Infrared, microcalorimetric, and electron spin resonance investigations of the acidic properties of the H-ZSM-5 zeolite

Védrine, J.C.; Auroux, A.; Bolis, V.; Dejaifve, Pierre; Naccache, C.; Wierzchowski, P.; Derouane, Éric G.; Nagy, J.B.; Gilson, Jean‐Pierre; Vanhooff, J

doi:10.1016/s0021-9517(79)80029-9

Cited by 314 publications

(84 citation statements)

References 20 publications

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“…9a and c which is in accordance to literature. 7,12,14,17,18 STXM data presented in Fig. 8 reveal both inter-, and intraparticle heterogeneities in the distribution of phosphorus.…”

Section: Effect Of Thermal Treatment On Phosphated Samplesmentioning

confidence: 88%

“…5,6 The selectivity towards propylene is increased even more with the introduction of phosphorus. [6][7][8][9][10] Usually, the improved selectivity towards propylene is attributed to the decrease in the acid site strength that is so often observed in phosphated H-ZSM-5, although steric factors have also been suggested to be responsible. [6][7][8][9][10][11][12] Even though there is still some debate on the effect of acid site strength on the MTO product distribution, the promoting effect of phosphorus on the hydrothermal stability of H-ZSM-5 is undisputed.…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8][9][10] Usually, the improved selectivity towards propylene is attributed to the decrease in the acid site strength that is so often observed in phosphated H-ZSM-5, although steric factors have also been suggested to be responsible. [6][7][8][9][10][11][12] Even though there is still some debate on the effect of acid site strength on the MTO product distribution, the promoting effect of phosphorus on the hydrothermal stability of H-ZSM-5 is undisputed. 4,9,[13][14][15][16][17][18][19][20][21][22][23][24][25] Zeolite H-ZSM-5 catalysts that contain phosphorus are more stable under hydrothermal conditions i.e.…”

Section: Introductionmentioning

confidence: 99%

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Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

126

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In order to elucidate phosphorus-zeolite H-ZSM-5 interactions, a variety of phosphorus-modified zeolite H-ZSM-5 materials were studied in a multi-spectroscopic manner. By deploying single pulse 27 Al, 31 P MAS NMR, 2D heteronuclear 27 Al-31 P correlation (HETCOR), 27 Al MQ MAS NMR spectroscopy, TPD of pyridine monitored by FT-IR spectroscopy, and Scanning Transmission X-ray Microscopy (STXM) the interplay and influence of acidity, thermal treatment and phosphorus on the structure and acidity of H-ZSM-5 were established. It was found that while acid treatment did not affect the zeolite structure, thermal treatment leads to the breaking of Si-OH-Al bonds, a decrease in the strong acid site number and the formation of terminal Al-OH groups. No extra-framework aluminium species was observed. Phosphorus precursors interact with the zeolitic framework through hydrogen bonds and physical coordination, as phosphorus species can be simply washed out with hot water. After phosphatation and thermal treatment two effects occur simultaneously, namely (i) phosphorus species transform into water insoluble condensed poly-phosphoric acid and (ii) phosphoric acid binds irreversibly to the terminal Al-OH groups of partially dislodged four-coordinated framework aluminium, forming local silico-aluminophosphate interfaces.These interfaces are potentially the promoters of hydrothermal stability in phosphated zeolite H-ZSM-5.

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“…9a and c which is in accordance to literature. 7,12,14,17,18 STXM data presented in Fig. 8 reveal both inter-, and intraparticle heterogeneities in the distribution of phosphorus.…”

Section: Effect Of Thermal Treatment On Phosphated Samplesmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

126

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“…This suggested that there should be a maximum in acid site activity and in catalytic reaction rate at a specific aluminum content. Vedrine et al [44] report that the acid sites present in H-ZSM-5 (Si/Al = 19.2) are similar to, but slightly stronger than, those present in hydrogen mordenite ("Zeolon", Si/Al = 5). The concentration of acid sites is substantially higher in the lower Si/Al mordenite.…”

Section: Transition In Propertiesmentioning

confidence: 99%

Molecular sieve zeolite technology - the first twenty-five years

Flanigen¹

1980

Pure and Applied Chemistry

111

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In twenty-five years molecular sieve zeolites have substantially impacted adsorption and catalytic process technology throughout the chemical process industries; provided timely solutions to energy and environmental problems; and grown to over a hundred million dollar industry worldwide. The evolution in zeolite materials with improved or novel properties has strongly influenced the expansion of their applications, and provided new flexibility in the design of products and processes.

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“…The shape selective conversion of xylenes over ZSM-5 has been investigated in detail by several workers [1][2][3][4][5][6][7][8][9][10][11][12]. Modifications of ZSM-5 by various compounds have been employed to enhance p-xylene selectivity from xylene transformation process [13][14][15][16]. Similarly, para selectivity has been improved by the selective coking of the external surface of ZSM-5 [17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Enhancing p -xylene selectivity during m -xylene transformation using mildly pre-coked ZSM-5 catalyst

Al-Khattaf

2007

Chemical Engineering and Processing - Process Intensification

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In the present work, the transformation of m-xylene was studied over fresh and pre-coked H-ZSM-5 catalyst in a riser simulator over the temperature range of 350-500 o C.Significant differences were observed in both the activity and product selectivity pattern for the two forms of the catalyst.While, the fresh catalyst generally gave higher m-xylene conversion, the pre-coked catalyst produced higher Isomerization/Disproportionation (I/D) and Para/ Ortho xylene (P/O) ratios .For both forms of the catalyst, m-xylene conversion was found to increase with both reaction temperature and reaction time (0-15 s). A maximum conversion of 30.8% was achieved at 500 o C for a reaction time of 15 s using the fresh catalyst. The corresponding value for the pre-coked catalyst was 24.6%. P/O and I/D ratios as high as 2.5 and 10 respectively were observed with the pre-coked catalyst. It was also observed that the P/O and I/D ratios decreased with increasing temperature for both catalyst and that the difference between these ratios for the two catalysts is more pronounced between 400 and 450 o C than at higher temperatures. Kinetic modeling of the m-xylene transformation over the pre-coked catalyst yielded a lower activation energy for p-xylene formation compared to the fresh catalyst. And an activation energy of 17.5 kcal/mol for the of m-xylene dispropotionation was obtained for the precoked catalyst compared to 7.82 kcal/mol for the fresh catalyst. These values are indicative of the restriction posed on disproportionation by the pre-coked catalyst as reflected by higher I/D ratios.

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Infrared, microcalorimetric, and electron spin resonance investigations of the acidic properties of the H-ZSM-5 zeolite

Cited by 314 publications

References 20 publications

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Molecular sieve zeolite technology - the first twenty-five years

Enhancing p -xylene selectivity during m -xylene transformation using mildly pre-coked ZSM-5 catalyst

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