Coke deposition and characterization on titanium silicalite-1 catalyst in cyclohexanone ammoximation

Zhang, Xiangjing; Wang, Yan; Feng, Xin

doi:10.1016/j.apcata.2006.03.050

Cited by 71 publications

(27 citation statements)

References 16 publications

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“…[24] It can thus be concluded that Cp 2 Fe is destroyed by the grafting reaction. The adsorption and reactivity of Cp 2 Fe on the surface of HY zeolite were also confirmed by the interaction of Cp 2 Fe with DY (deuterated Y zeolite), as shown in Figure S 1 in the Supporting Information.…”

mentioning

confidence: 98%

A Mononuclear Cyclopentadiene–Iron Complex Grafted in the Supercages of HY Zeolite: Synthesis, Structure, and Reactivity

Long

Wang

Zhang

et al. 2007

Chemistry A European J

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The reaction of ferrocene with the acidic hydroxy groups in the supercages of zeolite HY dehydrated at 673 K and the reactivity of the resultant surface species towards CO and O(2) were investigated by temperature-programmed decomposition (TPD) and reduction (TPR) and IR, X-ray absorption fine structure analysis (XAFS), and X-ray photoelectron (XP) spectroscopy. In situ FTIR, TPD, TPR, and chemical analysis reveal that the Cp(2)Fe molecule adsorbed on the zeolite surface loses one cyclopentadienyl group under vacuum at 423 K, which leads to the formation of a well-defined mononuclear surface Fe-C(5)H(6) complex grafted to two acidic sites and one ([triple bond]Si-O-Si[triple bond]) unit, as confirmed by the lack of Fe-Fe contributions in the EXAFS spectra. Each iron atom is coordinated, on average, to three oxygen atoms of the zeolite surface with a Fe--O distance of 2.00 A and to five carbon atoms with a Fe--C distance of 2.09 A. IR spectra indicate that the cyclopentadiene-iron species grafted on the surface of the zeolite is quite stable in vacuo or under an inert or hydrogen atmosphere below 423 K, and is also relatively stable under oxygen at room temperature. However, the cyclopentadiene ligand readily reacts with CO to form a compound containing carbonyl at 323 K, and even at room temperature. The single carbonyl band in the IR spectra provides evidence for the nearly uniform formation of a cyclopentadiene-iron species on the surface of the zeolite.

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mentioning

confidence: 98%

A Mononuclear Cyclopentadiene–Iron Complex Grafted in the Supercages of HY Zeolite: Synthesis, Structure, and Reactivity

Long

Wang

Zhang

et al. 2007

Chemistry A European J

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“…Regarding the reusability properties of the catalyst, no deactivation was observed in the stability investigation conducted in the previous study using high grade furfural, despite the fact that deactivation of TS-1 by fouling is a common phenomenon found in the epoxidation of other molecules [25][26][27] and that leaching of both Ti species was observed upon reutilization [9]. In the previous study, the reutilization studies were conducted after 24 h of reaction.…”

Section: Introductionmentioning

confidence: 95%

Oxidation of furfural in aqueous H2O2 catalysed by titanium silicalite: Deactivation processes and role of extraframework Ti oxides

