Catalytic Removal Of Templates From Porous Materials

Caprolactam is an important chemical product, mainly used as the popular monomer for the versatile nylon-6 polyamide. A large amount of undesired ammonium sulfate is produced during the oximization and beckmann rearrangement process in the traditional route, which does not meet the criterion of green chemistry. The by-product free route is heterogeneous catalytic ammoximation coupled with beckmann rearrangement over solid acids. An advanced route is integrating the ammoximation and beckmann rearrangement reaction over heterogeneous catalysts. The critical role of this route is the availability of nanoporous aluminophosphate molecular sieves functionalized with acid centers and ammoximation active centers, such as MnMgAPO4-5.Removal of templates is an important step for preparing the MnMgAPO4-5 as well as other aluminophosphate molecular sieves. This dissertation presents a new method for the removal of templates—catalytic hydrocracking method. The template can be removed by catalytic hydrocracking method at mild temperatures (<350oC), which is different from the calcination at high temperatures.This method is also suitable for removing templates from mesoporous materials, such as wormhole mesoporous silicoaluminophosphate (WMSA)/Ti containing silica (Ti-HMS) and so on. It is revealed by ammoximation activity tests that the ammoximation activity and selectivity of MnMgAPO4-5 molecular sieve is much lower than that of TS-1 molecular sieve. These phenomena can be accounted by the hydrophilic framework of MnMgAPO4-5 molecular sieve. Therefore, the porous topological structure can not play a role for adsorping cylcohexanone and stabilizing H2O2. Thus, MnMgAPO4-5 is not active for selectively catalyzing the ammoximation reaction. Similarly, for the ammoximation reaction, mesoporous Ti-HMS is much less active than TS-1. This difference is reasoned from the amorphous framework of Ti-HMS. It is shown that MnMgAPO4-5, WMSA and Ti-HMS possess poor activity for liquid beckmann rearrangement at 110~130oC.Moreover, it is demonstrated by the gas permeation that the perfection of AFI- and MFI-type molecular sieve membranes can be kept after activated by the catalytic hydrocracking method. But the perfection cannot be kept for the molecular membranes activated by calcination, due to the thermal cracks. Meaningfully, the successful application of catalytic hydrocracking method for removing templates enlarges the application domain of catalysis. This new domain can be suggested as materials catalysis, i.e., the application of catalysis for preparing inorganic materials.