Structural characterization of coke deposits on industrial spent paraffin dehydrogenation catalysts

Sahoo, S. K.; Rao, P.V.C.; Rajeshwer, D.; Krishnamurthy, K. R.; Singh, I. D.

doi:10.1016/s0926-860x(02)00603-8

Cited by 51 publications

(24 citation statements)

References 18 publications

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“…It is well known that alumina is a widely used support material for the dehydrogenation catalysts due to its superior capability in holding high dispersion of active phase [10,11]. However, the alumina supported catalyst for dehydrogenation may suffer from its acidity.…”

Section: Introductionmentioning

confidence: 99%

Coupling dehydrogenation of isobutane to produce isobutene in carbon dioxide over NiO/γ-Al2O3 catalyst

Ding

Shao

et al. 2010

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The dehydrogenation of isobutane to produce isobutene coupled with reverse water gas shift (RWGS) reaction in the presence of carbon dioxide was investigated over a NiO/c-Al 2 O 3 catalyst. The results illustrated that the coupling dehydrogenation of isobutane in carbon dioxide over NiO/c-Al 2 O 3 catalyst is effective, and the NiO/Al 2 O 3 catalyst was modified with deposited carbon by impregnation of alumina with an aqueous solution of Ni(H 2 NCH 2 CH 2 NH 2 ) x (NO 3 ) 2 . Carbon modification can decrease the total acidity of the NiO/c-Al 2 O 3 catalyst and enhance the dispersion of NiO active phase. Furthermore, carbon has low acidity and anti-coking performance, so the carbon modification is effective in suppressing the coke formation and side reactions occurrence. Therefore, the catalyst stability and the isobutene selectivity are improved significantly by the carbon modification.

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Section: Introductionmentioning

confidence: 99%

Coupling dehydrogenation of isobutane to produce isobutene in carbon dioxide over NiO/γ-Al2O3 catalyst

Ding

Shao

et al. 2010

Reac Kinet Mech Cat

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“…It has also been observed that the carbon deposition is the main cause of deactivation in alkane dehydrogenation catalysts. Sahoo et al 27 proposed that the coke formation is a bi-functional reaction, requiring the dehydrogenating capacity of the metallic function and the condensation-polymerization capacity of the acidic function.…”

Section: Discussionmentioning

confidence: 99%

The influence of the amount and impregnation sequence of potassium on the catalytic performance of VOx/Al2O3 for the non-oxidative dehydrogenation of n-butane

Volpe

García

2012

J. Braz. Chem. Soc.

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A dehidrogenação não-oxidativa de n-butano foi estudado usando catalisadores de vanádio suportados em alumina e potássio como promotor (a 873 K e pressão atmosfera), a fim de se explorar a influência da quantidade e da ordem de agregação do metal alcalino na atividade catalítica e seletividade de olefinas. A atividade e seletividade da dehidrogenação não-oxidativa diminuíram com o aumento da razão molar K/V. O melhor desempenho catalítico foi obtido com 1 wt.% de potássio e quando o promotor foi agregado pela primeira vez nos catalisadores de vanádio suportados em alumina. A ordem de agregação do promotor tem efeitos na atividade catalítica. Dados de TPR (redução à temperatura programada) indicam que menos espécies de vanádio são acessíveis à redução quando baixa quantidade (1 wt.%) de promotor metal alcalino foi impregnada no catalisador antes do vanádio. Após tratamento de regeneração, estes catalisadores não recuperam a plena atividade. Tendo em conta os resultados de TPR, essa desativação do catalisador pode estar relacionada com a transformação estrutural irreversível de espécies de óxido de vanádio superficiais pelo potássio.The non-oxidative dehydrogenation of n-butane was studied over potassium-promoted supported vanadium alumina catalysts (at 823 K under atmosphere pressure) to explore the influence of the amount and the order of potassium aggregation on the catalytic activity and selectivity towards olefins. The non-oxidative dehydrogenation activity and selectivity decreased with increasing K/V molar ratio. The best catalytic performance was obtained with 1 wt.% of potassium loading and when the promoter was first aggregated in the supported vanadium alumina catalysts. The order of promoter aggregation has effects in the catalytic activity. TPR (temperature programmed reduction) data indicate that less vanadium species are accessible to the reduction when low amount (1 wt.%) of alkali metal promoter was first introduced in these samples. After regeneration treatment, these promoted catalysts did not recover the full activity. Taking in account TPR results, this catalyst deactivation may be related to the irreversible structural transformation of surface vanadium oxide species by potassium.

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“…The mass of coke was determined as where y CO 2 and y CO denote the volume proportions detected by the carbon analyzer; V air represents the volume flow rate of synthetic air; ρ CO 2 and ρ CO are the densities of CO 2 and CO, respectively; and t 0 and t 1 are the starting and end times, respectively, of the TPO experimental run. According to previous research, coke deposits consist of condensed rings with 7–12 carbon atoms, in which carbon accounts for more than 95% of the mass. In this study, the main component of coke is therefore assumed to be carbon.…”

Section: Methodsmentioning

confidence: 96%

Coke Deposition Inhibition for Endothermic Hydrocarbon Fuels in a Reforming Catalyst-Coated Reactor

et al. 2019

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Coke formation is an obstacle in using hydrocarbons as the coolant in hypersonic flight vehicles. In this paper, effective inhibition of coke deposition was realized by the addition of wall catalytic steam reforming, and the corresponding mechanism was revealed. The anticoking tests were evaluated during the thermal cracking and catalytic steam reforming processes of an endothermic hydrocarbon fuel under 3.0 MPa and outlet temperature from 600 to 680 °C. The amount and properties of coke deposited in the thermal cracking with and without steam reforming were investigated on the basis of their temperature-programmed oxidation profiles and scanning electron microscopy. The results show that the mass percentages of filamentous and amorphous cokes deposited during thermal cracking without steam reforming are 20.32 and 79.68%, respectively. The amount of coke deposited in a bare reactor is nearly twice that deposited in a reforming catalyst-coated reactor, and the coke formation rate in the former case is 8 times that in the latter case. The absence of filamentous deposits during catalytic steam reforming is ascribed to the catalyst layer on the inner surface, which prevents contact between the hydrocarbon fuel and active metal sites. Filamentous coke formation is therefore totally inhibited. Moreover, catalytic steam reforming also inhibits amorphous coke deposition. Analyses of the gaseous products and residual liquids from thermal cracking of jet fuel show that the monocyclic and polycyclic aromatic hydrocarbon contents decrease significantly under catalytic steam reforming. The large amount of hydrogen generated from the wall catalytic steam reforming reaction suppresses dehydrogenation, Diels–Alder, and condensation reactions; therefore, coke deposition decreases.

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Structural characterization of coke deposits on industrial spent paraffin dehydrogenation catalysts

Cited by 51 publications

References 18 publications

Coupling dehydrogenation of isobutane to produce isobutene in carbon dioxide over NiO/γ-Al2O3 catalyst

Coupling dehydrogenation of isobutane to produce isobutene in carbon dioxide over NiO/γ-Al2O3 catalyst

The influence of the amount and impregnation sequence of potassium on the catalytic performance of VOx/Al2O3 for the non-oxidative dehydrogenation of n-butane

Coke Deposition Inhibition for Endothermic Hydrocarbon Fuels in a Reforming Catalyst-Coated Reactor

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