1a. Objectives (from AD-416):
The objective of FarmBio3 is twofold: (i) to leverage the existing synergies among partners to further research and optimize pyrolysis pathways to commodity fuels and chemicals and improve the TRL 4 status already achieved at ARS and (ii) increase to on-farm scale that will enable the current state of technology to, TRL 6, commercial status.
1b. Approach (from AD-416):
Will focus on three feedstocks that are important to U.S. agriculture including switchgrass, horse manure and woody biomass. The primary conversion platform will be catalytic and non-catalytic fast pyrolysis for production of stable fuel intermediates. Because barriers to utilization of such intermediates are high we will develop more robust multi-functional heterogeneous catalysts to balance deoxygenation pathways to minimize oxygenate production while increasing carbon efficiency for the selected feedstock pool. Bifunctional catalysts will be developed to upgrade and optimize carbon distribution in the condensed phase pyrolysate to achieve C6-C14 hydrocarbons and target entry to gasoline, diesel and jet range fuels markets. We will develop and optimize homogeneous catalysts to break C-O bonds of the lignin fraction of lignocellulosic pyrolysate to produce specialty chemicals. Pyrolysis process improvements will be integrated at on- the-farm scale using an existing patent-pending dual fluidized bed, combustion-reduction integrated pyrolysis, unit (CRIPS) designed to mimic the fluid catalytic cracking (FCC) process. Using real process data from this scale up and optimized upgrading, an exergetic LCA will be performed to describe not only economics and greenhouse gas emissions but also resource depletion and loss of quality for distributed on-farm thermolysis; this will be the first complete economic, environmental, and social sustainability analysis for on-farm pyrolysis.
3. Progress Report:
This is a sub-award for a NIFA funded Biomass Research & Development Initiative project (FarmBio3) for which ARS is the principal investigator. The collaborator is producing novel catalysts for the pyrolysis of biomass, with the goal of making robust, coke resistant catalysts. The collaborator has prepared three different silica samples based on SBA-15 having mean pore size of 70A. The parent SBA-15 has been modified with zirconia using both synthetic and post-synthetic routes. For each ZrSBA-15 a Si/Zr ratio of 10 has been achieved. In addition to the long-range order SBA-15 silica samples, the collaborator has also obtained silicas having pore properties that are larger and smaller than the SBA-15 and compared the behavior of these supports with varying amounts of phosphoric and sulfuric acid for the pyrolysis of pinewood. The activity experiments were done in a CDS micropyrolyzer and the vapors produced analyzed using a GC/MS. Fast pyrolysis in this system at 500°C gave a broad range of results depending on the strength of the acid and amount present. Consistent with the underlying hypothesis, we found that the weaker phosphoric acid on a standard silica gel provided a shift in product distribution towards lighter hydrocarbons. Surprisingly the same phosphoric acid loading on SBA-15 samples did not alter the product distribution away from the typical mixture of phenolic compounds found for uncatalyzed samples. However, the stronger sulfuric acid was much more reactive with the pyrolysis vapor and gave a broad range of products depending on the nature of the silica support. A monolayer of sulfuric acid on SBA-15 was found to be more selective for formation of levoglucosone. Analysis of the products from a successful initial commissioning test run on the continuous pyrolyzer with pinewood are in progress. This run provides proof of operations for the continuous unit and provides a benchmark for comparison of the products generated from catalytic pyrolysis studies. To facilitate the study of ex-situ catalytic pyrolysis by using the CDS micropyrolyzer, a heated tubular reactor system module to be added to the existing micropyrolyzer has been ordered. The add-on tubular reactor system will allow the placement of catalyst inside the tubular reactor downstream of the micropyrolyzer. Also preliminary design of the external tubular reactors for both the batch and continuous pyrolyzers has been performed. Current focus is placed on the construction of the tubular reactor for the batch pyrolyzer system. The collaborator is also preparing novel supports for post-production upgrading of pyrolysis oil. The approach being taken to prepare catalysts supports with improved hydrothermal stability and resistance to coking is two-pronged and based on the best leads from the recent literature. Mixed oxide silicas reported to exhibit high hydrothermal stability are being prepared and evaluated for hydrothermal stability. Those preferred supports will be converted into highly dispersed catalysts and evaluated for deoxygenation performance with respect to model bio-oil compounds. The second approach involves modifying carbon based supports to facilitate activation of the C-O bond. Samples of the commercial SBA-15 support have been prepared, as well as two samples of SBA-15 with zirconium added either during the synthesis or by post modification of the SBA-15. A method to test the hydrothermal stability has been defined, equipment acquired, and the shakedown studies initiated. In addition, a series of activated carbon supports varying in mean pore size and surface functionality have been obtained. Two modified carbon catalysts have been produced with a high nickel content and tungsten modification.