Investigation of the distribution of acidity strength in zeolites by temperature-programmed desorption of probe molecules. 2. Dealuminated Y-type zeolites

Karge, Hellmut G.; Dondur, V.; Weitkamp, Jens

doi:10.1021/j100154a053

Cited by 167 publications

(81 citation statements)

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“…Fig. 4 depicts the NH 3 -TPD profiles of AS10, AS80, parent SBA-15 and post-modified analogues to assess the accessibility of new-formed acidic site, in which the peak of desorbed NH 3 is deconvoluted by using Gaussian function with temperature as variant [29]. SBA-15 had only one desorption around 368 K with a small amount (0.07 mmol g −1 ).…”

Section: Characterization Of the Modified Adsorbentsmentioning

confidence: 99%

Capturing 1,3-butadiene by the highly ordered Al-containing SBA-15

Gao

Zhou

et al. 2009

Journal of Hazardous Materials

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Section: Characterization Of the Modified Adsorbentsmentioning

confidence: 99%

Capturing 1,3-butadiene by the highly ordered Al-containing SBA-15

Gao

Zhou

et al. 2009

Journal of Hazardous Materials

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“…Two types of acid sites are found on the surface of (69) and these are quite important in reactions such as catalytic cracking and in the skeletal isomerization of 1-butene to isobutene (67). In general, it is accepted that NH 3 is an excellent molecular probe to measure the total surface acidity of catalysts, since due to its strong basicity and small molecular size, it allows the measurement of acid surface sites inside narrow pores (71)(72)(73)(74)(75). In this work, the adsorption process of NH 3 was carried out at 373 K in order to minimize adsorption on the support.…”

Section: Total Surface Acidity Of the Supported Tungsten Catalystsmentioning

confidence: 99%

Tungsten catalysts supported on activated carbonI. Preparation and characterization after their heat treatments in inert atmosphere

Álvarez-Merino¹,

Carrasco-Marín²,

Fierro³

et al. 2000

Journal of Catalysis

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Tungsten catalysts supported on activated carbon, and with different metal content, were prepared from both ammonium tungstate and tungsten hexacarbonyl precursors. The catalysts were subjected to heat treatments, in He flow, between 623 and 1223 K for 4 h and characterized to determine their surface area and pore texture, the chemical state and dispersion of the metallic phase, and the total surface acidity. For this purpose, different techniques were used such as adsorption of N 2 at 77 K and mercury porosimetry; X-ray diffraction and X-ray photoelectron spectroscopy; temperatureprogrammed desorption of previously adsorbed NH 3 ; and behavior in the decomposition reactions of isopropanol. Results show that in the case of the catalysts prepared from ammonium tungstate an increase in the treatment temperature between 623 and 1223 K leads to a drop in the O/W ratio to below 3, resulting in the appearance of nonstoichiometric oxides such as W 25 O 73 , W 20 O 58 , and W 18 O 49 . At 1223 K, a mixture of W, tungsten carbides, and tungsten trioxide was detected. The catalysts prepared from tungsten hexacarbonyl presented a higher dispersion and no X-ray diffraction peaks. Total surface acidity, as measured by ammonia desorption, decreased with increasing treatment temperature, and the study of the decomposition reactions of isopropanol showed that the catalysts were essentially of acid character, with a much higher selectivity (or rate) to propene than to acetone. Moreover, there was a linear relationship between the reaction rate to propene and the amount of NH 3 desorbed from the catalysts, irrespective the method of preparation and treatment temperature.

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“…TP techniques are effective in studying 10 different catalyst features, allowing to obtain insights in catalytic 11 activity, reaction mechanisms, catalysts deactivation, surface 12 structure and also in the development and design of new catalysts 13 [4]. Nowadays, different TP techniques are available and commonly 14 used such as: Temperature Programmed Reduction (TPR), Tem- 15 perature Programmed Oxidation (TPO), Temperature Programmed 16 Sulphidation (TPS), Temperature Programmed Desorption (TPD) 17 and Temperature Programmed Surface Reaction (TPSR).…”

Section: Introductionmentioning

confidence: 99%

“…Major 29 drawbacks of this technique have been well described in the 30 literature [3,10]: in fact, NH 3 can be adsorbed on the non-acidic 31 part of the surface, the peak temperature might be not related 32 directly to the acid strength for its relation with experimental 33 conditions applied and redox reactions might happen producing 34 N 2 or NO x . 35 According to the literature, TPD can be performed by a wide 36 variety of methods: the analyses of the outlet gas stream with 37 techniques such as mass spectroscopy [11,12], thermal conductivi- 38 ty detectors (TCD) [12][13][14], flame ionization detectors (FID) [12], or 39 a combination of infrared and mass spectrometry (IRMS) detectors 40 [10,15,16]. Alternatively, the heat flow curve is acquired during 41 this process and the amount of desorbed species as a function of 42 time is measured either by mass variation, using a microbalance 43 [11,17,18], or by particular systems such as a Quantachrom 44 Autosorb-1 instrument [19], NH 3 -TPD apparatus (Nihon Bell, 45 Japan, BEL-CAT) connected to a Q-Mass analyser (Pfeiffer Vacuum, 46 Omnistar GCD301, Germany) [20].…”

Section: Introductionmentioning

confidence: 99%