Catalytic vapour phase epoxidation of propene with nitrous oxide as an oxidant II. Development of a kinetic model

Thömmes, Thomas; Reitzmann, Andreas; Kraushaar‐Czarnetzki, Bettina

doi:10.1016/j.ces.2008.07.010

Cited by 3 publications

(7 citation statements)

References 12 publications

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“…The maximum value for S P is 0.43, indicating that a maximum selectivity to PO of 43% at almost zero conversion can be obtained. As mentioned before, , this comparably low selectivity is a result of the parallel and consecutive formation of coke and higher molecular weight products, which are formed with selectivities between 50 and 80%. Product stability reached a maximum value of 0.21 for the sample Fe1.0Cs2.4ex.…”

Section: Resultsmentioning

confidence: 71%

“…Previous studies with a catalyst containing 0.1 wt % Fe and 0.2 wt % Cs on SiO 2 revealed that low propene concentrations (1 vol %) and a surplus of N 2 O (15 vol %, rest: He) are necessary for high PO selectivities. , The product spectrum is known to a large extent, and a detailed reaction network was postulated, which provided a basis for the development of a kinetic model . The current study continues these investigations and is divided in two parts: In the first part, it will be shown how preparation and physicochemical characteristics (e.g., iron and alkaline content and calcination temperature) affect catalytic properties of the CsO x /FeO y /SiO 2 catalyst in the propene epoxidation using N 2 O as oxidant.…”

Section: Introductionmentioning

confidence: 77%

“…To compare the catalytic properties of the different catalysts, all reaction conditions except volumetric flow were kept constant at T = 648 K and p = 1.3 × 10 5 Pa, and the reactants propene (purity 99.5%) and N 2 O (purity 99.995%) were diluted with helium (purity 99.995%) to a reaction mixture of propene/N 2 O/He = 1/15/84 vol %. These conditions were identified to deliver the best results in previous studies …”

Section: Methodsmentioning

confidence: 99%

“…% consider KCl to be the best promoter. ,,, The investigations by Moens et al resulted in Rb 2 SO 4 being the best promoter. Cesium acetate was used in our recent works, , which led to better results than sodium acetate…”

Section: Introductionmentioning

confidence: 99%

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Catalytic Vapor Phase Epoxidation of Propene with Nitrous Oxide as an Oxidant: Investigations on Catalyst Composition and Reaction Conditions

Thömmes

Gräf

Reitzmann

et al. 2010

Ind. Eng. Chem. Res.

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The vapor phase epoxidation of propene with nitrous oxide (N 2 O) was experimentally investigated in a fixed bed reactor using different Cs x /Fe y /SiO 2 catalysts. This was done with a systematic approach which comprises the derivation of kinetic parameters for directly comparing catalyst performance. Therefore, kinetic measurements were made for each catalyst by variation of the residence time. It was found that the addition of an alkali promoter to the Fe y /SiO 2 catalyst is essential for the formation of propylene oxide and a proper alkali/Fe molar ratio is crucial for both activity and selectivity. Maxima in both activity and selectivity were observed for alkali/Fe ratios in the region 1.2-1.7. A further increase in activity without any loss in selectivity was obtained by adjusting the calcination temperature to 783 K. The conversion of PO was used as a tool to measure the product stability and a minimum reaction rate was also found for alkali/Fe ratios in the region 1.2-1.7. The promoter is responsible for the formation of active centers and it reduces surface acidity which leads to an increased stability of PO through the inhibition of the consecutive conversion. Maximum selectivities to PO of about 40% at 5-10% conversion were achieved at moderate reaction temperatures of 648 K. Because of parallel and consecutive formation of carbonaceous deposits on the catalyst, the catalyst deactivated within 2 h of operation to a remaining activity of around 40%. Neglecting the carbonaceous deposits as a reaction product and considering only the vapor phase products, PO selectivity is more than 75% at 5-10% propene conversion. The attempt to slow down the deactivation through the addition of supplementary gases (H 2 , O 2 , NH 3 , H 2 O) was partially successful, but unfortunately this is always accompanied by lower PO selectivity.

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Section: Resultsmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Catalytic Vapor Phase Epoxidation of Propene with Nitrous Oxide as an Oxidant: Investigations on Catalyst Composition and Reaction Conditions

Thömmes

Gräf

Reitzmann

et al. 2010

Ind. Eng. Chem. Res.

Self Cite

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“…According to Lifshitz and Tamburu [34] the formation of PA and ACT as a result of PO isomerization is a simple process involving C-O rapture and hydrogen shift. However, according to Thömmas et al [35] a very high rate of PA conversion, especially in the presence of N 2 O, results in a lowering of the PA contribution in the oxidation product. Taking into account the high concentration of the active centers on V/MCF catalysts it is possible to explain the low selectivity to PA in propene oxidation recorded on the studied samples, especially with higher vanadium concentration.…”

Section: Discussionmentioning

confidence: 99%

MCF Material as an Attractive Support for Vanadium Oxide Applied as a Catalyst for Propene Epoxidation with N2O

et al. 2018

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Vanadium modified mesocellular silica foams (MCF) materials (V content ca. 3 and 5 wt%) prepared by the impregnation method show mainly isolated or low-polymeric VO x species, which was confirmed by means of Raman spectroscopy and DR UV-Vis. Textural measurements, and also XRD and TEM results indicate that the characteristic mesocellular structural features of MCFs are preserved after vanadium incorporation. The MCF-supported vanadia catalysts exhibit much higher propene conversion and propene oxide productivity when compared to vanadium modified mesoporous silicas of 2D structure, demonstrating that apart from the presence of highly dispersed isolated vanadium species, internal molecular transport within three-dimensional ultra large pores of MCF materials also plays an important role in gas-phase propene epoxidation. Graphical Abstract

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Emerging sustainable technology for epoxidation directed toward plant oil-based plasticizers

Chua

Guo

2012

Process Biochemistry

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Catalytic vapour phase epoxidation of propene with nitrous oxide as an oxidant II. Development of a kinetic model

Cited by 3 publications

References 12 publications

Catalytic Vapor Phase Epoxidation of Propene with Nitrous Oxide as an Oxidant: Investigations on Catalyst Composition and Reaction Conditions

Catalytic Vapor Phase Epoxidation of Propene with Nitrous Oxide as an Oxidant: Investigations on Catalyst Composition and Reaction Conditions

MCF Material as an Attractive Support for Vanadium Oxide Applied as a Catalyst for Propene Epoxidation with N2O

Emerging sustainable technology for epoxidation directed toward plant oil-based plasticizers

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