Date of Award
Doctor of Philosophy
Chemical and Biological Engineering
Glenn L. Schrader
The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9--14 m2/g, and compositions were within the solid solution regime, i.e. below 15.0 mol% MoO3/(MoO3 + V2O 5). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V+4 and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to malefic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The addition of water to the reaction stream substantially increased catalyst activity and improved selectivity to crotonaldehyde and furan at specific reaction temperatures. At higher water addition concentrations, furan selectivity increased from 12% to over 25%. The catalytic effects of water addition were related to competitive adsorption with various V 2O5-based surface sites, including the vanadyl V=O, corner sharing V-O-V and edge sharing V-O oxygen. Higher levels of water addition were proposed to impose acidic character by dissociative adsorption. In addition, a novel combinatorial synthesis technique for VMoO was used to investigate the phase transitions of V2O5, solid solutions of Mo in V2O5, V9Mo6O40, and other reduced VMoO compounds, characterized by laser Raman spectroscopy. The natural composition gradient imposed by the sputter deposition apparatus was used to create VMoO arrays containing 225 samples ranging from 7.0--42 mol% MoO3/(V2O5 + MoO 3), determined by EDS analysis.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
William David Schroeder
Schroeder, William David, "Pathway and surface mechanism studies of 1,3-butadiene selective oxidation over vanadium-molybdenum-oxygen catalysts " (2001). Retrospective Theses and Dissertations. 455.