Hydrogen peroxide synthesis over metallic catalysts

Olivera, P.Paredes; Patrito, E.M.; Sellers, Harrell

doi:10.1016/0039-6028(94)91154-1

Cited by 104 publications

(47 citation statements)

References 33 publications

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“…It is assumed that one of the key steps in the reaction mechanism involves the formation of a peroxide reaction intermediate out of the hydrogen and oxygen, which would be the true oxidizing species in the reaction mechanism. This view is supported by a number papers containing theoretical work and experimental studies which have appeared recently [8,[10][11][12][13][14][15]. In these papers it is shown that gold nanoparticles are capable of producing hydrogen peroxide or adsorbed OOH intermediates.…”

Section: Introductionsupporting

confidence: 48%

The direct epoxidation of propene over gold–titania catalysts—A study into the kinetic mechanism and deactivation

Nijhuis

Weckhuysen

2006

Catalysis Today

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A reaction scheme is presented for the epoxidation of propene over gold-titania catalysts based on information from catalytic experiments and a detailed infrared study. The reaction mechanism involves the formation of a bidentate propoxy species on titania sites by means of a reactive adsorption of propene, which is catalyzed by the gold nanoparticles. The bidentate propoxy species can react with a peroxide species, produced on the gold from hydrogen and oxygen, to produce propene oxide. Catalyst deactivation occurs via a consecutive oxidation of the bidentate propoxy intermediate to strongly adsorbed carboxylate species. A kinetic model including these reaction steps was fitted to a series of catalytic experiments and provided a good description of the measurements and yielded realistic kinetic parameters. #

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Section: Introductionsupporting

confidence: 48%

The direct epoxidation of propene over gold–titania catalysts—A study into the kinetic mechanism and deactivation

Nijhuis

Weckhuysen

2006

Catalysis Today

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“…The fact that this oxidation reaction requires hydrogen to be present next to oxygen, as well as the fact that propene can be epoxidized very selectively by hydrogen peroxide over titania, creates the common assumption that the reaction mechanism involves a peroxide species that would be produced by gold. [87][88][89] Theoretical calculations have shown that, indeed, OOH 90 or hydrogen peroxide 91,92 can be produced on small gold particles. However, currently, no experimental evidence exists that this is also occurring during the propene epoxidation, which makes this peroxide mechanism speculative.…”

Section: Gold-titania Catalystsmentioning

confidence: 99%

The Production of Propene Oxide: Catalytic Processes and Recent Developments

Nijhuis

Makkee

Moulijn

et al. 2006

Ind. Eng. Chem. Res.

478

405

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Propene oxide, which is one of the major commodity chemicals used in chemical industry, desperately requires a new process for its production, because of the disadvantages that are encountered with the currently available processes. This paper discusses the existing processes used for the production of propene oxidesthe chlorohydrin and hydroperoxide processessand their advantages and disadvantages. Furthermore, the new processes and catalysts under development for the propene oxide production are discussed, as well as the challenges that are still limiting the applications of some of those prospects. The most important new developments for the production of propene oxide discussed in this paper are: the hydrogen peroxide combination process, the ethene oxide alike silver catalysts, the molten salt systems, and the gold-titania catalyst systems.

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“…The potential capacity of Au surfaces to form peroxo species has been predicted and later confirmed experimentally. [18][19][20][21] The presence of this oxygen species was proved for propylene epoxidation with H 2 O 2 in MeOH solvent over a TS-1 catalyst. [22] Once the H 2 O 2 is produced on the gold particles, it can be converted into hydroperoxo species at tetrahedrally coordinated Ti cation sites.…”

mentioning

confidence: 99%

Trimethylamine as a Gas‐Phase Promoter: Highly Efficient Epoxidation of Propylene over Supported Gold Catalysts

Chowdhury¹,

Bravo-Suárez²,

Daté³

et al. 2006

Angew Chem Int Ed

199

130

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Propylene oxide (PO) is an important bulk chemical for the production of a wide variety of derivatives, among which polyether polyols and propylene glycol are the main end products.[1] The world PO production of about 5 million tons per year comes from two current industrial processes: the chlorohydrin process and the organic hydroperoxide process (Halcon method). These two methods consist of two reaction stages and produce large amounts of by-products and coproducts, which makes optimization difficult. [2] Although bulk gold was for a long time regarded as a poor catalyst, gold nanoparticles (2-5 nm) deposited on a variety of metal oxides are surprisingly active for many reactions.[3] An alternative route for synthesizing PO by reductive activation of O 2 by H 2 over nanoparticulate gold catalysts has been under investigation for the past few years. [4][5][6][7] We have estimated that the requirements for a viable industrial process are a propylene conversion of 10 %, a PO selectivity of 90 %, and a H 2 efficiency of 50 % for the H 2 O 2 formed in situ for epoxidation purposes. Recently, we reported a trimethylsilylated Ba(NO 3 ) 2 -Au/titanosilicate (Ti/Si 3:100) catalyst that thus far exhibits the highest PO yield among the gold catalysts.[8] The main hurdles for the industrial application of this catalyst are its fast deactivation caused by the accumulation of oligomerized and oxidized PO by-products around the gold nanoparticles, the lower activity of the successively regenerated catalyst, and its low H 2 efficiency. Nowadays, the development of catalysts for use on a commercial scale seeks high atom efficiencies of chemical reactions to reduce manufacturing costs and to minimize burdens on the environment. A comparison of different processes shows that the epoxidation with O 2 and H 2 at 90 % PO selectivity and 50 % H 2 efficiency gives an atom efficiency of 50 %, which is close to the 76 % PO selectivity for the epoxidation with O 2 alone (Supporting Information). This clearly demonstrates that, at present, a more feasible and rational path towards higher atom efficiency is the direct epoxidation of propylene with O 2 and H 2 .We now report that the presence of trimethylamine (TMA), a strong Lewis base with a pK a value of 9.9, [9] at extremely low concentrations (10-20 ppm) in the reactant gas mixture can remarkably improve the catalytic performance of gold nanoparticles deposited on titanosilicate in terms of catalyst lifetime, catalyst regeneration, PO selectivity, and H 2 efficiency to a level where commercial requirements are almost fulfilled. We have previously shown that a small amount of H 2 O can act as a gaseous promoter by drastically altering the catalytic activity of supported gold nanoparticles for low-temperature CO oxidation.[10] The concept behind this investigation was that gaseous trimethylamine should have a positive effect on the overall PO catalyst efficiency. One of the assumptions is that TMA can poison the Lewis acidic sites of the support, mainly isolated Ti 4+ centers. By oligome...

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Hydrogen peroxide synthesis over metallic catalysts

Cited by 104 publications

References 33 publications

The direct epoxidation of propene over gold–titania catalysts—A study into the kinetic mechanism and deactivation

The direct epoxidation of propene over gold–titania catalysts—A study into the kinetic mechanism and deactivation

The Production of Propene Oxide: Catalytic Processes and Recent Developments

Trimethylamine as a Gas‐Phase Promoter: Highly Efficient Epoxidation of Propylene over Supported Gold Catalysts

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