Stability of Pt/γ-Al2O3 Catalysts in Model Biomass Solutions

Ravenelle, Ryan M.; Copeland, John R.; Pelt, Adam H. Van; Crittenden, John C.; Sievers, Carsten

doi:10.1007/s11244-012-9785-3

Cited by 93 publications

(137 citation statements)

References 57 publications

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“…The C from guaiacol molecules and non-carbidic C thus appear to have had similar effects with respect to mitigating H2O-induced bulk oxidation of Mo2C-A and Mo2C-B, respectively (see lower bulk MoO2 detected by XRD in Figure 1). Similar beneficial effects, i.e., preventing hydration and metal particle agglomeration, have been reported for carbonaceous surface species derived from biomass compounds dissolved in liquid water over alumina catalysts [27]. The surface area increase of Mo2C-B despite the pore blocking could be explained by increased surface roughness.…”

Section: Structural Evaluation Of Mo Carbides Subjected To Hot Aqueousupporting

confidence: 72%

“…However, the liquid products (so-called bio-oils) are not suitable for direct application as fuels in internal combustion engines due to their high content of oxygen (35)(36)(37)(38)(39)(40) wt.%, dry basis) and water (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) wt.%) [1]. For instance, various oxygenated hydrocarbon species present in raw bio-oils make these liquids unstable for long-term storage, corrosive, low in heating value, and poorly miscible with conventional hydrocarbon fuels.…”

Section: Introductionmentioning

confidence: 99%

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Structural Evolution of Molybdenum Carbides in Hot Aqueous Environments and Impact on Low-Temperature Hydroprocessing of Acetic Acid

et al. 2015

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Abstract:We investigated the structural evolution of molybdenum carbides subjected to hot aqueous environments and their catalytic performance in low-temperature hydroprocessing of acetic acid. While bulk structures of Mo carbides were maintained after aging in hot liquid water, a portion of carbidic Mo sites were converted to oxidic sites. Water aging also induced changes to the non-carbidic carbon deposited during carbide synthesis and increased surface roughness, which in turn affected carbide pore volume and surface area. The extent of these structural changes was sensitive to the initial carbide structure and was lower under actual hydroprocessing conditions indicating the possibility of further improving the hydrothermal stability of Mo carbides by optimizing catalyst structure and operating conditions. Mo carbides were active in acetic acid conversion in the presence of liquid water, their activity being comparable to that of Ru/C. The results suggest that effective and inexpensive bio-oil hydroprocessing catalysts could be designed based on Mo carbides, although a more detailed understanding of the structure-performance relationships is needed, especially in upgrading of more complex reaction mixtures or real bio-oils. OPEN ACCESSCatalysts 2015, 5 407

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Section: Structural Evaluation Of Mo Carbides Subjected To Hot Aqueousupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Structural Evolution of Molybdenum Carbides in Hot Aqueous Environments and Impact on Low-Temperature Hydroprocessing of Acetic Acid

et al. 2015

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“…One of the most common supports for metal catalysts, galumina, is known to undergo ap hase transformation to boehmite in the presence of water. [401,402] Recently,c atalyst stability was examined for liquid-phase reforming of lignin over aP t/g-Al 2 O 3 catalyst. [403] In this study,i tw as found that catalyst deactivation occurred by the formation of boehmite, which encapsulates the metal particles,dramatically reducing the quantity of catalytic sites.Inthe presence of lignin-derived mono-aromatics (e.g., guaiacol), the transformation of galumina into boehmite is inhibited by the coordination of phenolates onto the support surface.L ignin itself also has agreat affinity for alumina, forming acoating and stabilising the textural properties of the catalyst support.…”

