Phosphatation of Zeolite H‐ZSM‐5: A Combined Microscopy and Spectroscopy Study

Abstract

A variety of phosphated zeolite H-ZSM-5 samples are investigated by using a combination of Fourier transfer infrared (FTIR) spectroscopy, single pulse (27)Al, (29)Si, (31)P, (1)H-(31)P cross polarization (CP), (27)Al-(31)P CP, and (27)Al 3Q magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, scanning transmission X-ray microscopy (STXM) and N2 physisorption. This approach leads to insights into the physicochemical processes that take place during phosphatation. Direct phosphatation of H-ZSM-5 promotes zeolite aggregation, as phosphorus does not penetrate deep into the zeolite material and is mostly found on and close to the outer surface of the zeolite, acting as a glue. Phosphatation of pre-steamed H-ZSM-5 gives rise to the formation of a crystalline tridymite AlPO4 phase, which is found in the mesopores of dealuminated H-ZSM-5. Framework aluminum species interacting with phosphorus are not affected by hydrothermal treatment. Dealuminated H-ZSM-5, containing AlPO4 , retains relatively more framework Al atoms and acid sites during hydrothermal treatment than directly phosphated H-ZSM-5.

Aluminum-Phosphate Binder Formation in Zeolites as Probed with X-ray Absorption Microscopy

“…In contrast, 32 we have shown that the intensity of the bands corresponding to terminal Al-OH groups decrease significantly after the phosphatation of H-ZSM-5. 19,58 From the X-ray absorption maps in Figure 9 it follows that location of phosphorus and aluminum does not correlate, which further indicates that most phosphorus does not interact with aluminum in zeolite H-ferrierite. A schematic representation of this effect is shown in Scheme 1c.…”

“…From Figure 8 it can be observed that H-ferrierite steamed at 500 °C, shows a strong contribution of the 27 Al MAS NMR resonance at 32 ppm, corresponding to {Al} EF species. 19,68,69 The resonance at 30 ppm is even more pronounced for H-ferrierite steamed at 600 °C. Furthermore, in Figure 9, the Al K- The inaccessible nature of these {Al} EF species follows from our results as well.…”

On the use of infrared spectrometer as detector for Temperature Programmed (TP) techniques in catalysts characterization

“…Interestingly, with an increased 288 amount of phosphorus (6PZ sample), only one peak is observed at 289 intermediate temperature (ca. 610 K), although with a pronounced 290 tail toward higher temperature, suggesting that strong "zeolitic" 291 Brønsted sites progressively disappear by P addition[42]. Together 292 extraframework Lewis acid sites also disappear, while weaker 293…”

“…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]. A new sensor for the detection 47 of ammonia, based on zeolites, has been recently proposed 48 although the comparison with conventional measurements is still 49 unclear [21].…”

New micro and mesoporous materials for the reaction of methanol to olefins

“…Since it was firstly reported, the phosphorus modification of ZSM-5 has been applied to different reactions such as fluid catalytic cracking, toluene alkylation, and also methanol to hydrocarbons [108]. The introduction of phosphorus also play an important role in enhancement the hydrothermal stability of the ZSM-5, as it was first reported by Lischke et al [107], and confirmed by other researchers [109][110][111][112][113]. This is especially important for the application of ZSM-5 in the MTH reaction, since water is present in the reaction media and causes progressive dealumination and therefore irreversible deactivation of the catalyst.…”