator institution working with various collaborators (University of Oklahoma) we have successfully scaled up the best candidate catalysts for production of aromatic hydrocarbons to the process development unit (PDU) scale. (2) Through the interagency project, FarmBio3, our own in house work and working with collaborators from Embrapa Argoenergy (Brazil), we have completed screening of several metal (Ga, Mo, Zn, Ni, Fe) modified HZSM-5 catalysts for their effectiveness in further increasing yield of selectivity of aromatic hydrocarbons in bio-oil via catalytic fast pyrolysis (CFP) and determined that Ga is the best candidate metal zeolite catalyst modification. We have gone on to test such Ga-modified catalyst on the PDU scale and preliminarily determined that lower rates of catalyst deactivation are possible at this scale. (3) On reactive atmosphere pyrolysis named tail gas reactive pyrolysis (TGRP), an alternative process to CFP invented in-house, we have begun to study the role of process parameters including gas flow rates, residence times and reaction atmosphere for producing stable, deoxygenated bio-oils. (4) We have engaged in a cooperative agreement with the University of Delaware to begin to develop chemical-mathematical models of the chemical mechanisms underlying TGRP. (5) On production of commodity chemicals via pyrolysis, we have screened potassium modified zeolites for the production of alkyl phenols from pure cellulose and biomass and have achieved modest yield increases of these target chemicals over the non-catalytic pyrolysis or pyrolysis over HZSM-5. (6) We have tested the microwave pyrolysis of lignin with 1,4-butanediol as a co-reactant and radical scavenger and achieved a higher yield of phenolic monomer products and bio-oil with lower average molecular weight indicating the suppression of secondary re-polymerization reactions. (7) To improve our ability to predict product yield based on biomass composition near-infrared (NIR) chemometric models for compositional analysis and prediction of pyrolysis product yield for switchgrass biomass have been completed. These models are being used to characterize biomass conversion potential among switchgrass cultivars grown across multiple sites and harvested at different times. This work was done in collaboration with NIFA coordinated agricultural project (CAP) entitled “Sustainable Production and Distribution of Bioenergy for the Central USA (CenUSA)”, led by Iowa State University. (8) The effect of biomass pre-processing such as hot-water extraction and mild thermal roasting (torrefaction), are currently being evaluated for their impacts on fast pyrolysis conversion using biomass from cultivars of shrub willow. This work was done in collaboration with reimbursable, NIFA funded coordinated agricultural projects (CAP) program led by Penn State University called Northeast Woody/Warm-season Biomass Consortium (NewBio). Objective 2: (1) Using principles developed from our previous studies on bio-oil distillation, we designed and began construction of a continuous process for bio-oil separations. As part of a Penn State master’s thesis project, the construction is currently underway. (2) Progress has been made in evaluating optimal conditions for the direct catalytic cracking of bio-oil and/or bio-oil residues in the condensed phase. Reaction pathways were deduced based on the products produced from both regular bio-oil and ARS TGRP bio-oil. Products from both were fully deoxygenated successfully, down to less than 1% and consisted of fuel-quality compounds. Levels of solid carbon byproduct were excessive in certain cases. (3) To improve on our separation capabilities for the production of usable/salable products from condensed phase pyrolysis oil we have demonstrated the optimization of bio-oil catalytic upgrading in combination with extraction to remove oxygen and nitrogen. Bio-oils that are rich in both oxygen and nitrogen respond well to this procedure successfully reducing oxygen and nitrogen to below detectable limits. (4) As part of a materials transfer agreement (MTRA), working with our collaborator, we demonstrated improvement to making quality bio-oil-derived calcined coke byproduct. Laboratory tests carried out at ARS and by the collaborator revealed an improvement to the crystalline nature of the coke, a critical characteristic specification necessary for its use by the aluminum industry. (5) As part of FarmBio3, working with our collaborators (University of South Carolina), stable catalysts developed for bio-oil upgrading made by our university partners were tested ARS. The catalysts were shown to have small, highly controlled sizes within a narrow range; the catalysts remained the same even after exposure to the chemically harsh reaction conditions. Technoeconomic analysis of distillation and catalytic upgrading (Drexel University) has begun, with a process model put together in ASPEN. Objective 3: In a continuation effort to utilize pyrolysis oil for combustion applications such as home heating we carried out several spray-atomization experiments in search of appropriate nozzles that could be applied to the successful combustion of pyrolysis oil. Externally-mixed nozzles used for the combustion of heavy-fuel oils were found to be most successful for bio-oil use. We designed a combustion chamber, instrumented and installed a modified burner nominally rated at 100 kilowatts (350,000 BTU/h) for testing and found out that, the externally mixed nozzle allowed for a successful stable combustion of neat bio-oil with only a slight furnace derating. We have begun a literature search on appropriate methods for bio-oil gasification using the same furnace setup. Various engineering modifications and trial runs were carried out on the CRIPS system so we could achieve the design scale of 2 metric ton per day (MTPD) biomass. The modifications include an upgrade to the feed injection system that greatly improved the handling of low-density biomass (typical of the switchgrass biomass) as well as adding an air slide within the sand duct between the combustion and reductions beds providing better control of the sand motility. In order for us to test various catalysts that come in small quantities a small scale PDU (K.2) was designed and fabricated. The system is now undergoing initial tests.

Accomplishments

None.

U.S. DEPARTMENT OF AGRICULTURE

Sustainable Biofuels and Co-products Research: Wyndmoor, PA