A characterization study of the surface acidity of solid catalysts by temperature programmed methods

Arena, Francesco; Dario, R.P.; Parmaliana, A.

doi:10.1016/s0926-860x(98)00041-6

Cited by 177 publications

(81 citation statements)

References 27 publications

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“…7). It can be seen that two NH 3 desorption peaks for both of precursor and MMM-ZrS-1 were detected, indicating the desorption of weak and strong acid sites [39,40]. The fact that the desorption temperature of NH 3 from the strong acid sites on the MMM-ZrS-1 (670°C) was much higher than that of zirconosilicate precursor (450°C) with an amorphous framework and nanosized zeolite ZSM-5 (Al-doped silicalite, around 500°C), might be attributed to the corresponding highly crystallinity of the framework and the introduction of Zr heteroatom in MMM-ZrS-1.…”

mentioning

confidence: 99%

Multimodal Zr-Silicalite-1 zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macroporous architecture and enhanced mass transport property

Chen

et al. 2012

Journal of Colloid and Interface Science

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mentioning

confidence: 99%

Multimodal Zr-Silicalite-1 zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macroporous architecture and enhanced mass transport property

Chen

et al. 2012

Journal of Colloid and Interface Science

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“…NH 3 -TPD is now widely used for evaluating the surface acidity of the solid catalysts [22,23]. The distribution of acid sites and total acidity values of the different systems are shown in Table 2.…”

Section: Resultsmentioning

confidence: 99%

Environmentally benign Friedel-Crafts benzylation over nano-TiO2/SO42-

2013

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During the past decade, much attention has been paid to the replacement of homogeneous catalysts by solid acid catalysts. Friedel-Crafts benzylation of toluene with benzyl chloride (BC) in liquid phase was carried out over highly active, nano-crystalline sulfated titania systems. These catalysts were prepared using the sol gel method. Modification was done by loading 3% of transition metal oxides over sulfated titania. Reaction parameters such as catalyst mass, molar ratio, temperature, and time have been studied. More than 80% conversion of benzyl chloride and 100% selectivity are shown by all the catalysts under optimum conditions. Catalytic activity is correlated with Lewis acidity obtained from perylene adsorption studies. The reaction appears to proceed by an electrophile, which involves the reaction of BC with the acidic titania catalyst. The catalyst was regenerated and reused up to four reaction cycles with equal efficiency as in the first run. The prepared systems are environmentally friendly and are easy to handle.

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“…The total surface acidity of the supported catalysts was determined by TPD of previously adsorbed NH 3 (41)(42)(43)(44)(45)(46)(47). The catalysts were heated in He flow (60 cm 3 min −1 ) to the maximum temperature, ranging between 623 and 1223 K, and held for 4 h. After that, the sample was cooled to 373 K in flowing He, and then the He flow was switched to NH 3 flow at a rate of 30 cm 3 min −1 over 30 min.…”

Section: Methodsmentioning

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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A characterization study of the surface acidity of solid catalysts by temperature programmed methods

Cited by 177 publications

References 27 publications

Multimodal Zr-Silicalite-1 zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macroporous architecture and enhanced mass transport property

Multimodal Zr-Silicalite-1 zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macroporous architecture and enhanced mass transport property

Environmentally benign Friedel-Crafts benzylation over nano-TiO2/SO42-

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

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