Catalyst characterization, SAPO molecular

Catalysts Characterization. Following pretreatment of the SAPO molecular sieves, the catalysts were characterized by temperature programmed desorption (TPD) of ammonia and infrared spectroscopy. To assess the acidity of the samples, the desorption of ammonia from the catalysts was performed in a manner similar to that described by van Hooff et. al. [11]. For the ammonia TPD experiments, typically 0.1 gram of the molecular sieve sample was supported on quartz wool inside a 9 mm O.D. quartz reactor equipped with axial thermowell which contacted the top of the... 

Catalyst Characterization. The three SAPO molecular sieves employed in this study represents the three pore sizes of molecular sieves, ranging tom 0.4 nm to 0.8 nm. While SAPO-5 and SAPO-11 have unidimensional pores, SAPO-34 has a multidimensional pore system with supercages. The chemical composition and total ammonia uptake of the tifiree SAPO molecular sieves are listed in Table I. 

However, this level of deactivation will be overcome by the catalyst make-up required to replace material lost to physical attrition in the fluidized bed reactors. A slight shift in the ethylene and propylene selectivities was also observed during the initial portion of this run. Characterization of the catalyst during the multi-cycle test shows that there is no change in the microporosity of the SAPO-34 molecular sieve,... 

Characterization of the catalyst acid sites by infrared spectroscopy correlated well with the results of ammonia desorption experiments. The transmission spectra of HZSM-5 (Figure 2a), and SAPO-34 (Figure 2b) following in vacuo pretreatment at 650 K all showed absorbance bands near 3610 cm. Since these two molecular sieves were the only samples to show high-temperature NH3 desorption peaks... 

The as-synthesized and calcined CrAPO-5 and CrS-1 were characterized by XRD which showed that the samples were pure and had an API and MFI structure respectively. ICP analysis showed that both catalysts contained about 1 % chromium. The results observed in the decomposition of cyclohexenyl hydroperoxide over several redox active moleular sieves are presented in Table 1. CrAPO-5 and CrS-1 displayed rougly equal activity and selectivity in the decomposition of cyclohexenyl hydroperoxide. Blank reactions carried out with Silicalite-1 (S-1) and silicon incorporated Aluminophosphate-5 (SAPO-5) show low conversions confirming that the chromium was responsible for the catalysis. Other transition- metal subsituted molecular sieves showed low conversions. 

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