Vapor-phase Stabilization of Biomass Pyrolysis Vapors Using Mixed-metal Oxide Catalysts

Abstract

<div>Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilization of biomass pyrolysis products. For materials derived from layered double hydroxides, understanding the effect of divalent cation species and divalent/trivalent cation stoichiometric ratio on catalytic behavior is critical to their successful implementation. In this study, four mixed-metal oxide catalysts consisting of Al, Zn, and Mg in different stoichiometric ratios were synthesized and tested for ex-situ catalytic fast pyrolysis (CFP) using pine wood as feedstock. The catalytic activity and deactivation behavior of these catalysts were monitored in real-time using a lab-scale pyrolysis reactor and fixed catalyst bed coupled with a molecular beam mass spectrometer (MBMS), and data were analyzed by multivariate statistical approaches. In comparing Mg- and Zn-Al catalyst materials, we demonstrate that the Mg-Al materials possessed greater quantities of basic sites, which we attribute to their higher surface areas, and they produced upgraded pyrolysis vapors which contained less acids and more deoxygenated aromatic hydrocarbons such as toluene and xylene. However, detrimental impacts on carbon yields were realized via decarbonylation and decarboxylation reactions and coke formation. Given that the primary goals of catalytic upgrading of bio-oil are deoxygenation, reduction of acidity, and high carbon yield, these results highlight both promising catalytic effects of mixed-metal oxide materials and opportunities for improvement.</div>

Catalyst Deactivation and Its Mitigation during Catalytic Conversions of Biomass

“…74,75 The catalytic reactions occurring in CFP include dehydration, decarbonylation, decarboxylation, ketonization, aldol condensation, aromatization, hydrodeoxygenation, hydrogenation, and cracking. 74,75 Catalysts applied in both in situ and ex situ CFP include zeolites (for example, ZSM-5) and acid-functionalized mesoporous materials (for example, MCM-41), 19,44,74,76 acidic metal oxides (for example, Al 2 O 3 , TiO 2 , and ZrO 2 ), 77−80 basic metal oxides (for example, MgO and CaO), 81−83 and mixedmetal oxides with both acidic and basic sites (for example, MgO/ZnO with Al 2 O 3 , 83 and Mn 2 O 3 /ZrO 2 with CeO 2 84 ). In addition, supported noble metal bifunctional catalysts (for example, Pt/TiO 2 85 and Ru/TiO 2 86 ) together with H 2 are used in ex situ CFP for hydrodeoxygenation of the pyrolysis vapor.…”

Energy recovery from banner waste through catalytic pyrolysis over cobalt oxide: Effects of catalyst configuration

“…Other than CaO and ZnO, CuO, Fe 2 O 3 , 13 TiO 2 , ZrO 2 , 14 NiO, MgO, 15 and Al 2 O 3 16 have been examined for use in the catalytic biomass pyrolysis. Edmunds et al showed that a Mg‐Al oxide catalyst was effective at upgrading the pyrolysis vapor evolved from biomass feedstock (eg, pine wood), which led to high toluene and xylene yields 17 …”

“…Edmunds et al showed that a Mg-Al oxide catalyst was effective at upgrading the pyrolysis vapor evolved from biomass feedstock (eg, pine wood), which led to high toluene and xylene yields. 17 Beyond biomass conversion, metal oxides have recently attracted interest in plastic waste treatment catalysts. For example, red mud (a mixture of a variety of metal oxides) was employed in the catalytic pyrolysis of different plastics.…”

Hidróxidos duplos lamelares como precursores de nanopartículas metálicas e nanoestruturas de carbono

“…A partir da pirólise de HDLs intercalados com espécies orgânicas, a estrutura e propriedades dos compostos obtidos depende de parâmetros como: (i) atmosfera (inerte, oxidante, redutora, estática, dinâmica); (ii) temperatura e taxas de aquecimento e de resfriamento; (iii) composição do HDL (variabilidade no número de oxidação dos cátions metálicos); e (iv) propriedades da espécie confinada (natureza química, estabilidade térmica). 55,73,74 Nesse sentido, poucos estudos sistematizam a variação das condições de tratamento térmico com as estruturas produzidas. Em geral, os trabalhos focam na obtenção (i) das estruturas carbonáceas, onde o HDL e estruturas derivadas atuam apenas como agente porogênico, removido após tratamento ácido; ou (ii) das nanopartículas metálicas, onde o intercalante orgânico é utilizado apenas como fonte de espécies redutoras.…”