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 investigated by nitrogen and carbon monoxide adsorption and temperature programmed reduction. MCM-48 and MCM-41 materials with different pore diameters can be synthesized 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 somewhat reduced quality as evident from X-ray diffraction patterns and nitrogen adsorption measurements. Carbon monoxide adsorption proves the absence of Zn2+ cations in the channels after calcination indicating zinc located in the amorphous walls. The reducibility of copper in the channels of the mesoporous molecular sieves has been investigated by temperature programmed reduction. The maximum of the reduction profile is influenced by the copper concentration, the pore diameter of the supporting mesoporous material and the presence of zinc. These factors are found to influence CuO dispersion and particle size and therefore the reduction temperature. The results of this study allow the preparation of mesoporous molecular sieves with remarkable redox properties compared with materials obtained by impregnation of silica or Al2O3. (C) 1999 Elsevier Science B.V. All rights reserved.