Alba

Fierro

León‐Reina

et al. 2017

Applied Catalysis B: Environmental

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2 Graphical abstract Highlights  The use of TS-1 for the oxidation of furfural to maleic acid with H2O2 is reported.  Extraframework TiO2 nanodomains can also be located in the channels and cavities of TS-1.  When present, it blocks the access of reactants to active sites.  Coke deposition and Ti leaching are identified as the main causes of deactivation. AbstractTitanium silicalites (TS-1) with different Ti/Si atomic ratio (0.01-0.08) have been prepared, characterised by different techniques (X-Ray Diffraction, Transmission Electron Microscopy and Raman, Diffuse Reflection Infrared Fourier Transform and XRay Photoelectron spectroscopies), and their catalytic properties were investigated for the liquid phase oxidation of furfural with aqueous H2O2. For samples prepared with an initial Ti/Si > 0.01, extraframework Ti oxide is present and become more important as Ti loading increases. Two types of extraframework Ti have been identified: (i) anatase Ti oxide located at the external surface of zeolite crystals and (ii) Ti oxide nanodomains occluded within the channels and cavities of the zeolite. The latter can block the access of reactants to the active framework Ti(IV) sites for samples prepared with an initial Ti/Si > 0.04 and their removal results in an improvement in the selective oxidation of furfural to valuable products. The fouling by deposition of heavy by-products and Ti leaching were identified as two main causes of catalyst deactivation. The former can be reverted by removal of the deposits through calcination under air at 773 K. Leaching affects both the extraframework Ti and the active framework Ti species. During the first runs of reutilization, the Ti leaching is severe, affecting mainly to extraframework Ti oxide. Initially this leaching may be positive because its removal leads to the 3 elimination of species blocking the access of reactants to the active Ti species; but in the longer term, the continuous leaching of active framework Ti irreversibly deactivates the catalyst.

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“…The amounts of the deposited materials after reaction were determined by a Shimadzu TGA-50 thermogravimetric analyzer. The samples were combusted from room temperature to 700°C at 10°C/min in the flow of air and the weight loss between 200 and 700°C was attributed to the burning of the deposit [31].…”

Section: Methodsmentioning

confidence: 99%

“…n 0 and n represent the initial and the final amount in moles, respectively. It has been reported that the conversion of cyclohexanone is constant during the stable time, but declines sharply within a short time when the catalyst deactivates in the continuous system [21,31]. So we consider that TS-1 is deactivated when the conversion of cyclohexanone decreases below 97 % and the time before deactivation is regarded as the catalyst lifetime.…”

Section: Catalytic Reaction Of Ammoximationmentioning

confidence: 98%

“…However, the catalyst lifetime of TS-1 in the cyclohexanone ammoximation limits its application in industry. The activity of TS-1 in the ammoximation decreases sharply after a period time of operation due to the formation of high molecular weight byproducts on the internal surface, which is unable to diffuse to the external surface limited by the micropore channels [31].…”

Section: Introductionmentioning

confidence: 99%

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Effect of triethylamine treatment of titanium silicalite-1 on cyclohexanone ammoximation in a continuous system

Zhang

Wang

et al. 2014

Reac Kinet Mech Cat

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TS-1 has been hydrothermally treated by aqueous solutions of triethylamine, characterized by a number of techniques and studied in the ammoximation of cyclohexanone with NH 3 and H 2 O 2 in a continuous system. Some irregular hollow cavities are created after the treatment by desilication. The catalytic activities of TS-1 are not affected, but the catalyst stabilities significantly increase after the treatment, which can be attributed to the generation of the cavities. The treatment conditions are optimized, with the catalyst stability being extended to ten times of the conventional TS-1. After the treatment, triethylamine can be separated simply through distillation and recycled. The causes of deactivation are elucidated to be the deposition of higher weight byproducts formed on the surface of the catalysts and the deactivated TS-1 can be effectively regenerated through calcination in air.

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Coke deposition and characterization on titanium silicalite-1 catalyst in cyclohexanone ammoximation

Cited by 71 publications

References 16 publications

A Mononuclear Cyclopentadiene–Iron Complex Grafted in the Supercages of HY Zeolite: Synthesis, Structure, and Reactivity

A Mononuclear Cyclopentadiene–Iron Complex Grafted in the Supercages of HY Zeolite: Synthesis, Structure, and Reactivity

Oxidation of furfural in aqueous H2O2 catalysed by titanium silicalite: Deactivation processes and role of extraframework Ti oxides

Effect of triethylamine treatment of titanium silicalite-1 on cyclohexanone ammoximation in a continuous system

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