Characterization of copper and zinc containing MCM-41 and MCM-48 mesoporous molecular sieves by temperature programmed reduction and carbon monoxide adsorption

Copper and zinc containing mesoporous molecular sieves have been investigat ed by nitrogen and carbon monoxide adsorption and temperature programmed re duction. MCM-48 and MCM-41 materials with different pore diameters can be s ynthesized in the presence of copper and zinc salts. While the addition of copper acetate to the synthesis gel has no influence on the quality of the materials, the introduction of zinc sulfate leads to materials with somewha t reduced quality as evident from X-ray diffraction patterns and nitrogen a dsorption measurements. Carbon monoxide adsorption proves the absence of Zn 2+ cations in the channels after calcination indicating zinc located in the amorphous walls. The reducibility of copper in the channels of the mesopor ous molecular sieves has been investigated by temperature programmed reduct ion. The maximum of the reduction profile is influenced by the copper conce ntration, the pore diameter of the supporting mesoporous material and the p resence of zinc. These factors are found to influence CuO dispersion and pa rticle size and therefore the reduction temperature. The results of this st udy allow the preparation of mesoporous molecular sieves with remarkable re dox properties compared with materials obtained by impregnation of silica o r Al2O3. (C) 1999 Elsevier Science B.V. All rights reserved.