Activation of n-octane using vanadium oxide supported on alkaline earth hydroxyapatites

Dasireddy, Venkata D.B.C.; Singh, Sooboo; Friedrich, Holger B.

doi:10.1016/j.apcata.2013.02.006

Cited by 38 publications

(39 citation statements)

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“…3) and it was observed that the conversion profile was proportional to the number of acidic sites (Table 3) on the surface of the hydroxyapatites. 21 There was no contribution towards conversion from redox properties of the catalysts since they are stable under reduction as shown by TPR studies. The conversion is therefore due to the surface oxygen species chemisorbed on the hydroxyapatites.…”

Section: Catalytic Resultsmentioning

confidence: 99%

“…This is probably due to the difference in the acidity of the surfaces of Sr-HAp and Ba-HAp and it has been shown that Brønsted acidity favours the formation of aromatics and oxygenates. 21,25 The cis-and trans-2-octenes (3.6-14.5 %) are the dominant products in the octenes product stream over all the catalysts. The yield towards trans-2-octene (2.1-8.4 %) is higher than the cis-2-octene (1.5-6.1 %) due to the relative thermodynamic stability of trans-isomers compared to the respective cis-isomers.…”

Section: Catalytic Resultsmentioning

confidence: 99%

“…1) show that the samples have uniform pore size distribution. 21 The surface areas of the hydroxyapatites are in the 40 to 70 m 2 g -1 range and are shown in Table 2. From powder XRD (Fig.…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

“…21,23 Weak, strong and some moderate acidic sites are attributed to the three peaks present in the TPD profile of the loaded HAp catalysts, at 350-450 °C weak acidic sites, at 450-550 °C moderate acidic sites and above 650°C strong acidic sites. 24 Lewis acidity is due to the main group metal ions RESEARCH ARTICLE c X s = 0.9 l/FWHMcos q, where X s is the crystallite size (nm), l is the wavelength of the monochromatic X-ray beam (l= 0.15406 nm for CuKa radiation), FWHM is the full width at half-maximum for the diffraction peak under consideration (radians) and q is the diffraction angle (degrees) 21 . d X c = 1-(V 112/300 /I 300 ), where X c is degree of crystallinity, V 112/300 is the intensity of the shoulder between the (112) and (300) diffraction peaks and I 300 is the intensity of the (300) peak 21 .…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

“…24 Lewis acidity is due to the main group metal ions RESEARCH ARTICLE c X s = 0.9 l/FWHMcos q, where X s is the crystallite size (nm), l is the wavelength of the monochromatic X-ray beam (l= 0.15406 nm for CuKa radiation), FWHM is the full width at half-maximum for the diffraction peak under consideration (radians) and q is the diffraction angle (degrees) 21 . d X c = 1-(V 112/300 /I 300 ), where X c is degree of crystallinity, V 112/300 is the intensity of the shoulder between the (112) and (300) diffraction peaks and I 300 is the intensity of the (300) peak 21 . e Measured using iTEM software (count of 50-70 particles, with a standard deviation of ±3 nm).…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

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A kinetic insight into the activation of n-octane with alkaline-earth metal hydroxyapatites

2015

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Alkaline-earth metal hydroxyapatites are prepared by the co-precipitation method and characterized using XRD, ICP, NH 3 -TPD, SEM-EDX, TEM and N 2 physisorption analysis. The metal present in the hydroxyapatite influences the acidity of the catalyst. Oxidative dehydrogenation reactions carried out in a continuous flow fixed bed reactor showed that the selectivity towards desired products was dependent on the alkaline-earth metal in the hydroxyapatite. All hydroxyapatite catalysts showed high selectivity towards carbon oxides, followed by cracked products, octenes and aromatics. The highest selectivity and turnover numbers towards C8 products and a high specific rate was shown by Sr-HAp. The activation of n-octane over these catalysts followed the Eley-Rideal mechanism.

