Direct Synthesis of H2O2 from H2 and O2 on Pd Catalysts: Current Understanding, Outstanding Questions, and Research Needs

Flaherty, David W.

doi:10.1021/acscatal.7b04107

Cited by 177 publications

(192 citation statements)

References 67 publications

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“…have revealed the production of H 2 O 2 may take place at the interface between Pd and PdO indicating a strong dependence on both phases ,. The work of Flaherty and co‐workers also indicates the need for a proportion of nanoparticles to exist in the reduced state, with a signifcant induction time required for PdO nanoparticles to exhibit activity towards H 2 O 2 formation, with no such induction period exisits for Pd 0 nanoparticles …”

Section: The Direct Synthesis Of H2o2 As An Alternative To the Anthramentioning

confidence: 99%

“…[67,68] The work of Flaherty and co-workers also indicates the need for a proportion of nanoparticles to exist in the reduced state, with a signifcant induction time required for PdO nanoparticles to exhibit activity towards H 2 O 2 formation, with no such induction period exisits for Pd 0 nanoparticles. [69] Although the nature of the active site responsible for the cleavage of the OÀ O bond and production of H 2 O is unkown it is likely that H 2 O 2 degradation is promoted by the high energy, low co-ordiaiton Pd centres. [70] Plauck et al have, through a combination of density functional theory and reaction kinetic studies, reported that both the close-packed Pd (111) and more open Pd (100) facets can represent the active site for H 2 O 2 decomposition for supported Pd nanoparticles.…”

Section: The Direct Synthesis Of H 2 O 2 As An Alternative To the Antmentioning

confidence: 99%

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Recent Advances in the Direct Synthesis of H₂O₂

2018

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Hydrogen peroxide (H2O2) is a highly effective, green oxidant that has found application in sectors ranging from the synthesis of fine chemicals and waste stream treatment to the extraction of precious metals and the bleaching of paper pulp and textiles. The growing demand for H2O2 has seen it become one of the 100 most important chemicals in the world. The direct synthesis of H2O2 from H2 and O2 has been a challenge for the scientific community for over 100 years and represents an attractive alternative to the current means of production. Herein we discuss the historical perspective of the direct synthesis process, the recent literature regarding catalyst design and the role of additives as well as the application of H2O2 as an in situ oxidant. We discuss the key problems that remain and conclude that although there has been progress with respect to the selectivity of hydrogen utilisation, there is a need to now concentrate on catalyst activity as the key remaining problem requiring a solution is the concentration of H2O2 that can be achieved, especially in flow reactors.

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Section: The Direct Synthesis Of H2o2 As An Alternative To the Anthramentioning

confidence: 99%

Section: The Direct Synthesis Of H 2 O 2 As An Alternative To the Antmentioning

confidence: 99%

Recent Advances in the Direct Synthesis of H₂O₂

2018

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“…H 2 O 2 is an environmental friendly and selective oxidizer which can replace chlorine in many industrial applications including wastewater treatment, paper and pulp bleaching, and epoxidation reactions . However, H 2 O 2 is not economical because its current method of production, the Riedl–Pfleiderer (RP) process, relies on successive oxidative and reductive treatments of anthraquinones and hydroquinones, involving energy‐intensive separations that lead to high capital and operating expenses .…”

Section: Introductionmentioning

confidence: 99%

Form of the catalytically active Pd species during the direct synthesis of hydrogen peroxide

Priyadarshini

Flaherty

2019

AIChE Journal

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Direct synthesis of H 2 O 2 could produce H 2 O 2 at lower cost than the Riedl-Pfleiderer process, which would enable the broader use of H 2 O 2 for industrial oxidations. The addition of inorganic acids and halides to the solvent increase H 2 O 2 selectivities on Pd nanoparticles but also dissolve Pd and produce dynamic mixtures of complexes including heterogeneous (Pd 0 ) and homogeneous (Pd 2+ ) species, any of which may contribute to H 2 O 2 formation. We combine kinetic measurements and in operando UV-vis spectroscopy to determine how H 2 O 2 rates and selectivities depend on concentrations of these forms of Pd. Introducing HCl to the solvent increases the concentration of Pd 2+ complexes by oxidizing Pd 0 nanoparticles. The rates of primary H 2 O 2 formation and H 2 O 2 selectivities do not depend directly on the population of the Pd 2+ species for catalysts tested in water or methanol. These results suggest that Pd nanoparticles form H 2 O 2 and detectable homogeneous complexes do not act as catalysts.

