Improvement in hydrogen production from hard-shell nut residues by catalytic hydrothermal gasification

• Published in: The Journal of supercritical fluids Vol. 95; pp. 339 - 347
• Main Authors: Güngören Madenoğlu, Tülay, Yıldırır, Eyüp, Sağlam, Mehmet, Yüksel, Mithat, Ballice, Levent
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2014
• Subjects: Biomass; Borax [Na2B4O7·10H2O]; Catalysis; Catalysts; Dolomite; Dolomite [CaMg(CO3)2]; Gasification; Hard-shell nut; Hydrogen; Hydrogen production; Hydrothermal gasification; Trona; Trona [Na3(CO3)(HCO3)·2H2O]; Hard-shell nut; Dolomite [CaMg(CO3)2]; Borax [Na2B4O7·10H2O]; Hydrogen; Biomass; Hydrothermal gasification; Trona [Na3(CO3)(HCO3)·2H2O]
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2014.09.033

•We examine effects of natural mineral catalysts on hydrothermal gasification of hard-shell nut residues.•Natural mineral catalysts increase hydrogen yield and decrease the amount of residue.•Gaseous product and hydrogen yields were found slightly higher when Trona used as catalyst.•Main degradation product in aqueous phase was found as acetic acid for all biomass types used. The hydrothermal gasification of some hard-shell nut residues (hazelnut, walnut and almond shells) was performed in a batch type reactor at temperature and pressure ranges of 300–600°C and 88–405bar, respectively. The biomass samples were converted into gaseous product (hydrogen, carbon dioxide, methane, carbon monoxide and C2–C4 compounds), aqueous product (carboxylic acids, furfurals, phenols, aldehydes and ketones) and solid products after hydrothermal gasification. Hydrogen production was improved by using natural mineral catalysts (Trona, Dolomite and Borax). The activity of selected natural mineral catalysts in hydrothermal gasification can be ordered as being Trona [Na3(CO3)(HCO3)·2H2O]>Borax [Na2B4O7·10H2O]>Dolomite [CaMg(CO3)2]. The most effective catalyst was found to be Trona at 600°C leading enhancement in hydrogen yields (molH2/kgC in biomass) for hazelnut, walnut and almond shells as 82.4%, 74.1% and 42.4%, respectively.