INFLUENCE OF TEMPLATE EXTRACTION ON STRUCTURE, ACTIVITY, AND STABILITY OF MCM-41 CATALYSTS

Up to 73% of the template in MCM-41 can be removed by extraction with solutions of an acid or salt in ethanol. When extracting with acidic e thanol, ion exchange of the sodium ions for protons is achieved simult aneously After calcination to remove the residual template, the result ing catalysts show high activity for the acetylation of 2-methoxynapht halene. The activity depends on the sodium content and on the Si/Al ra tio of the catalyst. MCM-41 materials which had not been extracted, bu t directly calcined to remove all template ions and subsequently ion e xchanged, had a mesoporous structure that deteriorated with repeated c alcinations. The acid extracted catalysts, on the other hand, retained their highly ordered pore structure throughout several thermal treatm ents. This stabilization results from the precondensation of silanol g roups previously associated with template ions during the extraction. The extraction in acidic medium produced a MCM-41 catalyst with more B ronsted acid sites than the not extracted material. Al-27-NMR measurem ents showed that the observed increase in octahedral aluminium upon ca lcination usually ascribed to dealumination can also be explained by a change of coordination number depending on chemical environment as pr eviously reported for zeolite beta. (C) 1997 Academic Press.