Addition of in situ clay catalysts at different process points in a cascaded hydrothermal carbonization-pyrolysis process for agro-industrial waste valorization

• Published in: Bioresource technology 2023-03, Vol.372, p.128649-128649, Article 128649
• Main Authors: Adair, James L., Karod, Madeline, Goldfarb, Jillian L.
• Format: Article
• Language: English
• Subjects: Bio-oil; Biochar; Carbon - chemistry; Clay; Clay catalyst; Hydrothermal carbonization; Industrial Waste; Pyrolysis; Temperature
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2023.128649

[Display omitted] •Cascaded hydrothermal carbonization (HTC) followed by pyrolysis of apple pomace.•Added clay catalyst either prior to HTC or to hydrochar prior to pyrolysis.•Bio-oils made from hydrochar + clay have higher aldehyde concentration.•Bio-oils from clay-catalyzed hydrochars have more ketones and hydrocarbons.•Clay added prior to HTC decreases surface area of pyrolyzed biochars. Agro-industrial wastes can be thermochemically converted to sustainable fuels and upcycled carbon products. However, processing such feedstocks through pyrolysis or hydrothermal carbonization (HTC) alone yields fuels that require significant downstream upgrading. In this work, apple pomace was treated via a cascaded HTC-pyrolysis process using inexpensive and abundant clay catalysts, montmorillonite and attapulgite. Clays were added pre-HTC to raw biomass or to hydrochar pre-pyrolysis to examine the effect of addition as a function of process insertion point. Both clays produce similar bio-oils when they are added at the same process point. However, bio-oil was affected by the point in which clay was added to the process (before or after HTC). When clay was added pre-HTC, the bio-oil had an average hydrocarbon content twice that when clay was added to the hydrochar after HTC, prior to pyrolysis.