Effects of potassium addition on the acidity and reducibility of chromia/alumina dehydrogenation catalysts

Rombi, Elisabetta; Cutrufello, Maria Giorgia; Solinas, V.; Rossi, S. De; Ferraris, Giovanni; Pistone, Alessandro

doi:10.1016/s0926-860x(03)00308-9

Cited by 72 publications

(38 citation statements)

References 35 publications

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“…Decrease of the dehydrogenation rate at the final stage of the cycle is due to the catalyst coking. The decrease of the cracking rate during the first 30 min (Figure 14b) is also caused by covering of the acid sites by coke deposits [15]. …”

Section: Isobutane Dehydrogenation Performance Of Catalystsmentioning

confidence: 97%

“…Potassium in catalyst forms potassium chromates at the expense of the low-active crystalline Cr2O3 phase. These chromates are reduced to catalytically active Cr(III) phase in dehydrogenation conditions [15,26]. However, an excessive In the synthesized catalysts an optimum mass ratio of chromium to potassium was used (Cr/K = 8) which was established by Kataev [25] for alumina supports obtained by the sequential thermal-hydrothermal treatment of gibbsite.…”

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

“…Potassium as a promoter performs several functions in chromia-alumina catalysts. It neutralizes the strong acid sites [15] and thus decreases the activity of the catalyst in hydrocarbon cracking reactions (Table 4). Potassium in catalyst forms potassium chromates at the expense of the low-active crystalline Cr 2 O 3 phase.…”

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

“…Potassium in catalyst forms potassium chromates at the expense of the low-active crystalline Cr 2 O 3 phase. These chromates are reduced to catalytically active Cr(III) phase in dehydrogenation conditions [15,26]. However, an excessive amount of potassium poisons the catalyst due to the coverage of the active Cr(III) sites [26] and neutralization of the weak and medium acid sites which adsorb alkane molecules [15].…”

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

“…These chromates are reduced to catalytically active Cr(III) phase in dehydrogenation conditions [15,26]. However, an excessive amount of potassium poisons the catalyst due to the coverage of the active Cr(III) sites [26] and neutralization of the weak and medium acid sites which adsorb alkane molecules [15]. Optimal potassium content depends not only on the surface area and acidity of the support but also on the concentration of chromium because potassium as aluminate and chromates is distributed both on the open areas of alumina and on the Cr 2 O 3 particles [26].…”

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

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Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

et al. 2016

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Due to the continuously rising demand for C 3 -C 5 olefins it is important to improve the performance of catalysts for dehydrogenation of light alkanes. In this work the effect of modification by SiO 2 on the properties of the alumina support and the chromia-alumina catalyst was studied. SiO 2 was introduced by impregnation of the support with a silica sol. To characterize the supports and the catalysts the following techniques were used: low-temperature nitrogen adsorption; IR-spectroscopy; magic angle spinning 29 Si nuclear magnetic resonance; temperature programmed desorption and reduction; UV-Vis-, Raman-and electron paramagnetic resonance (EPR)-spectroscopy. It was shown that the modifier in amounts of 2.5-7.5 wt % distributed on the support surface in the form of SiO x -islands diminishes the interaction between the alumina support and the chromate ions (precursor of the active component). As a result, polychromates are the compounds predominantly stabilized on the surface of the modified support; under thermal activation of the catalyst and are reduced to the amorphous Cr 2 O 3 . This in turn leads to an increase in the activity of the catalyst in the dehydrogenation of isobutane.

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Section: Isobutane Dehydrogenation Performance Of Catalystsmentioning

confidence: 97%

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

“…Potassium in catalyst forms potassium chromates at the expense of the low-active crystalline Cr 2 O 3 phase. These chromates are reduced to catalytically active Cr(III) phase in dehydrogenation conditions [15,26]. However, an excessive amount of potassium poisons the catalyst due to the coverage of the active Cr(III) sites [26] and neutralization of the weak and medium acid sites which adsorb alkane molecules [15].…”

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

Section: Composition Crystal and Pore Structure Acidity Of Catalystsmentioning

confidence: 99%

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Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

et al. 2016

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Emphasis on the Properties of Metal‐Containing Zeolites Operating Outside the Comfort Zone of Current Heterogeneous Catalytic Reactions

et al. 2020

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The development of catalysts that can operate under exceptionally harsh and unconventional conditions is of critical importance for the transition of the energy and chemicals industries to low‐emission and renewable chemical feedstocks. In this review we will highlight materials and more specifically metal‐containing zeolite catalysts that have been tested under harsh reaction conditions such as high temperature light alkane conversion and biomass valorization. Particular attention will be given to studies that explore the stability and recyclability of metal‐containing zeolite catalysts operating in continuous modes. Metal‐containing zeolites are considered as an important class of catalysts operating outside the comfort zone of current heterogeneous catalytic reactions in both gas and liquid phase reactions. The relationship between the properties of the metal‐containing zeolite and catalytic performance will be explored.

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Emphasis on the Properties of Metal‐Containing Zeolites Operating Outside the Comfort Zone of Current Heterogeneous Catalytic Reactions

et al. 2020

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Effects of potassium addition on the acidity and reducibility of chromia/alumina dehydrogenation catalysts

Cited by 72 publications

References 35 publications

Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

Emphasis on the Properties of Metal‐Containing Zeolites Operating Outside the Comfort Zone of Current Heterogeneous Catalytic Reactions

Emphasis on the Properties of Metal‐Containing Zeolites Operating Outside the Comfort Zone of Current Heterogeneous Catalytic Reactions

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