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“…[9] There is the demand for new processes, offering potential better economics on a small-medium scale (for distributed production) and lower capital costs and environmental impact. [9,10] Among the alter-native processes of production of H 2 O 2 explored, the direct synthesis of H 2 O 2 is considered the most promising one. [1][2]5,[9][10][11][12][13][14][15][16][17] In this case, water is the only by-product, and the production is intensified in a single reactor.…”

Section: Introductionmentioning

confidence: 99%

“…[9,10] Among the alter-native processes of production of H 2 O 2 explored, the direct synthesis of H 2 O 2 is considered the most promising one. [1][2]5,[9][10][11][12][13][14][15][16][17] In this case, water is the only by-product, and the production is intensified in a single reactor. Besides for the production of H 2 O 2 , the direct synthesis has also been investigated coupled to the direct synthesis of propylene oxide [18] and thiophene.…”

Section: Introductionmentioning

confidence: 99%

Direct Synthesis of H₂O₂ on Pd Based Catalysts: Modelling the Particle Size Effects and the Promoting Role of Polyvinyl Alcohol

2018

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Sol immobilization is a relevant preparation method, particularly for the preparation of Pd‐based catalysts for the direct synthesis of H2O2. In this preparation, polyvinyl alcohol (PVA) acts as capping agent for Pd particles. Modelling the role of PVA on the Pd nanoparticle size and its promoting effect on the selectivity is important to understand better these catalysts. Here, Pd based catalysts prepared by sol immobilization have been tested in a semi‐batch reactor with an H2/O2 ratio ≈1, analysing the influence of the Pd nanoparticle size and the effect of PVA on the rate constants of the reaction network and their change during the reaction. A stepwise testing protocol coupled with transmission electron microscopy characterization as a function of reaction time has been used. These catalysts were compared with other catalysts prepared by hydrazine reduction and impregnation‐decomposition, where PVA is absent. The results are analysed in terms of rate constants for the various rates in the reaction network in relation with the Pd average particle size and related sites distribution, as a function of the changes occurring during extended catalytic tests. The SI‐series of catalysts (prepared by sol‐immobilization) shows enhanced properties, attributed to the effect of PVA capping agent in forming less defective Pd nanoparticles. This induces both a decrease of direct combustion and secondary hydrogenolysis reactions, and an enhancement of the direct synthesis route. The PVA layer limits H2O2 back‐diffusion with a negative influence on the productivity and selectivity, with its removal leading to initial enhanced performances, but in long‐term to a worsening due to sintering of Pd nanoparticles in extended operations.

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Direct Synthesis of H₂O₂ from H₂ and O₂ on Pd Catalysts: Current Understanding, Outstanding Questions, and Research Needs

Cited by 177 publications

References 67 publications

Recent Advances in the Direct Synthesis of H₂O₂

Recent Advances in the Direct Synthesis of H₂O₂

Form of the catalytically active Pd species during the direct synthesis of hydrogen peroxide

Direct Synthesis of H₂O₂ on Pd Based Catalysts: Modelling the Particle Size Effects and the Promoting Role of Polyvinyl Alcohol

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Direct Synthesis of H2O2 from H2 and O2 on Pd Catalysts: Current Understanding, Outstanding Questions, and Research Needs

Cited by 177 publications

References 67 publications

Recent Advances in the Direct Synthesis of H2O2

Recent Advances in the Direct Synthesis of H2O2

Form of the catalytically active Pd species during the direct synthesis of hydrogen peroxide

Direct Synthesis of H2O2 on Pd Based Catalysts: Modelling the Particle Size Effects and the Promoting Role of Polyvinyl Alcohol

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Product

Resources

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Direct Synthesis of H₂O₂ from H₂ and O₂ on Pd Catalysts: Current Understanding, Outstanding Questions, and Research Needs

Recent Advances in the Direct Synthesis of H₂O₂

Recent Advances in the Direct Synthesis of H₂O₂

Direct Synthesis of H₂O₂ on Pd Based Catalysts: Modelling the Particle Size Effects and the Promoting Role of Polyvinyl Alcohol