In-situ FTIR measurements of diffusion in coking zeolite catalysts

Karge, Hellmut G.; Nießen, W.; Bludau, H.

doi:10.1016/s0926-860x(96)00175-5

Cited by 110 publications

(49 citation statements)

References 11 publications

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“…Especially in the case of ethanol, bands arise at higher frequencies and the theoretical values listed in Table 3 suggest that these might also originate from larger aromatic compounds. This is accompanied by growth of the C=C band at 1607 cm −1 with shoulder at 1640 cm −1 for methanol and 1600 cm −1 with shoulder at 1660 cm −1 for ethanol (see Figure 8 (b) and (d)) which also demonstrate the formation of aromatic carbenium ions as suggested in literature earlier [36,35,92,93,94] and is in line with the calculated IR spectra of Figure 7 (b). Once formed, these bands remain rather stable throughout the entire period of reaction though the relative stronger intensity in the case of ethanol is evident.…”

Section: Formation Of Hydrocarbon Pool Speciessupporting

confidence: 90%

Experimental and theoretical IR study of methanol and ethanol conversion over H-SAPO-34

Hemelsoet

Ghysels

et al. 2011

Catalysis Today

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Theoretical and experimental IR data are combined to gain insight into the methanol and ethanol conversion over an acidic H-SAPO-34 catalyst. The theoretical simulations use a large finite cluster and the initial physisorption energy of both alcohols is calculated.Dispersive contributions turn out to be vital and the final adsorption of ethanol is predicted to be stronger compared to methanol (difference of 14 kJ mol −1 ). Calculated IR spectra of the alcohols and of formed aromatic cations upon conversion are also analyzed and support the peak assignment of the experimental in situ DRIFT spectra, in particular for the C-H and C=C regions. Theoretical IR spectra of the gas phase compounds are compared with those of the molecules loaded in a SAPO cluster and the observed shifts of the peak positions are discussed. To get a better understanding of these framework-guest interactions, a new theoretical procedure is proposed based on a normal mode analysis.A cumulative overlap function is defined and enables the characterization of individual peaks as well as induced frequency shifts upon adsorption.

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Section: Formation Of Hydrocarbon Pool Speciessupporting

confidence: 90%

Experimental and theoretical IR study of methanol and ethanol conversion over H-SAPO-34

Hemelsoet

Ghysels

et al. 2011

Catalysis Today

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“…Figure 4a shows the results of FTIR-TPO profiles, determined in a single run, of the species deposited on the catalyst at 325 °C. The MS spectrometry has been used to track the CO2 signal and the FTIR spectroscopy has been used to analyze the derivative of absorbance bands (dA/dt) of four groups of species trapped on the catalyst [48][49][50]: -CH3 at 2960 cm −1 ; -CH2 and -CH at 2930 cm −1 ; conjugated double bonds in dienes or aromatics at 1610 cm −1 ; condensed aromatics at 1580 cm −1 .…”

Section: Coke Naturementioning

confidence: 99%

Nature and Location of Carbonaceous Species in a Composite HZSM-5 Zeolite Catalyst during the Conversion of Dimethyl Ether into Light Olefins

et al. 2017

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Abstract:The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the matrix) has been analyzed by comparing the properties of the fresh and deactivated catalyst after runs at different temperatures, while the nature of those species has been studied using different spectroscopic and thermogravimetric techniques. The reaction occurs on the strongest acid sites of the zeolite micropores through olefins and alkyl-benzenes as intermediates. These species also condensate into bulkier structures (polyaromatics named as coke), particularly at higher temperatures and within the mesoand macropores of the matrix. The critical roles of the matrix and water in the reaction medium have been proved: both attenuating the effect of coke deposition.

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“…After 30 min onstream, a band at 1635 cm −1 was first observed, along with weaker CH bands at 2921 cm −1 . With time on stream, bands at 1588, 1540, and 1515 cm −1 were also observed, which were assigned to aromatic coke-like species (33). This is supported by the fact that the CH deformation and stretching signals remained low.…”

Section: Figmentioning

confidence: 71%

“…5, spectra b and c). The growth of bands in the region around 1600 cm −1 indicates that more hydrogendeficient coke species is formed with time onstream (33). In parallel, a band appeared at 3339 cm −1 , characteristic of Brønsted acid hydroxyl groups hydrogen-bonded to an aromatic species ( ν ≈ 250 cm −1 ).…”

Section: Reaction Of 13-butadiene At 623 Kmentioning

confidence: 96%

In Situ IR Study of the Nature and Mobility of Sorbed Species on H-FER during But-1-ene Isomerization

Meunier

Domokos

Seshan

et al. 2002

Journal of Catalysis

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The sorption and reaction of but-1-ene over a ferrierite sample was studied by in situ IR spectroscopy to relate the selectivity to isobutene and the sorbed species. The spectra highlighted the presence of various unsaturated species including polyenes, which were readily formed upon contacting H-FER with but-1-ene while a poor selectivity to isobutene was observed. Aromatic compounds were concluded to be subsequently formed via dehydrogenation/cyclization of the polyenic deposits while the isobutene selectivity increased via suppression of by-products. These data support earlier assumptions that the initial high yield of by-products was produced by the reaction of butenes with reactive deposits, which were gradually converted into more inert aromatic deposits. Upon purging the catalyst with an inert, branched C 8 hydrocarbons and aromatic molecules such as xylenes desorbed. The rates of desorption showed an initially linear variation with the square root of time and were fitted to a monodimensional Fickian model. Because the slowly diffusing species were rather abundant during the course of the reaction, it is proposed that the skeletal isomerization was effectively limited to the acid sites close the pore mouth of H-FER crystallites. c 2002 Elsevier Science (USA)

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In-situ FTIR measurements of diffusion in coking zeolite catalysts

Cited by 110 publications

References 11 publications

Experimental and theoretical IR study of methanol and ethanol conversion over H-SAPO-34

Experimental and theoretical IR study of methanol and ethanol conversion over H-SAPO-34

Nature and Location of Carbonaceous Species in a Composite HZSM-5 Zeolite Catalyst during the Conversion of Dimethyl Ether into Light Olefins

In Situ IR Study of the Nature and Mobility of Sorbed Species on H-FER during But-1-ene Isomerization

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