Fast pyrolysis of biomass produces organic bio-oils, which can be refined into finished hydrocarbon fuels. If the process is optimized to produce oils of relatively low oxygen (&lt; 15 wt%), the oils can distill into relatively purer fractions, leaving behind a solid carbonaceous residue. While we have shown that these residues can be converted into valuable solid materials like calcined coke, some residues prove more difficult for use in those applications. Residues from protein-containing biomasses like spirulina contain high levels of nitrogen (&gt; 10 wt%), which interfere with product purity and quality. Some residues emanate from lighter oils with low fixed carbon content which limits the potential yield of solid co-products. While hydrothermal liquefaction (HTL) and solvent liquefaction have been examined for upgrading biomasses, lignin, and other problematic wastes, very little work – if any – has looked at its use on distillate residues.<br/> <br/>Herein we will discuss liquefaction screening studies performed on distillate residues from various bio-oil types produced by tail-gas reactive pyrolysis: 1) Spirulina bio-oil 2) switchgrass bio-oil and 3) switchgrass bio-oil phenolic fraction. A variety of solvents and additive combinations were explored for each residue, including water, ethanol, HCl, NaOH, and ethanol/HCl mixtures. Microreactors were assembled using Swagelok union fittings and pressure-resistant plugs, and we conducted reactions in parallel at 320 <sup>o</sup>C for 1 hr. GC-MS results indicated preferential liquefaction occurred in some solvents over others, depending on the residue examined. Spirulina-based residue was more effectively depolymerized in ethanol, whereas aqueous media was more effective for other residues. Using the most optimal results from microreaction experiments, we will also discuss scaled-up experiments in a 100 mL pressurized Parr reactor.

Liquefaction of fast pyrolysis bio-oil distillate residues using various solvents

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ACS Fall 2022

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