Michael A. Risch and Eduardo E. Wolf,

Chemical Engineering Department,

University of Notre Dame, Notre Dame, IN 46556 USA.

Abstract.

The preparation of a high surface area, mesoporous sulfated zirconia catalyst has been investigated by direct and secondary synthesis procedures. The synthesized materials have been characterized by XRD, N2 adsorption, TGA/DTA, FTIR, XPS, and SEM. Synthesis by a surfactant assisted method reported for the silica MCM-41 structure was extended to zirconia. Mesostructures of zirconia surfactant composites were formed. However, thermally stable mesoporous materials were not obtained upon surfactant removal. A method of preparing a novel, non-uniform, disordered mesoporous sulfated zirconia catalyst via a surfactant free synthesis was developed. Refluxing a slurry of freshly precipitated hydrous zirconia at 90°C for twenty hours produces a mesoporous form of zirconia with a surface area of approximately 500 m 2 /g. Conventional sulfated zirconia catalysts typically measure 100-120 m 2 /g.

The mesoporous sulfated zirconia catalysts are thermally stable under reaction conditions and are active for n-butane isomerization. No long range order tetragonal phase zirconia is observed by XRD on these catalysts. The presence of water on the surface of these mesoporous catalysts was found to contribute to their activity, as it has been recently reported to be the case with the conventional catalysts. Catalyst deactivation on sulfated zirconia is rapid at 250°C. The deactivation of the conventional sulfated zirconia was studied in detail and a two site model is proposed to interpret the results.

Eduardo E. Wolf has been active in the past in collaborations with researchers from Chile and Argentina in South America as well as researchers from Europe and Asia. An NSF sponsored grant supported the stay for one year of Mr. Paulo Araya from the Departamento de Ingenieria Quimica, Universidad de Chile, Santiago . Mr. Araya was at that time a junior faculty member in his Department. He spent two years (1987-89) in my Laboratory doing research that later on formed part of his Thesis for a Doctoral degree awarded by the Universidad de Chile. This connection has indeed being very rewarding as Dr. Araya is now the Chairman of the Department and has recently secured a grant from the CONYCIT for continuing the research work including visits to his laboratory in Santiago (1998-2001). Another collaboration with South American researchers was with, Dr. E. Miro, from the Universidad del Litoral Santa Fe, Argentina, who spent one year (1988) in my laboratory as a post Doctoral Fellow. A summary of papers that were written as result of these collaborations listed is presented at the end.

In the Fall, a junior faculty member from the Universidad de Chile, Santiago, Mr. Francisco Gracia, will be joining the group to work in his Ph.D. and then return to teach in Chile. This will be a great opportunity to act on the proposal from Rio and support this join effort.

Membrane Reactors. We have developed a novel fast flow porous membrane reactor that favors the partial oxidation of light alkanes and at the same time it permits the safe operation of the reactor with mixtures that otherwise will be explosive. We plan to extend these ideas to partial oxidation reactions involving liquid phase reactions as well as to develop reaction engineering models describing the operation of these non-isothermal cross-flow reactors.

Design of novel micro and mesoporous materials for the conversion of hydrocarbons. We have synthesized new mesoporous sulfated zirconia catalysts for the isomerization of n-butane. While these materials exhibit high surface area and activity, the catalysts deactivate significantly and further work is now underway to reduce deactivation. It has been found that supporting the zirconia on acid oxides reduces significantly the deactivation. Work is underway to extend this finding to the isomerization of higher alkanes. Other studies involve synthesis using polymer-ceramic technology to develop meso-microporous materials for hydrocarbon conversion.

STM studies of the electronic effects during metal-support interactions. We have been using STM to characterize the morphology of model catalysts and correlate surface parameters with reactivity and selectivity. A new joint effort with industrial researchers is now underway to use Scanning Tunneling Spectroscopy (STS) to measure electronic properties of model catalyst and relate these measurements with other surface analysis techniques (IR, XPS, XAFS) to probe the atomic nature of metal support interactions. Work is underway in both the experimental front as well as theoretical aspects of these interactions, known to catalytic researchers for so long, yet not completely elucidated. Knowing the atomic nature of these interactions will permit to fine tune catalysts to meet the challenges of reformulated fuels and other constraints placed on current processes by environmental regulations.

68. Wolf. E. E., (with E. Miro, Z. Kalenik and J. Santamaria), "Transient Studies during Methane Oxidative Coupling", Catal. Today, 6, 511-518 (1990).

69. Wolf, E. E., (with E. Miro and J. Santamaria), "Transient Studies of Methane Oxidative Coupling and Characterization of Alkali Promoted Nickel Titanate Catalysts", J. Catal, 124, 451-464 (1990).

70. Wolf, E. E., (with E. Miro and J. Santamaria), "Kinetics and Mechanism of Methane Oxidative Coupling on Alkali-Promoted Nickel Titanate Catalysts", J. Catal, 124, 465-476 (1990).

72. Wolf, E. E., (with P. Araya and W. Porod), "Monte Carlo Simulation of FTIR Studies on Pt/SiO2 Catalysts", Surf. Sci., 230, 245-254 (1990).

76. Wolf, E. E., (with J. Santamaria and E. Miro), "Reaction Simulation Studies during Methane Oxidative Coupling on Na/NiTiO3 Catalysts", I&EC Research, 30, 1157-1165 (1991).

97. Wolf, E.E.. (with P. Araya) Activity and Infrared Studies during CO Oxidation over Bimetallic Pd-Rh/SiO2 Catalysts", Appl. Catal. 92, 17-27 (1992).