One-step synthesis of benzyl acetate by gas phase acetoxylation of toluene over highly active and selective Pd–Sb–TiO<sub>2</sub>catalysts

Benhmid, A.; Narayana, K.V.; Martin, Andreas; Lücke, Bernhard

doi:10.1039/b406396a

Cited by 22 publications

(15 citation statements)

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“…1,2 This chemical synthesis produces unwanted side product 3,4 and it also has an associated problem of catalyst deactivation. 5 There has been some work on the formation of benzyl esters using enzymes.…”

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confidence: 99%

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Majumder

Singh

Dutta

et al. 2006

Bioorganic & Medicinal Chemistry Letters

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confidence: 99%

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Majumder

Singh

Dutta

et al. 2006

Bioorganic & Medicinal Chemistry Letters

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“…[7][8][9] Vapor-phase processes were previously not successful in terms of obtaining higher yields of BA with acceptable time-on-stream stability of the catalysts. [10,11] However, the recently developed Pd-Sb/TiO 2 catalysts [12][13] displayed remarkably higher conversion of toluene (> 90 %) and yields of BA (> 75 %) with a space-time yield of up to 700 g kg À1 h À1 . To our knowledge, this is the best result reported so far under gas-phase conditions.…”

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confidence: 99%

Deactivation of Pd Acetoxylation Catalysts: Direct Observations by XPS Investigations

et al. 2005

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Catalyst deactivation is a problem of great concern in industrial catalytic processes. Hence, prevention of catalyst deactivation poses substantial challenges in the design and operation of large-scale catalytic processes. The usual way to overcome the deactivation problem is to modify the catalyst composition by using different promoters. Although various promoters have been used for different oxidation reactions, [1][2][3][4] their precise role is not known. Unfortunately, most of the interpretations on the role of promoters are rather hypothetical probably owing to the lack of information about the exact surface structure. Among the known promoters, bismuth has very attractive properties as a promoting element in numerous heterogenous oxidation catalysts, particularly in association with noble metals. [1][2][3][4][5][6] However, the origin of the promoting role of Bi is still a matter of discussion.Acetoxylation is an industrially important reaction for producing esters in a single step. Benzyl acetate (BA), the desired product from acetoxylation of toluene, is widely used in the food, perfumery, and chemical industries. Most of the work reported so far on the acetoxylation of toluene is confined to liquid-phase and batch reactors. [7][8][9] Vapor-phase processes were previously not successful in terms of obtaining higher yields of BA with acceptable time-on-stream stability of the catalysts. [10,11] However, the recently developed Pd-Sb/TiO 2 catalysts [12][13] displayed remarkably higher conversion of toluene (> 90 %) and yields of BA (> 75 %) with a space-time yield of up to 700 g kg À1 h À1. To our knowledge, this is the best result reported so far under gas-phase conditions. However, these catalysts are observed to undergo deactivation readily after several hours of operation as a result of coke deposits, which obviously hampers their application on a commercial scale.Considering the limited lifetime of these catalysts, we have directed our research efforts to develop stable and novel Pd compounds that have improved catalyst lifetime as well as the higher activity and selectivity of the earlier catalysts. To achieve this objective, we modified the composition of the PdSb/TiO 2 catalysts by adding promoters such as Bi, Cu, and Sn. [14][15] Among these promoters, the Bi modification improved both the catalyst life as well as the selectivity for desired product (BA). However, the precise role of Bi remained unclear. In the present study we examine the catalyst deactivation phenomenon of Pd-Sb/TiO 2 catalysts and the role of Bi in improving catalyst lifetime and selectivity.In the earlier investigations on Pd-Sb/TiO 2 catalysts [13] we clearly detected differences between the fresh and used catalysts. The used catalysts displayed drastic increase in Pd particle size, coke deposition, loss of both Pd and Sb at the surface etc. In view of this, a TiO 2 -supported catalyst with 10 wt % Pd and 8 wt % Sb was then chosen as a model catalyst (designated as 10Pd8Sb) and subjected to reaction conditions for a wide ran...

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“…The gas-phase aerobic acetoxylation of toluene with acetic acid catalyzed by TiO 2 -, γ-Al 2 O 3 -, SiO 2 -, and ZrO 2 -supported Pd–Sb particles was also reported [ 233 – 236 ].…”

Section: Reviewmentioning

confidence: 99%

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

Krylov

Vil

Terent’ev

2015

Beilstein J. Org. Chem.

171

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SummaryThe present review summarizes primary publications on the cross-dehydrogenative C–O coupling, with special emphasis on the studies published after 2000. The starting compound, which donates a carbon atom for the formation of a new C–O bond, is called the CH-reagent or the C-reagent, and the compound, an oxygen atom of which is involved in the new bond, is called the OH-reagent or the O-reagent. Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C–O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups (amide, heteroaromatic, oxime, and so on) and compounds with activated C–H bonds (aldehydes, alcohols, ketones, ethers, amines, amides, compounds containing the benzyl, allyl, or propargyl moiety). An analysis of the published data showed that the principles at the basis of a particular cross-dehydrogenative C–O coupling reaction are dictated mainly by the nature of the C-reagent. Hence, in the present review the data are classified according to the structures of C-reagents, and, in the second place, according to the type of oxidative systems. Besides the typical cross-dehydrogenative coupling reactions of CH- and OH-reagents, closely related C–H activation processes involving intermolecular C–O bond formation are discussed: acyloxylation reactions with ArI(O2CR)2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc.).

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One-step synthesis of benzyl acetate by gas phase acetoxylation of toluene over highly active and selective Pd–Sb–TiO₂catalysts

Abstract: Significantly high benzyl acetate selectivity of 85% at a toluene conversion of ca. 93% was achieved for the first time in a single step by gas phase acetoxylation over highly active and selective Pd-Sb-TiO2 catalysts.

Cited by 22 publications

References 7 publications

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Deactivation of Pd Acetoxylation Catalysts: Direct Observations by XPS Investigations

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

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One-step synthesis of benzyl acetate by gas phase acetoxylation of toluene over highly active and selective Pd–Sb–TiO2catalysts

Abstract: Significantly high benzyl acetate selectivity of 85% at a toluene conversion of ca. 93% was achieved for the first time in a single step by gas phase acetoxylation over highly active and selective Pd-Sb-TiO2 catalysts.

Cited by 22 publications

References 7 publications

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Lipase catalyzed synthesis of benzyl acetate in solvent-free medium using vinyl acetate as acyl donor

Deactivation of Pd Acetoxylation Catalysts: Direct Observations by XPS Investigations

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

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One-step synthesis of benzyl acetate by gas phase acetoxylation of toluene over highly active and selective Pd–Sb–TiO₂catalysts