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Section: Catalytic Resultsmentioning

confidence: 99%

Section: Catalytic Resultsmentioning

confidence: 99%

Section: Characterization Of Catalystsmentioning

confidence: 99%

Section: Characterization Of Catalystsmentioning

confidence: 99%

Section: Characterization Of Catalystsmentioning

confidence: 99%

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A kinetic insight into the activation of n-octane with alkaline-earth metal hydroxyapatites

2015

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Synthesis and Characterization of Hydroxyapatite and Hydroxyapatite‐Based Catalysts

Jemli¹,

Abdelouahdi²,

Minh

et al. 2022

Design and Applications of Hydroxyapatite‐Based Catalysts

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Structure and Surface Study of Hydroxyapatite‐Based Materials

Costentin

Drouet

Salles

et al. 2022

Design and Applications of Hydroxyapatite‐Based Catalysts

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In addition to designing catalytic materials ever more active and selective, the emergence of new classes of greener catalysts remains very challenging. The apatite family system with hydroxyapatite (HA) structure appears as a good candidate for catalysis due to its ecocompatibility properties, its sorption ability toward organic molecules, and its tunable composition resulting into modulation of its surface properties. Depending on their mode of preparation, these inexpensive and environment-friendly apatitic calcium phosphates exhibit properties of relevance to catalysis, such as large surface area and various morphologies.However, most studies focused so far on the catalytic performance of these compounds, while the study of structure-reactivity relationships required for rationalized optimization remains rather limited. This chapter aims at providing tools to help understand the catalytic behavior of apatite compounds, giving details about their structure, surface properties, and reactivity; this will include both stoichiometric and nonstoichiometric compounds, sometimes biomimetic and potentially substituted. A special attention is dedicated to recent advances in the characterization of their structural properties (bulk and surface/interphase) that have a strong impact on their reactivity, through both experimental and computational approaches to study the mechanisms occurring in the structure or at the crystals surface, as well as thermodynamic and dynamical properties. Remaining characterization challenges for apatite-based catalysts will also be discussed. 1.an influence on the charges carried by the cation and on the related strength of the Ca-O interaction [127], which results in different adsorption properties with guest molecules. To go further, quantum calculations coupled with NMR (Nuclear Magnetic Resonance) resultsshowed the impact of the presence of OHions on the migration of Ca 2+ as well as the rotation of PO4 3groups [128]. In the hydroxyapatite structure, phosphate ions PO4 3are the largest components of the structure. As such, they provide a primary backbone via 3D compact-like piling, generating interstitial sites for the other ions of the structure. Metal cations such as Ca 2+ occupy two types of crystallographic sites, denoted Ca1 (4 sites per unit formula) and Ca2 (6 sites per unit formula), see Figure 2. Ca1 sites are localized along the trigonal axis with the coordinates (1/4, 3/4, 1/2) and (3/4, 1/4, 1/2), forming linear columns along the c-axis. Ca2 sites in contrast form equilateral triangles at z = 1/4 and z = 3/4 on the sixfold screw (senary) 63 axes. Adjacent Ca1 and Ca2 sites are linked through shared oxygen atoms from PO4 tetrahedra. Ca1 sites generate (distorted) polyhedra where the metal ion is in ninefold coordination, while in Ca2 sites it is in sevenfold coordination.The Ca2 triangles contribute to delimit so-called "apatitic channels" where ions such as OHare axially located (Figure 3) [116,120]. In calcium hydroxyapatite, the Ca2 triangular sites correspond to the narrow...

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Activation of n-octane using vanadium oxide supported on alkaline earth hydroxyapatites

Cited by 38 publications

References 57 publications

A kinetic insight into the activation of n-octane with alkaline-earth metal hydroxyapatites

A kinetic insight into the activation of n-octane with alkaline-earth metal hydroxyapatites

Synthesis and Characterization of Hydroxyapatite and Hydroxyapatite‐Based Catalysts

Structure and Surface Study of Hydroxyapatite‐Based Materials

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