The synthesis of MCM - 41
The synthesis of MCM-41 is different from the synthesis of traditional Molecule molecular sieve in that the template used is different. The synthesis of traditional zeolite or Molecule molecular sieve takes a single organic Molecule or metal ions as the template, taking zsm-5 as an example. The typical template used is tetrapropylamine ion, and the crystal is formed by condensation of acid salt around the template. The synthesis of MCM-41, on the other hand, is different. It is based on the surfactant of large Molecule as a template. The alkyl chain of the template is generally more than 10 carbon atoms.
Compared with other zeolite materials, the thermal stability of the skeleton aluminum species of MCM-41 is relatively poor. During the roasting process, the skeleton aluminum species shed from the skeleton to the non-skeleton aluminum species.
The pure silicon MCM-41 is weak in acidity and has low activity as a catalyst. Therefore, they are often modified to increase their catalytic activity. The main modification methods include:
(1) to synthesize McM-41 mixed with heteroatoms in the framework structure, the surface center of anion generated by non-tetranscriptional ions in the framework, such as Al3+, Cu2+, Fe3+, Zn2+, Ga3+, can be counterbalanced by protons or other transition metal ions to form the catalytic active center.
(2) a series of heterogeneous catalysts suitable for different reactions can be prepared by means of supporting heteropoly acid, such as :B acid hydrogen type McM-41;Doped l-acid McM-1;Alkaline or amphoteric McM-41 doped with metal oxides;McM-41 loaded with heteropoly acids such as PW12, SIW12 and PMo12;And McM-41 supporting TiO2/SO42-, ZrO2/SO42- and other solid super strong acid type.
(3) immobilized macromolecular transition metal complex is assembled in hole McM-41.
