Influence of doping with copper on the texture of pillared montmorillonitecatalysts

Modification of the textural properties of Al-, Zr-, and Ti-pillared montmo rillonites upon doping with copper has been investigated by nitrogen adsorp tion/desorption at 77 K. The doping methods included addition of copper dur ing the post-pillaring treatment of uncalcined or calcined solids, and co-p illaring, i.e., the use of the pillaring agent containing copper ions. All investigated pillared samples are predominantly microporous, the dominant m icropore radii of Al- and Zr-pillared samples (<3.50 <Angstrom>) being much lower than in the case of the Ti-pillared clay (5.25 Angstrom). The influe nce of the copper additive on the texture of pillared matrices depends on t he nature of the pillars and on the method of doping, and affects both the micropore and the mesopore system. The results are interpreted in terms of the physicochemical properties of the samples as determined by the chemical , XRD and ESR analyses. The strong influence of post-pillaring doping on th e texture of the Al-pillared clay, resulting in a decrease of microporosity , is assigned to the enhanced formation of clustered copper ions. An increa se of the adsorption potential of the co-pillared samples is attributed mai nly to a better structural order induced by the competitive exchange. It is suggested that the sensitivity of the mesopore system of the Ti-pillared c lay to the repeated post-pillaring doping is due to crystallisation effects in the extra-framework titania. (C) 2000 Elsevier Science B.V. All rights reserved.