Naturally-Occurring Silicates as Carriers for Copper Catalysts Used in Methanol Conversion

M. R. Sun Kou, S. Mendioroz, J. L. G. Fierro, I. Rodriguez-Ramos, J. M. Palacios, A. Guerrero-Ruiz and A. M. De Andres
Instituto de Catálisis y Petroleoquímica, C.S.I.C. Campus UAM, Cantoblanco, 28049 Madrid, Spain
Departamento de Química Inorgánica, UNED, Senda del Rey, s/n 28028 Madrid, Spain
Instituto de Ciencia de Materiales, C.S.I.C., Serrano 119, 28006 Madrid, Spain

Abstract: Bentonite- and sepiolite-supported copper catalysts have been prepared either by adsorption of Cu(II) from aqueous solutions of copper nitrate at pH ∼4.5 or by adsorption ofa [Cu(NH3)4]2+ complex from an ammonia solution of CuSO4 at pH ∼9.5. The structure and composition of the calcined preparations have been studied by X-ray diffraction, chemical analysis, and energy dispersive X-rays. Textural characteristics have derived from the analysis of the adsorption-desorption isotherms of N2. All catalysts have been tested for the dehydrogenation of methanol to methyl formate. For this reaction, bentonite-based catalysts were found to have very little activity, which indicates that copper located in the interlamellar spaces is inaccessible to methanol molecules. On the contrary, copper-sepiolite catalysts showed a very high specific activity even for those catalysts with a very low copper content. The chemical state of copper in the catalysts on-stream has been revealed by X-ray photoelectron spectroscopy and X-ray-induced Auger techniques. In most of the catalysts Cu+ is the dominant copper species.

Key Words: Bentonite • Copper catalysts • Methanol dehydrogenation • Sepiolite

Clays and Clay Minerals; April 1992 v. 40; no. 2; p. 167-174; DOI: 10.1346/CCMN.1992.0400205

Clay Minerals Society (www.clays.org)