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SAPO-5, large crystals

In order to illustrate the general applicability of the methodology we have extended our approach to other large zeolite crystals, such as SAPO-34, SAPO-5 and ZSM-5. Our study on the rhombic SAPO-34 crystals reveals a four-pointed star fluorescence pattern at 445 K, which is transformed into a square-shaped feature at 550 K. This is illustrated in Figure 4a. Confocal fluorescence slices, summarized in Figures 4b-d, recorded at different temperatures show the cubical pattern, which proceed from the exterior of the crystal inwards. Both observations are consistent with a model which involves six components of equal tetragonal pyramids as illustrated in Figure 3b. [Pg.7]

Almost identical uptake and steady-state diffusivities were found on the 2.5 and 25 pm crystals, indicating that the resistance to intracrystalline diffusion is dominating in the SAPO-34 s crystals with sizes larger than 2.5 pm. Therefore, the proper uptake and steady-state diffusivity of intercrystalline diffusion can be measured with such large crystals. The steady-state diffusivity of methanol is about 1.65 X 10 m /s, as shown in Fig. 14. [Pg.373]

The SAPO-34 external surface is relatively large for the small crystal material used in this study. The role of the external surface in the MTO reaction is quite interesting but not clear. Coke deposition on HZSM-5 during methanol conversion was reported to occur essentially on its external surface [12]. Whether coke deposition during MTO on small crystals of SAPO-34 occurs in the same way is less clear. Experiments with controlled coke formation at the external surface were performed using i-butanol as a probe molecule. i-Butanol will dehydrate to i-butene on acidic sites on the external surface, but i-butanol and i-butene are too large to enter the pores of SAPO-34. Therefore, i-butene is a potential coke precursor on those external acidic sites. [Pg.162]

Discrimination among rival substitution mechanisms has been attempted for several SAP04-n topologies. In SAPO-5 up to 25% of the T atoms was replaced by large siliceous patches [48], concentrating at the crystals surface [50]. During SAPO-11 crystalbzation, the ISp mechanism dominates with dipropylamine as template, while with diisopropylamine both ISp mechanisms occur [51]. [Pg.248]

The isomerization of xylenes catalyzed by SAPO-5 type crystals with compositions consisting of aluminum, phosphorus, and, in several cases, additional elements, including Ti, Mg, Zn and Fe has been described [4]. The data show that these large-pore materials have catalytic activity for the isomerization of xylene mixtures. [Pg.266]


See other pages where SAPO-5, large crystals is mentioned: [Pg.8]    [Pg.8]    [Pg.11]    [Pg.148]    [Pg.148]    [Pg.153]    [Pg.250]    [Pg.165]    [Pg.538]    [Pg.25]    [Pg.545]    [Pg.5]    [Pg.164]    [Pg.615]    [Pg.36]    [Pg.155]    [Pg.299]    [Pg.94]    [Pg.214]    [Pg.1600]    [Pg.249]    [Pg.446]    [Pg.248]   
See also in sourсe #XX -- [ Pg.148 ]




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