Diffusion macro”-FTIR

Since the investigation of diffusion phenomena in zeolites by macro-FTIR and micro-FTlR spectroscopy is still not a routine technique, the experimental aspects will be described in more detail. 

Fig. 5 Experimental setup for diffusion measurements in zeolites. Schematic arrangement around the IR flow-through cell (6), which for macro-FTIR measurements may be that described in Vol. 4, Chap. 1, p 42 of this series (see also [23]) or for micro-FTIR measurements the cell represented in Fig. 4b. Detailed explanation of main parts (1) ionization gauge (2) ionization gauge controller (3) baratron (4) pressure controller (5) magnetic valve (6) IR flow cell with sample (7) temperature controller (8) mass flow controllers (9) thermostatted saturators (10) four-way valves...

Diffusion of Benzene, Ethylbenzene, and p-Xylene in H-ZSM-5 by "Macro"-FTIR... 

Fig. 27 Set of spectra monitored via macro-FTIR spectroscopy during co-diffusion of benzene (partial pressure 460 Pa) andp-xylene (partial pressure 115 Pa) from a gas stream (with helium as carrier gas) into H-ZSM-5. First, benzene is preferentially sorbed, then it is partially replaced by p-xylene, which is more strongly interacting with the adsorbent (see Fig. 28)...

Moreover, the macro - and micro -FTIR techniques enable us to obtain spectra in situ from a working catalyst, since the cells used (see Sect. 2.1.1) may be operated as flow-through reactors. Thus, coking of zeolite catalysts upon reaction of ethane or ethylbenzene was investigated in situ, and the decrease of diffusivities (e.g., of benzene) in the coking samples was measured as a function of the amount of coke deposited [15]. Similarly, the sorption of para-, meta-, and ortho-diethylbenzene from the gas phase into H-ZSM-5... 

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