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Biofuels produced via thermochemical conversions of waste biomass could be sustainable alternatives to fossil fuels but currently require costly downstream upgrading to be used in existing infrastructure. In this work, we explore how a low-cost, abundant clay mineral, bentonite, could serve as an in situ heterogeneous catalyst for two different thermochemical conversion processes: pyrolysis and hydrothermal carbonization (HTC). Avocado pits were combined with 20 wt% bentonite clay and were pyrolyzed at 600 °C and hydrothermally carbonized at 250 °C, commonly used conditions across the literature. During pyrolysis, bentonite clay promoted Diels–Alder reactions that transformed furans to aromatic compounds, which decreased the bio-oil oxygen content and produced a fuel closer to being suitable for existing infrastructure. The HTC bio-oil without the clay catalyst contained 100% furans, mainly 5-methylfurfural, but in the presence of the clay, approximately 25% of the bio-oil was transformed to 2-methyl-2-cyclopentenone, thereby adding two hydrogen atoms and removing one oxygen. The use of clay in both processes decreased the relative oxygen content of the bio-oils. Proximate analysis of the resulting chars showed an increase in fixed carbon (FC) and a decrease in volatile matter (VM) with clay inclusion. By containing more FC, the HTC-derived char may be more stable than pyrolysis-derived char for environmental applications. The addition of bentonite clay to both processes did not produce significantly different bio-oil yields, such that by adding a clay catalyst, a more valuable bio-oil was produced without reducing the amount of bio-oil recovered.
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Effects of Carrier Gas Flow Rate and ZSM-5 Catalyst on Yields and Quality of Bio-oil from Pyrolysis of Lignocellulosic Biomass Using a Fixed-bed Reactor
This experimental process demonstrates the potential of advancing the technology of lignocellulosic-based biofuels. Maximized bio-oil yields and gasoline range aromatics were obtained from the pyrolysis of switchgrass biomass in a medium-scale fixed bed reactor (48.2 L). The reaction’s final temperature was set at 520ºC while the carrier gas flow rate was varied at (50 L min-1, 75 L min-1 and 100 L min-1) both without and with the use of the ZSM-5 catalyst. Bio-oil yields of 18.2%, 26.9%, and 34.1% were generated without catalyst. Using the ZSM-5 catalyst, bio-oil yields of 20.2%, 41.5%, and 47.7% were generated. At 75 L min-1, 9.6% gasoline range organics (GROs) were detected without the catalyst and 12.4% aromatics were detected in the experiment with ZSM-5 catalyst. At 100 L min-1, 10.5%, and 13.7% of aromatics were detected without and with ZSM-5 catalyst respectively. At 75 L min-1, 14.5% of oxygen content recorded without catalyst, and 5.6% with ZSM-5 catalyst. At 100 L min-1, oxygen content was 10.4% without catalyst, and 8.6 % with ZSM-5 catalyst. The effects of carrier gas flow rate variations and a ZSM-5 catalyst on bio-oil yields and quality were experimentally demonstrated using a single-step thermochemical conversion process. This is a major development towards improving U.S energy security and achieving global CO2 emissions mitigation targets.
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- Award ID(s):
- 2110760
- PAR ID:
- 10521356
- Editor(s):
- Roosa, Stephen A
- Publisher / Repository:
- Association of Energy Engineers
- Date Published:
- Journal Name:
- International journal of strategic energy and environmental planning
- Edition / Version:
- Volume 5 | Issue 2 | 2023
- Volume:
- 5
- Issue:
- 2
- ISSN:
- 2643-6930
- Page Range / eLocation ID:
- 21-37
- Subject(s) / Keyword(s):
- Bio-oil Bio-reactor, ZSM-5 Catalyst
- Format(s):
- Medium: X Size: 890KB Other: pdf
- Size(s):
- 890KB
- Sponsoring Org:
- National Science Foundation
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