Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming

Héroguel, Florent; Rozmysłowicz, Bartosz; Luterbacher, Jeremy S.

doi:10.2533/chimia.2015.582

Cited by 43 publications

(36 citation statements)

References 78 publications

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“…In the past, catalyst research focused on controlling metal particle size and screening suitable supports to enhance catalytic activities. As synthetic techniques increasingly allow us to control the material's nanoenvironment, the importance of catalyst structure and surface properties has begun to be recognized as it is found to be closely related to catalyst stability and selectivity . Catalyst overcoating is an emerging postsynthesis modification strategy for engineering the surface nanostructure and functionality of various catalysts .…”

Section: Introductionmentioning

confidence: 99%

Slowing the Kinetics of Alumina Sol–Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity

Héroguel

Luterbacher

2018

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Catalyst overcoating is an emerging approach to engineer surface functionalities on supported metal catalyst and improve catalyst selectivity and durability. Alumina deposition on high surface area material by sol-gel chemistry is traditionally difficult to control due to the fast hydrolysis kinetics of aluminum-alkoxide precursors. Here, sol-gel chemistry methods are adapted to slow down these kinetics and deposit nanometer-scale alumina overcoats. The alumina overcoats are comparable in conformality and thickness control to overcoats prepared by atomic layer deposition even on high surface area substrates. The strategy relies on regulating the hydrolysis/condensation kinetics of Al( BuO) by either adding a chelating agent or using nonhydrolytic sol-gel chemistry. These two approaches produce overcoats with similar chemical properties but distinct physical textures. With chelation chemistry, a mild method compatible with supported base metal catalysts, a conformal yet porous overcoat leads to a highly sintering-resistant Cu catalyst for liquid-phase furfural hydrogenation. With the nonhydrolytic sol-gel route, a denser Al O overcoat can be deposited to create a high density of Lewis acid-metal interface sites over Pt on mesoporous silica. The resulting material has a substantially increased hydrodeoxygenation activity for the conversion of lignin-derived 4-propylguaiacol into propylcyclohexane with up to 87% selectivity.

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Section: Introductionmentioning

confidence: 99%

Slowing the Kinetics of Alumina Sol–Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity

Héroguel

Luterbacher

2018

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“…The shift to renewable substrates often involves liquid-phase catalytic processing. Such conditions are required because biomass-derived molecules usually have low volatility and are produced by biomass depolymerization or biological transformation in dilute aqueous or solvent streams [4][5][6]. Irreversible deactivation, including by sintering and leaching, tends to be more pronounced in liquid-phase conditions, which makes catalyst stability even more critical [1,2,7].…”

Section: Introductionmentioning

confidence: 99%

Catalyst stabilization by stoichiometrically limited layer-by-layer overcoating in liquid media

Héroguel

Monnier

Brown

et al. 2017

Applied Catalysis B: Environmental

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a b s t r a c tThe use of metal oxide overcoats over supported nanoparticle catalysts has recently led to impressive improvements in catalyst stability and selectivity. The deposition of alumina is especially important for renewable catalysis due to its robustness in liquid-phase conditions. However, there are limited reports of work on alumina deposition and stabilization that goes beyond atomic layer deposition (ALD). Here, we present a layer-by-layer deposition technique for the controlled formation of conformal alumina overcoats in the liquid phase. This technique is easy to perform in common wet chemistry conditions. Alternated exposure of the substrate to stoichiometric amounts of aluminum alkoxide and water in liquidphase conditions leads to the formation of a porous overcoat that was easily tunable by varying synthesis parameters. The deposition of 60 Al 2 O 3 layers onto Al 2 O 3 -supported copper nanoparticles suppressed irreversible deactivation during the liquid-phase hydrogenation of furfural -a key biomass-derived platform molecule. The porous overcoat leads to highly accessible metal sites, which significantly reduces the partial site blocking observed in equivalent overcoats formed by ALD. We suggest that the ease of scalability and the high degree of control over the overcoat's properties during liquid-phase synthesis could facilitate the development of new catalyst overcoating applications.

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“…Applied Catalysis A, General 551 (2018) [13][14][15][16][17][18][19][20][21][22] Specifically, the amorphous alumina phase of the fresh catalyst changed to flake-like boehmite patches. In addition, the Pt particles and bulk alumina phase seem enveloped by a thin layer (red circle in Fig.…”

Section: F Liu Et Almentioning

confidence: 99%

“…For instance, the yields of liquid products for Pt/Al 2 O 3 and Pt/Al 2 O 3 -4, 8, 12 were 11%, 16%, 24% and 29%, respectively, at ∼60% glycerol Al NMR spectra of a Si-free catalyst and a catalyst modified by silylation, calcination and reduction before (fresh) and after (spent) APR. [13][14][15][16][17][18][19][20][21][22] conversion. Among those liquid products, the amount of HA and 1,2-PD increased significantly as a function of modification time.…”

Section: Catalyst Performance In Glycerol Aprmentioning

confidence: 99%

“…Pt/γ-Al 2 O 3 is commonly used as APR catalyst [14,18], showing good activity, high H 2 selectivity and limited alkane formation, albeit that this catalyst is unstable under the applied hydrothermal conditions [19,20]. It has been demonstrated that supported metal particles can suffer irreversible sintering under the high temperature and pressure conditions often applied in biomass reactions [20]. Besides, under APR conditions, oxidic supports such as γ-alumina can be hydrated, leading to phase changes in the support and, as a result, deactivation [21,22].…”

Section: Introductionmentioning

confidence: 99%

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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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Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming

Cited by 43 publications

References 78 publications

Slowing the Kinetics of Alumina Sol–Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity

Slowing the Kinetics of Alumina Sol–Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity

Catalyst stabilization by stoichiometrically limited layer-by-layer overcoating in liquid media

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

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