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Pyrolysis of raw and hydrothermally carbonized (HTC) Chlamydomonas debaryana with and without activated carbon (AC) or β-zeolite as the catalyst were studied. Monoaromatic hydrocarbon yields from the pyrolysis of raw and HTC treated algae without a catalyst were relatively low at optimum yields of 11.2% and 12.0% obtained at 600 °C, respectively. The maximum yields of monoaromatic hydrocarbons from the AC catalyzed pyrolysis of raw and HTC treated algae were 43.8% obtained at 600 °C and 43.5% obtained at 800 °C, respectively, compared to 32.3% and 32.7% for the maximum yields from the β-zeolite catalyzed pyrolysis at 500 °C and 600 °C, respectively. However, β-zeolite catalyzed pyrolysis produced higher yields of total hydrocarbons (aromatic + aliphatic) for raw and HTC algae compared to AC catalyzed pyrolysis. This means while β-zeolite was more effective in producing total hydrocarbon content, AC was more effective in aromatization of oxygenates. The combination of HTC pretreatment and catalytic pyrolysis were effective in reducing nitrogen content in bio-oil. The yields of nitriles and nitrogenous compounds were negligible for the AC catalyzed pyrolysis of HTC treated algae at 600 °C, compared to 8.3% using the β-zeolite at the same temperature. The AC catalyst had a lower tendency towards coking
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This content will become publicly available on March 12, 2026
Hydrocarbon Deposition during Polyolefin Upcycling: Irreversible Adsorption and Surface Reactions of Polyethylene and Ethylene Oligomers on Silica Supports
Catalytic conversion of polyolefins to value-added products offers an alternative route to capture value from plastic waste. Here we initially examine reactions of a polyethylene model (hexatriacontane, C36H74) on a Pt/SiO2 catalyst under typical hydrogenolysis and hydrocracking temperatures, which leads to irreversibly adsorbed surface hydrocarbons identified after extraction of hexatriacontane with excess hot toluene. The IR spectra of these catalysts after extraction reveal only aliphatic C–H stretches. SiO2 alone leads similar hydrocarbon adsorption on the surface where extended extraction fails to fully remove the adsorbed hydrocarbons from neat silica. The amount of hydrocarbon irreversibly adsorbed increases nearly 10-fold when the reactant is changed from hexatriacontane to polyethylene (Mn = 4000 Da), but the adsorbed quantity is insensitive to reaction temperature (200–300 °C). These results demonstrate significant, nonextractable hydrocarbon deposition on catalyst support surfaces without dehydrogenation catalyst present at temperatures typical of catalytic deconstruction of polyolefin waste, which may limit catalyst turnover and impact the product distribution.
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- Award ID(s):
- 2229168
- PAR ID:
- 10641468
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Industrial & Engineering Chemistry Research
- Volume:
- 64
- Issue:
- 12
- ISSN:
- 0888-5885
- Page Range / eLocation ID:
- 6475-6486
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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