Propene, adsorption

The appearance of volcano type behaviour is perfectly consistent, via Global Rule G3 (Chapter 6), with the kinetic (Fig. 9.18) which show strong competitive adsorption of propene and NO with propene adsorption being stronger on the Na-free surface (Uwr>0 V). Negative Uwr and AO favors the adsorption of electron acceptor NO vs electron donor C3H6 and this is manifest both by the kinetics (Fig. 9.18) and by the observed volcano behaviour (Fig. 9.17). This system is a nice confirmation of Global Rule G3. 

Keywords IR spectroscopy, integral molar extinction coefficients, propene, adsorption, zeolites. 

Zeolite Y samples with Si/Al = 2.5 modified with Na+, Ca2+, Mg2+ or Zn2+ ions were used in the present study for propene adsorption at room temperature. Ca (42 % of ion exchange) and Mg (35% of ion exchange) samples were prepared by multiple ion... 

The transmittance IR spectra of propene adsorbed by the Ca and Mg forms of Y zeolite correspond to a superposition of the bands of weakly adsorbed molecules with those of molecules that are more strongly specifically adsorbed by the bivalent cations. Upon reducing the propene pressure, the bands from the weaker form were eliminated, while the stronger forms of adsorption predominate. Therefore, to separate the spectral contributions of the species strongly adsorbed by Ca2+ or Mg2+ cations from those of the weakly adsorbed species, we recorded spectra at very low propene pressures of 0.5 mbar. For propene adsorption by NaY the adsorbed species were homogeneous and all of the bands in the IR spectra increased in intensity with increasing pressure up to 15 mbar without changing their positions. 

Figure 1. Propene adsorption by different Figure 2 IR spectra of propene adsorbed cationic forms of zeolite Y. on ZnY at room temperature (initial...

C-Propene adsorption on platinum—alumina and platinum—silica [66] differs from ethylene adsorption insofar as a fraction of the initially retained 14C-propene is relatively easily exchanged or removed by hydrogen treatment. This suggests less extensive dissociation of the adsorbed propene and a 7T-allyl species (structure F) has been proposed in this case, viz. 

A CuO—MgO solid solution was investigated by Davydov and Budneva [97]. Propene adsorption complexes (n and a) were detected at room temperature and appeared to react by heating to 300° C. 

A methyl-rich spectrum from propene adsorption had been earlier observed after hydrogenation during work on Pt supported on porous glass (250). The marked contrast between this spectrum and that from a n-propyl group chemisorbed on a Ni catalyst had led to the hypothesis that the former arose from chemisorbed 2-propyl species. It was subsequently shown to be caused instead by physically adsorbed propane that was present because of the greater propensity for complete hydrogenation of the initial surface species on Pt. 

Note A polymer blend color change is indicative of propene adsorption. Only entry 2 was effective. 

DSC has been used to determine the heat effects associated with propene adsorption [84] on Mo/Si Ti catalysts with different K Mo molar ratios. The heats associated with reversible (-3.193 x 10 mjm pie) and irreversible (-0.126 X10 mj msampie) adsorption of propene were found to decrease with the addition of potassium. 

Figure 7. The optimized geometry of the propene adsorption complex.

Isotherms for propene adsorption on NiO, vanadium pentoxide, and cuprous oxide at 100° are shown in Fig. 2. All isotherms are described by Freundlich s equation and correspond to a heterogeneous surface with exponential distribution as to heats of adsorption. 

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