Section: Prevention Of Recondensation In Lignin Oilsmentioning

confidence: 99%

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

et al. 2016

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Lignin is an abundant biopolymer with a high carbon content and high aromaticity. Despite its potential as a raw material for the fuel and chemical industries, lignin remains the most poorly utilised of the lignocellulosic biopolymers. Effective valorisation of lignin requires careful fine‐tuning of multiple “upstream” (i.e., lignin bioengineering, lignin isolation and “early‐stage catalytic conversion of lignin”) and “downstream” (i.e., lignin depolymerisation and upgrading) process stages, demanding input and understanding from a broad array of scientific disciplines. This review provides a “beginning‐to‐end” analysis of the recent advances reported in lignin valorisation. Particular emphasis is placed on the improved understanding of lignin's biosynthesis and structure, differences in structure and chemical bonding between native and technical lignins, emerging catalytic valorisation strategies, and the relationships between lignin structure and catalyst performance.

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“…For each spectrum, a minimum of 2400 scans was recorded. The fractions of tetrahedrally and octahedrally coordinated Al nuclei were obtained by fitting the spectra using dmfit [26]. Thermal gravimetric analysis (TGA) was performed using a Perkin-Elmer Pyris 1 apparatus.…”

Section: Characterizationmentioning

confidence: 99%

“…Previous studies suggested this transformation to start with hydrolytic attack of the Lewis acid sites of the alumina support [24,25]. Indeed, supported metal particles as well as biomass-derived oxygenates in the reaction solution were reported to have a beneficial effect [26,27] on catalyst stability by "capping" specific, coordinatively unsaturated surface Al atoms. For example, Copeland et al found that biomass-derived polyols can block Lewis acidic Al sites of γ-Al 2 O 3 by formation of multidentate alkoxy surface species that protect the alumina from hydrolytic attack [25].…”

Section: Introductionmentioning

confidence: 99%

Silica deposition as an approach for improving the hydrothermal stability of an alumina support during glycerol aqueous phase reforming

Liu

Okolie

Ravenelle

et al. 2018

Applied Catalysis A: General

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A B S T R A C TSilica deposition on the benchmark aqueous phase reforming (APR) catalyst Pt/γ-Al 2 O 3 is studied to prevent or limit hydrolytic attack of the support under hydrothermal APR conditions, for which boehmite formation by support hydration is a known cause for catalyst deactivation. Tetraethyl orthosilicate (TEOS) is employed as a silicon source in a straightforward liquid-phase, silylation process followed by catalyst calcination and reduction. Characterization by X-ray diffraction, temperature-programmed desorption of NH 3 , infrared, 27 Al nuclear magnetic resonance and X-ray photoelectron spectroscopy of the fresh catalysts suggests that silica addition occurs preferentially on the support surface, resulting in weak Brønsted acid sites as well as in the formation of Si-O-Al linkages at the expense of specific surface Lewis acid sites. Silylation and calcination of Pt/γ-Al 2 O 3 causes partial blockage of the metal surface area (12% loss), whereas γ-Al 2 O 3 surface silica modification prior to Pt deposition makes controlled metal deposition difficult. Catalytic performance tests show the overcoated samples to be active in the APR of 5 wt% glycerol, albeit with lower H 2 production rates compared to the benchmark catalyst. Characterization of spent APR catalysts clearly demonstrates that silylation/calcination treatments effectively slows down the transformation of the γ-Al 2 O 3 support due to the formation of a Si-O-Al interface. Overall, the lifetime of the catalyst is increased three-fold as a result of the surface overcoating treatment, with repetitive recycling ultimately leading to loss of the protective silica layer.

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Stability of Pt/γ-Al2O3 Catalysts in Model Biomass Solutions

Cited by 93 publications

References 57 publications

Structural Evolution of Molybdenum Carbides in Hot Aqueous Environments and Impact on Low-Temperature Hydroprocessing of Acetic Acid

Structural Evolution of Molybdenum Carbides in Hot Aqueous Environments and Impact on Low-Temperature Hydroprocessing of Acetic Acid

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

Silica deposition as an approach for improving the hydrothermal stability of an alumina support during glycerol aqueous phase reforming

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