Deactivation of sulfated-zirconia and H-mordenite catalysts during n-butane and isobutane isomerization

Fogash, K.B.; Hong, Zhe; Kobe, J.M.; Dumesic, James A.

doi:10.1016/s0926-860x(98)00112-4

Cited by 46 publications

(23 citation statements)

References 43 publications

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“…One possibility is that the reaction initially proceeds through a monomolecular mechanism, and only as (i) enough branched species are available on the surface and/or (ii) alkenes have been formed, alkylation to give C 8 species (bimolecular mechanism) can take place. The accumulation of contaminant butenes from the feed stream as a reason for the induction phase appears unlikely, because the length of the induction period at constant feed flow is a function of temperature (see Figure 1) and the initial isomerization activity is almost independent of the alkene concentration in the feed stream (10), although there is a significant influence of the alkene concentration on the overall reaction profile (10,36). Traces of propane in the product stream throughout the entire reaction profile indicate that the reaction never proceeds exclusively through the monomolecular isomerization mechanism.…”

Section: Evolution Of the Band At 310 Nm With Time During N-butane Ismentioning

confidence: 99%

“…Several suggestions have been made in order to explain the deactivation process, among them: 1-Formation of hydrocarbon surface deposits ("coke") (2-11), 2-surface reduction (Zr 4+ → Zr 3+ ) by the reacting hydrocarbon (4), 3-reduction of the surface sulfate groups and H 2 S formation (5), 4-change in the surface phase of zirconia from tetragonal to monoclinic (12), and 5-surface poisoning by water (7). Evidence for these hypotheses mainly arises from investigations of the fully or partially deactivated catalyst (2)(3)(4)(7)(8)(9)(10)(11)(12), often after removal from the reactor. A true in situ experiment, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Isomerization of n-butane and of n-pentane in the presence of sulfated zirconia: formation of surface deposits investigated by in situ UV–vis diffuse reflectance spectroscopy

Ahmad

Melsheimer

Jentoft

et al. 2003

Journal of Catalysis

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Catalytic performance and formation of carbonaceous deposits were studied simultaneously during alkane isomerization over sulfated zirconia in a fixed bed flow reactor with an optical window for in situ UV-vis diffuse reflectance spectroscopy. The reactions of n-butane (5 kPa) at 358 and 378 K and of n-pentane (0.25 kPa) at 298 and 308 K passed within 5 h or less through an induction period, a conversion maximum, and a period of deactivation; a steady activity of 41 and 47 µmol g -1 h -1 (isobutane formation) and ≈2.5 µmol g -1 h -1 (isopentane, both temperatures) remained. UV-vis spectra indicate the formation of unsaturated surface deposits; the band positions at 310 nm (n-butane reaction) and 330 nm (npentane) are within the range of monoenic allylic cations. More highly conjugated allylic cations (bands at 370 and 430 nm) became evident during n-butane reaction at 523 K. The chronology of events suggests that the surface deposits are (i) a result only of the bimolecular and not the monomolecular reaction mechanism, and (ii) are formed in a competitive reaction to the alkane products.

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Section: Evolution Of the Band At 310 Nm With Time During N-butane Ismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Isomerization of n-butane and of n-pentane in the presence of sulfated zirconia: formation of surface deposits investigated by in situ UV–vis diffuse reflectance spectroscopy

Ahmad

Melsheimer

Jentoft

et al. 2003

Journal of Catalysis

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“…It is obviously important for researchers to find the exact reasons for the deactivation of the catalysts, to pave the way for solving the problem. Many deactivation researches were focused on sulfate-promoted zirconia in alkane reactions [17,18]. There put out some possible reasons for the deactivation of sulfate-promoted zirconia [17], such as acidity degradation, coke formation, sulfur loss, phase transformation, and so on.…”

Section: Introductionmentioning

confidence: 99%

A New Deactivation Mechanism of Sulfate-Promoted Iron Oxide

Shi

2013

Catal Lett

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“…Besides, they also exhibit high catalytic activities in many kinds of acid catalyzed organic reactions. However, there is a fatal problem that they can be readily deactivated despite their initial high activities [9,10]. Some possible deactivation reasons [9,10] can be summarized as follows for sulfated zirconia: (1) acidity degradation; (2) surface sulfur species can be reduced from S 6?…”

Section: Introductionmentioning

confidence: 99%

“…However, there is a fatal problem that they can be readily deactivated despite their initial high activities [9,10]. Some possible deactivation reasons [9,10] can be summarized as follows for sulfated zirconia: (1) acidity degradation; (2) surface sulfur species can be reduced from S 6? to a lower valance state; (3) coke formation; (4) sulfur loss; (5) phase transformation from catalytically active tetragonal ZrO 2 to catalytically inactive monoclinic ZrO 2 .…”

Section: Introductionmentioning

confidence: 99%

A deactivation mechanism of sulfated titania in the esterification of acetic acid and n-butanol

Shi

2013

Reac Kinet Mech Cat

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The present work systematically investigated the deactivation of sulfated titania in the esterification of acetic acid and n-butanol. Under the set conditions, sulfated titania was used 20 times and for 10 h accumulatively. The catalyst had the largest catalytic activity of 95.69 % at the second cycle and then the catalytic activities gradually dropped, and the last-cycle conversion of acetic acid was 46.15 %, suggesting a serious deactivation of the catalyst of sulfated titania after use in 20 cycles. XPS, FTIR, XRD, BET, TG-DSC, TEM and NH 3 -TPD were employed to characterize the new and deactivated catalysts, to systemically study the deactivation phenomena of sulfated titania and to find some reasons for the considerable deactivation of sulfated titania in the esterification. Some deactivation phenomena were observed on the deactivated catalyst when compared with the new one.(1) The deactivated catalyst decreased its acidity, based on the IR and NH 3 -TPD characteristic results. (2) The deactivated catalyst increased its surface specific area and its pore volume, and decreased its pore diameter, based on the BET characteristic results. (3) Some carbon deposits appeared on the surface of the deactivated catalyst, and some originally active sulfate groups may have been lost, poisoned and turned into less-catalytic and non-catalytic sulfur species based on the XPS and TG-DSC results. (4) The deactivated catalyst decreased its crystallinity based on the XRD results. (5) The deactivated catalyst diminished in particle aggregation, based on the SEM results. Thus, a deactivation mechanism is tentatively proposed. Namely, some originally active surface sulfate groups may have been gradually turned into the undesired free sulfuric acid and organic sulfate esters hydrolysis by H 2 O and their alcoholysis by n-butanol, which may lead to a gradual acidity degradation of the catalyst so as to lead to a gradual deactivation of sulfated titania. All the characteristic results more or less support the proposed deactivation mechanism.

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Deactivation of sulfated-zirconia and H-mordenite catalysts during n-butane and isobutane isomerization

Cited by 46 publications

References 43 publications

Isomerization of n-butane and of n-pentane in the presence of sulfated zirconia: formation of surface deposits investigated by in situ UV–vis diffuse reflectance spectroscopy

Isomerization of n-butane and of n-pentane in the presence of sulfated zirconia: formation of surface deposits investigated by in situ UV–vis diffuse reflectance spectroscopy

A New Deactivation Mechanism of Sulfate-Promoted Iron Oxide

A deactivation mechanism of sulfated titania in the esterification of acetic acid and n-butanol

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