Abstract
The aluminophosphate molecular sieves AlPO4-11 and VPI-5 have been prepared in the presence of dipropylamine (Pr2NH), a structure-directing organic incorporated into their synthesis gels. The AlPO4-11 molecular sieve's unidimensional channel system contains occluded Pr2NH, detected by TG, in its straight channel structural voids; VPI-5 contains no significant amount of Pr2NH (also determined via TG). The as-synthesized Pr2NH-AlPO4-11 was placed in a mass spectrometer probe (ca. 0.1 mg), which was evacuated to ca. 10–6 mbar and heated at 2 °C s–1, and its cracking pattern analysed with time. The Pr2NH cracking pattern was observed from ca. 275 °C and above, peaking at ca. 350 °C. This is assigned as Pr2NH removed from the AlPO4-11 channel system during the direct mass-spectrometric analysis. Trace amounts of Pr2NH were also observed from the as-synthesized VPI-5. For each material, the above results also indicated that the Pr2NH was unprotonated. Thus, temperatureprogrammed mass spectrometry proves to be a rapid method for the qualitative analysis of guest molecules in molecular-sieve hosts.
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