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Preparation of mullite micro-vessels by a combined treatment of zeolites

A controlled thermal treatment of NH4-exchanged zeolite 4 results in the formation of a mixture of mullite and amorphous silica by the chain of the pseudomorphic transformation processes: zeolite &reg ; ; ; ; ; ; amorphous phase &reg ; ; ; ; ; ; (mullite + amorphous SiO2). In contrast to the structural changes, particulate properties (particle shape and size, respectively) do not change or change a little during the heating. This implies that the resulting mixture of mullite and amorphous SiO2 does not appear as the separate particulate systems, and thus that the transformation processes occur inside single particles (micro-reactors). Base treatment of the final product (mullite + amorphous SiO2) results in the extraction of the amorphous SiO2 from the interior of each particle and formation of mullite micro-vessels.

ammonium-exchanged zeolite A; thermal treatment; amorphous aluminosilicate; mullite; amorphous silica; base treatment; mullite micro-vessels

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