Vapor-Phase Stabilization of Biomass Pyrolysis Vapors Using Mixed-Metal Oxide Catalysts

Abstract

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. File list (3) download file view on ChemRxiv ex-situ pine v00 FINAL SUBMIT.docx (1.19 MiB) download file view on ChemRxiv ex-situ pine v00 FINAL SUBMIT.pdf (875.30 KiB) download file view on ChemRxiv ex-situ pine SI v03.docx (5.

Catalytic pyrolysis of biomass to produce bio‐oil using layered double hydroxides (LDH)‐derived materials

“…Various oxides such as ZnAl-LDO, Zn 2 Al-LDO, MgAl-LDO, and Mg 2 Al-LDO were prepared by calcining the respective LDH precursor at 500°C for 3 h and were used as catalysts for the ex situ fast pyrolysis of pine wood (Edmunds et al, 2019) (Table 2;(12)(13)(14)(15). Compared to non-catalyzed process, the LDOs showed a drop in the relative yield of acetic acid, methoxyphenols, and total phenols with the enhancement in the relative yield of aromatics, H 2 O, CO, and CO 2 .…”

“…Various oxides such as ZnAl‐LDO, Zn 2 Al‐LDO, MgAl‐LDO, and Mg 2 Al‐LDO were prepared by calcining the respective LDH precursor at 500°C for 3 h and were used as catalysts for the ex situ fast pyrolysis of pine wood (Edmunds et al., 2019) (Table 2; No. 12–15).…”

Catalyst Deactivation and Its Mitigation during Catalytic Conversions of Biomass

“…CFP can be divided into in situ CFP and ex situ CFP. In situ CFP has catalysts directly mixed with biomass feedstock in the pyrolysis reactor, whereas in ex situ CFP, catalysts only come into contact with the pyrolysis vapors in a separate reactor. , The catalytic reactions occurring in CFP include dehydration, decarbonylation, decarboxylation, ketonization, aldol condensation, aromatization, hydrodeoxygenation, hydrogenation, and cracking. , 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), ,,, acidic metal oxides (for example, Al 2 O 3 , TiO 2 , and ZrO 2 ), − basic metal oxides (for example, MgO and CaO), − and mixed-metal oxides with both acidic and basic sites (for example, MgO/ZnO with Al 2 O 3 , and Mn 2 O 3 /ZrO 2 with CeO 2 ). In addition, supported noble metal bifunctional catalysts (for example, Pt/TiO 2 and Ru/TiO 2 ) together with H 2 are used in ex situ CFP for hydrodeoxygenation of the pyrolysis vapor.…”

Upgrading Fast Pyrolysis Oil through Decarboxylation by Using Red Mud as Neutralizing Agent for Ketones Production and Iron Recovery

“…Among the various approaches of biomass utilization, fast pyrolysis is a relatively mature and promising technology in terms of the economy and flexibility in operation. The yield of bio‐oil can reach up to 75 wt% [2] . However, bio‐oil is a thermodynamic non‐equilibrium product, [3] so that it contains many reactive oxygenated components which result in polymerization and low heating value [4] .…”

“…The yield of bio-oil can reach up to 75 wt%. [2] However, bio-oil is a thermodynamic non-equilibrium product, [3] so that it contains many reactive oxygenated components which result in polymerization and low heating value. [4] Most notably, bio-oil possesses strong corrosiveness because it contains up to 30 wt % of carboxylic acids, thus not suitable for direct application in the internal combustion engine.…”